Tunable UV generation to 0.185 μm inCsB3O5

CsB₃O₅ has been found to be phase matchable for SFG down to 0.185 μm by mixing the fifth harmonic of a Nd:YAG laser at 1.0642 μm and the output of a KTP parametric oscillator pumped by the second harmonic of the same Nd:YAG laser at 20.0°C. Improved Sellmeier's equations and nonlinear optical constant of this crystal are reported     

Phasematching of infrared nonlinear laser devices using AgGaS2

Refractive indexes of AgGaS₂ are measured using a tunable CO₂ laser at 9-11 μm, Nd:YAG, and He-Ne laser lines and compared with previous values. The phasematching angles calculated for difference-frequency mixing, upconversion, and parametric oscillation are found to agree better with the experimental values     

Simultaneous multiple wavelength laser action in various neodymiumhost crystals

The oscillation condition of a simultaneous multiple wavelength laser has been established and used to analyze the possibility of simultaneous oscillation in various neodymium host crystals, such as Nd:YAG, Nd:YLF, Nd:BEL, and Nd:YAP crystals at the transitions from ⁴F_3/2-⁴I_13/2 and ⁴F_3/2-⁴I _11/2. It is shown that this kind of laser can be realized in all the described crystals in a pulsed state. In general, continuous wave (CW) operation, however, can only be achieved for Nd:YAP. On the basis of these results, CW simultaneous double wavelength lasing has been achieved in a Nd:YAP crystal for the first time at both 1.0795 μm and 1.314 μm     

Nd:Y2O3透明陶瓷4F3/2-4I11/2跃迁光谱及高效激光输出

报道了采用真空烧结法结合热等静压技术制备的Nd:Y₂O₃透明陶瓷的荧光光谱特性及相关激光输出。通过与Nd:YAG透明陶瓷的荧光光谱对比,表明Nd:Y₂O₃透明陶瓷的4F_3/2-4I_11/2跃迁光谱存在着多个增益相当的谱线,这更有利于实现同时双波长段激光振荡;不同斯塔克子跃迁光谱的离散特性有利于通过腔镜镀膜控制不同波长损耗,获得丰富的1.0~1.1 μm波段激光。利用简单的平平两镜腔结构完成进一步的实验,通过选择的输出镜片镀膜获得了输出功率3.62 W、转换效率40.4%的1074.6 nm和1078.8 nm的双波长输出和输出功率1.7 W、转换效率19.4%的1130.3 nm波长输出。     

Third harmonic generation of Nd:YAG laser light in periodicallypoled LiNbO3 waveguide

The authors propose and first demonstrate an LiNbO₃ waveguide device with cascading quasi-phase-matched second harmonic generation and quasi-phase-matched sum-frequency generation for generation of a third harmonic wave. Ultraviolet light of 355 nm wavelength, which was the shortest value ever reported for LiNbO₃ waveguide wavelength-convertors, was obtained with Nd:YAG laser light     

Performance of a continuous-wave forsterite laser with krypton ion,Ti:sapphire, and Nd:YAG pump lasers

The authors characterize continuous-wave operation of a chromium-doped forsterite (Cr⁴⁺:Mg₂SiO₄) laser using krypton ion, Ti:sapphire, and Nd:YAG lasers as pump sources. Measurements were made pumping at 647 nm and 676 nm with the krypton ion laser, between 690 and 1010 nm with the Ti:sapphire laser, and at 1.06 μm with the Nd:YAG laser. Threshold pump powers and slope efficiencies are compared for output coupler transmissions varying between 1 and 15.5%. Room-temperature operation was only achieved using the Nd:YAG pump laser. Forsterite laser output power as a function of both temperature and pumping wavelength is discussed     

High power, CW single-frequency, TEM00,diode-laser-pumped Nd:YAG laser

255 mW of 1.06 μm, CW, single-longitudinal-mode, TEM₀₀ output has been obtained by end-pumping a twisted-mode cavity Nd:YAG laser with a 1 W diode laser. The key elements of the laser are two λ/4 waveplates (zero-order) placed at both ends of the laser crystal (Nd:YAG, φ3×8 mm). The fast axes of the waveplates are rotated by 90° with respect to each other and rotated by 45° with respect to an intercavity Brewster polariser. In addition, one of the waveplates acts as a resonator and mirror and input coupler for the pump radiation     

High-efficiency, high-power difference-frequency generation at 2-4 µm in LiNbO3

High-efficiency generation of high-peak power and high-average power difference-frequency radiation, continuously tunable over the range of 2 to 4 μm, has been achieved by mixing the Nd:YAG laser radiation with the output of a near-infrared dye laser pumped by the second harmonic of the same Nd:YAG laser in LiNbO3. A peak power as high as 1.6 MW with an average power of 130 mW was obtained near 2.3 μm.     

