Highly-Efficient Ho:S<Subscript>i</Subscript>Sc<Subscript>2</Subscript>O<Subscript>5</Subscript> Laser Pumped by a Narrow Line-Width Tm:YAP Laser at 1.94 <Emphasis Type="Italic">μ</Emphasis>m

We present a highly-efficient continuous-wave Ho:SSO laser pumped by a diode-pumped Tm:YAP laser with a narrow linewidth (NL) of 0.3 nm. With the free-running (FR) Tm:YAP laser, we obtain a maximum output power of 2.23 W at an absorption pump power of 7.2 W, corresponding to an optical conversion efficiency of 31% and a slope efficiency of 42.6%. With the NL Tm:YAP laser, we obtain a maximum output power of 2.88 W at the same absorption pump power. The optical conversion efficiency increases to 40% when the slope efficiency increases to 55.5%. The output linewidth of the Ho:SSO laser is 0.8 nm when we use the Tm:YAP laser with a narrow linewidth of 1.8 nm pumped by a FR Tm:YAP laser. The beam quality also changes from 1.31 to 1.22.     

Efficient laser operation and continuous-wave diode pumping of Cr2+:ZnSe single crystals

Efficient continuous-wave laser operation of Cr²⁺:ZnSe was demonstrated with an output power of 1400 mW at an absorbed pump power of 1900 mW from a Tm:YAG laser. Under continuous-wave diode pumping at 1.54 μm an output power of 15 mW was obtained from a Cr⁺²:ZnSe laser. Excited state absorption is shown to be negligible in the pump and laser spectral region. Received: 12 October 2000 / Published online: 30 November 2000     

掺Er光纤飞秒激光器载波包络位相偏移的探测

本文介绍了基于掺Er光纤飞秒激光器光学频率梳中光学部分的研制. 实验上采用重复频率为230 MHz的掺Er光纤飞秒激光器,通过放大、光谱展宽以及单臂f—2f系统,在优化及分析相关参数影响的基础上,获得了~30 dB信噪比f₀的输出,为光纤光学频率梳的建立奠定了基础. 关键词： 掺Er光纤激光器 光学频率计量 光纤光学频率梳 光谱展宽     

A linearly polarized continuous-wave 1357-nm Nd:YAG laser

We demonstrated a linearly polarized continuous-wave Nd:YAG laser operating at a 1357-nm single-wavelength, by a 808-nm diode as an end-pump source. We chose a Brewster-angle-cut Nd:YAG laser host crystal, due to its two salient features as follow: linearly polarized laser output and single-wavelength oscillation can be easily obtained. In this paper, a continuous-wave all-solid-state single-wavelength laser operating at 1357 nm is demonstrated with a diode-end-pumped Brewster-cut Nd:YAG laser. The laser had a 1.03-W maximum output power under an incident pump power of 15.0 W, a 12.7% slope efficiency, a 6.9% optical-to-optical conversion efficiency, a 0.14-nm spectral linewidth and a 3% power-output stability within 30 min. PACS 42.55.Rz; 42.55.Xi; 42.70.Hj     

Noise characterization of an all-solid-state mirror-dispersion-controlled 10-fs Ti:sapphire laser

We characterized the phase and amplitude noise of a mirror-dispersion-controlled 10-fs Ti:sapphire laser pumped by a frequency-doubled cw diode-pumped Nd:YVO₄ laser and compared with these of the Ti:sapphire laser pumped by an Ar-ion laser. The rms timing jitters and rms amplitude noise for the all-solid-state and Ar-ion laser pumped Ti:sapphire lasers are calculated to be 0.31 ps rms and 0.71 ps rms and 0.15% rms and 0.32% rms, in the frequency range from 20 kHz to 400 kHz, respectively. The phase and amplitude noise characteristics of the Ti:sapphire laser were greatly improved by using the diode-pumped solid state laser as a pump source.     

