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In general, pulsed lasers with high peak power have been used for the micro-groove formation. However, the processing speed is limited by the pulse repetition rate. On the other hand, CW laser can be expected to perform the high-speed processing by continuous energy input. The mechanism of micro-groove formation by CW laser was investigated by high-speed observation and the thermal fluid analysis. In the perpendicular irradiation of CW laser, the molten metal flows symmetrically around the keyhole to the backward direction, and micro-grooves remain at both edges of molten region. In contrast, in the angled irradiation, the molten metal at the reflection-side scatters as spatters. The remained molten metal flows from the reflection-side to the incident-side through the bottom of keyhole, since the recoil pressure is generated from the reflection-side to the incident-side. In addition, high-speed scanning contributes to keeping the sufficient time and force to move the molten metal in the backward direction. Then, the micro-groove remains at the reflection-side, while the upheaval is formed at the incident-side by gathering the molten metal from the reflection-side and the front of keyhole. Asymmetrical behavior of molten metal flow in angled irradiation of CW laser can create micro-groove in the reflection-side.

We report on a high-power continuous-wave (CW) intracavity frequency-doubled laser at 670.8 nm, which is produced by the second-harmonic generation of a diode side-pumped Nd:YAP crystal laser with a type-II noncritically phase-matched LBO crystal. A maximum output power up to 13 W at 670.8 nm is obtained with an optical-to-optical $$(808\mathrm{ nm}\to 671\mathrm{ nm})$$ efficiency of 2.4%. The beam quality factor M2 is measured to be 8.85, and the fluctuation (RMS) of output power is < ± 0.6% over 30 min. To the best of our knowledge, this is the highest power for the CW laser at 670.8 nm.

Background and Aim: Recent studies have shown that low-intensity laser therapy (LILT) enhances chronic wound healing, reduces pain, reduces inflammation, and improves post-operative rehabilitation. However, clinical outcomes in the veterinary use of LILT vary between different experimental studies. This is explained by improper laser parameter settings and limits of its penetration depth. This study aimed to investigate the penetration depth of 830 nm LILT on living dog tissue in different operating modes. This entailed continuous wave (CW) versus pulse wave (PW) and with contact versus non-contact techniques of the laser probe at different tissue-laser probe distances. The results can be applied for use in clinical practice. Materials and Methods: Twenty-four dogs that had undergone abdominal surgery were included in this study. The laser parameters were set at 200 mW, fluence of 4 J/cm2 and the laser power output denoted as mean output power (MOP) was measured by a power meter. Results: The MOP of the 830 nm CW laser was significantly higher than the PW laser (p

This study proposes an integrated passive and active laser thermography (IPALT) system comprising a continuous wave (CW) laser and an infrared (IR) camera for fully noncontact monitoring and instantaneous evaluation of a fatigue crack in a metallic structure. The IPALT system operates in two phases: (1) passive thermography (PT) mode, and (2) active thermography (AT) mode. The PT mode monitors the fatigue crack initiation by measuring the thermoelastic effects on the fatigue crack tip in real time using the IR camera. Once the crack tip is identified, the AT mode is automatically triggered, and the corresponding fatigue crack is precisely quantified using the CW laser and the IR camera. Through this effective crack monitoring system under operating conditions, time dependent crack propagating behavior analysis, as well as early crack detection, can be achieved. The feasibility of the proposed IPALT system is experimentally validated by monitoring a metallic structure under a 10 Hz cyclic loading. The validation tests indicate that fatigue crack initiation is detected at 10,000 cycles by the PT mode, and the fatigue crack length is quantified as 10.45 mm with an accuracy of 99.43% compared to the microscope observed ground truth of 10.51 mm.

Represented here is a continuous-wave (CW) operation laser and a passively Q-switch (PQS) Ho:SSO microchip laser with a Cr2+:ZnSe saturable absorber (SA). An end-pumped Tm:YAP laser pumping was employed, which operated at room temperature. Up to our knowledge, it is the first time to report a PQS microchip Ho:SSO laser. A maximum 418 mW CW laser output was realized with an absorbed pump power of 2.5 W. The slope efficiency was 59.4%. In the PQS mode, the maximum output power was 332 mW, at the same time the slope efficiency was down to 57.1%. The maximum repetition frequency was 0.69 kHz. The maximum pulse energy of 481 μJ was realized corresponding to the pulse width of 103 ns. The pulsed characteristics were studied in this work. The output wavelength for different modes were also investigated.

