This PDF file contains the front matter associated with SPIE Proceedings Volume 12864, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

We present experimental results that show how diode-pumped Tm:YLF can be used to develop the next generation of lasers with high peak and high average power. We demonstrate the production of broad bandwidth, λ≈ 1.9 μm wavelength, high energy pulses with up to 1.6 J output energy and subsequent compression to sub-300 fs duration. This was achieved using a single 8-pass amplifier to boost stretched approximately 50 μJ pulses to the Joule-level. Furthermore, we show the average power capability of this material in a helium gas-cooled amplifier head, achieving a heat removal rate almost ten times higher than the state-of-the-art, surpassing 20 W/cm². These demonstrations illustrate the capabilities of directly diode-pumped Tm:YLF to support TW to PW-class lasers at kW average power.

Tm³⁺-doped media are actively researched due to the 2 μm laser transition ³F₄ →³H₆ of Tm³⁺ⁱon. A diode pumping of the ³H₄ manifold has become a standard excitation method, utilizing the availability of 0.8 μm GaAlAs-based diodes and efficient cross-relaxation energy transfer. An essential drawback of this scheme results from a strong inter-ionic distance dependence of the cross-relaxation, which therefore requires sufficient Tm³⁺doping to achieve the desired quantum efficiency. This can in turn result in an increased probability of up-conversion losses, clustering of Tm³⁺ions, increased generated heat, more difficulties with material growth, and less favorable thermal properties. In this proceeding, we aim to bring attention to the resonant diode pumping of the 3F4 manifold in the 1.6-1.8 μm region and its feasibility. This excitation scheme has a low quantum defect, it circumvents the cross-relaxation requirements, and it is supported by broad absorption peaks. The commercial availability and output power of such diodes is already adequate for a solid-state laser pump source. To illustrate the feasibility, we summarize and expand our results with lasers based on Tm:YAG, Tm:YAP, Tm:YLF, Tm:GGAG and Tm, Ho:GGAG. Crystals were pumped using a 25 W fiber-coupled 1:1 focused diode laser (core diam. = 400 μm, waist diam. = 376 μm, NA = 0.22, M2 = 52) emitting in the 1.68-1.71 μm region. Despite the relatively low spatial and spectral quality of the used 1.7 μm diode emission, favorable results were obtained, such as an efficiency of 80% with respect to absorbed power, multi-watt output power in CW regime, or efficient operation of low-concentration crystals.

It is well documented that the primary limits to power scaling in fiber amplifiers are Stimulated Brillouin Scattering (SBS), Stimulated Raman Scattering (SRS), Thermal Lensing (TL), Transverse Modal Instability (TMI), and Diode Pump Brightness (DPB). These effects are well known in glass host fiber amplifiers and still garner active research in mitigating techniques for higher power scaling. In this paper, we present power thresholds for these limitations in crystalline host fiber amplifiers. We have leveraged a Coupled Mode Theory (CMT) model to simulate and analyze crystalline YAG fiber lasers for multiple dopants and with variation in step-index fiber core diameters and lengths. The dopants of interest are Ytterbium (Yb), Holmium (Ho), Thulium (Tm), and Erbium (Er). We have generated Power Scalability Maps (PSM) with varying fiber lengths and diameters which depicts the influence of the aforementioned limitations. We have leveraged a higher fidelity CMT-based model to develop comprehensive PSMs for crystalline fibers and for Yb, Ho, Tm, and Er dopants. To produce the PSMs for Tm and Er, additional considerations are required. Both Tm and Er have nonlinear energy transfer processes that make predicting the population concentration, given pump and signal intensities, challenging. We applied a specialized fit function based on a sigmoidal structure to allow analytic interpolation within the CMT-TMI model to accommodate for the complicated energy transfer effects that occur in Tm and Er. The PSMs serve as references for determining limits and potential of crystalline fibers.

