Generation of all-solid-state, high-power continuous-wave 213-nm light based on sum-frequency mixing in CsLiB6O10

Achievement of more than 100 mW of pure continuous-wave deep-ultraviolet radiation at 213 nm has been demonstrated in an efficient all-solid-state laser system that uses two Brewster-cut CsLiB6O10 (CLBO) crystals. The first crystal is used for 266-nm generation by external resonant doubling of 532-nm radiation from a frequency-doubled Nd:YVO4 laser. Subsequent sum-frequency mixing is performed in a second CLBO crystal placed in a diode-pumped Nd:YAG laser cavity to mix the single-pass 266-nm output with circulating 1064-nm light.     

Generation of 5-W deep-UV continuous-wave radiation at 266 nm by an external cavity with a CsLiB6O10 crystal

A Brewster-cut CsLiB6O10 crystal is employed as an external resonant frequency doubler to generate cw deep-UV radiation at 266 nm. We have generated 5.0 W of usable cw output power, which is 6.1 W in the crystal, for an incident green power of 9.6 W, corresponding to an internal conversion efficiency of 61.8%. The power obtained is, to our knowledge, three times higher than previously reported for cw 266-nm generation.     

利用椭圆高斯光束产生266nm紫外连续激光

本文采用商用532 nm激光器作为基频光源,利用偏硼酸钡(β-BBO)晶体进行外腔倍频,实现了266 nm连续激光的高效输出.文中详细模拟了BBO晶体中的束腰形状对倍频效率的影响,仿真和实验结果均表明椭圆高斯光束可以有效改善走离效应,提高倍频转换效率.通过优化蝶形倍频腔,可以使椭圆高斯光束在腔内共振,当1 W基频光输入时可输出约180 mW的266 nm紫外连续激光,倍频转换效率达到18%.     

The 266-nm ultraviolet-beam generation of all-fiberized super-large-mode-area narrow-linewidth nanosecond amplifier with tunable pulse width and repetition rate

We report on a compact, stable, all-fiberized narrow-linewidth (0.045 nm) pulsed laser source emitting laser beam with a wavelength of 266 nm, and tunable pulse width and repetition rate. The system is based on all-fiberized nanosecond amplifier architecture, which consists of Yb-doped fiber preamplifiers and a super-large-mode-area Yb-doped fiber power amplifier. The fiber amplifier with a core of 50 μ is used to raise the threshold of the stimulated Brillouin scattering (SBS) effect and to obtain high output power and single pulse energy. Using lithium triborate (LBO) crystal and beta-barium borate (BBO) crystal for realizing the second-harmonic generation (SHG) and fourth-harmonic generation (FHG), we achieve 17 μJ (1.73 W) and 0.66 μJ (66 mW), respectively, at wavelengths of 532 nm and 266 nm and a repetition rate of 100 kHz with pulse width of 4 ns. This source has great potential applications in fluorescence research and solar-blind ultraviolet optical communication.     

Correction of walk-off-induced wavefront distortion for continuous-wave laser

We theoretically and experimentally investigate the wave front distortion in critically phase-matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM₀₀ mode efficiently. Theoretically, we simulate the correction effect of 266-nm laser generated with SHG. The experiment results accord well with the theoretical simulation and an above 80% TEM₀₀ component is obtained for 266-nm continuous-wave laser with a 4.8°-walk-off angle in beta barium borate (BBO) crystal.     

Efficient frequency doubling of a vertical-extended-cavity surface-emitting laser diode by use of a periodically poled KTP crystal

Blue light with a cw power in excess of 42 mW is generated from a frequency-doubled, extended-cavity InGaAs/GaAs 980-nm surface-emitting laser by use of a periodically poled KTP crystal.     

Generation of 740 mW of blue light by intracavity frequency doubling with a first-order quasi-phase-matched KTiOPO(4) crystal

We report on efficient intracavity frequency doubling of a cw diode-pumped Nd:YAG laser on the (4)F(3/2)?(4)I(9/2) laser transition at 946 nm. The nonlinear crystal used in the experiments was a first-order quasi-phase-matched flux-grown KTiOPO(4) crystal (period, 6.09mum ; thickness, 1 mm; length, 9 mm). The fluctuations in the generated second-harmonic wave were lower than 3% at output powers of as much as 500 mW. The overall optical-to-optical efficiency was 5.7%. A maximum output power of 740 mW of blue light was generated, which was stable for only 0.5 min. The decrease the output power at this power level was attributed to heating and thermal lensing in the periodically poled KTiOPO(4) crystal. The short-term behavior of the second-harmonic wave exhibited switching between a cw mode and chaotic intensity fluctuations.     