Spectral properties of Nd, Gd:CaF2 crystals were investigated. In comparison with Nd:CaF2, the spectral parameters of Nd, Gd:CaF2 were altered in a large scale. LD-pumped true CW laser has been demonstrated in the crystals. The slope efficiency with the value of 45% in 0.5 at.% Nd, 5 at.% Gd:CaF2 was achieved, it is the highest slope efficiency in Nd doped CaF2 single crystals by LD-pumping. The system is a promising candidate for highly efficient lasers.

We demonstrate a single-longitudinal-mode Ho:GdVO4 continuous-wave (CW) laser at 2048.6 nm. We achieved excellent single-longitudinal-mode performance using a unidirectional ring cavity with an isolator and a half-wave plate. We obtain the maximum output power equal to 965 mW corresponding to a slope efficiency of 12.7%.

Single-crystal fibers (SCFs) have a great application potential in high-power lasers due to their excellent performance. In this work, high-quality and crack-free Yb3+:Lu3Al5O12 (Yb:LuAG) SCFs were successfully fabricated by the micro-pulling-down (&mu, PD) technology. Based on the laser micrometer and the X-ray Laue diffraction results, these Yb:LuAG SCFs have a less than 5% diameter fluctuation and good crystallinity along the axial direction. More importantly, the distribution of Yb ions is proved to be uniform by electron probe microanalysis (EPMA) and the scanning electron microscope (SEM). In the laser experiment, the continuous-wave (CW) output power using a 1 mm diameter Yb:LuAG single-crystal fiber is determined to be 1.96 W, at the central wavelength of 1047 nm, corresponding to a slope efficiency of 13.55%. Meanwhile, by applying a 3 mm diameter Yb:LuAG SCF, we obtain a 4.7 W CW laser output at 1049 nm with the slope efficiency of 22.17%. The beam quality factor M2 is less than 1.1 in both conditions, indicating a good optical quality of the grown fiber. Our results show that the Yb:LuAG SCF is a potential solid-state laser gain medium for 1 &mu, m high-power lasers.

Laser operation of the Er3+:Y 2 O 3 ceramics pumped by 976 nm laser diode in CW and passively Q-switched modes was studied. The CW laser power at 2.7 μm reached 1.2 W at 8°C temperature. The passively Q-switched operation in kHz repetitively-pulsed mode was obtained by a polycrystalline Fe2+:ZnSe saturable absorber.

We present the growth of electrically pumped continuous-wave (CW) quantum dash (QDash) lasers on planar (001) Si emitting at 1.5 μm, with different active region structures. After growth optimization, the lowest threshold current, 2 kA/cm2 was obtained on a device grown on planar silicon.

A laser-diode-pumped short cavity CW laser was investigated. The beam quality factors of the pump beam for the slow axis was 20. The optical conversion efficiency of 58.4% versus incident pump power was obtained.

At Fraunhofer IWS Dresden, different, partially prototypic high-power continuous wave (cw) beam sources for the remote laser processing of nonmetals with galvanometric-driven scanner systems are available. The emitted wavelengths of the lasers cover the range from visible light to mid-infrared. A spectroscopic analysis was performed to gain insight into the processability of typical nonmetal materials with single wavelengths. The wavelength-depending absorption was calculated based on the measured reflectivity and transmissivity of the selected materials. Relating to these results, the theoretic potential of the beam sources was verified in a comparable cutting research. The investigated work pieces are representatives of the groups of thermoplastics and thermosets, fiber-reinforced polymers, glasses, natural fiber textiles, and cellulosic based materials. The laser systems were divided in two groups for the investigation. To get a reference of the processability with state-of-the-art cw systems, a CO2 laser with a wavelength of 10.6 mm and a solid-state Yb:YAG fiber laser with 1.07 mm were used. The new prototypic beam sources were a green laser with a wavelength of 0.515 mm, a CO laser with a range of 5.3-5.8 mm, and a CO2 laser with 9.3 mm in a power range from 1 to 1.5 kW. Differences in the possible focusability are caused by the wavelengths and given beam qualities. For a direct comparison, these differences needed to be compensated. To get comparable intensities, the spot diameter in the working distance for each laser was set to 250 mm. This allows to process the materials with almost the same intensities. Since the laser sources with the short wavelengths offer a better focusability, experiments with the smallest possible focus diameters for the used optics were performed to get an optimized ablation result. Finally, the aim of the research was to evaluate the suitability of the available beam sources for new fields of application. The latest results of experimental and theoretical investigations on the remote laser processing of nonmetals with a wide range of laser wavelength will be presented and discussed.