Sub-ns pulse mid-IR lasers have many important scientific and industrial applications including optical parametric chirped-pulse amplification pump sources and material processing. Unfortunately, effective sub-ns mid-IR laser sources are limited. In this study, we report on the numerical simulation and optimization of a spike-like oscillation dynamic in room temperature mid-IR Fe:ZnSe lasers operating at 4.4 µm to obtain sub-ns relaxation oscillation pulses from 15 ns Q-switched Er:YSGG pump pulses. Optimizing cavity length, iron ion concentration, and output coupler reflectivity yielded a single 588 ps pulse (FWHM) with an output energy of 1.7 mJ. This was achieved using a pump pulse energy of 17mJ (140 mJ/cm²) at a 2.79 μm wavelength.

Information on the spatial distributions of methane and vertical profiles of water vapor are essential in better understanding the carbon cycle, atmospheric dynamics and their roles in climate change and numerical weather prediction. Fibertek is developing Er:YAG laser technology for differential absorption lidar (DIAL) that can simultaneously access methane (1645.55 nm) and water vapor (822.92 nm) absorption lines. In this paper we will present data on a hardened 1kHz single-frequency oscillator that is frequency doubled to produce 3 mJ at 823 nm and 3 mJ at 1645 nm for airborne DIAL on the NASA Langley HALO platform. Status and challenges addressed in power scaling experiments on the Er:YAG system for a space-based mission will also be presented. Finally, we will present small signal gain measurements in Er:YAG which show the benefits of low temperature operation for power scaling.

The Global Ecosystems Dynamics Investigation (GEDI) Lidar, is a global three-dimensional biomass lidar instrument aboard the International Space Station (ISS) and the Japanese Experiment Module (JEM). Its core mission is to measure the global carbon balance of Earth’s forests with three laser transmitters using multi-beam waveform-capture methods. GEDI’s laser transmitter concept was originally funded by NASA Goddard’s Earth Science Technology Office (ESTO) for future Earth Altimetry and Lidar missions approximately 20 years ago, and after a winding story of stops and starts, the first flight-ready transmitter was a 10 mJ-class system for GEDI’s ISS-based specifications. Furthermore, no adjustment in drive parameters has been required nor significant decay detected after four years of near continuous operation of three on-board lasers, designed for a two-year mission. We present an overview of the GEDI laser development process, report on their mission performance, the major lessons learned, and some critical insight into our in-house flight quality development process that enabled their delivery within budget, schedule, and low risk extended mission life capability.

The Acousto-Optic Tunable Filter (AOTF) devices are used in a variety of applications including hyperspectral and spectrapolarimetric based imaging. The AOTF devices provide several advantages including speed and random access to desired spectral bands and enable all-solid-state operation that are attractive for space applications. In this paper, the performance of Tellurium Dioxide (TeO₂) and Mercurous Bromide (Hg₂Br₂) AOTF devices in space environment carried out under the NASA’s Materials International Space Station Experiments 11 (MISSE-11) mission is discussed. The purpose of the MISSE-11 mission was to study materials and devices subjected to space conditions for long term while attached to the International Space Station (ISS). The TeO₂ AOTF was developed for Short Wavelength IR (SWIR) operation while the Hg₂Br₂ AOTF device was developed for Long Wavelength IR (LWIR) operation. These devices were attached to the ISS platform for more than a year. Pre-flight and post-flight performance characterization were performed on these devices. In the case of TeO₂ AOTF, the preflight efficiency was around 87% with a center frequency at 68MHz while the post-flight efficiency was around 83%. However, the optical transmission of Hg₂Br₂ AOTF had deteriorated considerably. The details of performance testing and analysis of both AOTF devices are discussed.

NASA’s Dragonfly mission will sample surface materials from multiple sites on Saturn’s largest moon, Titan, in exploration of prebiotic chemistry. We report on the performance of our short-pulsed UV laser transmitter, developed for the Dragonfly’s on-board Mass Spectrometer (DraMS). Our Engineering Test Unit (ETU) has completed flight qualification and demonstrated its operational science requirements, such that the final spaceflight unit build can begin. The Titan Hydrocarbon Analysis Nanosecond Optical Source (THANOS) ETU laser produces 266 nm laser pulses at programmable energy levels to perform high resolution Laser Desorption Mass Spectrometry (LDMS) measurements. The laser operates in bursts of one to 50 pulses, each at ⪅ 2 ns pulse width with a pulse energy of 0 - 200 uJ, at a 100 Hz repetition rate. This paper details the qualification process of the THANOS laser as well as the rigorous characterization performed to ensure consistent performance of the system during laboratory testing, while integrated onto the DraMS instrument and most critically, while operating on the distant surface of Titan.

