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We conducted a study to explore a real-time monitoring variable of a coherently combined beam returned from a scattering target. The effect of a spatial filtering on the speckle pattern generated from the interference of the scattered beam was examined in a coherent beam combining (CBC) system, including three-channel laser output, the scattering target, and receiver optics in free space. We were able to recognize the arrangement of the original beams from the speckle pattern by applying a proper spatial filter with a size of 2 mm. The power-in-the-bucket value in the monitoring system was also investigated as a function of the spatial filter size. Our research implies that a complex speckle pattern can be analyzed using spatial filtering to derive a single-output real-time variable in the CBC monitoring system.

An efficient electro-optic transition control is reported in all-fiber graphene devices over a broad spectral range from visible to near-infrared. The ion liquid–based gating device fabricated onto a side-polished fiber with high numerical aperture significantly enhances the light-matter interaction with graphene, resulting in strong and nonresonant electro-optic absorption of up to 25.5 dB in the wavelength ranging from 532 to 1950 nm. A comprehensive analysis of the optical and electrical properties of the device fabricated with monolayer and bilayer graphene revealed that the number of graphene layers significantly impacts on the performance of the device, including modulation depth and driving voltage. Wavelength-dependent optical response is also measured, which clearly characterizes the electronic bandgap dispersion of graphene. The device exhibited more efficient electro-optic modulation in the longer wavelength region, where the maximum light modulation efficiency of 286.3%/V is achieved at a wavelength of 1950 nm.

Large-scale growth of mostly monolayer molybdenum disulfide (MoS2) on quartz, sapphire, SiO2/Si, and waveguide substrates is demonstrated by chemical vapor deposition with the same growth parameters. Centimeter-scale areas with large flakes and films of MoS2 on all the growth substrates are observed. The atomic force microscopy and Raman measurements indicate the synthesized MoS2 is monolayer with high quality and uniformity. The MoS2 field effect transistors based on the as-grown MoS2 exhibit carrier mobility of 1–2 cm2V−1s−1 and On/Off ratio of ~104 while showing large photoresponse. Our results provide a simple approach to realize MoS2 on various substrates for electronics and optoelectronics applications.

A theoretical model to describe in-band pumped holmium doped silica fiber lasers is presented. The model is established based upon theory and parameters obtained from published research works. Both core-pumped system and cladding-pumped system are simulated with the model. The simulation results agree well with most experimental results, and for the cases in which the simulation results show discrepancy with the experimental results the disagreement can be reasonably explained. Through numerical analysis it is found that besides common negative factors such as non-radiative decay, fiber loss, and non-optimized resonator configuration, energy transfer upconversion plays a deleterious role in the performance of in-band pumped holmium doped silica fiber lasers. In particular, inhomogeneous upconversion associated with ion clustering is found to cause significant degradation of slope efficiencies of lasers, a fact that is useful to understand the unsolved problem regarding the lower-than-expected slope efficiencies observed in previous studies of in-band pumped holmium doped fiber lasers.

Wide-spectral saturable absorption (SA) in low-dimensional (LD) nanomaterials such as zero-, one-, and two-dimensional materials has been proven experimentally with outstanding results, including low saturation intensity, deep modulation depth, and fast carrier recovery time. LD nanomaterials can therefore be used as SAs for mode-locking or Q-switching to generate ultrafast fiber laser pulses with a high repetition rate and short duration in the visible, near-infrared, and mid-infrared wavelength regions. Here, we review the recent development of emerging LD nanomaterials as SAs for ultrafast mode-locked fiber laser applications in different dispersion regimes such as anomalous and normal dispersion regimes of the laser cavity operating in the near-infrared region, especially at ~1550 nm. The preparation methods, nonlinear optical properties of LD SAs, and various integration schemes for incorporating LD SAs into fiber laser systems are introduced. In addition to these, externally (electrically or optically) controlled pulsed fiber laser behavior and other characteristics of various LD SAs are summarized. Finally, the perspectives and challenges facing LD SA-based mode-locked ultrafast fiber lasers are highlighted.