Walk-off Compensated 266-nm Generation with Two β-BaB2O4 Crystals

A walk-off compensation arrangement of two β-BaB₂O₄ (BBO) crystals is used to generate 266-nm (4ω) light from 532-nm (2ω) light that is produced by an intracavity frequency-doubled Nd:YAG laser. While this arrangement is effective in terms of conversion efficiency, back conversion from 4ω to 2ω can easily occur in the second BBO when the phase difference between the 2ω and 4ω in the air gap between the two crystals shifts to ϖ. Performance characteristics are discussed here with particular reference to the angular bandwidth of the second BBO.     

A comparative study on dual colour soft aperture cascaded second-order mode-locking with different nonlinear optical crystals

A comparative study in terms of optimized output power and stability is made on cascaded second-order nonlinear optical mode-locking with KTP, BBO and LBO crystals for both 1064 nm and 532 nm. Large nonlinear optical phase shift achieved in a non-phase-matched second harmonic generating crystal, is transformed into amplitude modulation through soft aperturing the nonlinear cavity mode variation at the laser gain medium to mode-lock a Nd:YVO4 laser. The laser delivers stable dual wavelength cw mode-locked pulse train with pulse duration 10.3 ps and average power of 1.84 W and 255 mW at 1064 nm and 532 nm respectively for the optimum performance in type-II KTP crystal. The exceptional stability achieved with KTP is accounted by simulating the mode-size variation with phase mismatch.     

Efficient resonant frequency doubling of a cw Nd:YAG laser in bulk periodically poled KTiOPO(4)

A cw Nd:YAG laser was quasi-phase-matched frequency doubled by a bulk periodically poled flux-grown KTiOPO(4) crystal in an external resonant cavity. The conversion efficiency and the second-harmonic power with a pump of 225 mW were 55% and 123.5 mW, respectively. The loss of the 1-cm-long crystal, which operated near room temperature, was 1.3% and was dominated by scatter from the cleaved facets of the crystal. No damage, photorefractive or other, was observed at intensites of 370Wmm(-2) , but beam size had to be optimized to eliminate thermal-induced instabilities in the doubling cavity.     

LD泵浦Nd：YAG/Cr：YAG腔外频率变换高功率紫外激光器

用KTP晶体对激光二极管端面泵浦的Nd:YAG晶体;Cr:YAG被动调Q产生的1064nm脉冲激光器进行腔外倍频,用BBO晶体四倍频产生266 nm紫外激光.用15 W的LD阵列;当LD泵浦功率为12 W的情况下;红外(1064 μm)调Q平均输出功率为2.2 W;脉冲序列周期为40 μs;脉宽为18ns;峰值功率高达4.9kW.采用KTP腔外二倍频;532nm的绿光输出平均功率为850mW;用BBO腔外四倍频;266nm的紫外光输出平均功率高达215mW，绿光-紫外光光转换效率为25.2%, 红外到紫外总的转换效率为9.8%.     

Sum-frequency generation of continuous-wave sodium D(2) resonance radiation

Sum-frequency generation utilizing two cw single-mode Nd:YAG lasers and a congruent lithium niobate crystal yielded 3.4 mW of very narrow-band (10 kHz over 1 ms) tunable 589-nm cw radiation. This simple solid-state light source is well suited for high-resolution spectroscopy of the sodium D(2) line, as was demonstrated with both conventional and FM-modulated saturation spectroscopy.     

全固态多波长飞秒脉冲激光系统

利用棱镜对引进频谱空间啁啾来补偿飞秒脉冲激光二次谐波产生中的相位失配,提高了倍频效率建立了一套全固态、多波长(1065nm, 532nm,823.1nm, 402nm)飞秒脉冲激光系统自制的Nd:YVO4激光器输出532nm绿光激光,最高平均功率可达5.6W当用2.5W绿光激光泵浦时,从自制的钛宝石激光器及经BBO倍频可分别输出中心波长为823.1nm和402nm,平均功率300mW和73mW,谱宽32.3nm和5.1nm,脉宽22fs和33.3fs、重复率108MHz的近红外和蓝光激光整个系统具有结构紧凑、倍频效率高、运行稳定的特点.     

