Diode-pumped Yb:Sr(3)Y(BO(3))(3) femtosecond laser

We have developed a diode-pumped Yb(3+)Sr(3)Y(BO(3))(3) (Yb:BOYS) laser generating 69-fs pulses, at a central wavelength of 1062 nm. This laser is mode locked by use of a semiconductor saturable-absorber mirror and emits 80 mW of average power at 113 MHz. This is, to our knowledge, the first mode-locked Yb:BOYS laser and the shortest duration obtained from an ytterbium laser with a crystalline host. The central wavelength can be tuned from 1051 to 1070 nm, for sub-100-fs pulses. We have also achieved an average power as high as 300 mW with pulse duration of 86 fs at 1068 nm.     

Photoemission study of YBa(2)Cu(3)O(y) thin films under light illumination

Heterojunctions of Nb-doped SrTiO3 substrate and YBa(2)Cu(3)O(y) thin films show photoconductivity and photovoltaic effects due to photocarrier injection. Photocarrier injection is expected to be a new carrier doping method in strongly correlated systems instead of chemical substitution. We have studied the nature of photocarrier injection in YBa(2)Cu(3)O(y)/SrTiO(3):Nb using x-ray photoemission spectroscopy with pulsed laser excitation. The core-level spectra shift to higher binding energy by 0.78 eV under pulsed laser illumination at 30 Hz. The energy shift corresponds to the photovoltage, which arises at the interface. In addition, we have observed that the energy shift strongly depends on the frequency of the laser. The lifetime of the injected photoholes has been estimated to be 40 ms by analyzing the frequency dependence.     

Continuous-wave rotational Raman laser in H(2)

A diode-pumped, far-off-resonance cw Raman laser in H(2) with rotational Stokes emission is reported for the first time to our knowledge. The Raman laser can produce single-wavelength emission at either 830 nm (rotational Stokes) or 1180 nm (vibrational Stokes) depending on the frequency tuning of the pump laser. The mirrors for the rotational cw Raman laser are easier to produce; the laser also exhibits a wider continuous tuning range and is less sensitive to thermal effects than the previously studied vibrational Raman laser [Opt. Lett. 26, 426 (2001) and references therein].     

High-power self-mode-locked Yb:Y(2)O(3) ceramic laser

We have experimentally demonstrated a high-power self-mode-locked Yb:Y(2)O(3) ceramic laser. Without any additional active or passive element in the cavity, self-started cw mode-locking was achieved. The maximum output power was as high as 2.7 W with a pulse duration of 1.1 ps. Numerical studies show that the diffraction loss induced by thermal lens aberration, in combination with the Kerr self-focusing effect in the gain medium, results in the mode locking of the laser. To our knowledge, this is the first self-mode-locked ceramic laser.     

High-energy self-starting femtosecond Cr(4+):Mg(2)SiO(4) oscillator operating at a low repetition rate

We describe a self-starting high-power femtosecond laser based on the Cr(4+):Mg(2)SiO(4) crystal that produces 17-nJ pulses of 40-fs duration at 26.5-MHz repetition rate. This low repetition rate is achieved by employment of a one-to-one telescope in the cavity. The pulse energy is five times greater than with a short-resonator laser. To our knowledge, the laser produces the highest energy ever achieved from this type of laser directly from the resonator without cavity dumping or external amplification. We believe that this laser source can be used for many applications, including nonlinear optics, microscopic imaging, and micromachining of silicon and other semiconductor materials.     

实用型放电泵浦XeF(B-X)准分子激光器

 研制了一台实用型放电泵浦的351 nm XeF(B-X)准分子激光器,激光器采用新型开关电源、结构紧凑型张氏电极及放电火花预电离的激光腔结构,通过优化储能电容和放电电容量及比值,选取合理的工作气体压力和配比,优化了激光器性能,提高了激光器输出参数:单脉冲能量153 mJ,平均功率12.9 W,转换效率最高达到0.88%,重复频率1~80 Hz,能量不稳定度小于4%,近场光斑尺寸7 mm×22 mm。激光器已应用到常规抗蚀剂曝光的印刷电路板(PCB)激光投影成像照明系统的实验中。     

