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International audience; A single-oscillator monolithic thulium-doped fiber laser in which the 793 nm core absorption of 8.42 dB/m allows emitting 193 W (46 % of slope efficiency) at 2.09 µm is presented. An 8 •-cleaved angle of the fiber facet suppresses the parasitic cavity that formerly limited the power scaling. The characteristics of the thulium laser operating at the uncommon 2.09-µm long wavelength is compared to the power performances of a similar thulium-holmium codoped fiber laser.

A Tm,Ho:YAP laser at cryogenic temperature is demonstrated for the first time with simultaneous emission at 2000 nm and 2119 nm. The feasibility of switching wavelength and achieving balanced output powers at two widely separated wavelengths has been confirmed by investigating the temperature dependence of the laser spectra. The optimal temperature for balanced output evidently diminishes as the pump power density increases, thereby manifesting a rate of change quantified at 1.19 K/W. At the optimal temperature of 43.1 K, the optical-to-optical conversion efficiency of the Tm,Ho:YAP simultaneous dual-wavelength laser (SDWL) with a pump power of 11.8 W is 12.7%, corresponding to a slope efficiency of 15.8%.

Tracking electron motion in molecules is the key to understanding and controlling chemical transformations. Contemporary techniques in attosecond science are able to generate and trace the consequences of this motion in real time, but not in real space. Scanning tunnelling microscopy, on the other hand, can locally probe the valence electron density in molecules, but cannot alone provide dynamical information at this ultrafast timescale. Here we show that, by combining scanning tunnelling microscopy and attosecond technologies, quantum electronic coherences induced in molecules by, By combining scanning tunnelling microscopy and attosecond technologies, the coherent electronic motion generated in molecules by carrier-envelope-phase-stable laser pulses is visualized at angstrom-scale spatial resolution and subfemtosecond temporal resolution.

It was reported that a double-peaked mid-infrared laser was generated based on an intracavity difference frequency generation (DFG). The double-peaked pump source was achieved by suppressing the intensity at the central wavelength of the pump source. The double-peaked mid-infrared generation had a double-peaked spacing of 23–37 nm, and the full width at half-peak (FWHM) of the peaks was up to 30 nm. It was demonstrated that a tilted Bragg fiber grating (TFBG) with a specific transmission spectral depth and bandwidth can generate a double-peaked mid-infrared laser with controllable double-peaked spacing. It was the first generation of a double-peaked mid-infrared laser based on a near-infrared pumping spectral modulation. Furthermore, the double-peaked mid-infrared generation was tunable, and the FWHMs of the peaks were controllable by an intracavity DFG. It had a high potential for the monitoring and absorption of gas molecules by differential absorption lidar (DIAL).

We have demonstrated the stable Q-switched Er-doped fluoride fiber laser with the help of the few-layered Ta2NiS5 in the mid-infrared spectral range. We fabricated the mid-infrared saturable absorber mirror (SAM) by depositing the layered Ta2NiS5 on a gold mirror. The layered Ta2NiS5 exhibited saturable absorption behavior with modulation depth 36% and saturation intensity 32.2 GW/cm2 at 2800 nm, respectively. With the Ta2NiS5-SAM, stable Q-switched pulses around 2.8 μm wavelength can be delivered with a pulse duration of 1.20 μs and a repetition rate of 102 kHz under an incident pump power of 860 mW from the ZBLAN fiber laser cavity. The experimental results confirm that Ta2NiS5 has great potentials as broadband saturable absorber in mid-infrared regions, paving the way for the application of low-dimensional ternary chalcogenide in broadband optoelectronic devices.

We demonstrated highly-efficient pulsed mid-infrared generation based on intracavity difference frequency mixing inside a continuous-wave (CW) PPLN optical parametric oscillator (OPO). The near-infrared pulsed fiber source was located at 1120 nm with variable pulse width and repetition rate. The pump source of OPO was a CW linearly-polarized high-power 1060 nm fiber laser. The 1120 nm and 1060 nm pump beams were simultaneously incident into the OPO cavity. The 1060 nm pump beam built parametric oscillation firstly and generated high-power resonant signal beam inside the cavity. By controlling the PPLN temperature properly, the phase-matched difference frequency generation (DFG) occurred between the signal beam and 1120 nm pulsed pump beam in the PPLN crystal. Finally, the pulsed 1120 nm pump beam was successfully transformed to 3593 nm mid-infrared radiation at every power level and temporal characteristic. Both the slope efficiency and pump-to-idler conversion efficiency of the intracavity DFG process reached over 20%. In addition, the pulse shape of newly generated 3593 nm idler beam was basically the same as 1120 nm pump beam. The experimental results exhibited huge potential in frequency down conversion of low-power laser sources with special temporal characteristics.

In this paper, a novel high efficient dual-wavelength mid-infrared optical parametric oscillator (OPO) was demonstrated, which was pumped by a dual-wavelength Raman fiber oscillator for the first time. The adoption of oscillator structure reduced the waste of power, increased Raman pump power and promoted its frequency conversion. The dual-wavelength pump source was fixed at 1070 nm and 1120 nm and the Raman conversion efficiency was greatly enhanced from 26.7% to 72.1%. The high Raman efficiency and low Raman threshold enabled the Raman laser to build optical parametric oscillation easily and the pump-to-idler conversion efficiency of Raman laser improved greatly from 4.2% to 13.3%. The generated dual-wavelength mid-infrared laser was fixed at 3272 nm and 3663 nm, with a maximum power of 6.87 W, indicating a 13.9% pump-to-idler conversion efficiency. The highest mid-infrared output power generated by optical parametric oscillation of Raman laser was also achieved, which is almost ten times than before.