Passive synchronization of two independent laser oscillators with a Fabry-Perot modulator

By optical modulation of the reflectivity of an intracavity nonlinear Fabry-Perot semiconductor mirror, the pulse train from a passively mode-locked picosecond Nd:YVO(4) laser oscillator is synchronized to an independent femtosecond-mode-locked Ti:sapphire laser. We obtain stable synchronized pulse trains at central wavelengths of 1064 and 850 nm, and the Ti:sapphire laser is still independently tunable over a large wavelength range. The tolerable cavity-length difference between the two laser oscillators exceeds 20mu;m .     

Performance of gain-switched all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system

We have made a gain-switched all-solid-state quasi-continuous-wave （QCW） tunable Ti：sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd：YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti：sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti：sapphire laser from 700 to 950nm can be achieved. It has a maximum average output power of 5.6W at 800nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 mn pump laser to the Ti：sapphire laser.     

Hybrid laser processing for microfabrication of glass

Hybrid laser processing for the precision microfabrication of glass materials, in which the interaction of a conventional pulsed laser beam and a medium on the material surface leads to effective ablation and modification, is reviewed. A major role of the medium is to produce strong absorption of the conventional laser beam by the material. Simultaneous irradiation by a vacuum ultraviolet (VUV) laser beam that possesses an extremely small laser fluence and an ultraviolet (UV) laser greatly improves the ablation quality and modification efficiency for fused silica (VUV-UV multiwavelength excitation process). The metal plasma generated by the laser beam effectively assists high-quality ablation of transparent materials by the same laser beam, resulting in microstructuring, cutting, color marking, printing, and selective metallization of glass materials (laser-induced plasma-assisted ablation (LIPAA)). The detailed discussion presented here includes the ablation mechanism of hybrid laser processing. Received: 18 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +81-48/462-4682, E-mail: ksugioka@postman.riken.go.jp     

1064 nm Nd:YAG laser intracavity pumped at 946 nm

We present for the first time a Nd:YAG laser emitting at 1064 nm intracavity pumped by a 946 nm diode-pumped Nd:YAG laser. A 885 nm laser diode is used to pump the first Nd:YAG crystal emitting at 946 nm, and the second Nd:YAG laser emitting at 1064 nm intracavity pumped at 946 nm. We achieved an output power of 7.97 W at 1064 nm for an absorbed pump power at 946 nm of 9.55 W, corresponding to an optical efficiency of 83.4%. The beam quality M² quality factor is about 1.1 at the maximum output power.     

Color center laser pumped with a DCM dye laser

A CW, DCM dye laser has been used to pump a RbCl:Li crystal in a color center laser. The DCM dye laser was pumped by the 488 nm and 514.5 nm lines of an argon ion laser. When used in a broad band configuration the dye laser had a power output in the TEM₀₀ mode in excess of 600 mW at a wavelength of 655 nm. An output power in excess of 10 mW at 2.73 μm was possible from the RbCl:Li crystal in a Burleigh FCL for an input power of 600 mW at 655 nm. This method of pumping for the RbCl:Li alleviates the need for both argon ion and krypton ion laser pumps for the Burleigh FCL. All three crystals can be pumped to the specification power levels with a single argon ion laser.     

Comparison of eye-safe KTA OPOs pumped by Nd:YVO4 and Nd:YLF lasers

An eye-safe KTA OPO pumped by a Nd:YLF laser is demonstrated and a comparison with that pumped by a Nd:YVO₄ laser is performed. Although the slope efficiency of the continuous-wave free-running Nd:YLF laser is lower than that of the Nd:YVO₄ laser, the performance of KTA OPOs pumped by the Q-switched Nd:YLF laser is better, especially at lower repetition rates. The slope efficiency of KTA OPO pumped by a Nd:YLF laser is 14.6% at 30 kHz and 11.04% at 10 kHz. The better energy storage ability of Nd:YLF makes it an excellent laser medium in IOPOs.     

