全固态紫外激光器研究

本文报道了具有增强谐振倍频腔的全固态紫外激光器研究半导体激光二极管(LD)泵浦的Nd:YVO₄激光晶体产生波长为1064nm的近红外光,腔内倍频输出波长为532nm的绿光,再送入增强谐振腔进行四倍频,输出波长为266nm的深紫外激光产生深紫外激光的基频绿光输入阈值可低到2.5mW据我们所知,这是国内首次报道的全固态紫外激光器.     

Optically-Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CH3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new far-infrared laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically-pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2-m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

Optically Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CD3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new FIR, far-infrared, laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2 m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

全固化自锁模飞秒Ti:S激光器实验研究

首次在国内系统报道了以腔内LBO倍频Nd:YVO₄激光器为泵浦源的全固化自锁模飞秒钛宝石激光器的实验结果.设计了一种热不敏腔内LBO倍频线性折叠腔结构,获得到了25.5%的光转换效率,泵浦功率为22W时得到了5.6W的基模绿光输出功率;以该激光器为泵浦源,在线性Z型腔的基础上,使用了一种能够通过改变腔内凹面聚焦镜折叠角消除象散的方法,直接由钛宝石激光器得到了脉冲宽度为22fs、功率为300mW的光脉冲.整个激光系统稳定性好,噪音明显低于Ar³⁺激光器的泵浦情况.     

激光二极管端面抽运的1.34μm Nd:YVO4平凹腔型激光器

理论上分析了端面抽运的1.34μm Nd:YVO₄平凹腔型激光器的各项参数；实验 上实现了LD端面抽运的1.34μm Nd:YVO₄平凹腔型激光器的运转. 关键词： 固体激光 4晶体')" href="#">Nd:YVO₄晶体 平凹腔     

Développement de lasers visibles pompés par diode à base de cristaux de Nd:GdCOB autodoubleurs de fréquence

We present the performances of a diode-pumped solid-state laser operating in the visible by self-frequency-doubling. A cw output power of 115 mW at 545 nm has been obtained in a stable concave–concave cavity by using a crystal of Nd:GdCa₄O(BO₃)₃ pumped by a 2 W high-brightness laser diode. In a plano–plano cavity, similar to a microchip laser, we have obtained, for the first time to our knowledge, an output power of 22 mW in the green.     

Tunable erbium-doped fiber ring laser for applications of infrared absorption spectroscopy

We fabricate a low noise erbium-doped fiber ring laser that can be continuously tuned over 102 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity with a novel cavity structure and the optimal gain medium length. As an application of this fiber ring laser, we performed the absorption spectroscopy of acetylene (¹³C₂H₂) and hydrogen cyanide (H¹³C¹⁴N) and measure the absorption spectra of more than 50 transition lines of these gases with an excellent signal to noise ratio (SNR). The pressure broadening coefficients of four acetylene transition lines are obtained using this fiber ring laser and an external cavity laser diode.     

Temporal evolution of the xenon laser pulse

An experimental investigation was made of the xenon excimer laser. Several laser cavities have been employed with excitation by electron beams of cross section (15×2) cm² and (55×4) cm² and current density 100–150 A cm^-2 injected transverse to the cavity axis. A numerical model of the xenon laser is compared with experimental results. The laser pulse width was found to be dependent on laser intensity and cavity mirrors. Early termination of the laser pulse was observed consistent with changing reflectivity of the cavity mirrors. An uncoated MgF₂ retroreflector produced a laser output of significantly longer pulse width. Quasi-cw laser action was observed.     

Operating parameter optimization of optically pumped CH3OH far-infrared laser

By solving the density matrix equations of a quantum system, the output power intensity of an optically pumped CH₃OH FIR laser (CH₃OH-OPFIRL) was calculated by means of iteration method, and the spectral characteristics were got. Base on the calculation, optimization of operating parameters including operating gas pressure, pumped power and output coupling coefficient of the CH₃OH cavity laser were systematically studied. Experimental, a series of FIR emissions of the CH₃OH cavity laser pumped by TEA-CO₂ laser with 9P(16) line were measured. The experimental results were in good agreement with theoretical calculations. The project was supported by the Special Research Foundation of Doctorate Station in University of P.R.C.     

Chirp reduction in three-cavity semiconductor laser diodes

The oscillation frequency shift ratio (OFSR) of a three-cavity coupled laser diode, which is caused by refractive index changes due to current modulation and temperature variation, has been investigated. It is found that the OFSR is significantly reduced by using a laser with an AR coated facet and a high external-mirror reflectivity, in addition to large external cavity lengths. Also, compared with an external cavity laser, the three-cavity laser has a smaller OFSR provided that the external cavities' reflectivities r₀ and r₃, are not identical (that is, r₃ > r₀). The analysis indicates that the structural parameters affect the OFSR of the three-cavity laser, which was shown to have a high longitudinal mode discrimination¹.     