Two laser crystals of Er3+:KLu(WO4)2 and Er3+/Pr3+:KLu(WO4)2 were successfully grown using the top-seeded solution growth technique with K2W2O7 as flux. Segregation coefficients of Er3+ ions in Er3+:KLu(WO4)2 and Er3+/Pr3+:KLu(WO4)2 crystals were 0.664 and 0.9, respectively. The density of the Pr3+ ions in the Er3+/Pr3+:KLu(WO4)2 crystal was 1.19 × 1019 cm−3, and the segregation coefficient was 0.18. The absorption and fluorescence spectra of the two crystals with Y-oriented polarization (parallel to the b axis) light were recorded. Judd–Ofelt (J–O) theory was adapted to analyze the main parameters and they were crucial for evaluating the potential of laser crystals with output wavelength of 2.7 µm. Results showed that the Er3+/Pr3+:KLu(WO4)2 crystal had good J–O intensity parameter Ωt (t = 2, 4, 6) and relatively large emission cross section at 2.7 µm. The lifetimes of the 4I11/2 state in the Er3+:KLu(WO4)2 and Er3+/Pr3+:KLu(WO4)2 crystals were fitted to be 87.13 ms and 79.36 ms, respectively. The lifetime of 4I13/2 state decreased sharply from 5.59 s in Er3+:KLu(WO4)2 to 53.19 ms with co-doping of Er3+ ions and Pr3+ ions. Laser oscillation was accomplished at 2.7 µm wavelength using a b-cut Er3+/Pr3+:KLu(WO4)2 crystal sample with size of 4 × 4 × 10 mm3. Finally, a continuous-wave (CW) laser was realized with the highest slope of 15.94%. The center wavelength of the laser output was 2740 nm, and its FWHM was approximately 1.8 nm. Therefore, the Er3+/Pr3+:KLu(WO4)2 crystal has remarkable potential for generating 2.7 µm lasers.

We report on the spectropic and continuous-wave (CW) laser properties of a novel Er3+-doped mixed garnet (Er:LuYSGG) crystal. The maximum phonon energy of Er:LuYSGG was measured to be 720 cm−1, which is lower than that of Er:YSGG crystal. Fluorescence lifetimes of 4I11/2 and 4I13/2 levels amounts to 2.1 ms and 3.2 ms, indicating a potential capability for mid-infrared laser emission. For the CW laser operation, a maximum output power of 472 mW was achieved at 2797 nm, with a slope efficiency of as high as 24%.

We report the CW laser operation and wavelength tunability of 10 at%, 15 at% and 20 at% Yb 3+ -doping LuAG ceramics pumped at 970 nm. The absorption saturation effects were taken into account herein. For 10 at% Yb 3+ -doping sample, the maximum slop efficiency and output power was 60.7% and 1.8 W, respectively. Furthermore, the slop efficiencies of 52.3% (15 at%) and 46.5% (20 at%) were reported. What's more, the maximum optical-to-optical efficiency for our samples was determined to be 40.1%, 36.8%, and 33.1% at the incident pump power of 4 W, respectively. The round-trip cavity loss of the laser system based on our Yb 3+ :LuAG ceramics were evaluated. The tuning curve of a 20 at% Yb 3+ :LuAG ceramic extended from 1018 nm up to 1062 nm, and that of 10 at% and 15 at% samples became much more broader, making Yb 3+ :LuAG ceramics possible candidates for ultrashort pulse generation.