200 mJ半导体端面泵浦MOPA激光器研究

采用高功率激光二极管阵列(LDA)端面泵浦Nd:YAG激光棒方式, 结合凸凹非稳腔的设计，获得20 Hz运转条件下小束散角激光输出平均能量约为83 mJ。以该激光为振荡源，同样采用LDA端面泵浦Nd:YAG激光棒的方式进行能量放大，组成LDA端面泵浦振荡-放大(MOPA)激光器，最终获得重频频率20 Hz、平均能量＞200 mJ、发散角＜2.1 mrad、能量波动＜±2.5%的脉冲激光输出。该激光器光光转换效率约为14.6%，体积为175×91×49 mm3，质量＜1 kg，激光经8倍发射天线后发散角＜0.3 mrad。     

Non-contact subsurface temperature measurements following mid-infrared laser irradiation

A difficult challenge in laser processing at nanosecond time scales is monitoring substrate temperature in the laser focal volume, particularly for mid-infrared laser irradiation where the absorption depth is relatively large and the attained temperatures are often relatively low. Here, we describe time-dependent measurements of the subsurface temperature of a target material following absorption of pulsed mid-infrared (MIR) laser irradiation, by detecting the luminescence from micron-size ceramic phosphor particles (Gd-doped YAG:Ce) embedded in the target material at a concentration of up to 10 %. Temperature calibrations were obtained by measuring the luminescence decay of the probe particles in an oil-bath heater. A silica-nanoparticle film was irradiated by an Er:YAG laser operating in a free-running mode over a fluence range up to but below the ablation threshold, while the third harmonic of the Nd:YAG laser excited the luminescence of the probe particles. From the temperature calibrations, it was possible to infer the thermal history of the target as a function of time delay between the Er:YAG and Nd:YAG laser pulses.     

采用飞秒光纤激光同步泵浦的自启动锁模钛宝石激光研究

针对常规连续激光泵浦钛宝石激光振荡器不能自启动锁模的缺点,采用倍频飞秒光纤激光同步泵浦,通过调节振荡器腔长与泵浦腔长匹配,实现了飞秒钛宝石激光的自启动锁模。实验中采用3.4 W的倍频掺镱光纤激光同步泵浦钛宝石激光振荡器,获得了平均功率大于130 mW、重复频率75 MHz、光谱宽度大于47 nm、脉冲宽度17 fs的锁模脉冲输出,不仅能够稳定可靠地实现自启动锁模,解决了常规钛宝石激光振荡器锁模启动的困难,而且还具有同步输出1040,800,520 nm三束飞秒激光的特点,为进一步开展飞秒激光相干合成以及光参量放大等研究提供了优势基础。     

Laser-diode pumped self-Q-switched microchip lasers

Optical properties of Cr,Yb:YAG, Cr,Nd:YAG crystals, and composite Yb:YAG/Cr:YAG ceramics self-Q-switched solid-state laser materials are presented. The merits of these self-Q-switched laser materials are given and the potentials of such lasers can be chosen by the applications. Cr,Yb:YAG and composite Yb:YAG/Cr:YAG ceramics self-Q-switched laser are conducted. Although several tens of kW peak power can be obtained with a monolithic microchip Cr,Yb:YAG laser, the experimental results show that the performance of this laser is limited by the absorption of Cr⁴⁺ ions at a pump wavelength of 940 nm and strong fluorescence quenching at high Cr concentration. Composite Yb:YAG/Cr:YAG ceramics are more suitable to realize high pulse energy and peak power (up to MW level) with optimized lasing and Q-switching parts. In addition, the instabilities induced by the multi-longitudinal mode competition in Cr,Nd:YAG and Cr,Yb:YAG microchip lasers are addressed. The different gain bandwidths of Yb:YAG and Nd:YAG play an important role in the instability of the output laser pulse trains. Stable laser pulses from the Cr,Yb:YAG microchip laser were obtained due to the antiphase dynamics. For the Cr,Nd:YAG microchip laser, the instability caused by the multi-longitudinal mode competition is an intrinsic property. Different transverse patterns were observed in Cr,Nd:YAG microchip lasers when a pump beam with larger diameter was used. Saturated inversion population distribution inside the gain medium plays an important role in the transverse pattern formation. Different transverse patterns were reconstructed by combining different sets of the Hermite-Gaussian modes.     