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) is a versatile technique used for identifying the composition of geological materials and quantifying element abundances. The PLASMA (Pulsed Laser Ablation Sampling and Mass Analysis) investigation, supported through the NASA DALI (Development and Advancement of Lunar Instrumentation) program, is focused on the technical development of an LA-ICPMS instrument comprising a multiwavelength pulsed laser, low power plasma source, collision cell designed to separate Rb and Sr for radiometric dating, and heritage quadrupole mass spectrometer based on the analyzer flown on the Sample Analysis at Mars (SAM) instrument onboard the Curiosity rover. Multi-wavelength laser pulses at 1064 nm, 532 nm, 266 nm, and 213 nm enable the analysis of water-bearing phases, support Raman spectroscopy, enhance the desorption of aromatic hydrocarbons, and promote the ablation of refractory geological phases, respectively. We report on the PLASMA’s solid-state, multiwavelength pulsed laser technology development. The fundamental 1064 nm laser, based on heritage spaceborne laser transmitter design, generates 4mJ, 5ns pulses at 10 Hz from ceramic Nd:YAG slab oscillator pumped by 885nm laser diode array. The ceramic Nd:YAG is highly doped with approximately 4 at% Nd, and with the use of an 885 nm in-band pumping, allows to operate at approximately twice the nominal performance of a 1% crystalline Nd:YAG pumped with 808 nm diode. Second, fourth and fifth harmonic generation of the fundamental laser is achieved using LBO and BBO crystals with optimizing the output energies of 532 nm, 266 nm, and 213 nm to reach the energy fluences up to 5 J/cm². The wavelength of laser output is selectable on-demand.

To open up new opportunities in laser material processing, combining multiple processes in parallel or fast sequence schemes is a promising concept. A single laser source with dynamic and flexible operation modes is highly demanded for these tasks. In this contribution, we will present a versatile laser system which is the first step toward the Universal Laser Machine capable of being used for a broad range of laser-based manufacturing tasks. The laser system presented here consists of a single thin-disk multipass amplifier capable of sequentially or simultaneously amplifying both Continuous Wave (CW) and Ultra-Short Pulsed (USP) laser radiation and delivering kW-class average output power. The approach uses a polarization-multiplexing scheme to amplify two seeds (CW and sub-10 picoseconds) within a common amplifier. This allows for the generation of a single, nearly diffraction-limited output beam composed of CW or USP or both CW and USP radiation at a wavelength of 1030 nm. High versatility of the system is achieved by the implementation of multiple acousto-optic modulators, which enables fast (on a microsecond timescale) switching capabilities between different powers and operation modes. A quick change between the operation state of sole CW, sole USP, and combined output radiation with arbitrary power ratio can thus be realized. Furthermore, our system includes the possibility of a seamless adjustment of the absolute average output power values of each CW and USP fraction of the generated beam.

This paper presents a first-ever experimental demonstration of coherent beam combining for optical vortexes with topological charges from one to five realized in a Yb-doped fiber short-pulsed laser system. The combing efficiency varies depending on the topological charge and beam pattern quality generated by the spatial light modulators. The maximum combining efficiency of 96.9% was achieved for the topological charge one. These results open a pathway to high-intensity optical vortexes with enormous potential applications in science and industry by utilizing advances in light-matter interactions.

We report nonlinear broadening and pulse compression in two consecutive multipass cells based on dielectric mirrors. The 120 fs pulses at 14 MHz containing 12.8 μJ were compressed to 7.2 fs with 146 W average power. After the first multipass cell, the driving pulses were compressed to 37 fs. After the second stage, the pulses were compressed to a few-cycle regime with an overall system’s throughput of 81%. To our knowledge, this is the highest average power amplification-free few-cycle laser source.