Photonic-crystal (PC) surface-emitting lasers (SELs) with double-hole structure in the square-lattice unit cell were fabricated on GaSb-based type-I InGaAsSb/AlGaAsSb heterostructures. The relative shift of two holes was varied within one half of the lattice period. We measured the lasing wavelengths and threshold pumping densities of 16 PC-SELs and investigated their dependence on the double-hole shift. The experimental results were compared to the simulated wavelengths and threshold gains of four band-edge modes. The measured lasing wavelength did not exhibit switching of band-edge mode, however, the calculated lowest threshold mode switched as the double-hole shift exceeded one quarter of the lattice period. The identification of band-edge lasing mode revealed that modal gain discrimination was dominated over by its mode wavelength separation.

This paper presents a comparative assessment of Cu(acac)2 and {[Cu(μ-O,O′-NO3) (L-arg)(2,2′-bpy)]·NO3}n as potential precursors for the electroless metallization of laser activated polymer materials. Coatings consisting of polyurethane resin, one of the two mentioned precursor compounds, and antimony oxide (Sb2O3), as a compound strongly absorbing infrared radiation, were applied on the polycarbonate substrate. The coatings were activated with infrared Nd: YAG laser radiation (λ = 1064nm) and electroless metallized. It was found that after laser irradiation, a micro-rough surface structure of the coatings was formed, on which copper was present in various oxidation states, as well as in its metallic form. For selected parameters of laser irradiation, it was possible to deposit a copper layer on the coating containing Cu(acac)2 and Sb2O3,which is characterized by high adhesion strength. It was also found that the {[Cu(μ-O,O′-NO3) (L-arg)(2,2′-bpy)]·NO3}n complex was not an effective precursor for the electroless metallization of Nd:YAG laser activated coatings. An attempt was made to determine the influence of the precursor chemical structure on the obtained metallization effects.

In this paper, we demonstrated efficient mid-infrared generation using a low-power 1064 nm single-frequency (SF) fiber laser based on phase-matched intracavity difference frequency generation (DFG) in a continuous-wave (CW) periodically poled lithium niobate (PPLN)-based optical parametric oscillator (OPO). This is the first time that the frequency down conversion of a low-power SF light source has been achieved using intracavity difference frequency mixing. A high power 1018 nm fiber laser was firstly used for building the parametric oscillation and providing the high power resonant signal wave. To realize an efficient DFG process between the SF pump wave and the intracavity signal wave, the temperature of periodically poled lithium niobate (PPLN) crystal was properly adjusted to satisfy the phase-matching conditions. Finally, the low-power 1064 nm SF pump wave was successfully converted to a 3.7 &mu, m mid-infrared wave with a conversion efficiency of 21.6%. The conversion efficiency, to the best of our knowledge, is the highest for SF lasers in DFG processes. Meanwhile, taking advantage of SF laser pumping, a narrow linewidth of 271 pm (5.9 GHz) in the mid-infrared region was achieved without adding any etalons or devices in the cavity.

Human activities, at a personal and at an industrial level, cause the release of numerous molecular species in the atmosphere. Even a very low level of certain molecules can lead to the alteration of the air quality. Gas sensors are therefore required for monitoring the concentration of such molecules and must fulfill various features. They should be able to detect very little quantity of molecules (sensitivity), should respond only to the target species and not to other species (selectivity), have moderate footprint (compactness) and effective cost. However, actual commercial sensors often lack one of these properties. One promising technology to meet these requirements is based on laser spectroscopy and photoacoustic detection, and in particular a technique called QEPAS. The objective of this PhD is to develop a gas sensor for monitoring the air quality based on the QEPAS technique. In order to achieve low limits of detection, quantum cascade lasers are employed as they emit in the mid-infrared region where strong molecular absorption occurs. The QEPAS sensor is optimized, using a specific acoustic characterization setup. It demonstrates good performances for the detection of methane, ethylene and carbon monoxide and is also used for a biomedical application. Eventually, the stability of the sharply resonant mechanical resonator is studied. A setup is developed to measure its resonance and proved to successfully prevent the sensor drift, showing a strong enhancement potential for next QEPAS sensors.; L’activité humaine, à l’échelle d’un particulier ou à l’échelle industrielle, libère de nombreuses molécules dans l’atmosphère. Même une petite quantité de certaines de ces molécules peut dégrader la qualité de l’air. Des capteurs de gaz sont donc essentiels pour mesurer la concentration de ces molécules dans l’environnement. Ils doivent satisfaire plusieurs propriétés : détecter de très faibles concentrations de molécules (sensibilité), répondre uniquement à la molécule cible et non aux autres molécules (sélectivité), avoir une bonne compacité et un faible coût. Actuellement, les capteurs sur le marché ne satisfont pas toutes ces propriétés. Une technologie prometteuse pour répondre à ce besoin repose sur la spectroscopie laser et la spectroscopie photo acoustique, en en particulier une technique appelée QEPAS. L’objectif de cette thèse est de développer un capteur de gaz pour la surveillance de la qualité de l’air, basé sur la technique QEPAS. Afin d’obtenir des seuils de détection faibles, des lasers à cascade quantiques sont employés : ils présentent une émission dans l’infra-rouge, là où de nombreuses espèces présentent de fortes absorptions moléculaires. Le capteur QEPAS est optimisé grâce à un banc de caractérisation acoustique spécifique. Le capteur a démontré de bonnes performances pour la détection du méthane, de l’éthylène et du monoxyde de carbone et a également permis de réaliser des mesures biomédicales. La stabilité du résonateur mécanique a également été étudiée. Un banc de mesure a été conçu pour la mesure de la résonance du résonateur et a permis de corriger efficacement la dérive du capteur, offrant un fort potentiel d’amélioration pour les prochains capteurs QEPAS.