Electrical characteristics of ion gels prepared by loading different amounts of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) in Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) are investigated and compared with those of ion liquid, [EMIM][TFSI] for possible application as a gate stack for flexible electronic devices. Capacitance and impedance as a function of frequency are measured, which can be well accounted for by a simple circuit model identifying the local device components. The operation of a flexible field effect transistor based on graphene and the ion gel as a top gate stack is also demonstrated.

We demonstrated four different laser operational states in the same passive fiber ring laser cavity by controlling solely the polarization state in a saturable absorber. The demonstrated laser operational states were continuous wave, mode-locking, Q-switching, and Q-switched mode-locking. The saturable absorber was fabricated by spin-coating a single-walled carbon nanotubes (SWCNT)/polymer composite on a side polished fiber providing enhanced nonlinear interaction with the SWCNT. The wide tuning range of the saturable absorber allows the simple means to generate different forms of laser output from a single laser cavity.

Spatiotemporal changes in the surface temperature of an absorbing medium irradiated by using 532-nm laser pulses were measured using an infrared camera. Relevant numerical simulations of the heat transfer equation were performed. The simulations showed that the maximum temperature increase was linearly proportional to the absorption coefficient with no dependence on the thermal conductivity and that the decay time constant depended on both the absorption coefficient and the thermal conductivity. The absorption coefficient and the thermal conductivity of the medium were determined by fitting the simulated results for the maximum temperature increase and decay time constant to the measured results.

We examine the radiation-induced properties changes of evanescent-field-interacting type graphene-saturable absorbers (SAs). The graphene-SA inserted to the mode-locked laser was exposed to 60Co gamma-ray radiation up to 1.02 kGy at a 50 Gy/hr dose rate. To see how the graphene-SA affects to the laser performance, the graphene-SA-based mode-locked laser was also monitored simultaneously. The mode-locking was broken at 0.75 kGy irradiation dose, which corresponds to 15.6 years operation in low-earth orbit satellites. The optical properties of the graphene-SA was also compared before and after radiation.

We demonstrate a high pulse energy and low pulse rate 2 µm femtosecond fiber laser potentially applicable to laser surgery and vehicle laser detection and ranging. The laser is configured by a half kilometer long all-fiber ring cavity with two thulium-doped fiber gains deployed separately and is hybrid mode-locked by the coaction of a graphene saturable absorber and nonlinear polarization rotation. Numerical simulations were carried out to back up the mode-locking stability and estimate the maximally extractable pulse energy. We achieved a pulse energy of about 54.6 nJ, to the best of our knowledge the highest as a seed femtosecond pulse, and a pulse rate of 427 kHz, the lowest ever reported. The pulse duration was about 456 fs as measured by an intensity autocorrelator, and the output optical spectrum showed a wide FWHM of about 51.7 nm. We also examined the stability of the laser output over tens of hours.

We implemented a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA) that evanescently interacts with light on a side-polished polarization-maintaining fiber (PMF) platform. A high-quality SWCNT/polymer composite was spin-coated onto a side-polished PMF embedded in a quartz block, where the slow optical birefringence axis of the PMF was perpendicular to the polished surface. The fabricated in-line SA had an insertion loss of –1.5 dB with a modulation depth of 0.5% for the polarization direction associated with the transvers magnetic mode. An all-PMF laser was built using the fabricated in-line SA to demonstrate self-starting, turn-key operation of Er-doped, all-fiber lasers delivering stable scalar soliton pulses. The measured 3-dB spectral bandwidth and pulse duration of the laser output were 5.1 nm and 510 fs, respectively, resulting in a time-bandwidth product of 0.320. We examined the polarization state of the soliton fiber laser output and found that the laser stably generated linearly polarized ultrashort pulses with a polarization extinction ratio of –18.4 dB.

We studied the thermal and the mechanical effects induced by pulsed laser absorption in human skin by numerically solving the heat-transfer and the thermoelastic wave equations. The simulation of the heat-transfer equation yielded the spatiotemporal distribution of the temperature increase in the skin, which was then used in the driving term of the thermoelastic wave equation. We compared our simulation results for the temperature increase and the skin displacements with the measured and numerical results, respectively. For the comparison, we used a recent report by Jun et al. [Sci. Rep. 5, 11016 (2015)], who measured in vivo skin temperature and performed numerical simulation of the thermoelastic wave equation using a simple assumption about the temporal evolution of the temperature distribution, and found their results to be in good agreement with our results. In addition, we obtained solutions for the stresses in the human skin and analyzed their dynamic behaviors in detail.

