Studies on the SFD Properties of Nd_xGd_(1-x)Ca_4O(BO_3)_3 Solid-solution Crystal

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Studies on the SFD Properties of NdxGd1-xCa4O(BO3)3 Solid-solution Crystal

NdxGd1-xCa4O(BO3)3 (NdGdCOB) is a new self-frequency-doubling (SFD) solid-solution crystal. The second-harmonic generation (SHG) phase-matching (PM) curves were calculated by using refractive indices. The deff of NdGdCOB crystal along different PM directions were calculated according to the sellmeier equation and dijk data in which the (θ=66.8°, φ=132.6°) PM direction has the highest deff. SFD experiments were carried out with Ti:sapphire CW laser and pulsed dye-laser. A green laser output power up to 225 mW at 530 nm was achieved from a 7×3×3 mm3 crystal sample pumped by 1560 mW CW Ti:sapphire laser. The lasing threshold of SFD was lower than 1.8 mW along the PM direction (66.8°,132.6°). The optical-optical conversion efficiency was 14.4%. The conversion efficiency was 7.7% when 10×3×3 mm3 sample was side-pumped by the pulsed dye-laser tuned to 595.4 nm with 17.5 mJ energy and the lasing threshold is 1.2 mJ.     

飞秒紫外激光脉冲振荡的实验研究

本文讨论了采用空间光脉冲光谱的啁啾特性和选择聚焦透镜焦距相结合的技术大大提高二次谐波转换效率和产生紫外飞秒光脉冲的实验研究.采用一类相位匹配的BBO晶体,当飞秒钛宝石光脉冲平均功率为560mW时,二次谐波输出功率为352mW,二次谐波转换效率高达63%;采用一类相位匹配的LBO晶体时,获得高光束质量的倍频蓝光输出,输出平均功率为170mW,转换效率大于30%.运用LBO倍频产生的蓝光脉冲和剩余的基频光脉冲进行了三次谐波的振荡研究.三倍频晶体采用BBO,通过优化设计倍频光与基频光之间的空间模匹配及精确时间延迟,得到飞秒紫外光输出,输出功率为2mW,中心波长约为280nm,重复率为100MHz.     

990 mW average power, 52% efficient, high-repetition-rate picosecond-pulse generation in the blue with BiB3O6

Efficient single-pass second-harmonic generation (SHG) of tunable high-repetition-rate picosecond pulses into the blue is reported in the nonlinear crystal BiB3O6. Using 2.4 ps fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz and a 10 mm crystal cut for type I (e + e --> o) phase matching in the optical yz plane, second-harmonic average powers as high as 990 mW with excellent stability have been generated at 52% conversion efficiency, and a tunable range of 370-450 nm is demonstrated. From measurements of single-pass SHG in the continuous-wave regime an effective nonlinear coefficient of 3.7 pm/V has been verified for BiB3O6, and direct comparison with beta-BaB2O4 confirms a SHG power enhancement of approximately 23% for the same crystal length. Autocorrelation measurements in a 200 microm crystal of beta-BaB2O4 result in durations of 2.8 ps for the second-harmonic blue pulses.     

Highly Efficient Frequency Doubling with a KNbO3 Semi-Monolithic Resonator

A semi-monolithic standing-wave resonator has been constructed and employed for frequency doubling of a Ti:sapphire laser. The resonator consists of a 5 mm long KNbO₃ crystal with dielectric coatings on both end faces and a spherical mirror with 20 mm radius of curvature. With 31.2 mW input power at 861.4 nm second harmonic power of 11.4 mW has been generated corresponding to the conversion efficiency of 36.5%.     