Q-switched microchip lasers are very compact sources of directional radiation. To construct such a radiation source in the 1.3 μm spectral region, Nd:YAG active medium with V:YAG saturable absorber can be used. Radiation in this spectral range is safer for the eye in comparison with 1.06 μm radiation due to its higher absorption in the water. For this reason, Nd:YAG/V:YAG microchip laser could be suitable for free-space light manipulation applications such as LIDARs. Nd:YAG/V:YAG microchip lasers and optimization of their output parameters based on diode-pumping beam parameters variation are presented here. For this optimization, aspheric lenses were used, which made it possible to increase the pumping beam area in the waist more than four times from 0.13 mm² to 0.58 mm². Two Nd:YAG/V:YAG microchip lasers with a total length of 2.6 mm and 4.7 mm were tested. In both cases, the initial transmission of the V:YAG saturable absorber was 80 % @ 1.34 μm and the output coupler reflectivity was 90 % @ 1.34 μm. Lasers were pumped longitudinally by a fiber-coupled laser diode (core diameter 400 μm, numerical aperture 0.22) in a pulse regime at a wavelength of around 805 nm in the range of repetition frequencies of 10 − 1000 Hz. Both Nd:YAG/V:YAG lasers provided Q-switched pulses at a wavelength of 1338 nm. By increasing the pumping beam area it was possible to achieve almost twice as high pulse energy and peak power up to 76 μJ and 85 kW using a 2.6 mm long laser. In the case of a 4.7 mm long laser, the pulse energy and peak power increased more than four times up to 139 μJ and 84 kW. The output pulse duration hardly depended on used pumping optics and its mean value was 0.92 ns/2.6 mm and 1.91 ns/4.7 mm. Higher spatial transverse modes were not observed for most pumping pulse repetition frequencies.

In this paper, we report for the first time, control of the output-pulse-energy characteristics of a CW pumped, high repetition rate, passively Q-switched Nd:YVO4/Cr:YAG microchip laser by using the large reduction of the stimulated emission cross-section of the Nd:YVO4 crystal on increasing its temperature. We demonstrate our results by showing the very significant improvement in the supercontinuum generated in a photonic crystal fiber by the microchip laser output, when the Nd:YVO4 crystal temperature is increased from 25℃ to 55℃. The results will be very useful for achieving very compact, high repetition rate and high pulse energy lasers for various applications.

A diode pumped single rod Yb:YAG amplifier for pumping high repetition rate OPCPA was developed providing high energy nanosecond pulses with 20 Hz repetition rate. A ring–shaped resonator was built with a number of round trips controlled by a BBO Pockels cell. A module with stacks of laser diodes with a possibility to provide 5 kW peak power at 50 Hz for future upgrade was implemented in order to provide double-sided end pumping. Active cooling by thermoelectric cooler and flowing water, crystal’s undoped endcaps and housing architecture yielded in high gain and low lensing effect.

We present an advanced field propagation model for end-pumped Ho³⁺:YAG laser resonators, enabling highly accurate predictions of their performance and spectral properties. The model incorporates two key improvements to our previously published model: simulation of pulsed operation through active Q-switching and spectral resolution for pump and laser fields. Pulsed simulation is achieved by solving the crystal rate equations with a time resolution, capturing dynamic behavior. Spectrally resolved rate equations and cross-sections enable comprehensive analysis of spectral properties. This advanced model provides unprecedented accuracy in simulating Q-switched Ho³⁺:YAG laser resonators, allowing the design and optimization of high-precision laser systems.

We present a high pulse energy blue laser based on a fiber master oscillator power amplifier pumped single-frequency optical parametric amplification for an in situ ⁸⁷Rb-⁸⁷Sr isochron dating and chemistry experiment on the moon. The laser has a simple and rugged configuration and can precisely control the wavelength on and off the Sr isotope resonance lines.