XeF(C-A)蓝绿激光线宽压缩技术

利用表面放电光泵浦XeF(C-A)蓝绿激光器开展了激光线宽压缩技术研究,分别采用谐振腔腔镜谱带重叠法和光栅谐振腔法实现了线宽小于10 nm的窄线宽激光输出。采用谐振腔腔镜谱带重叠法,激光输出线宽约7 nm,采用光栅谐振腔法可以将激光线宽压缩到约1 nm,并实现XeF(C-A)激光的可调谐输出,调谐范围为470~495 nm。     

Generation of 90-fs pulses from a mode-locked diode-pumped Yb(3+):Ca(4)GdO(BO(3))(3) laser

A diode-pumped Yb>(3+):Ca(4)GdO(BO>(3))(3) (Yb:GdCOB) laser generating 90-fs pulses at a center wavelength of 1045 nm is demonstrated. This is, to our knowledge, the shortest pulse duration obtained from an ytterbium laser with a crystalline host. This laser is mode locked with a high-finesse semiconductor saturable-absorber mirror and emits 40 mW of average power at a repetition rate of 100 MHz.     

Diode-pumped Pr(3+):KY(3)F(10) red laser

We report the first observation to our knowledge of room-temperature continuous-wave laser operation of a Pr(3+):KY(3)F(10) single crystal at 644.5 nm, pumped by a blue GaN laser diode emitting at 446 nm. With a 2.5% transmission output coupler and a nonoptimized optical cavity, an output power of 39 mW was obtained at 644.5 nm with a laser threshold of 125 mW and a differential slope efficiency of 23%.     

上海激光电子γ源

激光具有高强度、 高极化度等优异的性能。 用激光束轰击高能电子束就可以产生高强度、 高极化度的γ射线束。 上海激光电子γ源就是上海同步辐射装置上的这样一条束线站。 预计可以获得能量范围为1—22 MeV的准单色、 高强度（109—1011 s-1）和高极化度（线极化或圆极化）的γ射线束。 介绍了这条束线站目前的进展情况。 Shanghai Laser Electron Gamma Source (SLEGS) is a high intensity,short pulse and compact γ ray source which is based on inverse Compton scattering via interaction between pulsed high power laser beams and picosecond relativistic electron bunches. One of the attractive features of the laser Compton scattering is the easy control of polarization of the produced high energy photons that duplicates polarization of the applied laser beam. The γ ray with energy up to 22 MeV and intensity of 109—1011s 1 are expected to be produced by Compton backscattering of CO2 laser photons on the 3.5 GeV electrons bunches in the Shanghai Synchrotron Radiation Facility (SSRF). In this communication, we report same simulation results and the progressing status of SLEGS.     

Demonstration of room-temperature laser action at 2.5 mum from Cr(2+):Cd(0.85)Mn(0.15)Te

Room-temperature laser action from Cr(2+)-doped Cd(0.85)Mn(0.15)Te has been demonstrated for what is believed to be the first time. We achieved pulsed laser operation centered at ~2.5mu m by pumping into the mid-infrared absorption band of Cr(2+) ions by use of the 1.907- mum output of a H(2) Raman-shifted Nd:YAG laser. The output of the free-running Cr(2+):Cd(0.85)Mn(0.15)Te laser had a width of ~50 nm (FWHM), and the slope efficiency was calculated to be 5.5% under nonoptimum conditions.     

Angularly resolved coherent Raman spectroscopy (ARCS)

This new crossed beam configuration produces an angularly separated Coherent Anti-Stokes Raman spectrum, eliminating the need for a spectrometer. Since one of the driving laser beams is always linearly opposed to the dye laser, it may also be used as a dye pump and the experiment performed within the dye cavity for efficient laser energy utilization. With this arrangement, a broad bandwidth dye laser produces a several wavenumber resolution spectrum from a small volume with relatively simple alignment. The spectrum is scanned by varying the incidence angle of the probe beam or taken is a single pulse using a fan shaped probe beam.     

Chemically pumped O2(a-X) laser

A theoretical and experimental study was conducted aimed at achieving laser oscillation in the (a-X) electronic transition of oxygen molecules. Although this transition is highly forbidden by rigorous selection rules, it may nevertheless concede stimulated emission, if the population inversion is high enough. The idea is based on a recently developed apparatus, namely, a porous pipe type high-pressure chemical singlet oxygen generator. A numerical model which describes the characteristics of this generator was developed to estimate the population inversion and small-signal gain achievable in a laser cavity using this source. The calculations showed that the small-signal gain ought to be sufficient to achieve laser oscillation. Preliminary experiments were conducted, but lasing was not yet observed. It is shown that the scattering losses caused by water droplet aerosols are mainly responsible for preventing our system from laser oscillation.     