高效全固体脉冲蓝光系统实验研究

用半导体抽运的Q-YLF倍频激光器抽运钛宝石产生830nm的纳秒红外光,再用LBO晶体对该光 产生二次谐波得到415nm的脉冲蓝光.用3Ｗ的YLF抽运时可产生960mW基波光,效率达32%;经 倍频后输出285mW的蓝光,倍频效率可达322%.对影响倍频效率的主要因素如基波光源腔型 设计、聚焦效果、脉冲宽度等作了较详细的研究. 关键词： 全固体 倍频 蓝光     

高效全固化紫外四倍频激光器的研究

用半导体激光器抽运的调Q YLF倍频激光器抽运掺钛蓝宝石激光器，用LBO晶体在腔内产生二次谐波，再聚焦到BBO晶体上产生四次谐波深紫外激光。为了提高谐波转换效率，在腔内分别插入了单片、组合双折射滤光片和聚焦透镜，在平均功率为3.6W，波长为527nm的抽运光下得到410mW，417nm的蓝光。用长焦距的透镜聚焦二次谐波，得到34mW，208nm的紫外脉冲激光。从实验上详细研究了基频光的线宽对二次谐波效率的影响，二次谐波的线宽对四次谐波效率的影响、基频光的波长对四次谐波产生效率的影响。全面地分析了单片和组合大拆射滤光片及抽运功率对钛蓝宝石激光器基频光的脉宽、线宽等参量的影响。     

Development of a high-power deep-ultraviolet continuous-wave coherent light source for laser cooling of silicon atoms

We developed a deep-UV single-mode coherent light source through two-stage highly efficient frequency conversions by use of external cavities. In the first stage, second-harmonic power of 500 mW was obtained by frequency doubling of a 746-nm Ti:sapphire laser with a conversion efficiency of 40%. In the second stage, 50-mW power at ~252nm was obtained by doubly resonant sum-frequency mixing of 373-nm light from the first-stage conversion and 780-nm light from a diode laser. The output performance of this deep-UV light source is sufficient for laser cooling of neutral silicon atoms.     

Continuous-wave quasi-phase-matched generation of 60 mW at 465 nm by single-pass frequency doubling of a laser diode in backswitch-poled lithium niobate

We report continuous-wave single-pass second-harmonic generation (SHG) in 4-mum -period 0.5-mm-thick backswitch-poled lithium niobate. Pump sources at 920-930 nm include both Ti:sapphire and diode-oscillator-amplifier lasers. SHG of a Ti:sapphire laser at 6.1%/W efficiency, producing 61 mW of power at 460 nm, is demonstrated in 50-mm-long periodically poled lithium niobate samples with a nonlinear coefficient d(eff) approximately 9pm/V, and 60 mW at 465 nm and 2.8%/W efficiency is obtained by SHG of a laser-diode source.     

High-average-power femtosecond pulse generation in the blue using BiB3O6

Efficient generation of tunable femtosecond pulses in the blue is reported in the nonlinear crystal BiB3O6. By use of fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz, single-pass second-harmonic average powers of as much as 830 mW have been generated at 50% conversion efficiency, and a tunable range of 375-435 nm in the blue is demonstrated. Temporal measurements using cross correlation of the fundamental and second-harmonic pulses in a 100-microm-thick beta-BaB2O4 crystal result in blue pulse durations of 220 fs for 130-fs fundamental pulses. Direct experimental comparison with beta-BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulses.     

CONTINUOUS-WAVE LASER OSCILLATION OF Yb:FAP CRYSTALS AT A WAVELENGTH OF 1043nm

A continuous-wave laser oscillation was demonstrated with a Yb-doped fluorapatite (FAP) crystal pumped with a 905 nm Ti:sapphire laser. The output characteristics for different output couplers were investigated. A maximum power of 67mW at a 1043nm wavelength was obtained with 10% output coupler, pumped by a Ti:sapphire laser with 910mW power. This corresponds to a slope efficiency of 26.5%.     

Synchronously Pumped Femtosecond Optical Parametric Oscillator Based on MgO-Doped Periodically Poled LiNbO3

We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300hm and from 2080 to 2930nm, respectively, by changing the pump wavelength and the OPO cavity length. The maximum signal output power of 130mW at the wavelength of 1225nm is obtained, pumped by 900roW of 800hm laser radiation. This corresponds to a total conversion efficiency of 22.1%. The signal pulse duration is measured to be 167fs by intensity autocorrelation with chirped mirrors for intracavity dispersion compensation.     