A straightforward method of controlling laser-induced mechanical effects in biological tissues is to regulate the pulse energy of the irradiating laser. Because the local temperature of the irradiated region rises as the laser’s pulse energy increases, this method cannot independently control purely mechanical effects without changing the thermal effects. Here, a dual-wavelength irradiation method is proposed in which biological tissues are irradiated simultaneously by using two laser pulses with different wavelengths, and laser-induced mechanical effects are continuously controlled with no change in the maximum temperature increase by systematically varying the energy of each laser pulse. The proposed method is analyzed, and its feasibility is demonstrated through numerical simulations.

A new method to make an all-fiber nonlinear optic device for laser pulse generation is developed by depositing multi-layer graphene oxide (GO) selectively onto the core of the cleaved fiber facet by combining the electrical arc discharge and the laser-driven self-exfoliation. Using the GO colloid droplet with sub-nanoliter volume, we obtained a GO bulk layer deposited on a fiber facet of the order of milliseconds by using an electric arc. The prepared fiber facet was then included in an Er-doped fiber laser (EDFL) cavity and we obtained a few layers of GO having nonlinear optic two-dimensional (2D) characteristics selectively on the fiber core by the laser-driven self-exfoliation. The 2D GO layers on the fiber core served as a stable and efficient saturable absorber enabling robust pulse train generation at λ = 1600.5 nm , the longest Q -switched laser wavelength in EDFLs. Pulse characteristics were analyzed as we varied the pump power at λ = 980 nm from 105.2 mW to 193.6 mW, to obtain the maximum repetition rate of 17.8 kHz and the maximum output power of 2.3 mW with the minimum pulse duration of 7.8 μs. The proposed method could be further applied to other novel inorganic 2D materials opening a window to explore their novel nonlinear optic laser applications.

Electro-optic modulators which modulates the intensity or phase of the light through the electric signal control, have been extensively investigated for the diverse field applications including optical communication, bio-sensing, and security-monitoring based on lightwave. With recent technological advance of the fabrication of high quality graphene over large area, graphene have been intensively studied as a basic element to build novel photonic and electro-optic devices. However, low optical absorption in ultra-thin layered graphene often limits the performance of the device. Although there have been several attempts to increase graphene-light interaction, realization of efficient and broadband graphene-based electro-optic modulators is still challenging. In this work, we demonstrate an all-fiber graphene-based electro-optic modulator with a modulation depth of > 25 dB. In order to achieve non-resonant strong interaction with graphene, we employed a side-polished fiber (SPF) with high numerical aperture (NA) as a novel platform that evanescently interacts with graphene. The high NA fiber has about six times smaller mode-field area than that of the standard single-mode fiber, and we found that this can critically enhance the graphene-light interaction without significantly sacrificing the insertion loss. We experimentally fabricate the bi-layer graphene field-effect transistor onto the high-NA SPF, and covered index matched ion-liquid for further increase of the graphene-light interaction and effective gating. As a result, we observed that the fabricated device exhibits the modulation depth of 27.6 dB with low scattering loss at the applied voltage range within 2.5 V, which well agrees with our numerical expectation.

We demonstrated a high pulse energy, passively mode-locked thulium-doped fiber (TDF) laser with a repetition rate of 427 kHz, the lowest repetition rate at 2 μm to the best of our knowledge. Two stages of TDF amplifier is applied to obtain sufficient gain over high attenuation of 485 m long oscillator. The self-starting of passively mode-locking is realized by using a nonlinear polarization rotation technique in association with an in-line graphene saturable absorber. The mode-locked TDF laser delivers stable femtosecond pulses with a pulse energy of 54 nJ.