We demonstrate Ultra-Violet (UV) light generation using a diode-pumped Alexandrite laser and its Second Harmonic Generation (SHG) via Zn-indiffused MgO:PPLN waveguides. A wavelength range of 375-393 nm is obtained using third order SHG in Λ = 6.1−6.9 μm poled waveguides. Up to 1.3 mW UV power is obtained from 185 mW throughput infrared power. We believe that the wavelength and transverse mode flexibility from these waveguides gives rise to a wide range of applications for an efficient and compact laser module in the UVA range.

Yb³⁺,Li⁺ -codoped monoclinic zinc tungstate (ZnWO₄) crystals with optimized Li⁺ content providing efficient local charge compensation were grown by the Czochralski method. Heavy Li⁺ codoping makes the Yb³⁺-doped ZnWO₄ crystals less prone to cracking, improves the Yb³⁺ segregation, reduces the melting point and induces inhomogeneous spectral line broadening. The polarized absorption and stimulated-emission cross-sections of Yb³⁺ in ZnWO4 were determined. The maximum stimulated-emission cross-section σ_SE is 2.94×10^-20 cm² at 1055.5 nm corresponding to an emission bandwidth of 12.2 nm for light polarization E || N_p. The formation of Yb³⁺ optical centers in singly Yb³⁺-doped and Yb³⁺,Li⁺ -codoped zinc monotungstate crystals is revealed by low-temperature spectroscopy. The Yb,Li:ZnWO₄ laser pumped by a commercial 976-nm Yb-fiber laser generated 2.41 W at approximately 1.06 μm with a slope efficiency of 76.4%, a laser threshold of 143 mW and linear polarization.

Colloidal Quantum Dots (QDs) are heavily investigated for their applications in light emission such as light emitting diodes and, more challenging, lasers due to their appealing processing conditions, compared to e.g. epitaxy, lowering cost and enabling patterning, and tunable optical properties. Using quantum confined Cd-based QDs, several groups have shown light amplification and ensuing lasing action in the red part of the spectrum. Although impressive milestones were achieved, there is to date no single material that can provide the demanding combination of gain metrics to be truly competitive with existing epitaxial growth approaches. In this work, we take a look at CdS/Se nanocrystals in the regime of vanishing quantum confinement, so-called ‘bulk nanocrystals’. We show that these unique materials display disruptive optical gain metrics in the green optical region. Indeed, while showing similar gain thresholds compared to state-of-the-art QD materials, the gain window (440-600 nm, … ), amplitude (up to 50.000/cm) and gain lifetime (up to 3 ns) vastly outpace other QD materials. Using these novel gain materials, we demonstrate lasing in the highly demanded green spectral region (480 – 530 nm) and in the red (650 – 740 nm) both with pulsed and quasi-CW optical excitation. These lasers are made using a Photonic Crystal Surface Emitting Laser (PCSEL) type cavity. As a final step, we attempt to further optimize the lasing properties, be it either narrow linewidth lasers, or high-power output, based on in-depth understanding of the hybrid QD-PCSEL laser system.

Laser sources for future Gravitational Wave Detectors (GWDs) must meet demanding requirements including single-frequency output powers of above 700 W at 1064 nm, low noise and linear polarization with high beam quality and low higher-order mode content. Nd:YVO₄ is an excellent material to the amplify the output of a low power seed, as 195W output power at 1064 nm with low noise and linear polarization have already been demonstrated in multi-stage Nd:YVO₄ amplification. However, further power scaling was limited because of higher-order modes originating from aberrated thermal lensing. In this work, the aberrations of the thermal lens in Nd:YVO₄ were analyzed in a single-stage amplifier configuration. The crystal was seeded and pumped at 1064 nm and 878.6 nm, respectively, while probing the thermal lens with a beam at 976 nm. The wavefront of this probe beam was analyzed with a Shack-Hartmann sensor. The amplifier was characterized up to 43W output power with 46% extraction efficiency. We report a wavefront analysis with major contributions from defocus, astigmatism, and spherical aberration. The experimental results were complemented by an in-house developed numerical thermo-optical simulation model that, for the first time, included the major temperature-dependencies, i.e., of the emission cross-sections, thermal conductivity, thermal expansion, and heat capacity. We achieved excellent agreement of both output power and aberrations between simulations and experiment. Moreover, we introduced measures to compensate the aberrations in Nd:YVO₄ leading the path to full compatibility with the demanded GWD requirements.