The spectral properties of lightly doped Er:CaF 2 and Er,Pr:CaF 2 single crystals were investigated. Benefited from particular clustering effect, 2.79 μm continuous-wave (CW) laser operation was demonstrated in lightly doped 3 at.% Er:CaF 2 crystal. After co-doping small amount of Pr 3+ , the lifetime gap between Er 3+ : 4 I 11/2 and Er 3+ : 4 I 13/2 was shortened from 7.86 ms to about 1 ms. Moreover, the near-infrared and up-conversion fluorescence were significantly quenched. Thus, the CW laser performance was greatly improved. The slope efficiency was effectively improved from 8.0% to 15.8%.

The propagation of two-color laser fields through optically thick atomic ensembles is studied. We demonstrate how the interaction between these two fields spawns the formation of copropagating, two-color solitonlike pulses akin to the simultons found by Konopnicki and Eberly [Phys. Rev. A 24, 2567 (1981)PLRAAN0556-279110.1103/PhysRevA.24.2567]. For the particular case of thermal Rb atoms exposed to a combination of a weak cw laser field resonant on the D1 transition and a strong sub-ns laser pulse resonant on the D2 transition, simulton formation is initiated by an interplay between the 5s_{1/2}-5p_{1/2} and 5s_{1/2}-5p_{3/2} coherences. The interplay amplifies the D1 field at the arrival of the D2 pulse, producing a sech-squared pulse with a length of less than 10 μm. This amplification is demonstrated in a time-resolved measurement of the light transmitted through a thin thermal cell. We find good agreement between experiment and a model that includes the hyperfine structure of the relevant levels. With the addition of Rydberg dressing, quasisimultons may offer interesting prospects for strong photon-photon interactions in a robust environment.

Erbium-doped laser active media allow to generate a laser radiation close to the 3 μm which is interesting for many applications, e.g. medicine, spectroscopy, or for further mid-infrared conversion using OPO [1, 2]. The uniaxial Er:YLF crystal which can generate a naturally polarized laser radiation at 2.8 μm (laser transition 4I 11/2 →4I 13/2 ) [3] together with semiconductor saturable absorber mirror (SESAM) were chosen to generate a Q-switched pulse. The SESAM allow building a very compact laser resonator without requirements on additional power sources or special crystals, also it is a simple method to obtain the short pulses at∼ 3 μm. Moreover, the Er:YLF is low phonon energy crystal (ħω ph = 560 cm−1), so the self-termination effect is partly suppressed and the CW laser regime can be easily reached. In this paper, to the best author's knowledge, the passively Q-switched compact Er:YLF laser was build for the first time and nanosecond pulses were successfully generated.

We present cw laser emission from an erbium-doped aluminophosphosilicate all-fiber laser emitting at 1584 nm with a slope efficiency of 30% with respect to the absorbed pump power.

Regarding the amplification of pulsed single-frequency laser, the seed laser is generally obtained by modulating the output of a CW single-frequency laser with an electro-optic modulator (EOM) or acousto-optic modulator (AOM). As we discussed in Sect. 5.3, besides the disadvantage of compromised power, externally modulating CW laser could flexibly adjust the pulsing parameters such as pulse width and repetition rate. Therefore, the configuration of external modulation combines with MOPA that is beneficial for achieving high average/peak power single-frequency pulsing laser with adjustable parameters. Meanwhile, although it is feasible to realize relatively high average/peak power from a single Q-switched fiber resonator, by exploiting the high gain of heavily RE ion-doped multicomponent fiber, stable pulses are rather difficult to maintain in the high-power regime. Therefore, stable laser pulses from a Q-switched cavity also need to be externally amplified to higher power levels.

Inconel 718 superalloy has been widely used in the aerospace field. In this study, the effect of linear heat input and laser mode on the microtexture and tensile properties of laser powder-deposited (LPD) Inconel 718 was studied. Continuous-wave (CW) and quasi-continuous-wave (QCW) laser modes were conducted in the experiments. The results showed that under low linear heat input, the microtexture morphologies with CW LPD and QCW LPD were long directional columnar grains and chaotic grains, respectively. The grain size of QCW LPD is finer than that of CW LPD. With the increase of linear heat input, the directivity of microtexture morphology with CW LPD becomes unobvious, while the microtexture morphology of QCW LPD changes little with enlarged grain size. Due to the finer grain size, the tensile strength at 600 ℃ of sample with low linear heat input (60 J/mm) and QCW laser mode is 17.7% higher than that with high linear heat input (120 J/mm) and CW laser mode.