Using two-dimensional (2D) hybrid organic-inorganic (C 6 H 5 C 2 H 4 NH 3 ) 2 PbI 4 perovskite thin film as an in-line saturable absorber, we experimentally demonstrate an all-fiber mode-locked laser in both C and L band. We successfully generated self-started ultrafast pulses at the anomalous dispersion regime with a spectral bandwidth of 7 nm and a pulse duration of 381 fs at the center wavelength of 1565.9 nm. Moreover, by adjusting the optical gain, we also achieve a transform-limited soliton pulses with the spectral bandwidth of 6 nm at the center wavelength of 1604 nm.

We demonstrate the passive Q-switching operation of an erbium-doped fiberlaser using a few-layer WS 2 -based saturable absorber with evanescent field interaction.WS 2 flakes have been synthesized via a liquid-phase exfoliation method, and an opticalfiber taper was selected as a light-material template that causes to achieve a long inter-action length of the evanescent wave. Subsequently, the prepared solution was opticallydeposited around the 3-mm interaction length of the fabricated optical fiber taper with a5- m waist diameter. The proposed Q-switched fiber laser based on the WS 2 -depositedfiber taper saturable absorber could generate stable output pulses at 1565 nm, with apulsewidth ranging from 1.3 to 3 s and a repetition rate of 33–108 kHz.Index Terms: Tungsten disulfide, nonlinear optical materials, saturable absorber,Q-switched fiber laser. 1. Introduction Q-switched fiber lasers have attracted great attention owning to the relatively large pulse energyat relatively low repetition rates and pulse width of the scale from microsecond to nanosecond.These short pulsed lasers have extensive applications in material processing, telecommunica-tions, medicine, and sensing [1]. Q-switched pulses can be obtained via active or passiveQ-switching techniques. Passively Q-switched lasers have several advantages such as sim-plicity, compactness, and low cost compared to that of active techniques which require anactive optical component such as electro-optic or acousto-optic modulators [2].Passive Q-switched technique of lasers based on saturable absorber (SA) is the well-knownand most effective method to achieve Q-switching operation which has been widely investigated.In the past few decades, researchers investigated various kinds of SA materials, including toxicdye materials [3], semiconductor saturable absorber mirrors (SESAMs) [4], carbon nanotubes(CNTs) [5], and graphene [6], [7]. Although the SESAMs are very mature and commercialized

We investigated nonlinear optical characteristics of Tungsten disulfide (WS2) films and experimentally demonstrated their high potential for application as nonlinear saturable absorbers in passively mode-locked fiber lasers. Side polished fiber (SPF) was fabricated and WS2 film was overlaid to provide an efficient evanescent field interaction. The WS2 film was prepared using two methods: liquid phase exfoliation to form few-layer nano-sheets, and chemical vapor deposition (CVD) to grow uniform multilayer WS2 on a SiO2 substrate. Two SPF saturable absorbers were prepared by either spin coating WS2 solution or lifting off the multilayer CVD WS2 on SPF. An all-fiber ring cavity was built and the WS2 film overlaid on SPF was employed as a mode locker along with Er-doped fiber as a gain medium. Using the spin-coated WS2 SPF, stable soliton-like pulses were generated with a spectral width of 5.6 nm and 467 fs pulse duration. The fiber laser cavity containing CVD WS2 SPF generated a transform-limited soliton pulse train with a spectral width of 8.23 nm and a pulse duration of 332 fs. Our study confirmed a high potential of WS2 film as a novel 2-D nonlinear optical material for laser applications.

We demonstrate all-fiber mode-locked laser based on a tapered optical fiber saturable absorber (SA) enclosed in tungsten disulfide (WS2) nanosheets. Tapered fibers were fabricated using the standard flame brushing method to an interaction length of 3 mm with waist diameters of 10 and 15 $\mu \text{m}$ . WS2 nanosheets were prepared via a liquid phase exfoliation method to form a uniform dispersion. Subsequently, the WS2 nanosheets were optically deposited along the interaction length of the tapered fibers by evanescent field interactions. We built a ring laser including the fabricated mode-lockers. The SA with a 10- $\mu \text{m}$ taper diameter delivers the pulses with a pulse duration of 369 fs and 3-dB spectral bandwidth of 7.5 nm; on the other hand, the output pulses using the mode-locker with 15- $\mu \text{m}$ waist diameter were found to have 563-fs pulse duration and 5.2 nm of 3-dB bandwidth. It is shown that the smaller waist diameter of tapered fiber causes wider spectral bandwidth of the ultrafast pulses and narrower 3-dB bandwidth.