In this work we present a novel Distributed Face Cooling (DFC) chip based on interlayer surface activated (il-SAB) bounding at room temperature of Cr³⁺:LiSrAlF6 (Cr:LiSAF) and high thermal conductivity Sapphire in order to power scale the broadband visible emission of Cr:LiSAF. Preliminary calculations reveals an over seven time improvement of effective thermal conductivity of the DFC chip (17.5 W/mK) compared to Cr:LiSAF bulk (2.5 W/mK), resulting in better thermal management inside the gain medium even under 100 W diode pumping at 675 nm. Simulations shows a drastic drop of Cr:LiSAF temperature inside the DFC chip (47°C) compared to same gain length bulk crystal (260°C) in the same pumping conditions. Using linear plano-concave laser cavity (1 % output coupler mirror with 100 mm curvature), over 44 W laser output power can be expected at 810 nm with a laser threshold of 16.1 W using the designed DFC chip.

High-intensity ultrafast lasers are used as drivers for Laser Wakefield Acceleration (LWFA) and as a source for secondary radiation. A conceptual design is proposed for a high repetition rate petawatt-class laser system based on Cr:YAG operating at 1.45 μm, pumped by a Yb:YAG laser in a multi-slab, gas-cooled architecture. The concept leverages direct 1μm-pumping in Cr:YAG with a unique energy storage and extraction scheme for efficiency improvement as well as ASE management. Modelling results show post-compression energy can reach in excess of 80J, 80fs at 10Hz repetition rates, allowing laser-matter interaction experiments in a previously unexplored spectral region.

The spectroscopy properties and lasing of directly diode pumped Ho-doped mixed gadolinium-gallium-aluminium garnet Gd₃Ga₃Al₂O₁₂ (Ho:GGAG) single crystal in dependence on temperature were investigated for the first time. The crystal was grown by Czochralski method in a slightly oxidative atmosphere using an iridium crucible. The tested Ho:GGAG sample was cut from the grown crystal boule perpendicularly to growth direction (c-axis). For spectroscopy and laser experiments 9.8 mm thick plane-parallel face-polished plate (without AR coatings) with Ho-doping 1.26 at.% Ho/Gd was used. It was mounted in a temperature controlled cupreous holder, placed inside the vacuum chamber of the liquid nitrogen cryostat. The spectroscopy data, including absorption and emission spectra and upper laser level lifetime were measured in temperature range from 80 K up to room temperature. GaSb-based MIR laser diode (Dilas, BA-1908-1000-SE, power 1W at 1908 nm) was used for longitudinal Ho:GGAG pumping. The laser diode was operating in the pulsed regime (20 ms pulse length, 20 Hz repetition rate) or CW regime. The 145 mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 2.02 − 2.15 μm, HT @ 1.91 μm) and a curved (r = 150 mm) output coupler with a reflectivity of approximately 90 % @ 2.05 − 2.15 μm. For the crystal temperature 80 K the laser slope efficiency was 35 % in respect to absorbed pumping power. The laser emission wavelength was 2089 nm.

The 2 μm wavelength range provides a wide range of applications requiring short pulse durations, high peak power, and high atmospheric transmittance. Typically, Ho:YAG lasers are suitable for such applications due to their emission at 2.1 μm. Unfortunately, the existing literature reveals either short pulse durations with low energies using the cavity dumping method or high energies with longer pulse durations using the Q-switch method within this spectral range. Here, we present a novel approach that combines high energy per pulse and short pulse duration for a Ho:YAG laser, utilizing the Gain-switch method. The main advantage of the Gain- switch over Q-switch is the ability to design a short cavity, thereby achieving short pulse durations. Two different lengths of Ho:YAG crystals (20 mm or 7 mm) were tested using an actively (acousto optic modulator) or passively (Cr:ZnS) Q-switched Tm:YLF laser that was tuned to the Ho:YAG absorption peak, at 1879 nm, as a pump source. The Ho:YAG laser emitted at 2090 nm. Pulse durations of 3.35 ns with energies up to 0.7 mJ were obtained for the 20mm Ho:YAG crystal using the active or passive seed lasers. Shorter pulses of 2.3 ns with energies up to 0.35 mJ, were obtained for the 7mm Ho:YAG crystal using the passive seed laser. The reported results were limited by the output coupler’s damage threshold level. These results represent the highest achievements in terms of pulse duration and energy per pulse using the Gain-switch method.

