Broadly tunable compact continuous-wave Cr(2+):ZnS laser

We report the development of a continuous-wave, room-temperature Cr(2+) ZnS laser that is compact and tunable over 700 nm. The laser is pumped by a diode-pumped Er-fiber laser and generates 0.7 W of linearly polarized radiation at 2.35microm , at up to 40% slope efficiency. Cr(2+) ZnS directly diode-pumped at 1.6microm yields polarized radiation that is tunable over 400 nm at up to 25 mW of output power. A comparison of Cr(2+) ZnS with Cr ZnSe (70 mW, 350 nm) in a similar setup is given. As opposed to Cr ZnSe, the Cr ZnS laser is intrinsically polarized. Finally, we observe sensitization of the output radiation by a few milliwatts of the visible (470-500-nm) and near-infrared (740-770-nm) radiation.     

Spectral kinetic properties and lasing characteristics of diode-pumped Cr<Superscript>2+</Superscript>:ZnSe single crystals

The temperature and concentration quenching of the luminescence of Cr²⁺ ions in Cr:ZnSe crystals is experimentally investigated and the radiative lifetime of the upper lasing level is determined. The values of the cross sections of absorption from the ground state of Cr²⁺ ions in Cr:ZnSe crystals are refined. It is shown that the absorption from the excited state of Cr²⁺ ions is negligible near 1.5 μm. Lasing in Cr:ZnSe single crystals is implemented with an efficiency of 31% and an output power of 186 mW using laser diode pumping at a wavelength of 1.77 μm.     

Nd:YGG crystal laser at 1110 nm: a potential source for detecting carbon monoxide poisoning

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet crystal laser at 1110 nm for the first time to our knowledge. By suppressing the oscillation at about 1.06 μm, continuous-wave output power of 2.1 W at 1110 nm was achieved. With a Cr:YAG as the saturable absorber, the passive Q-switching performance at this wavelength was obtained. The shortest pulse width and largest pulse energy were 31.5 ns and 22.7 μJ, respectively. Laser radiation at this wavelength is an important source for detecting carbon monoxide poisoning by simple frequency doubling with a nonlinear crystal.     

向列相液晶染料可调谐激光器的研究

对向列相液晶染料的可调谐激光器进行了光学特性研究. 以650 nm为中 心波长设计了SiO₂和TiO₂多层膜的一维光子晶体, 以激光染料与向列相液晶的混合物作为增益介质层, 制备了波长可调谐激光器.用Nd: YAG倍频脉冲激光器输出的532 nm激光抽运所制备的激光器样品得出如下光学特性: 激光发射波长随温度调谐范围为605.5---639.8 nm, 达到34.3 nm, 随电压调谐范围为634.5---619.5 nm, 达到15 nm. 发射激光每脉冲的阈值能量为12.3 μJ, 激光线宽小于1 nm.     

Picosecond tunable mode locking of a Cr2+:ZnSe laser with a nonlinear mirror

We report on a nonlinear mirror (NLM) scheme that enables, for the first time to the best of our best knowledge, tunable mode locking of a Cr2+:ZnSe laser in the picosecond regime. The NLM-used as the output coupler of the laser cavity-consists of a periodically poled lithium niobate (PPLN) crystal with a fan-out grating coupled with a dichroic mirror and a wedged dispersive YAG plate. The Cr2+:ZnSe laser, pumped by a CW thulium-doped fiber laser, delivers 85?ps pulses at a repetition rate of 220?MHz with a 300?mW average power. Thanks to the use of a fan-out PPLN crystal, we benefit from the wide tunability of the Cr2+:ZnSe laser and achieve mode locking over the whole 2.44-2.55?μm range while maintaining a narrow-linewidth emission suitable for time-resolved nonlinear spectroscopy applications.     

Continuous-wave broadly tunable Cr2+:ZnSe laser

We report room-temperature operation of an all-solid-state broadly tunable continuous-wave Cr(2+):ZnSe laser. Output power of 250 mW, an absorbed power slope efficiency of 63%, and continuous tunability from 2138 to 2760 nm are demonstrated.     