The first CW single-crystal Fe:ZnSe laser optically pumped by Er:ZBLAN fiber laser with an output power of 2.1 W is reported. Temperature-dependent spectral characteristics and tuning (3.8-5.1 μm) are investigated.

A newly developed rotating continuous-wave laser equipment was adopted as an alternative laser-based surface cleaning method. To evaluate the thermal effects of laser cleaning on base material, a modified calculation method for laser-induced peak temperature distribution considering overlapping effects was proposed. Various laser-processing parameters were adopted to irradiate carbon steel plates. The re-melted zone (MZ) of laser-treated specimens was observed under optical microscopy and used to verify the calculation method. Surface morphologies and roughness of laser-treated specimens were also investigated. The results showed that the peak temperature distribution obtained from the modified calculation method properly describes the MZ depth in laser-treated specimens. Investigation on laser-treated specimens revealed that results of laser heat effects improved in rougher surface conditions, and that frequent overlapping of laser beam can induce surface defects. The modified calculation method could help to optimize laser processing parameters to reduce melting of base material and avoid surface defects.

We report, for the first time to our knowledge, on the spectroscopic properties and continuous-wave laser performance of Yb0.14:Y0.77Gd0.09Ca4O(BO3)3, a mixed rare earth calcium oxyborate Yb-ion crystal. Under simple end-pumping conditions with a 976-nm diode, efficient CW laser operation was demonstrated at room temperature, producing an output power of 14.1 W at 1084.4 nm with an optical-to-optical efficiency of 48%; while operating around 1045 nm, the laser could generate an output power as high as 23.0 W, with optical-to-optical and slope efficiencies amounting, respectively, to 57% and 70% with respect to incident pump power. The polarized absorption and emission cross sections are also presented. The impressive results demonstrated reveal the great potential of these mixed oxyborates in developing new promising Yb-ion laser crystals.

The photoacoustic (PA) signal of DR1 dye in six solvents with different polarity, density and the coefficient of viscosity were investigated by a simple experimental set up. The measurements were performed at 532 nm using a Nd; YAG CW laser with irradiation of 300 mW. In the middle of experiment, A sound produced when the sample exposed to the laser irradiation at a critical power therefore it acts as an acoustic sensor. It is demonstrated that the maximum photoacoustic frequency amplitude of PA in an exact frequency has an inverse proportion to viscosity coefficient of solvents and verify the theoretical equations.

Novel AgGa0.95In0.05Ge3Se8 single crystalline alloys were grown via Bridgman–Stockbarger route and characterized by XRD analysis. The titled compounds were used for laser stimulated piezoelectricity studies. Following the results of differential thermal method as well as XRD phase analysis the phase equilibrium diagrams of AgGaGe3Se8–AgInGeSe4 and AgGaGe3Se8–‘AgInGe3Se8’ sequences were built. The specific features of phase diagrams demonstrate the possible high sensitivity of the such kind of crystal to external light and mechanical fields. Piezoelectric coefficient of the crystal was found to be strongly sensitive to illumination with 532 nm cw laser light which led to up to 90% decrease of the piezoelectricity. Photo-thermal contribution to the observed drop in piezoelectric voltage was excluded.

We present a tunable three-level Nd:YAG laser using a birefringent filter (BF) based on the 4F3/2–4I9/2 transition, generally used for a 946 nm emission. Three-level Nd:YAG laser was performed at three different laser wavelengths of 869 (pure-three-level), 875 (pure-three-level), and 878 nm (quasi-three-level). Within three wavelengths, the 875 and 878 nm were demonstrated for what is believed to be the first time. The highest output power of 1.21 W was achieved at 869 nm with a slope efficiency of 9.9%. Moreover, a continuous-wave (CW) simultaneous dual-wavelength Nd:YAG laser at 875 and 878 nm was also demonstrated for the first time.