A direct modulated VCSEL illumination driver is fabricated and investigated for the compact direct-pulsed LIDAR sensor. The optics for VCSEL illumination includes focusing lenses and micro-lens arrays for flattened beam profile over the entire field of view (FoV) area. The performance of the proposed system is demonstrated in lab environment utilizing a FPGA-based platform. The return pulse from the FoV area is detected by a silicone photomultiplier (SiPM) sensor and a time-to-digital converter. Additional MEMS mirror is utilized for reconstruction of the 3D image up to 10 m.

The efficient Nd:YVO₄/KGW Continuous-Wave (CW) intracavity Raman lasers in linear and folded cavities were demonstrated. The coupled cavity scheme was utilized to control the beam sizes in the laser crystal and Raman crystal, to alleviate the thermal issues and enhance the Raman gain. With the 1064 nm fundamental laser polarized along Nm axis of the Np-cut KGW crystal, 6.63 W of linear cavity and 9.33 W of folded cavity Stokes output at 1177.3 nm were obtained under an incident laser diode pump power of 36.65 W, with an optical efficiency of 18.1% and 25.5%, respectively. Our results show that the compact intracavity Raman laser is capable of generating multi-watt CW output efficiently by proper cavity arrangement. 10-watt level Raman output can be realized in the V-shaped cavity through parameter design. In contrast, the folded cavity scheme is more favorable for higher Stokes output power as well as efficiency compared with the linear cavity scheme because of its better mode matching.

We developed a Continuous-Wave (CW) high power 213-nm light source based on a two-stage external cavity SHG scheme based on the scheme developed for 266-nm coherent continuous-wave light generation. We obtained a highest average 213-nm coherent light power of 270 mW and investigated its reliability and long-operation lifetime. Using a homegrown AR-coated β-BaB₂O₄ (BBO) with a large cavity mode size on the crystal, 100 hours continuous operation without spatial shift of the light spot was demonstrated at 50 mW, which shows more than 3000 hours lifetime with a spatial crystal shift.

The cooling system are indispensable components for high power laser transmitter. The laser system ensures compact, lightweight, energy-saving is a major challenge in laser manufacturing. This paper presents a novel thermal design for our compact high peak power Yb:Er:glass laser. The cooling system is based on thermoelectric cooler with heat dissipation of the TEC’s hot side using vapor chamber, heat sink and fan. The finite element analysis is applied for temperature distribution simulation. The simulation model is calibrated by experiment results to ensure that the error is less than 6%. The laser with cooling system stably operates at the peak power of 1 MW, the repetition rates are tunable from 1 Hz to 20 Hz, and the operation temperature range is from -20 °C to 60 °C.

We report on polarized spectroscopic properties of Ho³⁺ ions in orthorhombic (sp. gr. Pnma) yttrium orthoaluminate YAlO₃ crystals for laser development at 2 μm and 3 μm. This includes polarized Raman, absorption and luminescence spectra, fluorescence lifetime measurements and Stark energy-level study. The transition intensities for Ho³⁺ ions are calculated using the Judd-Ofelt theory. The peak stimulated-emission cross-sections are 2.01×10^-20 cm² at 1977 nm (⁵ I₇ → ⁵ I₈) and 2.31×10^-20 cm² at 2918 nm (⁵ I₆ → ⁵ I₇) for light polarization E || b. For both transitions, pump-induced polarization-switching is expected. The fluorescence lifetimes of the ⁵ I₇ and ⁵ I₆ Ho³⁺ manifolds are 7.27 and 0.36 ms, respectively (for 1 at.% Ho³⁺ -doping).