In this letter, we demonstrated a dual-wavelength (DW) mid-infrared optical parametric oscillator (OPO) that was pumped by two independent fiber lasers fixed at 1018 nm and 1080 nm, and realized phase-matched signal beam coupling by tuning grating period of PPLN. Based on signal beam coupling, two interesting phenomena were observed for the first time. One is that the OPO threshold for 1018 nm and 1080 nm pump beams could be drastically lowered from 15.4 W to 266 mW and from 13.5 W to 1.38 W separately. The other is that the total idler power obtained when the OPO was simultaneously pumped by two fiber lasers was higher than sum of idler power obtained when the OPO was independently pumped by two fiber lasers, revealing obvious parametric gain enhancement. It also indicated that the two independent OPO processes became coherent when two signal beams were coupled. The results exhibit great potential in practical applications such as frequency down-conversion of some special near-infrared laser sources such as pulsed single-frequency sources, spectrum high-speed swept sources, and ultra-short pulse sources with low duty cycle.

Human exhaled breath consists of more than 3000 volatile organic compounds, many of which are relevant biomarkers for various diseases. Although gas chromatography has been the gold standard for volatile organic compound (VOC) detection in exhaled breath, recent developments in mid-infrared (MIR) laser spectroscopy have led to the promise of compact point-of-care (POC) optical instruments enabling even single breath diagnostics. In this review, we discuss the evolution of MIR sensing technologies with a special focus on photoacoustic spectroscopy, and its application in exhaled breath biomarker detection. While mid-infrared point-of-care instrumentation promises high sensitivity and inherent molecular selectivity, the lack of standardization of the various techniques has to be overcome for translating these techniques into more widespread real-time clinical use.

We report, to the best of our knowledge, the first demonstration of a continuous-wave, dual-wavelength (DW) mid-infrared optical parametric oscillator (OPO) based on the stimulated Raman scattering (SRS) effect of periodically poled lithium niobate (PPLN). The OPO was pumped by two independent fiber lasers, one being fixed at 1018 nm and the other being tunable. The high-power 1018-nm source built parametric oscillation, induced SRS effect in PPLN and generated 1495-nm signal beam as well as 1506-nm Raman beam. The tunable fiber laser was set at 1080 nm and the phase-matched difference frequency generation (DFG) occurred between the 1506-nm Raman beam and 1080-nm pump beam. Finally, DW idler beam located at 3189 and 3819 nm was obtained whose power ranged from 8.044 to 8.115 W, in which the 3189-nm idler power made up the majority of about 8 W and the maximum 3819-nm idler power reached 0.154 W. The slope and conversion efficiency of DFG and OPO processes was also discussed separately.

We report on frequency down-conversion of dual-wavelength (DW) Raman fiber laser in a periodically poled lithium niobate-based optical parametric oscillator. The DW pump source was fixed at 1060 and 1111 nm that was obtained based on stimulated Raman scattering effect by combining a home-made linearly polarized 1060-nm fiber laser and 137-m-long polarization-maintaining passive fiber. The total pump power went through three stages, in the latter two of which the 1111-nm wave appeared. In the entire experiment, the 1060-nm pump beam achieved parametric oscillation and generated 1626-nm signal beam and 3056-nm idler beam. The 1111-nm pump beam generated 3503-nm idler beam based on difference frequency generation (DFG) between itself and 1626-nm signal beam in the second stage. With power enhancement, it built independent parametric oscillation in the third stage and generated 1621-nm signal beam as well as 3530-nm idler beam. The DW idler power ranged from 3.94 to 7.78 W in the latter two stages. The power and efficiency characteristics in frequency conversion processes of 1060- and 1111-nm pump beams were also analyzed separately.

A mode-locked laser with orthogonal polarization at the wavelength of 1342 nm is experimentally achieved by using the natural birefringence of the Nd:YVO4 crystal. A total output power of 2.64 W could be obtained at an incident power of 14.4 W and the pulse durations are measured to be 15.1 and 16.9 ps with pulse repetition rates of 6.0 and 6.45 GHz for the laser output along the π- and σ-polarization, respectively. The mode-locked output is further found to exhibit a complex temporal trace with beat frequencies originated from the different central frequencies and pulse repetition rates.

International audience; We report the design of a setup combining the simultaneous and independent optical trapping and second-harmonic generation (SHG) of 1 µm diameter silica microspheres with two independent laser beams. Optical trapping is achieved with a tightly focused continuous wave infrared laser beam whereas the SHG intensity from the trapped microparticles is obtained with a 810 nm femtosecond pulsed laser. The silica microparticles are dispersed in an aqueous solution, and a microfluidic channel flow is used to remove untrapped microparticles. We show by the perpendicular displacement of the optical trap from the microfluidic channel wall that it is possible to control the contribution of the channel wall/solution interface to the overall SHG intensity. Stable trapping and SHG detection of two microparticles is also demonstrated. Combining the independent trapping of centrosymmetrical silica microparticles with SHG offers new avenues for analytical studies like surface sensing or all-optical devices where the SHG intensity is controlled by the trapping beam.

We report a multiwavelength mid-infrared laser based on intracavity difference frequency generation in an MgO-doped periodically poled LiNbO3 optical parametric oscillator, which was pumped by a dual-wavelength fiber MOPA consisting of two parts: dual-wavelength seed and power amplifier. The maximum output power of the linearly polarized pump laser was 65.3 W, and the wavelengths were 1060 and 1080 nm. Three idler emissions with different wavelengths of 3127, 3303 and 3346 nm were obtained under the maximum pump power, and the total idler output reached 7.38 W, indicating a 15% pump-to-idler slope efficiency. The signal laser generated in the experiment had two wavelengths, which were 1594 and 1604 nm under the maximum pump power. Three nonlinear progresses occurred in the experiment, two of them being optical parametric oscillation and the one left being difference frequency generation.