We demonstrate an all-fiberized mode-locked laser by employing Molybdenum Disulfide (MoS 2 ) spin-coated onto a side-polished fiber (SPF) as an in-line saturable absorber. Single crystal MoS 2 has been exfoliated via the Li intercalation method and then dispersed with large population of few-layer MoS 2 nano-sheets in ethanol. Subsequently, a saturable absorber has been prepared using a relatively simple method: spin-coating the uniform MoS 2 solution on the fabricated SPF without using any polymer or toxic procedure. Power-dependent transmission property of the prepared MoS 2 nano-sheets on the SPF was experimentally analyzed, providing the feasibility to apply it as an efficient in-line saturable absorption behavior. By deploying the MoS 2 SPF into a fiber laser cavity with finely tuned laser pump power and cavity dispersion, mode-locked pulses were obtained at anomalous and normal dispersion of the laser cavity. The self-started soliton pulses at the anomalous dispersion regime were generated with a spectral bandwidth of 9.96 nm at 1584 nm and a pulse duration of 521 fs. Moreover, by managing the dispersion to the normal regime, stable pulses at net-normal intra-cavity dispersion with 11.9 ps pulse duration were obtained with a spectral bandwidth of 18.2 nm at 1570 nm. The results prove the effectiveness of developing MoS 2 saturable absorbers and applications for pulsed laser operation.

Molybdenum disulfide (MoS 2 ) nano-sheets have been successfully deposited directly on the cleaved facet of a silica optical fiber using optical trapping forces. By controlling the incident laser power, various types of MoS 2 films were deposited near the fiber core. An area selective deposition was successfully realized during the optical deposition process by using an optical reflectometry method. The presence of MoS 2 deposited layer at the fiber end was confirmed by microscopic Raman spectroscopy as well as scanning electron microscope images. Nonlinear response and power dependent transmission of the prepared sample was observed at the wavelength of 1552 nm, which can be used as an all-fiber saturable absorber. Moreover, the fabricated sample was inserted in a Er-doped fiber ring laser cavity and stable Q-switched pulses with the repletion rate from 26.6 kHz to 40.9 kHz were generated, which confirmed the potential of MoS 2 as a saturable absorber.

We demonstrate an all-fiber dissipative soliton fiber laser (DSFL) with a very broad spectral bandwidth by optimizing the cavity design of the fiber laser. Two different cavity schemes of the DSFL with simple cavity structures were built by employing a hybrid component, and their properties were investigated while varying the net cavity dispersion of the laser. By optimizing the cavity dispersion of the fiber laser, we achieved a DSFL that stably deliver linear chirped pulses with a pulse duration of 912.5 fs at a repetition rate of 52.2 MHz without additional pulse compression. The measured spectral bandwidth of the laser was 68 nm, which is the largest value ever reported for Er-doped DSFL oscillators.

An all-fiberized, in-band pumped Ho-doped fiber laser is presented. The laser is pumped by an in-house built Tm-doped fiber laser operating at 1.95 μm, and its operation wavelength is stabilized by a high-reflection (HR) FBG at 2.1 μm. 18.1 W output at 2.1 μm is generated by the laser, with a slope efficiency of 74.7 %.

Femtosecond mode-locked fiber lasers have been actively employed in many practical applications such as micro-machining, corneal surgery and multi-photon imaging, thanks to their compactness, alignment-free operation, and low cost. To enhance the long-term stability and self-starting operation of mode-locked lasers, saturable absorber (SA) devices, such as semiconductor saturable absorber mirrors (SESAMs), have been employed. Recently, planar waveguide-type SA device based on standard planar lightwave circuit (PLC) wafer fabrication process [1] has been developed and applied to high-repetition-rate all-fiber mode-locked lasers [2].