Internally folded Nd:YAG and Nd:YVO4 lasers pumped bylaser diodes

An efficient, scalable, diode-pumped Nd laser design is reported. The gain element can be longitudinally pumped along five separate axes and is relatively simple to fabricate. Both Nd:YAG and Nd:YVO₄ gain media were evaluated. Using five single-stripe laser diodes to pump the Nd:YAG, 3.94 W of absorbed power produced 2.1 W CW at 1.06 μm. The slope efficiency was 54 percent and the output was TEM₀₀. The threshold power was 40 mW. No evidence of thermal saturation was observed up to the maximum pump power. Repetitively Q-switched operation is also reported. The maximum output power for Nd:YVO₄ obtained with 2.9 W of pump power was 1.3 W. The slope efficiency was 47 percent     

Mode locking of a Nd:YAlO3 laser at 1.08 and 1.34 μmwavelengths using a single LiIO3 crystal

Passive mode locking of a Nd:YAlO₃ laser at 1.08 and 1.34 μm using a nonlinear mirror based on second harmonic generation is described. A single 30° cut frequency-doubling LiIO₃ crystal was used to mode lock both transitions, demonstrating the superiority of this mode-locking technique over that using saturable absorbers. Pulses as short as 50 ps at 1.08 μm and 15 ps at 1.34 μm were obtained. A comparative analysis of the mode-locking performance at the two fundamental wavelengths is presented, indicating that the longer pulse duration at 1.08 μm is due to the higher gain and an insufficient number of round-trips in the pulse train development     

Compositionally tuned 0.94-μm lasers: a comparative lasermaterial study and demonstration of 100-mJ Q-switched lasing at 0.946and 0.9441 μm

A new and innovative composite laser material Nd:YAG_xYSAG_1-x has been developed with several objectives in mind; tunability, efficiency, and minimization of the deleterious effects of amplified spontaneous emission (ASE) in Q-switched operation. Wavelength tuning to the requisite wavelength 0.9441 μm was achieved by using the technique referred to as compositional tuning; that is, using nonstoichiometric laser materials to shift the wavelength for precise tuning. Laser efficiency was achieved by studying the physics of 0.94-μm transitions in nonstoichiometric materials; i.e., by examining the effects of the host on the linewidth and cross section of of 0.94 μm neodymium (Nd) transitions, ASE was minimized by choosing materials with a small ratio of 1.06- to 0.94-μm peak cross sections. A comparative study of six different Nd-doped mixed garnet laser material systems was performed to meet the objectives above. Within these six material systems, over 20 laser materials were spectroscopically analyzed. The optimal laser material was found to be Nd:YAG_xYSAG_1-x, which has been demonstrated to lase at the preselected wavelength of 0.9441 μm, an important wavelength for remote sensing of water vapor. Operating this laser on the ⁴F_3/2→⁴I_9/2 transition in Nd:YAG_0.18YSAG_0.82 at 0.9441 μm, has produced for the first time over 100 mT in the Q-switched mode. This represents one of the few lasers that have been designed to operate at a specific, user-preselected wavelength     

Single-mode fibres with extremely high-Δ and small-dimensionpure GeO2 core for efficient nonlinear optical applications

Single-mode fibres with 8.2% Δ and a 1.4 μm diameter-GeO ₂ core have been prepared for efficient stimulated Raman effect. When pumping a 2.7 m-long fibre by a Q-switched and mode-locked Nd:YAG laser (λ=1.064 μm), the first Stokes light (λ=1.114 μm) and second Stokes light (λ=1.169 μm) have been observed at the input peak power levels of 24 W and 40 W, respectively. These results indicate that the above critical power levels are approximately 10^-2~10^-3 smaller than those for the high-silica single-mode fibre     

3 μm laser performance of Ho:YAlO3 andNd,Ho:YAlO3

A study of the 3-μm laser transitions in Ho:YAlO₃ and Nd,Ho:YAlO₃ using both flashlamp and laser pumping is discussed. Fluorescence measurements for the Nd,Ho:YAlO₃ rod indicate that the neodymium is effective in quenching the lower holmium laser level and in sensitizing the upper level. Intracavity laser pumping of Ho:YAlO₃ produced laser lines at 2.92 and 2.85 μm and demonstrated high efficiency     