Growth and laser properties of Nd:Ca4YO(BO3)3 crystal

Nd:Ca₄YO(BO₃)₃ (Nd:YCOB) crystal was grown by the Czochralski method, and its structure was measured by using a four circle X-ray diffractometer. The transparent spectrum from 200 to 2600 nm was measured at room temperature. The fluorescence spectrum near 1.06 μm showed that the main emission wavelength of Nd:YCOB crystal was centered at 1060.8 nm. Laser output at 1.06 μm has been demonstrated when it was pumped by a Ti:sapphire laser at the wavelength of 794 nm, the highest output power was 68 mW under pumping power of 311 mW, the pumping threshold was 163 mW and slope efficiency was 46.9%. The self-frequency doubled green light has been observed when it was pumped by a Ti:sapphire or a laser diode (LD). A 14.5 mm Nd:YCOB crystal sample cut at (θ, φ)=(90°, 33°) was used for type I second-frequency generation (SHG) of the 1.06 μm laser pulse. The SHG conversion efficiency was 22%.     

Design of the Seed Source for High Power KrF Excimer Laser System

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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.     

高效连续波钛宝石激光器的优化设计及实验研究

运用ABCD律及自再现条件对钛宝石线性腔的折叠角进行了优化,从而大大提高了钛宝石晶体中光束束腰的耦合效率同时实验上对连续钛宝石激光器进行了研究,采用20mm长的钛宝石晶体和10%输出耦合镜,并运用优化后的折叠角,最终用全线氩离子激光器泵浦的连续波钛宝石激光器的斜率效率高达34.2%,在泵浦功率为7.7W下,连续钛宝石激光器输出功率达1.89W.     

Continuous wave laser radiation at 693 nm from LiNbO3:ZnO:Nd3+ nonlinear laser crystal

Red laser radiation at 693 nm has been obtained from a LiNbO:ZnO:Nd crystal by self-frequency-doubling its fundamental laser line at 1386 nm. Pumping was achieved by means of a Ti:sapphire laser. In preliminary experiments a red laser power of 2.3 mW has been obtained for a total absorbed pump power of 800 mW. External second-harmonic experiments (1386–693 nm) are used to investigate some basic non-linear properties such as phase-matching angle, angular and thermal acceptances of this process. Received: 21 June 1999 / Revised version: 15 August 1999 / Published online: 30 November 1999     

High peak power green light generation using ytterbium fiber amplifier and lithium triborate crystal

We reported on a master-oscillator fiber power amplifier (MOPA) system and a second-harmonic generation (SHG) system. Actively Q-switched Nd:YVO₄ laser was used as a seed source of light pluses. The MOPA system produced as much as 76 kW of peak power at wavelength of 1064 nm, with 35 kHz repetition rate and 20 ns pulse duration. With a lithium triborate (LBO) crystal at type II phase matching, a maximum 16 kW of peak power had been demonstrated. The fiber nonlinear effects such as stimulate Brillouin scattering (SBS) and stimulate Raman scattering (SRS) and the SHG conversion efficiency were investigated.     

Violet light generation by frequency doubling of GaAlAs diode laser using a metallo-organic complex crystal ZnCd(SCN)4

Violet 404-nm radiation is generated by type-I single-pass frequency doubling of the output of an GaAlAs diode laser in critically phase-matched ZnCd(SCN)₄ (ZCTC) crystal, a metallo-organic complex crystal. In this paper, its refractive index and second-harmonic generation phase-matching angles are reported. Using a 3-mm-long ZCTC crystal, a diode laser power of 473 mW generated 390 μW of second-harmonic radiation. More recently, 380-nm, 20 μW ultraviolet (UV) radiation is also realized by frequency doubling of the 100 mW output of a continuous-wave Ti:sapphire laser at 760 nm. ZCTC is a promising UV nonlinear optical candidate material for frequency doubling of diode lasers.     

Generation of femtosecond laser pulses at 263 nm by K_3B_6O_(10)Cl crystal

The third harmonic generation(THG) of a linear cavity Ti:sapphire regenerative amplifier by use of a K_3B_6O_(10)Cl(KBOC) crystal is studied for the first time. Output power up to 5.9 mW is obtained at a central wavelength of 263 nm,corresponding to a conversion efficiency of 4.5% to the second harmonic power. Our results show a tremendous potential for nonlinear frequency conversion into the deep ultraviolet range with the new crystal and the output laser power can be further improved.