Highly efficient infrared-to-visible energy upconversion in Er(3+):Y(2)O(3)

Very intense green and red emission was observed at room temperature from the (4)S(3/2) and (4)F(9/2) levels of Er(3+):Y(2)O(3). A cw diode laser at 975 nm was used as a pump for resonant sequential excitation of the (4)I(11/2) and (4)F(7/2) levels. The fluorescence was easily visible to the naked eye, even with 27 mW of excitation power. It was found that at 850 mW of cw excitation power the total luminance was 39,000 cd/m(2). This corresponds to ~100 muW of green emission and 270 muW of red emission.     

High-power, continuous-wave, singly resonant optical parametric oscillator based on MgO:sPPLT

We report a high-power, widely tunable, cw singly resonant optical parametric oscillator (OPO) based on MgO:sPPLT. The OPO is pumped in the green by a cw diode-pumped Nd:YVO(4) laser at 532 nm and can provide continuously tunable output across 848-1430 nm. Using a 30 mm crystal and double-pass pumping, an oscillation threshold of 2.88 W has been obtained, and single-pass idler powers in excess of 1.51 W have been generated over 1104-1430 nm for 6W of pump power at an extraction efficiency of 25.2% and photon conversion efficiency of 56.7%.     

High spectral purity and tunable operation of a continuous singly resonant optical parametric oscillator emitting in the red

Continuous-wave oscillation of a singly resonant optical parametric oscillator operating from 619 to 640 nm has been obtained. Parametric gain is created in a MgO-doped periodically poled stoichiometric lithium tantalate crystal pumped at 532 nm. 100 mW of single-frequency red light have been generated. The signal frequency is tunable, and its frequency stabilization on an external reference has been achieved.     

Generation of ultraviolet (335-nm) light by intracavity frequency doubling from active mode-locking action of an external-cavity AlGaInP diode laser

An intracavity frequency-doubling scheme was merged with an actively mode-locked AlGaInP laser diode with an external cavity to provide efficient generation of 335-nm ultraviolet light. Intense pulses of <16ps were successfully generated inside the cavity at subgigahertz repetition frequencies. We applied those pulses to intracavity second-harmonic generation from a 5-mm-long LiIO(3) crystal, which resulted in average ultraviolet power of 70muW for an average fundamental power of 73 mW.     

Efficient continuous-wave self-frequency-doubling green diode-pumped Yb:YAl(3)(BO(3))(4) lasers

Efficient cw self-frequency-doubled green laser output of 160 mW has been obtained from Yb:YAl(3)(BO(3))(4) crystal pumped by 1.4-W incident power from a fiber-coupled 976-nm laser diode. The incident-pump-power-green-output-power conversion efficiency is greater than 11.3%, and the electrical-input-green conversion efficiency is 3.9%. Tunable green output from 513.0 to 545.8 nm is also demonstrated with a quartz birefringent filter.     

Phase-coherent optical frequency division by 3 of 532-nm laser light with a continuous-wave optical parametric oscillator

Phase-locked 3:1 division of an optical frequency was achieved with a continuous-wave monolithic optical parametric oscillator (OPO) pumped by a 532-nm Nd:YAG laser, by use of 5% MgO-doped LiNbO(3) as a nonlinear optical crystal. The OPO generated signal light (798 nm) with 4-mW power and idler light (1596 nm) with 3-mW power for a pump power of 68 mW. Approximately 2microW of second harmonics (SH's) of the idler light was produced by external-cavity-enhanced SH generation by use of a periodically poled LiNbO(3) crystal. The beat signal between the signal light and the SH of the idler light was observed with a signal-to-noise ratio of 40 dB at a 10-kHz bandwidth and was successfully phase locked to a signal from a synthesizer through the electro-optic effect of the crystal.     

1.9-W flash-lamp-pumped solid-state 266-nm ultraviolet laser

Deep ultraviolet lasers have various applications in industries and scientific researches. For 266-nm ultra- violet （UV） laser generation, the good beam quality of 1064-nm laser and the elimination of gray-tracking effect of KTP crystal are two key factors. Using a dynamically stable resonator design, 1064-nm laser with an average power of 52 W is realized with repetition rate of 16 kHz. The measured M^2 factor characterizing the beam quality is 1.5. By the elimination of gray-tracking effect of KTP crystal, an 18-W green laser is realized with the M2 factor of 1.6. Using a BBO crystal for the fourth harmonic generation, a 1.9-W 266-nm UV laser is achieved.