Efficient, kHz repetition rate, gain-switched Cr:forsterite laser

We have developed a gain-switched room-temperature Cr:forsterite laser operating at repetition rates of between 1 and 34 kHz, and pumped by a continuous wave, Q-switched Nd:YAG laser. With optimised output coupling, an output pulse energy of 52 μJ was measured at 1.5 kHz repetition rate, corresponding to 11% efficiency and 13% slope efficiency. Threshold pulse energy was 53 μJ. Output power of 370 mW was obtained at 10 kHz repetition rate and 4.4 W pump power. Water cooling was not required for repetition rates up to 10 kHz. In a tunable, folded resonator, the Cr:forsterite wavelength tuned between 1173 and 1338 nm. This laser operated with maximum pulse energy of 34 μJ, efficiency of 13%, and power of 307 mW. The laser output was close to diffraction-limited with M² of 1.2. Received: 6 January 1999 / Published online: 29 July 1999     

Eye-safe, high-energy, single-mode all-fiber laser with widely tunable repetition rate

We present a novel high-energy, single-mode, all-fiber-based master-oscillator-power-amplifier （MOPA） laser system operating in the C-band with 3.3-ns pulses and a very widely tunable repetition rate, ranging from 30 kHz to 50 MHz. The laser with a maximum pulse energy of 25 μJ and a repetition rate of 30 kHz is obtained at a wavelength of 1548 nm by using a double-clad, single-mode, Er：Yb co-doped fiber power amolifier.     

Dependence of Er:Yb-codoped 1.5 μm amplifier on wavelength-tuned auxiliary seed signal at 1 μm wavelength

We report on experiments performed with a cladding-pumped single-mode Er:Yb-codoped single-frequency fiber amplifier simultaneously seeded by a distributed-feedback diode at 1556 nm and a tunable external-cavity diode laser emitting at a wavelength of about 1 μm wavelength. The influence of the output wavelength of the external-cavity laser on amplification and reabsorption behavior of the Yb emission as well as the amplifier performance at a wavelength of 1556 nm is examined experimentally.     

Tunable,narrow linewidth,linearly polarized and gain-switched Cr<Superscript>2+</Superscript>:ZnSe laser

We demonstrate a tunable, narrow linewidth, linearly polarized and gain-switched Cr²⁺:ZnSe laser pumped by a Tm, Ho:YVO₄ laser at 10 kHz pulse repetition frequency. By setting a quartz birefringent filter with a Brewster angle in the cavity, the linearly polarized Cr²⁺:ZnSe laser can be continuously tuned from 2.45 to 2.50 μm, and the output power was almost not changed. In addition, the linewidth was compressed to about 5 nm. At the incident pump power to the crystal of 14 W, the maximum output power of 2.84 W was obtained, corresponding to a slope efficiency of 20.4%.     

Efficient Cr:ZnSe laser with a volume Bragg grating

An efficient and narrow linewidth Cr:ZnSe laser pumped by Tm,Ho:GdVO₄ laser with a volume Bragg grating (VBG) is reported. The Cr:ZnSe laser operated at 2580 nm with emitting linewidth (FWHM) about 0.8 nm. Using the volume Bragg grating, 3.57 W of output was achieved under total incident pump power of 13.1 W, corresponding to optical-to-optical conversion efficiency of 27.3%. By use of conventional mirror, 4.11 W of output was achieved the same incident pump power and the optical-to-optical conversion efficiency is 31.4%.     

Experiment Study of Dual Wavelength and Dual Pulse Q-switched Intracavity Frequency Doubling of a Tunable Cr:LiSAF Laser

In this paper, a flashlamp-pumped Q-switched Cr: LiSAF laser system with intracavity frequency doubling is designed to obtain dual pulse and dual wavelength laser output. The behaviors of second harmonic output of dual pulse and dual wavelength are studied experimentally. Good results are obtained in experiments: the output energy of each second harmonic pulse a round 448.1 nm is 10.2 mJ, the dual pulse time interval can be tuned widely, and the tunable range of each second harmonic wavelength is 448.1 to 465 nm.     

ZnS:Cr and ZnSe:Cr thin‐film waveguide structures as electrically pumped laser media with an impact excitation mechanism

ZnS:Cr and ZnSe:Cr are the focus of studies as media for broadly tunable optically pumped lasers operating in the near‐ and mid‐IR regions. It is of great interest to obtain such lasers electrically pumped. The effective electrical excitation of Cr²⁺ ions was demonstrated only in the case of the impact mechanism for thin‐film structures with insulator layers between an electroluminescent film and electrodes, which prevent avalanche breakdown at high electric field (≥ 1 MV/cm). To obtain lasing, the waveguide electroluminescent structures were used. For the first time, the stimulated emission and the laser oscillation were demonstrated in the ZnS:Cr waveguide structures. Although the lasing is unstable as yet, these results lay the foundations of a new direction in laser physics aimed at creation of electrically pumped lasers by dint of impact excitation. Published results concerning various aspects of ZnS:Cr and ZnSe:Cr thin films and waveguide structures as promising electrically pumped laser media are reviewed. The causes of the instability of the laser oscillation and means of improving their characteristics are also considered.     