We present the continuous-wave (CW) and passively Q-switched laser operation of disordered Nd:ABC3O7 crystals including Nd:SrLaGa3O7, Nd:SrGdGa3O7, and Nd:BaLaGa3O7. Among the Nd:ABC3O7 group members, Nd:SrLaGa3O7 exhibits superior laser properties. A maximum output power reaches 3.88 W under an absorbed pump power of 29.01 W, which is the highest CW output power using LD as the pump source for Nd:SrLaGa3O7 gain medium. Using a Cr4+:YAG crystal as a saturable absorber, the LD pumped passively Q-switched laser is also realized. With Nd:SrLaGa3O7, the shortest pulse width, the largest pulse energy, and the highest peak power are observed to be 10.6 ns, 60.3 μJ, and 5.3 kW, respectively. In the CW laser operation, wavelength tunings are also reported. The center wavelength of this Nd: SrGdGa3O7 laser shifts from 1062.48 to 1063.91 nm by changing the temperature from 60 °C to 135 °C.

Visible lasers emitting in the green spectral region are being routinely employed in various medical and defense fields namely treatment of pigmented lesions, tattoo inks, port wine stains, dazzling the target or mob dispersal. Despite their increasing applications, lasers also tend to pose occupational hazards to operators, ancillary personnel, individuals undergoing laser therapies. This study was aimed at investigating the effects of different doses of 532-nm continuous wave laser on rat skin. The present study demonstrated that higher fluences of 532-nm continuous wave (CW) laser induces significant tissue damage through induction of tumor necrosis factor-α, cyclooxygenase-2, tumor protein (p53), PARP 1, caspase3 which in turn leads to tissue damage and cell death. Furthermore, level of heat shock proteins, pAkt were found up-regulated as a cope up response to laser-induced stress. On the basis of the findings, irradiation with 532-nm CW laser up to 2.5 J/cm2 was found within the safe exposure limits. Thus, it is probably the first attempt to demonstrate the tissue damage induced by 532-nm CW laser on skin, which may help in choosing safe laser dose for certain skin-based applications and evolving methods to ameliorate laser-inflicted injuries.

We present what is, to the best of our knowledge, the first pure-three-level Yb:Ca4GdO(BO3)3 (Yb:GdCOB) laser emitting at 976 nm based on the F5/22-F27/2 transition, generally used for a quasi-three-level emission at 1032 nm. A maximum power of 782 mW at 976 nm has been achieved in continuous-wave (CW) operation pumped by a quasi-three-level Nd:SrLaAlO4 laser emitting at 902 nm. Moreover, a self-frequency-doubling CW blue laser has also been demonstrated with a maximum power of 133 mW at 488 nm.

For the first time CW laser oscillation on Er-Yb doped PTR glass with diode pumping is demonstrated. For the monolithic laser the maximum output power of 0.47W at wavelength of laser oscillation of 1574 nm and a slope efficiency of 6% was achieved.

The aim of this work is to investigate the influence of surface structures on the adhesion strength of metal-plastic hybrids. Aluminum substrates were structured with continuous wave and picosecond pulsed laser systems and overmolded with a thermoplastic polyamide material. The materials were examined in terms of structure topography, molding accuracy, and a tensile shear test. It was found that the surface pretreatment by laser structuring with continuous wave laser enhances the effective joining surface, creates a mechanical interlocking, and increases the adhesion strength of the hybrid compared to the untreated condition significantly. A shear strength of 11.9 MPa was achieved, which exploits 90% of the pure polyamide properties.

We report on a Ho:YAG SCF laser inband pumped by an all-fiber Tm-laser. CW laser of 12.5 W output power and Q-switched laser with 1.44 mJ pulse energy and 7.5 ns pulse duration are demonstrated.

Remote processes with brilliant continuous wave lasers enable highly efficient laser processes. When cutting and abrading metal or composite materials, a large amount of particles and emissions arise. In general the emissions will be exhausted. But a high amount of substances contaminates the treated part as well as the laser machine equipment and is a high health risk for the machine operator. Based on this challenge, scientific investigations were done during laser structuring with high power fiber lasers. The generated particles and emissions were evaluated and classified. To minimize the part decontaminations new air knife – cross jet solutions were tested and optimized using gas and particle flow simulations. The results of this work support the user of remote processes in guaranteeing the health and environmental regulations.

We present a design and analysis for the surface gain medium slab laser. This single slab laser is potential to output 12kW class laser. The experiment already achieved 5kW CW laser power output.