A method for determining the quantum efficiency and core propagation loss in thulium-doped silica fibres is presented. The results provide evidence that thermal management of the fibre is a critical experimental parameter for achieving accurate predictions of fibre performance with this method. By submerging this ‘nested-ring’ fibre in a temperature-controlled water bath, a quantum efficiency of 1.93 was measured, providing evidence that the high doping level is successfully promoting the ‘two-for-one’ cross-relaxation process. Measurements of core propagation loss gave 0.15 dB/m, which is suggestive that core propagation loss presents a major issue for efficient power scaling to the kilowatt regime.

Efficient multi-watt operation of a diode-pumped Yb:YLF laser at room temperature was demonstrated. In continuous-wave regime the laser produced up to 8.4 W of average power with ⪆74% of slope efficiency with respect to the absorbed pump power. The laser output had diffraction limited beam quality and its wavelength was tunable over 40 nm. To the best of our knowledge, this is the highest output power for diode-pumped room-temperature Yb:YLF lasers.

Dual-wavelength operation of a c-cut Nd:YVO laser at 1062.7/1066.6 nm was demonstrated by using a birefringent filter. The laser was pumped by a home-built Ti:sapphire laser operating at 808 nm. The maximum continuous-wave output power of 300 mW for 800 mW of pump power was obtained. This corresponded to 39% of optical-to-optical efficiency. The proposed design is also suitable for diode-pumping.

An efficient ultrashort pulse Yb:KGW laser oscillator pumped by a Nd:YAG laser is reported. The pump source was a continuous-wave Nd:YAG laser operating at 946 nm. In the mode-locked regime, 139 fs long pulses at 1028 nm were generated at a repetition rate of 54.6 MHz with an average output power of up to 0.86 W, corresponding to an optical-to-optical efficiency of 27.2% with respect to the absorbed pump power.

We report on a paratellurite (TeO₂) Brillouin laser utilising an etalon as a dichroic input coupler in a three-mirror standing wave cavity. In this free-space crystal Brillouin laser arrangement, the oscillator transitions between two modes to produce either a Brillouin frequency comb (mode one) or cascade-suppressed single laser line output (mode two) by adjustment of the cavity length. In mode one, the cavity is multiply-resonant for pump enhancement and cascaded Stokes orders. In this mode, the generation of a Brillouin frequency comb spanning 104 GHz was demonstrated. In mode two, a singly resonant configuration for only the first Stokes order is selected. We obtain a factor of four reduction in linewidth was measured from the pump seed laser to the Brillouin laser output.

High-energy ultrashort pulse lasers have been developed in a variety of applications such as medical treatment, defense, semiconductor and manufacturing. In terms of aesthetic dermatology, Alexandrite (Cr³⁺:BeAl₂O₄) lasers have an attractive and useful wavelength band (700 nm to approximately 800 nm). Therefore, Alexandrite lasers with shorter pulses and higher energy are required in the medical device market. Since alexandrite medium has a low energy gain at room temperature, it is not easy to make a flash-pumped picosecond alexandrite laser that produces sufficiently high output energy. To generate high-power picosecond laser pulses, we used self-injection and ultra short pulse generation techniques including Q-switching, mode-locking and cavity dumping. We have developed picosecond 755 nm alexandrite laser which can be operated at pulse width in the range from 600 to 2000 ps. A maximum average output energy of 400 mJ was achieved in the picosecond regime.

In the case of the medical lasers used for skin diseases and skin beauty, picosecond lasers with pulse durations of hundreds of picoseconds are mainly used. The picosecond laser breaks the pigment of the lesion into small pieces, enabling effective treatment without damaging the surrounding tissue. In the case, the beam profile is important because the laser must be uniformly irradiated to the desired area. In this paper, in order to obtain a uniform beam profile, the size of Nd:YAG Rod, which is a laser gain medium for each amplification stages, is different, and cap is used for the pre amplification stage. In addition, a beam shape compensator with an aspherical lens at the front of the handpiece was designed to realize a uniform beam in all handpieces.