Intracavity-pumped Cr2+:ZnSe laser with ultrabroad tuning range between 1880 and 3100 nm

We obtained, what is to our knowledge, record tuning from an intracavity-pumped gain-switched Cr2+:ZnSe laser. In the experiments, a polycrystalline Cr2+:ZnSe sample with an absorption of about 43% at 1570 nm was used to minimize reabsorption losses at the lasing wavelengths below 2000 nm. By placing the gain medium inside the cavity of a pulsed KTP optical parametric oscillator (OPO) operating at 1570 nm, smooth, continuous tuning was achieved in the 1880-3100 nm range with four different sets of cavity optics. As high as 145 mW of average laser output power was obtained at 2365 nm with 1.2 W of intracavity OPO power.     

Continuous-wave broadly tunable Cr:ZnSe laser pumped by a thulium fiber laser

We describe a compact, broadly tunable, continuous-wave (cw) Cr²⁺:ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 × 10¹⁸ cm⁻³ was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF₂ prism and a single set of optics.     

Experimental Study on Intracavity SHG of a Q-Switched Tunable Cr: LiSAF Laser

In this paper, a Q-switched intracavity frequency doubling Cr: LiSAF laser is reported. The relation of laser output behaviors with input energy was studied experimentally. The second harmonic output energy of 15.6 mJ at 450.1 nm for pumping energy of 83 J, the second harmonic output energy of 16 mJ at 445.1 nm for pumping energy of 75 J, and a tunable range of 445.1 ～465.1 nm were obtained in experiments.     

All-fiber wavelength-swept laser near 2 μm

We report, for the first time to our knowledge, an all-fiber wavelength-swept Tm-doped laser based on a fiber Fabry-Perot tunable filter in the 2 μm spectral region. The laser wavelength can be continuously tuned over 200 nm from 1840 to 2040 nm in a short period of time. The demonstrated tuning speed was 12.5 μm/s with a tuning efficiency of 17.5 nm/V. The spectral linewidth of the laser was measured to be approximately 300 MHz or 0.01 cm(-1). This kind of laser can find potential applications in both high-resolution laser spectroscopy and tunable mid-IR generation via nonlinear frequency conversion.     

Experimental Study on Intracavity SHG of a Q-Switched Tunable Cr:LiSAF Laser

In this paper, a Q-switched intracavity frequency doubling Cr: LiSAF laser is reported. The relation of laser output behaviors with input energy was studied experimentally. The second harmonic output energy of 15.6 mJ at 450.1 nm for pumping energy of 83 J, the second harmonic output energy of 16 mJ at 445.1 nm for pumping energy of 75 J, and a tunable range of 445.1 ～465.1 nm were obtained in experiments.     

Stable 10 W Er:ZBLAN fiber laser operating at 2.71-2.88 μm

We have developed a diode-pumped tunable 3 μm fiber laser with a cw output power of the order of 10 W with the use of an erbium-doped ZBLAN fiber. A tunability range of 110 nm (2770 to 2880 nm) with an output power between 8 and 11 W was demonstrated. As the pump power was increased, the center of the wavelength range was shifted toward longer wavelengths, but the width of the wavelength range was largely unaffected. The total tunability range for various pump power levels was 170 nm (2710 to 2880 nm). To our knowledge, this is the highest performance (output power and tunability) obtained from a tunable 3 μm fiber laser.     

超短激光脉冲调制上转换放大

在超短激光脉冲倍频过程中，由于调制不稳定性而产生多色圆锥辐射. 在多色圆锥辐射的任 意方向上同步注入一束宽带种子光，可以得到相应频率的调制上转换放大. 放大的光脉冲的 中心波长在500 nm时单脉冲能量最大可至150 μJ并且具有60 nm的频谱宽度. 通过改变种子 光的入射角度而实现上转换放大中心波长的连续调谐，范围约为290 nm. 关键词： 调制上转换放大 调制不稳定性 多色圆锥辐射