We report on a high-peak-power acousto-optically Q-switched Er:Y2O3 ceramic laser operating at room temperature. Stable pulses with a duration of 41-190 ns (FWHM) are generated at approximately 2.7 μm with the repetition rate varying from 0.3 to 10 kHz. The peak power at 0.3-kHz repetition rate is approximately 7.3 kW. An average output power of over 320 mW is generated at a repetition rate of 10 kHz using an output coupler with a transmission of 8%.

Selective metallization of polymeric materials using the technique known as laser direct structuring (LDS) is intensively developed. In this technique, metallized products can be manufactured by injection molding or by 3D printing process if rapid prototyping is need. Special additives present in the polymer matrix enable direct electroless metallization only on the surface which was laser activated. This paper presents the results of using copper microparticles introduced into the poly(acrylonitrile-butadiene-styrene) (ABS) matrix at various amounts (up to about 5 vol %). ABS was selected due to its good processing and mechanical properties and as one of the most common thermoplastics used in 3D printing. The influence of copper on structural, mechanical, and processing properties as well as on the effects of laser surface activation were determined. Two types of infrared lasers were tested for surface activation: Nd:YAG fiber laser (&lambda, = 1064 nm) and CO2 laser (&lambda, = 10.6 &micro, m). Various irradiation parameters (power, scanning speed, and frequency) were applied to find suitable conditions for laser surface activation and electroless metallization. It was found that the composites tested can be effectively metallized using the Nd:YAG laser, but only in a narrow range of radiation parameters. Activation with CO2 laser failed, regardless of applied irradiation conditions. It resulted from the fact that ablation rate and thickness of modified surface layer for CO2 were lower than for Nd:YAG laser using the same irradiation parameters (power, speed, and frequency of laser beams), thus the laser wavelength was crucial for successful surface activation.

Thermal energy is commonly used for surgery to control bleeding of the surgical plane. Many sophisticated techniques are used for preventing and stopping blood loss during surgery. Electrosurgery is one of the most used and one of the most common instruments in the operating theatre. Electrical currents are generated in a high frequency, which does not interfere with nerve stimulation. Besides electrosurgery, also other devices are used to create thermal effects based on various other physical principles, such as Radio Frequent Ablation (RFA), Ultrasonic, High-intensity Focussed Ultrasound (HIFU), plasma coagulation, microwave, high pressure waterjet and electroporation. Also, laser is used as an energy device for surgical applications. Lasers are unique light sources by emitting a small parallel beam of intense monochromatic light. This enables a high intensity at a small surface area inducing high temperature by absorption of light at the surface. Surgical lasers in the near and mid infrared spectrum (1470nm and above) are of interest for soft tissue excisions due to the high energy absorption in water, thus preventing heat conduction into the depth of the tissue. However, these lasers have strong differences in laser tissue effect and should be carefully considered before using in clinical practice. Since 2005, the Thulium laser has been clinically introduced. It has the highest wavelength (2013nm) that can be delivered through optical fibers. The aim of this thesis is to evaluate the advantages and additional value of the Thulium laser compared to other existing energy devices. The infrared region is very interesting as it is a wide region (810nm-10.600nm) with many kinds of laser tissue interaction. The Thulium laser (2013nm) is a relatively new laser in this region and could safely replace the 810 and 1064nm lasers for laser assisted third ventriculostomy. It is no longer necessary to pre-carbonize the laser fibers of the 810nm and 1064nm laser as the Thulium laser has direct absorption of the light in soft tissue (water) with a reproducible effect. It has good potential for endoscopic surgery in general as the laser has the ability to deliver the laser light through low OH fibers with CO2 laserlike properties. It fits through nearly every working channel due to the small dimensions of the laser fiber. For intra oral surgery the Thulium laser has an advantage over electrosurgery, especially for tumor surgery of the tongue. The absence of muscle contractions by the use of laser compared to electrosurgery has several potential benefits such as better overview of the operating field and less bleeding due to minimal tissue manipulation. The small vasculature can be easily cut and coagulated by the Thulium laser. The novel handpiece which has been developed with integrated smoke evacuation can also contribute to optimal Thulium laser usage in oral surgery. To conclude, there are more clinical applications in which the Thulium laser could be used for. There is a bright future for the Thulium laser for various applications when more surgeons become aware and appreciate the special characteristics/features of this laser.

Thermal energy is commonly used for surgery to control bleeding of the surgical plane. Many sophisticated techniques are used for preventing and stopping blood loss during surgery. Electrosurgery is one of the most used and one of the most common instruments in the operating theatre. Electrical currents are generated in a high frequency, which does not interfere with nerve stimulation. Besides electrosurgery, also other devices are used to create thermal effects based on various other physical principles, such as Radio Frequent Ablation (RFA), Ultrasonic, High-intensity Focussed Ultrasound (HIFU), plasma coagulation, microwave, high pressure waterjet and electroporation. Also, laser is used as an energy device for surgical applications. Lasers are unique light sources by emitting a small parallel beam of intense monochromatic light. This enables a high intensity at a small surface area inducing high temperature by absorption of light at the surface. Surgical lasers in the near and mid infrared spectrum (1470nm and above) are of interest for soft tissue excisions due to the high energy absorption in water, thus preventing heat conduction into the depth of the tissue. However, these lasers have strong differences in laser tissue effect and should be carefully considered before using in clinical practice. Since 2005, the Thulium laser has been clinically introduced. It has the highest wavelength (2013nm) that can be delivered through optical fibers. The aim of this thesis is to evaluate the advantages and additional value of the Thulium laser compared to other existing energy devices. The infrared region is very interesting as it is a wide region (810nm-10.600nm) with many kinds of laser tissue interaction. The Thulium laser (2013nm) is a relatively new laser in this region and could safely replace the 810 and 1064nm lasers for laser assisted third ventriculostomy. It is no longer necessary to pre-carbonize the laser fibers of the 810nm and 1064nm laser as the Thulium laser has direct absorption of the light in soft tissue (water) with a reproducible effect. It has good potential for endoscopic surgery in general as the laser has the ability to deliver the laser light through low OH fibers with CO2 laserlike properties. It fits through nearly every working channel due to the small dimensions of the laser fiber. For intra oral surgery the Thulium laser has an advantage over electrosurgery, especially for tumor surgery of the tongue. The absence of muscle contractions by the use of laser compared to electrosurgery has several potential benefits such as better overview of the operating field and less bleeding due to minimal tissue manipulation. The small vasculature can be easily cut and coagulated by the Thulium laser. The novel handpiece which has been developed with integrated smoke evacuation can also contribute to optimal Thulium laser usage in oral surgery. To conclude, there are more clinical applications in which the Thulium laser could be used for. There is a bright future for the Thulium laser for various applications when more surgeons become aware and appreciate the special characteristics/features of this laser.