A new extraordinary application of deoxyribonucleic acid (DNA) thin-solid-film was experimentally explored in the field of ultrafast nonlinear photonics. Optical transmission was investigated in both linear and nonlinear regimes for two types of DNA thin-solid-films made from DNA in aqueous solution and DNA-cetyltrimethylammonium chloride (CTMA) in an organic solvent. Z-scan measurements revealed a high third-order nonlinearity with n2 exceeding 10−9 at a wavelength of 1570 nm, for a nonlinarity about five orders of magnitude larger than that of silica. We also demonstrated ultrafast saturable absorption (SA) with a modulation depth of 0.43%. DNA thin solid films were successfully deposited on a side-polished optical fiber, providing an efficient evanescent wave interaction. We built an organic-inorganic hybrid all-fiber ring laser using DNA film as an ultrafast SA and using Erbium-doped fiber as an efficient optical gain medium. Stable transform-limited femtosecond soliton pulses were generated with full width half maxima of 417 fs for DNA and 323 fs for DNA-CTMA thin-solid-film SAs. The average output power was 4.20 mW for DNA and 5.46 mW for DNA-CTMA. Detailed conditions for DNA solid film preparation, dispersion control in the laser cavity and subsequent characteristics of soliton pulses are discussed, to confirm unique nonlinear optical applications of DNA thin-solid-film.

We investigate optical and electrical behaviors of a graphene saturable absorber (SA) and mode-locking performance of a graphene-SA-based mode-locked Er fiber laser in gamma-ray radiation. When irradiated up to 4.8 kGy at ∼100 Gy/hr dose rate, the overall nonlinear transmittance in transverse electric mode was increased, while maintaining modulation depth to >10%. The corresponding polarization-dependent loss was reduced at a 1.2-dB/kGy rate. In the electrical properties, the charge carrier mobility was reduced, and the Dirac voltage shift was increased to positive under gamma-ray radiation. The radiation-induced optical and electrical changes turned out to be almost recovered after a few days. In addition, we confirmed that the graphene-SA-based laser showed stable CW mode-locking operation while the inserted graphene SA was irradiated for 2-kGy at a 45-Gy/hr dose rate, which corresponds to >40 years of operation in low Earth orbit satellites. To the best of our knowledge, this is the first evaluation of graphene SAs and graphene-SA-based mode-locked lasers in gamma-ray radiation, and the measured results confirm the high potential of graphene SAs and graphene-SA-based lasers in various outer-space environments as well as other radiation environments, including particle accelerators and radiation-based medical instruments.

We demonstrate an all-fiber Tm-doped soliton laser with high power by using a monolayer graphene saturable absorber (SA). Large area, uniform monolayer graphene was transferred to the surface of the side-polished fiber (SPF) to realize an in-line graphene SA that operates around 2 mu m wavelength. To increase the nonlinear interaction with graphene, we applied an over-cladding onto the SPF, where enhanced optical absorption at monolayer graphene was observed. All-fiber Tm-doped mode-locked laser was built including our in-line graphene SA, which stably delivered the soliton pulses with 773 fs pulse duration. The measured 3-dB spectral bandwidth was 5.14 nm at the wavelength of 1910 nm. We obtained the maximum average output power of 115 mW at a repetition rate of 19.31 MHz. Corresponding pulse energy was estimated to be 6 nJ, which is the highest value among all-fiber Tm-doped soliton oscillators using carbon-material-based SAs. (C)2016 Optical Society of America

Mode-locked integrated mid-IR waveguide chip lasers with ultra-short pulse duration and high peak power are of great interest for a large range of applications like trace-gas spectroscopy and early-cancer detection. As those lasers are automatically embedded within a small block of doped glass, they are inherently robust and immune to environmental fluctuations. In this paper we investigate the suitability of various novel nanomaterials for the realisation of saturable absorbers for passive mode locking of femtosecond laser-written mid-infrared waveguide lasers. We compare and characterise saturable absorbers based on carbon nanotubes, graphene, topological insulators, transition metal dichalcogenides as well as black phosphorus and analyse their performance in a thulium-doped waveguide laser operating around 2 micron.