All-solid-state narrow-linewidth 455-nm blue laser based on Ti:sapphire crystal

A compact, all-solid-state, narrow-linewidth, pulsed 455-nm blue laser based on Ti：sapphire crystal is developed. Pumped by a 10-Hz, frequency-doubled all-solid-state Nd：YAG laser and injection-seeded by an external cavity laser diode, the narrow-linewidth 910-nm laser with pulse width of 20 ns is obtained from a Ti：sapphire laser. 3.43-mJ blue laser can be obtained from the laser system by frequency-doubling with BBO crystal. This research is very useful to determine the roadmap of developing the practical, high power blue laser. This kind of laser will have potential application for underwater communication.     

An Intracavity-Triggered Passively-Switched Nd:YVO<Subscript>4</Subscript> Laser

We demonstrate an intracavity-triggered passively Q-switched Nd:YVO₄ laser within a diode-end-pumped configuration. We employ a Cr⁴⁺:YAG saturable absorber as the passive Q switch and an Nd:LiYF₄ (YLF) laser as the laser triggering of the Q-switched laser. Since we use the same Cr⁴⁺:YAG crystal and output coupler with the Nd:YVO₄ laser, the Cr⁴⁺:YAG Q switch is triggered inside the Nd:YLF laser cavity. As a result, the timing jitter in standard deviation of Nd:YVO₄ laser can be reduced to 16 ns.     

High power and highly efficient Nd:YAG laser emitting at 1123 nm

A diode-end-pumped continuous-wave (CW) Nd:YAG laser emitting at 1123 nm is realized efficiently in a 25-mm-long cavity. A composite Nd:YAG (cNd:YAG) crystal is selected as the gain medium. With an incident diode power of 26.1 W, an output power of up to 9.3 W is obtained, corresponding to an optical-to-optical conversion efficiency of 35.6%. The laser performances at 1123 nm are compared between composite Nd:YAG and common Nd:YAG crystals. The results show that composite Nd:YAG is a better choice for 1123-nm laser generations.     

LD泵浦的Nd:GdVO4/KTP腔内倍频激光器

基于对Nd:GdVO4晶体热焦距的测量及其1.06 μm激光基本性能,用三镜折叠腔研究了半导体激光器(LD)泵浦的Nd:GdVO4/KTP晶体的内腔倍频性质.当用从直径为200 μm的单光纤输出的低功率的半导体激光泵浦时,绿光的阈值是26 mW,光光转换效率为17.3%.当用从直径为1.55 mm的光纤束输出的高功率的半导体激光泵浦时,绿光的阈值是200 mW,光光转换效率为19.35%.     

Diode-pumped passively Q-switched YAG/Yb:YAG laser with Cr4+:YAG as a saturable absorber

We design an efficient passively Q-switched laser using a composite YAG/Yb:YAG crystal as the laser gain medium and a Cr⁴⁺:YAG crystal as a saturable absorber. We obtain an average output power of 1.81 W in 1030 nm laser at an absorbed pump power of 4.8 W, corresponding to an optical-to-optical efficiency of 37.7% and a slope efficiency of 47.3%. The pulsed laser has a repetition rate of about 28.6 kHz and a pulse width of 15.8 ns, with the highest peak power of 4 kW. In addition, using a LBO as the intracavity frequency doubler, we obtain a maximum power of 246 mW in 515 nm pulsed laser at an absorbed pump power of 3.8 W.