InP-etched facet ridge lasers emitting in the optical C-band are heterogeneously integrated on Si substrates by microtransfer printing for the first time. 500 μm × 60 μm laser coupons are fabricated with a highly dense pitch on the native InP substrate. The laser epitaxial structure contains a 1-μm-thick InGaAs sacrificial layer. A resist anchoring system is used to restrain the devices while they are released by selectively etching the InGaAs layer with FeCl3:H2O (1:2) at 8 °C. Efficient thermal sinking is achieved by evaporating Ti-Au on the Si target substrate and annealing the printed devices at 300 °C. This integration strategy is particularly relevant for lasers being butt coupled to polymer or silicon-on-insulator (SOI) waveguides.

A diode-pumped dual-wavelength CW Tm, Ho: YAG ceramic laser was demonstrated for the first time to our knowledge. A maximum output power of ~1.2 W with a beam quality factor M2 = 1.19 has been generated from the 3at.% Tm, 0.5at.% Ho: YAG ceramic, corresponding to a slope efficiency of 16.7% with respect to the absorbed pump power. This Tm, Ho: YAG ceramic laser operated at dual-wavelengths around 2090 and 2096 nm. With the increase in the absorbed pump power and the output coupler transmittance, blue-shift of the emission wavelength was observed.

We present CPA-free linear amplification of 6:3 ps pulses in Ho:YLF crystals up to 100 μJ pulse energy at 10 kHz repetition rate. The seed pulses at a wavelength of 2:05 μm are provided by a Ho-based all-fiber system consisting of a soliton oscillator and a subsequent pre-amplifier followed by a free-space AOM as pulse-picker. Considering the achieved pulse peak power at MW-level, this system is a powerful tool for efficient pumping of parametric amplifiers addressing the highly demanded mid-IR spectral region. In detailed numerical simulations we verified our experimental results and discuss scaling options for pulse duration and energy. © 2018 SPIE.

This article presents the first implementation and the experimental characterization of a thermal infrared wavelength modulation laser heterodyne radiometer (WM-LHR) based on an external cavity quantum cascade laser. This novel WM-LHR system has demonstrated calibration-free operation, a superior signal to noise ratio and, more importantly, has opened the door for cost-efficient wide spectral range laser heterodyne radiometry in the near future. The work by P.M.-M. has been performed in the frame of the "Estancias de movilidad José Castillejo" from the Spanish Ministry of Education, Culture and Sports. P.M.-M. would also like to thank the Spanish Ministry of Economy and Competitiveness for supporting the project under the TEC2017-86271-R Grant. A.G., H. M. and B.L. acknowledge financial support received from the Austrian Research Promotion Agency FFG within the project 861581 (ATMOSENSE) of the ERA-NET Photonics program.

We demonstrate the first InGaN-LD-pumped room temperature and continuous-wave laser operation of a Pr3+: LiYF4 crystal at 915 nm. A maximum output power up to 78 mW with a laser slope efficiency of about 17% is obtained. The round-trip optical losses are estimated to be about 0.45%, and the M2 beam quality factors measured in x and y dimensions are about 1.07 and 1.04, respectively.

We present a timing jitter and amplitude noise characterization of a high-power mode-locked integrated external-cavity surface emitting laser (MIXSEL). In the MIXSEL, the semiconductor saturable absorber of a SESAM is integrated into the structure of a VECSEL to start and stabilize passive mode-locking. In comparison to previous noise characterization of SESAM-mode-locked VECSELs, this first noise characterization of a MIXSEL is performed at a much higher average output power. In a free-running operation, the laser generates 14.3-ps pulses at an average output power of 645 mW at a 2-GHz pulse repetition rate and an RMS amplitude noise of 0.15% [1 Hz, 10 MHz]. We measured an RMS timing jitter of 129 fs [100 Hz, 10 MHz], which represents the lowest value for a free-running passively mode-locked semiconductor disk laser to date. Additionally, we stabilized the pulse repetition rate with a piezo actuator to control the cavity length. With the laser generating 16.7-ps pulses at an average output power of 701 mW, the repetition frequency was phase-locked to a low-noise electronic reference using a feedback loop. In actively stabilized operation, the RMS timing jitter was reduced to less than 70 fs [1 Hz, 100 MHz]. In the 100-Hz to 10-MHz bandwidth, we report the lowest timing jitter measured from a passively mode-locked semiconductor disk laser to date with a value of 31 fs. These results show that the MIXSEL technology provides compact ultrafast laser sources combining high-power and low-noise performance similar to diode-pumped solid-state lasers, which enable world-record optical communication rates and low-noise frequency combs.