Novel saturable absorbers based on carbon nanotubes, graphene, topological insulators, transition metal dichalcogenides and black phosphorus were fabricated and characterized. Their performance for short pulse generation in Tm:ZBLAN waveguide chip lasers was analyzed. For the first time to our knowledge, Q-switched mode-locked operation of a mid-IR ZBLAN waveguide chip laser was realized using topological insulators.

We studied third order susceptibilities of mono- and randomly stacked multilayer graphene at four different wavelengths and three laser fluence regimes with z-scan experiment, and compared the values with optical Kerr gate experimental results.

We fabricate saturable absorbers and WDM/tap hybrid couplers using standard planar lightwave circuit (PLC) fabrication processes. The fabricated PLC devices are applied to modelocked all-fiber lasers, which show long-term stable and self-starting operation.

We studied operation characteristics of an Yb:YAG channel waveguide laser, Q-switched by employing monolayer graphene. Uniform monolayer graphene grown by thermal chemical vapor deposition is transferred directly onto one end facet of the channel waveguide which simultaneously serves as an output coupling mirror (OC), making a monolithic Q-switched waveguide laser possible. In this cavity configuration, the Q-switched laser delivers a maximum average output power of 85 mW, corresponding to a pulse energy of 64 nJ at 1.33-MHz repetition rate. The laser performance of this device is compared with another cavity configuration, in which the monolayer graphene is coated onto separate OCs. In this case a shorter pulse duration of 79 ns is achieved, but the laser operation performance is worse with respect to efficiency and output power. The proposed monolithic approach demonstrates the potential for developing more compact Q-switched laser devices. (C) 2016 Optical Society of America

We demonstrate passive mode-locking of a Cr:forsterite laser with a single-walled carbon nanotube saturable absorber mirror (SWCNT-SAM). Without compensation of intra-cavity dispersion, the self-mode-locked laser generates 11.7 ps pulses at a repetition rate of 86 MHz. The dispersion-compensated laser yields ultrashort pulses as short as 80 fs near 1.25 µm at 78 MHz with average output powers up to 295 mW, representing the highest power ever reported for mode-locked solid-state lasers based on saturable absorption of SWCNTs in this spectral region.

We demonstrate a novel method to characterize structural irregularities in a highly birefringent photonic crystal fiber (HB PCF) with high accuracy based on polarization coupling by torsional acoustic wave. Birefringence variation induced by the irregularities of air-hole structure in the fiber cross-section is analyzed via the transmission spectra of the acousto-optic coupling between two orthogonal polarization modes propagating along the fiber. The estimated maximum birefringence variation of two sections in the same batch of the HB PCF is 3 x 10-6 and 10-5, respectively, from nominal birefringence value of 4.86 x 10-4). The comparison between the experimental results and the numerical simulation resulted in the estimation of few tens of nm variation in the air-hole structure in the PCF.

A wide range of saturable absorbers composed of novel low-dimensional nanomaterials were fabricated, and their linear and nonlinear optical properties were characterized. Furthermore, their suitability for ultrashort-pulse generation in waveguide laser operating at a wavelength of 2 microns was demonstrated and passively q-switched mode-locked operation was achieved with all absorbers. The material systems that were studied in this work include nanosheet-based absorbers composed of graphene, carbon nanotubes, black phosphorus, transition-metal dichalcogenides, topological insulators and indium tin oxide. By utilizing a uniform few-layer spin coating fabrication technique and by employing a single, identical laser resonator, a direct comparison of the individual characteristics of these materials in the context of short-pulse generation in waveguide lasers was made possible. Each of the individually fabricated and characterized saturable absorbers was placed inside a thulium-doped fluoride glass waveguide chip laser cavity and the resulting output performance was analyzed and contrasted. It was further found that the few-layer spin coating approach enables fine-tuning of the absorber characteristics and that all low-dimensional nanomaterials under investigation can be utilized for ultrashort pulse generation in the 2-micron wavelength range. General guidelines for the design of passively modulated short-pulsed laser oscillators are presented based on those findings.