Although the nanostructure machining by AFM probe assisted with laser has gain a great progress, few studies has been done on the optical fiber probe guiding the continuous laser to irradiate on AFM probe to machining nanostructure. Using this technology to create nanodot and nano-groove was presented in this paper. The law of how the experiment parameters influenced the results was summarized in the paper. The scale of nanodot is about 450nm, and nano-groove is about 40nm. When the fabrication is completed, the wear of the AFM probe was observed by SEM and drew a conclusion. In the method of nano machining by AFM Probe combining with a CW Laser, there will be a combined field to achieve the fabrication, and the method is better than mechanical characterization with AFM probe.

We describe a CW laser stabilized to a low thermal expansion ceramic cavity which has a lower frequency drift rate than cavities based on ultralow-expansion glass (ULE), which are widely used as optical references. Two identical optical cavities with spacers of different material, ceramic and ULE, were assembled and the optical frequencies locked to each of these cavities were compared. The optical frequency drifts of both CW lasers were measured to within a precision of 10−11 in one second over the course of one year. The ceramic cavity had a long-term frequency drift rate of 4.9 mHz/s and the ULE cavity had one of 23 mHz/s.

The failure response of aluminum alloys (Al-6061 and Al-7075) under the condition of simultaneously pre-stressing and laser heating was investigated. Specimens were subjected to predetermined preloading states and then irradiated by continuous wave fiber (Yb) laser. For all specimens, it was found that the yield stress decreased with increasing laser power density. This implies that the load-bearing capacity of the specimens reduced under increased thermal or tensile loading. Consequently, the specimen’s failure time was shortened by increasing either laser power density or preloaded speed. For Al-6061, a remarkable reduction in failure time by the increase of laser power density is found. However, for Al-7075, under higher preloaded speeds, comparatively smaller impact of laser power density on the failure time is reported. Moreover, for Al-6061, relatively a more non-uniform variation in the average failure time with the increase of laser power density or preloaded speed is observed. The failure mode of Al-6061 turned from brittle to ductile at higher laser power densities; whereas for Al-7075, it changed from quasi-brittle to ductile. At higher preloaded speeds, a greater degree of melting and ablation phenomenon can be seen due to relatively higher temperatures and higher heating rates.

We developed a CW laser stabilized to a low expansion ceramic cavity with a frequency drift 7 mHz/s (δf/f ∼ 10−10 /year), which is lower than those achieved with ultra-low expansion glass cavities. OCIS codes: (140.4780) Optical resonators; (140.3425) Laser stabilization; (120.2230) Fabry-Perot

LARSS, a 24 kg, suitcase-sized, CW-laser remote-sensingspectrometer with a ~2 km range has been developed. Itdemonstrated its flexibility in measuring bothatmospheric CO2 from an airborne platform andterrestrial emission of CO2 from a remote mud-volcano,Bledug Kuwu, Indonesia from a ground-based sight. Thissystem scans the CO2 absorption line with 20 discretewavelengths as opposed to the typical two wavelengthonline offline instrument. This multi-wavelengthapproach offers an effective quality-control, bias-controland confidence-estimate of measured CO2 concentrationsvia spectral fitting. The simplicity, ruggedness andflexibility in the design allows for easy transportation,use on different platforms with quick setup in some ofthe most challenging climatic conditions. While morerefinement is needed, the results represent a step-stonetowards widespread use of active one-sided gas remotesensing in the Earth sciences.

We use an intra-cavity EOM to realize high speed synchronization of dual-comb. The relative linewidth is dramatically suppressed from 300kHz to sub-hertz without ultra-stable CW laser and the ranging accuracy is greatly improved.

Recently, ultrafast lasers exhibiting high peak powers and extremely short pulse durations have created a new paradigm in materials processing. The precision and minimal thermal damage provided by ultrafast lasers in the machining of metals and dielectrics also suggests a novel application in obtaining precise cross-sections of fragile, combustible paint layers in artwork and cultural heritage property. Cross-sections of paint and other decorative layers on artwork provide critical information into its history and authenticity. However, the current methodology which uses a scalpel to obtain a cross-section can cause further damage, including crumbling, delamination, and paint compression. Here, we demonstrate the ability to make controlled cross-sections of paint layers with a femtosecond pulsed laser, with minimal damage to the surrounding artwork. The femtosecond laser cutting overcomes challenges such as fragile paint disintegrating under scalpel pressure, or oxidation by the continuous-wave (CW) laser. Variations in laser power and translational speed of the laser while cutting exhibit different benefits for cross-section sampling. The use of femtosecond lasers in studying artwork also presents new possibilities in analyzing, sampling, and cleaning of artwork with minimal destructive effects.