We present the development of laser processes for flexible OPV on roll-to-roll (RR2R) produced thin film barrier with indium tin oxide (ITO) as transparent conductive (TC) bottom electrode. Direct laser structuring of ITO on such barrier films (so-called P1 process) is very challenging since the layers are all transparent, a complete electrical isolation is required, and the laser process should not influence the barrier performance underneath the scribes. Based on the optical properties off the SiN and ITTO, ultra-short pulse lasers inn picosecond and femtosecond regime with standard infrared (IR) wavelength as well as lasers with new a wavelength (22 μm regime) are tested for this purpose. To determine a process window for a specific laser a fixed methodology is adopted. Single pulse ablation tests were followed by scribing experiments where the pulse overlap was tuned by varying laser pulse fluence, writing speed and frequency. To verify that the laser scribing does not result inn barrier damage underneath, a new test method was developed based on the optical Ca-test. This method shows a clear improvement in damage analysis underneath laser scribes over normal optical inspection methods (e.g. microscope, optical profiler, SEM). This way clear process windows can be obtained for IR TC patterning. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We present the development of laser processes for flexible OPV on roll-to-roll (RR2R) produced thin film barrier with indium tin oxide (ITO) as transparent conductive (TC) bottom electrode. Direct laser structuring of ITO on such barrier films (so-called P1 process) is very challenging since the layers are all transparent, a complete electrical isolation is required, and the laser process should not influence the barrier performance underneath the scribes. Based on the optical properties off the SiN and ITTO, ultra-short pulse lasers inn picosecond and femtosecond regime with standard infrared (IR) wavelength as well as lasers with new a wavelength (22 μm regime) are tested for this purpose. To determine a process window for a specific laser a fixed methodology is adopted. Single pulse ablation tests were followed by scribing experiments where the pulse overlap was tuned by varying laser pulse fluence, writing speed and frequency. To verify that the laser scribing does not result inn barrier damage underneath, a new test method was developed based on the optical Ca-test. This method shows a clear improvement in damage analysis underneath laser scribes over normal optical inspection methods (e.g. microscope, optical profiler, SEM). This way clear process windows can be obtained for IR TC patterning. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We provide a theoretical analysis of the relative merits of tensile strain and n-type doping as approaches to realizing an efficient low-power germanium laser. Ultimately, tensile strain offers threshold reductions of over 200x, and significant improvements in slope efficiency compared with the recently demonstrated 0.25% strained electrically pumped germanium laser. In contrast, doping offers fundamentally limited benefits, and too much doping is harmful. Moreover, we predict that tensile strain reduces the optimal doping value and that experimentally demonstrated doping has already reached its fundamental limit. We therefore theoretically show large (>; 1%) tensile strain to be the most viable path to a practical germanium-on-silicon laser.

We present timing jitter measurements of an InGaAs quantum well vertical external cavity surface emitting laser (VECSEL) passively mode locked with a quantum dot semiconductor saturable absorber mirror (SESAM) at 2-GHz repetition rate. It generates 53-mW average output power in 4.6-ps pulses at 953 nm. The laser housing was optimized for high mechanical stability to reduce acoustic noise. We use a fiber-coupled multimode 808-nm pump diode, which is mounted inside the laser housing. No active cavity length stabilization is employed. The phase noise of the free-running laser integrated over a bandwidth from 100 Hz to 1 MHz corresponds to an RMS timing jitter of ≈212 fs, which is lower than previously obtained for mode-locked VECSELs. This clearly confirms the superior noise performance expected from a high-Q-cavity semiconductor laser. In contrast to edge-emitting semiconductor diode lasers, the cavity mode is perpendicular to the quantum well gain layers, which minimizes complex dispersion and nonlinear dynamics.

We review breakthroughs in the area of mid-infrared laser development. We summarize 2009 research across a broad range of mid-infrared laser technologies, including bulk solid-state lasers, fiber lasers, and nonlinear optics for the generation of infrared light between 2 and 8 ?m.

Spatio-temporal mode coupling in highly multimode physical systems permits new routes for exploring complex instabilities and forming coherent wave structures. We present here the first experimental demonstration of multiple geometric parametric instability sidebands, generated in the frequency domain through resonant space-time coupling, owing to the natural periodic spatial self-imaging of a multimode quasi-continuous-wave beam in a standard graded-index multimode fiber. The input beam was launched in the fiber by means of an amplified microchip laser emitting sub-nanosecond pulses at 1064 nm. The experimentally observed frequency spacing among sidebands agrees well with analytical predictions and numerical simulations. The first order peaks are located at the considerably large detuning of 123.5 THz from the pump. These results open the remarkable possibility to convert a near-infrared laser directly into a broad spectral range spanning visible and infrared wavelengths, by means of a single resonant parametric nonlinear effect occurring in the normal dispersion regime. As a further evidence of our strong space-time coupling regime, we observed the striking effect that all of the different sideband peaks were carried by a well-defined and stable bell-shaped spatial profile., 5 pages, 4 figures

We present, for the first time, the complete pulse characterization of the infrared pulse after generating harmonics. A systematic study of the high harmonic generation process, and the generating infrared pulse characterization, has been done by changing the focus-gas-jet relative position. We have concluded, supported by nonlinear propagation simulations, that there is a correlation between the spectral and temporal nonlinear evolution of the infrared generating field and the structures shown in the harmonic signal. We have identified two different pressure regimes: the low pressure regime, characterized by the effects produced by the plasma generated by the infrared pulse, and the high pressure regime where the plasma and the Kerr effect generated by the infrared field are both present. These observations highlight the important role played by the nonlinear propagation of the generating field in the high harmonic generation context., Spanish Ministerio de Ciencia e Innovación (MICINN) through the Consolider Program SAUUL ( CSD2007-00013) and Research Project FIS2009-09522, from the Junta de Castilla y León (Project No. SA116U13) and from Centro de Láseres Pulsados. B. A. acknowledges Fundaçao para a Ciencia e a Tecnologia (FCT) through grant No. SFRH/BPD/88424/2012. W. H. and I. J. S. also acknowledge support from the Spanish Ministerio de Ciencia e Innovación through the Formación de Personal Investigador and Ramón y Cajal grant programs respectively.