Barium borate optical parametric oscillator

Experimental results of the first BaB₂O₄ optical parametric oscillator (OPO) are presented. The pump source was the second harmonic output of a Q-switched TEM₀₀ mode Nd:YAG laser. The OPO had 1 mJ output energy with a peak power of 80 kW in a tuning range from 0.94 to 1.22 μm     

Efficient laser diode side pumped neodymium glass slab laser

The authors report efficient pulse operation of an Nd:glass slab laser-side-pumped by laser diode arrays. 7.5 mJ output and a slope efficiency of 29% were obtained with 35 nJ pump energy at 0.8 μm in 200 μs pulses. The wide absorption band at 0.8 and low laser loss in this phosphate glass allow for efficient pump light absorption and straightforward scalability to high power. The authors demonstrate 22% optical efficiency in a long pulse, multimode diode pumped laser oscillator based on a phosphate laser glass, LHG-8, highly doped with Nd ₂O₃. The strong and wide absorption bands in such phosphate glasses allow efficient pumping while somewhat relaxing the expensive wavelength selection requirements for laser arrays compared with crystal line host materials. With such materials, smaller slab thickness or rod diameters that are feasible with Nd:YAG can be used in the side-pumping geometry     

A kilohertz repetition rate 1.9 μm H2 Ramanoscillator

Raman conversion of a high-repetition-rate Q-switched Nd:YAG laser using a gaseous H₂ Raman medium is reported. With a H₂ cell placed in a focusing intracavity Raman oscillator, 3 W of average power at 1.9 μm was obtained from a 15-W 1.06-μm laser operating at 2 kHz. Although the pump beam was multimode, the Stokes output was diffraction limited. At kilohertz repetition rates, conversion efficiencies were improved with a flowing gas cell which substantially reduced the thermal lensing effect in the Raman medium. A rate equation approach was used to model the intracavity conversion process     

Modulation instability and soliton-Raman generation inP2O5 doped silica fiber

Generation of high-repetition-rate modulation instability pulse trains and high- energy soliton-Raman pulses of ≃60 fs durations, in a single-mode P₂O₅-doped silica fiber, is reported. The 7 mol.% concentration P₂O₅ fiber was pumped in a single pass arrangement by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm. Operating in the region of zero second-order dispersion, modulation instability Stokes sideband seeded resonantly cascade stimulated Raman scattering associated with Si-O-Si and P=0 vibration modes of the fiber. As a result, broad bandwidth and widely tunable 1.36-1.80 μm femtosecond pulses were obtained     

Rhodium-doped barium titanate nonlinear mirror for high beamquality pulsed Nd:YAG lasers

We review the recent results obtained with Rh:BaTiO₃ as a phase conjugate mirror for a pulsed Nd:YAG laser operating in the near infrared (1.06 μm). The phase conjugate reflectivity, the response time, and the fidelity obtained using an internal loop self-pumped phase conjugate geometry are presented. High beam quality master-oscillator power amplifier Nd:YAG lasers with an Rh:BaTiO₃ phase conjugate mirror are presented in both low-repetition rate flash-lamp pumped and high-repetition rate diode-pumped laser architectures. The performances of the Rh:BaTiO₃ crystal are compared with those obtained with a conventional Brillouin mirror     

A diode-pumped 1.4-W Tm3+:GdVO4 microchiplaser at 1.9 μm

GdVO₄ as a host for thulium has several advantages for diode pumping in comparison with other crystals. The absorption cross section of thulium in GdVO₄ is considerably stronger and broader than in YAG and YLF, and the spectrum is shifted closer to the emission wavelength of commercially available AlGaAs laser diodes. In our paper, we report on a diode-pumped monolithic Tm³⁺(6.9 at.%):GdVO₄ microchip laser at 1.9 μm. A maximum output power of 1.4 W is achieved. Two different arrangements for cooling the crystal are discussed. Furthermore, the input-output curves under Ti:sapphire pumping are compared for different pump wavelengths. Slope efficiencies of 58%, clearly exceeding the Stokes limit of 41%, are achieved     

The 13CH3OH optically pumped far-infraredlaser: new lines and frequency measurements

We report 18 new laser lines from ¹³CH₃OH generated in an optically pumped far-infrared laser; the laser lines are in the range of 54.2-420 μm and are all characterized in wavelength, polarization relative to the pumping CO₂ radiation, and pump offset relative to the CO₂ center frequency. The frequencies of seven of these new lines along with 10 previously reported lines were measured by an accurate heterodyne technique, mixing them in a metal-insulator-metal (MIM) point contact diode, with another laser line of known frequency