This paper considers the effect of the longitudinal lithium concentration distribution in PPLN converters on their efficiency in high-power cw laser second harmonic generation.

Considering the two most important factors, delamination and tensile strength temperature dependence, a tensile strength prediction model for orthogonal carbon fiber reinforced polymer (CFRP) under continuous wave (CW) laser irradiation is proposed. In the prediction model, delamination was judged by the thermal data recorded by a thermal imager. In order to eliminate the influence of heating rate on the tensile strength temperature dependence parameters, a two-sided laser irradiation method was proposed to test the tensile strength temperature dependence of CFRP. Furthermore, according to the temperature distribution in the thickness direction of the T700/E44 CFRP specimen and the tensile strength temperature dependence, the tensile strength for orthogonal CFRP under CW laser irradiation was calculated. The results show that the prediction model can reflect the decreasing process of tensile strength with laser irradiation, especially in the cases of high intensity laser irradiation and high tensile load. This research can make a reference for the tensile strength prediction of composite materials in high intensity CW laser irradiation and pre-tension loading conditions.

Three mixed Yb t Y x Lu 1− t − x VO 4 crystals, with x =0.923, 0.848 and 0.708, were grown by the Czochralski method. Polarized absorption spectra and fluorescence spectra were studied at room temperature. The absorption cross sections at 985 nm are 5.46×10 −20 cm 2 , 5.70×10 −20 cm 2 , and 5.97×10 −20 cm 2 , respectively, for π polarization. The broadest bandwidth of the absorption spectrum reaches up to 38.22 nm for σ polarization. Fluorescence lifetimes are almost the same (0.331 ms, 0.327 ms and 0.329 ms). CW laser operation was achieved at room temperature with a maximum output power of 1.19 W at a pump power of 8.8 W.

For Nd:La x Y 1− x VO 4 ( x = 0.11) crystal, the 4 F 3/2 → 4 I 13/2 transition property was investigated for the first time. The fluorescence peak of Nd:La 0.11 Y 0.89 VO 4 crystal exhibited obvious inhomogeneous broadening comparing with that of Nd:YVO 4 crystal. With laser diode array as pump source, 1.34 μm continuous-wave (CW) and active Q-switched laser operations based on 4 F 3/2 → 4 I 13/2 transition were realized. For CW laser operation, the maximum output power of 2.47, 2.13 W is obtained with slope efficiencies of 29.4%, 27.6%, and optical to optical conversion efficiency of 26.2%, 24.7%, respectively for a , c cut crystal samples. For acousto-optic (AO) Q-switched laser operation, the shortest pulse width, highest peak power and maximum pulse energy came from the a -cut sample, which were 13 ns, 2.69 kW and 35 μJ, respectively.

The photoinduced piezoelectric effect in the single crystals of AgGaGe 3 Se 8 was discovered under the influence of 532 nm cw laser with average power about 150 mW. The changes of the piezoelectricity were explored with respect to principal diagonal components d 11 , d 22 , and d 33 . To study the contributions of photostimulated thermal and piezooptical effects additional measurements of temperature dependent piezoelectricity and piezo-optical coefficients were done. Substantial changes were demonstrated and their time kinetics during photoillumination was explored. The three principal diagonal piezoelectric coefficients along the crystallographic axis were studied. The reversibility of the process after switching off of the photoinducing laser is given. The effect observed may be applied for laser operated piezotronic devices. The contribution of different mechanisms in the photostimulated piezoelectricity is explored.

Nonlinear refractive index n 2 , of the calyces of Hibiscus Rosa-Sinensis, in aqua solution, has been measured by varying the incident laser intensity from a continuous wave (CW) Ar-ion laser. The closed aperture Z-scan technique has been used to measure n 2 with incident laser wavelengths of 457, 488 and 514 nm. The results obtained are found to be of the order of ~10−14 esu.