A rate-equation analysis of the erbium 3-/spl mu/m ZBLAN fiber laser is performed. The computer calculation includes the longitudinal spatial resolution of the host material. It considers ground-state bleaching, excited-state absorption (ESA), interionic processes, lifetime quenching by co-doping, and stimulated emission at 2.7 /spl mu/m and 850 mn. State-of-the-art technology including double-clad diode pumping is assumed in the calculation. Pump ESA is identified as the major problem of this laser. With high Er/sup 3+/ concentration, suitable Pr/sup 3+/ co-doping, and low pump density, ESA is avoided and a diode-pumped erbium 3-/spl mu/m ZBLAN laser is predicted which is capable of emitting a transversely single-mode output power of 1.0 W when pumped with 7-W incident power at 800 nm. The corresponding output intensity which is relevant for surgical applications will be in the range of 1.8 MW/cm/sup 2/. Compared to Ti:sapphire-pumped cascade-lasing regimes, the proposed approach represents a strong decrease of the requirements on mirror coatings, cavity alignment, and especially pump intensity. Of the possible drawbacks investigated in the simulation, only insufficient lifetime quenching is found to have a significant influence on laser performance.

In coastal areas morphological changes of various kinds are caused by tidal flows, storms, climate change, and human activities. For these reasons a recurrent monitoring becomes necessary in order to detect undesired changes at early stages enabling rapid countermeasures to mitigate or minimize potential harm or hazard. The morphology of the terrain can be represented by highly precise digital terrain models (DTM). Airborne lidar (light detection and ranging) has become a standard method for DTM generation in coastal zones like Wadden Sea areas. In comparison to echo sounding systems, lidar is feasible for data acquisition of large areas. However, only the eulittoral zone can be covered by standard laser because the near-infrared laser pulses are not able to penetrate water which remains, for example, in some tidal channels even during low tide. In the framework of a German research project, we analyse the spatial and temporal variability of Wadden Sea areas in the North Sea. For a systematic monitoring and the detection of morphological changes we compare terrain models of two different epochs in order to determine height differences which can be caused by natural influences or human activities. We focus especially on the analysis of morphological changes near to tidal channels. In order to detect changes we compare the location of edges derived from each DTM based on the gray values' gradients. Our results for a test site in the German Wadden Sea show height differences up to 1 m due to the shifting of tidal channels and relocations of the channels up to 55 m within a period of two years.

Laser experiments on 1.5at.%, 5at.%, and 8at.% thulium-gadolinium-lutetium-yttrium co-doped, buried, ridgetype channel waveguides in a monoclinic potassium double tungstate demonstrate a maximum slope efficiency of 70% and output powers of 300 mW at ~1.9 μm.

Laser experiments on 1.5at.%, 5at.%, and 8at.% thulium-gadolinium-lutetium-yttrium co-doped, buried, ridgetype channel waveguides in a monoclinic potassium double tungstate demonstrate a maximum slope efficiency of 70% and output powers of 300 mW at ~1.9 μm.

Ultrashort-pulse lasers operating around the 2-μm spectral region are of great interest for applications in time-resolved spectroscopy, nonlinear frequency up-conversion to the mid/far-infrared spectral regions, mid-IR supercontinuum generation, optical communications and photomedicine. Tm 3+ doped crystalline gain media represent an attractive option for development of high-power, broadly tunable diode-pumped lasers around 2 μm that can be readily configured for ultrashort pulse generation through appropriate mode locking schemes. The best results in terms of pulse duration have to date been obtained with a Tm:KLu(WO 4) 2 laser [1] that produced 10-ps pulses at 1944 nm and a Tm:GdLiF 4 laser that generated ∼17-44 ps pulses tuned from 1868 nm to 1926 nm. [2] Here we report, for the first time to our knowledge, a femtosecond Tm 3+:KY(WO 4) 2 (Tm:KYW) laser that operates in the 1985-2065 nm spectral range by incorporating a semiconductor saturable absorber mirror (SESAM) © 2011 IEEE., 2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011, 22 May 2011 through 26 May 2011, Munich

We report an organic/inorganic hybrid optical amplifier with a function of converting infrared light to visible light. This device integrates an InGaAs/InP heterojunction phototransistor (HPT) and an organic light emitting device. © 2011 OSA., 2011 Conference on Lasers and Electro-Optics, CLEO 2011, 1 May 2011 through 6 May 2011, Baltimore, MD

We study the process of high-order harmonic generation using laser pulses with non-adiabatic turn-on and intensities well above saturation. As a main point, we report the existence of a valley structure in the efficiency of single-atom high-order harmonic generation with increasing laser intensities. Consequently, after an initial decrease, the high-frequency radiation yield is shown to increase for higher intensities, returning to a level similar to the case below saturation. Such behavior contradicts the general belief of a progressive degradation of the harmonic emission at ultrahigh intensities, based on the experience with pulses with smoother turn-on. We shall show that this behavior corresponds to the emergence of a new pathway for high-order harmonic generation, which takes place during the pulse turn-on. Our study combines trajectory analysis, wavelet techniques and the numerical integration of 3-Dimensional Time Dependent Schrödinger Equation. The increase in efficiency raises the possibility of employing ultrahigh intensities to generate high-frequency radiation beyond the water window., Spanish Ministerio de Ciencia e Innovación through the Consolider Program SAUUL ( CSD2007-00013) and research project FIS2009-09522, from Junta de Castilla y León through the Program for Groups of Excellence (GR27) and from the EC’s Seventh Framework Programme ( LASERLAB-EUROPE, grant agreement n 228334).