Single-walled carbon-nanotube absorbers are experimentally demonstrated for laser mode-locking. A saturable absorber device is used to mode-lock three different bulk solid-state lasers in a 500 nm-wide wavelength interval. The devices exhibit a low saturation fluence of

Chalcogenide glasses offer many attractive properties for all-optical signal processing including large Kerr nonlinearity (up to 500 × silica glass), an intrinsic ultrafast response time and low to moderate two-photon absorption (TPA). These properties together with the convenience of a fibre format allow us to achieve all-optical signal processing at low peak power and in a very compact form. In this paper, several nonlinear processing functions will be demonstrated including: femto-second pedestal free, pulse compression; all-optic wavelength conversion; and all-optical regenerator. In addition, we show enhanced nonlinearity for more efficient signal processing by tapering the As2Se3 fibre. These applications show chalcogenide glass fibres are very promising candidate materials for nonlinear all-optic signal processing.

We show the implementation of fiber-pigtailed, evanescent-field-interacting, single-walled carbon nanotube (CNT)-based saturable absorbers (SAs) using standard planar lightwave circuit (PLC) fabrication processes. The implemented PLC-CNT-SA device is employed to realize self-starting, high-repetition-rate, all-fiber ring oscillators at telecommunication wavelength. We demonstrate all-fiber Er ring lasers operating at 303-MHz (soliton regime) and 274-MHz (stretched-pulse regime) repetition-rates. The 303-MHz (274-MHz) laser centered at 1555 nm (1550 nm) provides 7.5 nm (19 nm) spectral bandwidth. After extra-cavity amplilfication, the amplified pulse train of the 303-MHz (274-MHz) laser delivers 209 fs (178 fs) pulses. To our knowledge, this corresponds to the highest repetition-rates achieved for femtosecond lasers employing evanescent-field-interacting SAs. The demonstrated SA fabrication method, which is based on well-established PLC processes, also shows a potential way for mass-producible and lower-cost waveguide-type SA devices suitable for all-fiber and waveguide lasers. (C) 2015 Optical Society of America

Background As the most abundant protein in human tissues, the use of collagen is essential in the fields of biological science and medicine. Objective The aim of this study is to investigate the mechanical effect of pulsed laser irradiation on collagen tissue. Methods With various laser parameters such as peak power, pulse width, and repetition rate, the induced stresses on samples were measured and analyzed. Monte Carlo simulation was performed to investigate the effect of laser parameters on the collagen sample. Results The results indicated that the magnitude of mechanical stress could be controlled by various laser parameters. Conclusions This study can be used in biostimulation for therapy and mechanoreceptor stimulation for tactile application.

We propose a s-switched channel waveguide laser operating near 1 μm in mirrorless resonator configuration. PMMA-assisted monolayer graphene acting as saturable absorber is grown by chemical vapor deposition and transferred onto an end facet of the waveguide.

Actively controlled all-fiber graphene device exhibiting strong graphene-light interaction is demonstrated through electrical gating of graphene layer, and its application as a tunable nonlinear saturable absorber in ultrafast fiber laser system is discussed.

We studied operation characteristics of a Gd3+ and Lu3+ co-doped Yb:KYW planar waveguide laser, Q-switched by carbon nanotube-based saturable absorbers in two direct interaction and one evanescent-field interaction regimes.

We show an all-planar, fiber-connected CNT saturable absorber manufactured by the planar lightwave circuit (PLC) process. The fabricated saturable absorber was successfully employed in an all-fiber soliton mode-locked Er-laser.

In this study, we successfully generated the large bandwidth of supercontinuum spectra through hollow fibers filled with DNA. Also, by observing that spectra bandwidth was the widest in the order of the hollow core fiber filled with DNA modified by copper ion, the hollow core fiber with only DNA, and the bulk hollow core fiber, we demonstrated that DNA material modified with copper ions can further enhance the spectral bandwidth of supercontinuum. As a result, we anticipate that the SCG as a broadband light source can be used in analytical methods to demonstrate a wide range of biological and environmental questions.

Recent researches on novel in-line graphene photonic devices that can passively or actively control the light in optical fibers are introduced and their application to ultrafast fiber laser systems are discussed.