Dynamical Stark Effect in the nu(2)/nu(4) Vibrational Polyad of SiH(4): Theory and Observation

We report a theoretical and experimental investigation of the dynamical Stark effect in a tetrahedral molecule, silane (SiH(4)). We use a tetrahedral formalism and Floquet theory to calculate the absorption spectra for the molecule dressed by an intense nonresonant pulsed laser. Experimentally, the dynamical Stark effect is observed for transitions of the nu(2)/nu(4) vibrational polyad of SiH(4) by means of nanosecond diode laser absorption spectroscopy and a Nd:YAG laser excitation. Copyright 2000 Academic Press.     

棱镜色散腔XeF(C-A)蓝绿激光线宽压缩

XeF(C-A)蓝绿激光的增益系数较低,仅为0.003 cm-1,要获得高能量窄线宽激光输出有一定难度。利用色散元件棱镜开展了高单脉冲能量窄线宽激光输出实验研究,结果表明:采用凹面输出镜的情况下,激光线宽可以压缩到约2.5 nm,激光输出能量最大为3.47 J;采用平面输出镜,激光线宽压缩到约0.7 nm,激光输出能量最大为2.93 J,激光光谱调谐范围最大可达到60 nm,在460～520 nm之间。     

Pulsed laser operation of Y b-dope d KY(WO(4))(2) and KGd(WO(4))(2)

Spectroscopic properties and laser performance of Y b-doped tungstates at pulsed Ti:sapphire laser pumping are reported. Room-temperature lasing near 1025nm is demonstrated in Yb:KY(WO(4))(2) and Yb:KGd(WO(4))(2), with a slope efficiency as great as 86.9%.     

Continuous-wave stimulated Raman scattering (cwSRS) microscopy

Stimulated Raman scattering (SRS) microscopy is a powerful tool for chemically sensitive non-invasive optical imaging. However, ultrafast laser sources, which are currently employed, are still expensive and require substantial maintenance to provide temporal overlap and spectral tuning. SRS imaging, which utilizes continuous-wave laser sources, has a major advantage, as it eliminates the cell damage due to exposure to the high-intensity light radiation, while substantially reducing the cost and complexity of the setup. As a proof-of-principle, we demonstrate microscopic imaging of dimethyl sulfoxide using two independent, commonly used lasers, a diode-pumped, intracavity doubled 532-nm laser and a He–Ne laser operating at 632.8-nm.     

Diode-pumped 65 fs Kerr-lens mode-locked Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramic laser

Diode-pumped Kerr-lens mode-locked laser operation of Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramics has been achieved; 65 fs pulses with an average power of 320 mW under 5 W of pump power were obtained at the center wavelength of 1032 nm. The spectral bandwidth and the time bandwidth product were 18.9 and 0.345 nm, respectively. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked laser operation based on Yb(3+):Lu(2)O(3) ceramic.     

10 J energy-level optically pumped XeF(C-A) laser with repetition mode

An optically pumped XeF(C-A) laser with 0.1-1 Hz pulse-repetition mode is demonstrated. The maximum output energy is up to 18.7 J, which corresponds to the conversion efficiency of the stored electrical energy to laser output energy of 0.25%. The laser active medium is optically excited by vacuum-ultraviolet radiation of two single-channel surface discharges initiated along opposite walls of the laser cell. The laser resonator output coupling is 10%, and the initial XeF2 concentration in the active gas mixture is ~1 x 10(17) cm(-3). The duration of the observed laser pulses is 0.8 to 1.2 micros, and the spectral band is 470-500 nm.     

双向光泵浦XeF(C-A)激光

 讨论了双向光泵浦XeF(C-A)激光技术,给出了双向泵浦情况下的XeF₂光解离波图像。在双向泵浦条件下XeF(C-A)激光输出能量提高了近3倍,最大输出达到3.3 J,激光脉宽增加到1 100 ns。激光输出特性受XeF2初始浓度的显著影响,激光形成时间随XeF₂初始浓度增大而加长,激光脉宽先增大后减小,激光近场光斑呈现出不同的形状,由方形变化为“X”形状。