The synthesis of isolated attosecond pulses (IAPs) in the extreme ultraviolet (XUV) spectral region has opened up the shortest time scales for timeresolved studies. It relies on the generation of high-order harmonics (HHG) from high-power few-cycle infrared (IR) laser pulses. Here we explore experimentally a new and simple route to IAP generation directly from 35 fs IR pulses that undergo filamentation in argon. Spectral broadening, self-shortening of the IR pulse and HHG are realized in a single stage, reducing the cost and experimental effort for easier spreading of attosecond sources. We observe continuous XUV spectra supporting IAPs, emerging directly from the filament via a truncating pinhole to vacuum. The extremely short absorption length of the XUV radiation makes it a highly local probe for studying the elusive filamentation dynamics and in particular provides an experimental diagnostic of short-lived spikes in laser intensity. The excellent agreement with numerical simulations suggests the formation of a single-cycle pulse in the filament. DFG/EXC/QUEST National Science Foundation/PHY-0449235

High-speed wavelength modulation is demonstrated in a standard middle-infrared quantum cascade laser by near-infrared optical excitation. The typical wavelength modulation spectrum is obtained, which is observed at frequency up to 1.6 GHz. © 2011 OSA., 2011 Conference on Lasers and Electro-Optics, CLEO 2011, 1 May 2011 through 6 May 2011, Baltimore, MD

Type-I interband laser diodes were developed for trace gas sensing applications in the 2-4um wavelength range. The devices were grown by molecular beam epitaxy on GaSb substrates using InGaAsSb/Al(In)GaAsSb active regions. Tunable, single-mode lasers were produced using distributed feedback grating processing or by incorporating Fabry-Perot lasers in an external cavity configuration. Sensitive gas detection was demonstrated using these lasers in tunable-diode laser absorption spectroscopy. © 2011 IEEE., 2011 ICO International Conference on Information Photonics, IP 2011, 18 May 2011 through 20 May 2011, Ottawa, ON

Red and near-infrared laser irradiation is reported to have a range of biological effects on cultured cells and different tissues, leading to the hypothesis that laser light can affect energy metabolism. Increased adenosine triphosphate (ATP) synthesis has been reported in cultured cells and rat brain tissue after irradiation at 632.8 nm and 830 nm, respectively. This study investigated whether diode pulsed laser irradiation enhances ATP production in lymphocytes.Aliquots (500 microL) of an extract of cultured lymphocytes of the Molt-4 cell line were irradiated with diode laser light (lambda = 904 nm, pulsed mode, 6 kHz frequency) with an average emission power of 10 mW for 60 min. A Spectra Physics M404 power meter was used to measure light intensity. Controls were treated similarly but not irradiated. The amount of ATP was measured by the luciferin-luciferase bioluminescent assay.The amount of ATP in irradiated cell cultures was 10.79 +/- 0.15 microg/L (SD; n = 10), and in non-irradiated cell cultures it was 8.81 +/- 0.13 microg/L (SD; n = 10). The average percentage increase of irradiated versus control cell cultures was about 22.4% +/- 0.56% SD (p0.001).This significant increase is probably due to laser irradiation; it cannot be attributed to any thermal effect, as the temperature during irradiation was maintained at 37.0 degrees +/- 0.5 degrees C. Thus the therapeutic effects of the biostimulating power of this type of laser are identified and its indications may be expanded.

Presentado en el IV Curso de Iniciación a la Investigación en Estructura de la Materia: Desde las partículas subatómicas hasta los compuestos moleculares (Instituto de Estructura de la Materia, CSIC, 28-30 de Marzo de 2007).

The evolution of the self-assembled quasi-regular micro- and nanodomain structures after pulse infrared laser irradiation in congruent lithium niobate crystal was studied by in situ optical observation. Several scenarios of domain kinetics represented covering of the irradiated zone by nets of the separated domain chains and rays have been revealed. The time dependence of the total domain length was analyzed in terms of modified Kolmogorov-Avrami theory. The domain structure evolution was attributed to the action of pyroelectric field appeared during cooling. The time dependence of the spatial distribution of the pyroelectric field during pulse laser heating and subsequent cooling was calculated by finite element method. The results of computer simulation allowed us to explain the experimental results and can be used for creation of tailored domain structures thus opening the new abilities of the submicron-scale domain engineering in ferroelectrics. © 2015 Author(s).

International audience; Spectra comprised of hundreds of time-components for absorption path lengths up to 130 km have been recorded around 1050 nm by combining two recent techniques, intracavity laser spectroscopy with vertical external cavity surface emitting multiple-quantum-well lasers and time-resolved Fourier transform spectroscopy. A sensitivity of 1 10^{-10} cm^{-1}.Hz^{-1/2} is achieved, for simultaneously acquired 10^4 spectral elements, three orders of magnitude better than the sensitivity obtained in previous similar experiments. Specific advantages of the method, especially for frequency and intensity metrology of weak absorption transitions, are discussed.

Based on recently published spectroscopic measurements of the relevant energy-transfer parameters, we performed a detailed analysis of the population mechanisms and the characteristics of the output from Er/sup 3+/-singly-doped and Er/sup 3+/, Pr/sup 3+/-codoped ZBLAN fiber lasers operating at 3 /spl mu/m, for various Er/sup 3+/ concentrations and pump powers. Whereas both approaches resulted in similar laser performance at Er/sup 3+/ concentrations