Radially polarized laser beam from a Nd:YAG laser cavity with a c-cut YVO4 crystal

We demonstrate the generation of a radially polarized beam by simply inserting an undoped c-cut YVO₄ crystal into a Nd:YAG laser cavity. In a hemispherical cavity, the cylindrically symmetric, positive birefringence of the YVO₄ crystal extends the stability limit of the cavity length for an extraordinary ray (radial polarization) compared to an ordinary one (azimuthal polarization). By adjusting the cavity length, a radially polarized beam with an output power up to 1 W was selectively obtained. In addition, a higher-order transverse mode was also generated by arranging the cavity design. The method demonstrated in this paper can be readily applied to laser systems with an isotropic laser medium. PACS 42.60.Da; 42.25.Lc; 42.25.Ja     

The tuning characteristics of optically pumped fir cavity laser

Based on the quantum mechanics theory of density matrix and the principle of multiple-beam interference, the tuning characteristics of optically pumped NH₃ FIR lasers were studied. A series of metallic mesh Fabry-Perot cavity lasers with sample tubes of 10cm, 20cm and 100cm in length were constructed and operated successfully, and the FIR laser spectra of the NH₃ cavity lasers pumped by a TEA-CO₂ laser were measured. Supported by the Natural Sciences Foundation of Guangdong Province, PRC     

New N2O laser band in the 10 μm wavelength region

Fifty new laser lines have been observed in continuous emission from an N₂O laser by placing a hot N₂O absorber cell inside the laser cavity to suppress the regular laser lines. The new lines are identified as rotation-vibration transitions of the (00⁰2–10⁰1) band of N₂O.     

Mode competition and frequency locking

A theoretical study is presented of frequency locking to be observed in lasers with broad homogeneous emission lines, when the cavity losses are reduced, at a certain frequency ω₀, by placing inside the cavity a suitable element (e.g., a selectively reflecting “mirror”). Two kinds of locking effects are analyzed: i) When tuning the center frequency of the laser output ω_f towards ω₀, by means of a filter or a grating, the laser frequency becomes locked to ω₀, when |ω_f ? ω₀| reaches a critical value. ii) In the absence of frequency-selective elements, the laser oscillates only in a narrow spectral range centered at ω₀. Special emphasis is given to the role played by mode competition in these locking phenomena.     

Diffraction longitudinal multidomain structures in a layered nonlinearly absorbing medium

A method for measuring the composed phase parameter ?=Ψ₁+Ψ₂?2Ф₁ (where Ψ₁ and Ψ₂ are the phases of the mirror reflectances and Ψ₁ is the phase of the mirror transmittance) of dielectric mirrors with small absorption coefficients is proposed. This method is based on the use of the properties of a laser with a three-mirror cavity, and the mirror under study is the internal mirror of this cavity. It is shown that the value of the parameter Ψ, differing slightly from π, can be measured, and the results of the measurement are independent of the character of saturation of the laser active medium. The phase parameter was also measured for mirrors with reflectances below 0.8 by using an external method in which the interferometer with the mirror under study was placed outside of the laser cavity. It turned out that the intracavity laser method for measuring Ψ has a number of advantages and ensures an appreciably higher accuracy in measuring the parameter ε=Ψ?π than do extracavity techniques.     

双光反馈半导体激光混沌系统中外腔延时反馈特征的抑制

在一个双光反馈半导体激光混沌系统中,固定其中一个反馈腔镜(固定腔M₁)的反馈延迟时间以及反馈强度,实验研究了另一个反馈腔镜(可变腔M₂)的反馈延迟时间以及反馈强度对系统混沌输出的延时反馈特征的影响.研究结果表明:在可变腔M₂与固定腔M₁的反馈强度相等的条件下,改变M₂的腔长,当其腔长约等于(但不能严格等于)M₁的腔长或者腔长的一半时,系统将呈现较好地抑制延时反馈特征效果;当M 关键词： 半导体激光器 双光反馈 混沌输出 延时特征     

Efficient and high-power laser-diode single-end-pumped Nd：YVO4 continuous wave laser at 1342nm

A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.     

Research and application of a pocket CO2 laser in the near field

The axisymmetrical structural traveling wave cavity (ASSC) CO₂ laser is introduced based on the propagation theory of the standing wave cavity CO₂ laser. Then the propagation characteristics of the elliptically polarized Gaussian beam are studied in detail. The transforms of the coordinate were used to solve the near field distributions of the output laser beams. The numerical calculations show that the combination of the output beams in the near field can be fulfilled. The diminutive ASSC CO₂ laser can be applied into the laser gyro and the measure of the angular velocity.     

Wavelength Tuning Characteristics of a Vertival Cavity Surface Emitting Laser Diode with an External Short Cavity

The characteristics of a wavelength tunable vertical cavity surface emitting laser diode (VCSEL) with an external short cavity are analyzed, in which the oscillation wavelength can be changed over several tens of nanometers with a nearly constant optical power by slightly altering the external cavity length. Analysis is based on rate equations for the optical power and carrier density, taking the effect of carrier-induced refractive index change into consideration, together with the study of behaviors of a complex resonator. The reflection coefficient r₂ of a laser facet facing the external mirror is shown to affect notably the characteristics of wavelength tuning, optical power and carrier density for a change of the external cavity length. It is also noticed that the wavelength change for this length becomes slower with relatively larger r₂ due to an increasing contribution of the effect of carrier-induced refractive index change, within the optical gain spectrum of the laser diode.     

Effects of pressure ratio on population inversion in a DF chemical laser with concurrent lasing

A numerical simulation is presented for investigating the effects of pressure ratio of D₂ injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The chemical laser is generally used for the industrial process and manufacturing as well as the military weapon system, which requires high power characteristic of laser system rather than the others. The population inversion is absolutely needed to generate the laser beam and is non-equilibrium process. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high-power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, a fully conservative implicit method and a second order total variation diminishing (TVD) scheme are used with the finite-volume method (FVM). An 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two D₂ injector pressure cases; 192 and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the D₂ injection pressure is lower. But, the higher D₂ injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of D₂ injector increases, the maximum small signal gain in the v_1-0 transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher.