连续腔内倍频拉曼激光器的归一化理论解析

腔内倍频拉曼激光器是获得黄光激光光源的重要途径,目前尚未有直接的表达式描述连续腔内倍频激光器的功率输出对抽运和激光器参数的赖关系。以速率方程为基础,对腔内倍频连续拉曼激光器的理论模型进行归一化处理,得到平面波近似下连续腔内倍频拉曼激光器的归一化速率方程组。对此方程组进行求解,得到描述激光器输出的表达式各变量以及参量与输出变量之间的归一化表达式,根据表达式获得了描述激光器运行的理论曲线。     

Stokes-Anti-Stokes Iterative Resonator Method for Modeling Raman Lasers

We present a novel modeling method to describe the steady-state and transient regimes of a continuous-wave pumped Raman laser emitting both Stokes and anti-Stokes photons. Our so-called "Stokes-anti-Stokes iterative resonator method" evaluates for every half round-trip time the longitudinal distribution of the intracavity pump, Stokes and anti-Stokes fields propagating in forward and backward directions. Although this Stokes-anti-Stokes iterative resonator method is widely applicable, its most important asset resides in its ability to accurately model Raman lasers that feature cavity enhancement of the pump power and that emit both Stokes and anti-Stokes photons. Important here is that our modeling method correctly incorporates the longitudinal intracavity field distributions, the generation of anti-Stokes photons, and the interference effects between incident and intracavity pump fields, and that it describes not only the lasers' steady-state operation but also their transient characteristics. We demonstrate for both a hydrogen-based and a silicon-based Raman laser with pump cavity enhancement that the Stokes-anti-Stokes iterative resonator method performs better than the modeling methods presently used for these categories of Raman lasers. Finally, to demonstrate the potentialities of our modeling method, we numerically simulate, for the first time according to our knowledge, the anti-Stokes emission generated by a silicon-based Raman laser     

1.54μm腔内喇曼激光器实验研究

喇曼激光器作为一种将基波频率转换成斯托克斯频率的高量子效率转换装置,实现激光频率的扩展,日益受到人们的重视。腔外喇曼频移过程,国内、外都有过充分的研究,而腔内喇曼频移激光器投入实际使用则只是近几年才发展起来。本文报道了脉冲Nd:YAG1.06μm基频经高压甲烷气体在封闭式激光腔内喇曼频移成1.54μm一阶斯托克斯脉冲输出的实验研究结果。     

An intracavity 16-μm Raman laser: a theoretical investigation

A theoretical model describing the dynamics of an intracavity 16-μm laser was developed. This laser consists of a TEA-CO₂ laser with an intracavity Raman cell. The Raman medium could be either hydrogen or deuterium, depending on the required wavelength. Stokes, anti-Stokes, and pump coupling were considered. Output energies as well as pulse shapes were calculated. Optimum output coupling was also determined. The model predicted that the intracavity Raman laser could be a viable alternative to a conventional multipass Raman cell for generating intense 16-μm pulses     

Far-infrared raman laser with high intensity laser pumping

Theoretical and experimental results are presented for a pulsed far-infrared (FIR) molecular gas laser with high intensity laser pumping. In these FIR lasers, high intensity pumping is found to produce stimulated Raman emission at very large offsets (up to 30 GHz) from resonance with the intermediate state. A theoretical, density matrix model is developed for these lasers to account for simultaneous Raman emission on rotational levels in the ground and excited vibrational states (double Raman resonance). This theoretical approach is necessary in the case of off-resonant, high intensity pumping. Theory predicts the FIR emission frequency, the FIR laser gain, and the pump threshold intensity as a function of pump laser frequency. Experimental results are obtained onP-,Q-, andR-branch transitions in¹²CH3F and¹³CH3F using a single-mode, grating tuned CO2TEA pump laser with an intensity of up to 40 MW/cm². Good agreement is obtained between theory and experiment for the observed values of FIR emission frequency and pump threshold intensity. These results indicate that a widely tunable (150-1200 mum), pulsed FIR CH3F laser could be constructed with a tunable, multiatmospheric CO2pump laser of modest power (about 2-5 MW).     

Theory of intracavity frequency doubling in passively mode-lockedfemtosecond lasers

The authors construct a quantitative theoretical model of an intracavity frequency-doubled and passively mode-locked laser, supported by experimental observations with a colliding pulse mode-locked femtosecond dye laser. The major findings are that for second-harmonic conversion efficiencies consistent with continuing laser operation (<5%): (1) a stable mode-locking regime always exists, although it narrows somewhat with increasing conversion efficiency; and (2) the duration of the fundamental pulses can always be preserved, even in the femtosecond time domain, by readjusting saturable gain and saturable loss under the same conditions. Both the model and observations contrast with previous studies of actively mode-locked and synchronously mode-locked lasers containing intracavity frequency-doubling crystals     

Modeling of Actively Q-Switched Intracavity Raman Lasers

The normalized space-dependent rate equations are deduced assuming the intracavity photon densities and initial population-inversion density to be of Gaussian spatial distributions in the diode-pumped actively Q-switched intracavity Raman lasers. Numerical calculations are carried out to investigate the influences of these normalized variables on the pulse parameters of the first Stokes. The rate equations under the planewave approximation are also normalized and solved numerically, and the results show the obvious discrepancies from those of the space-dependent theory. The spontaneous Raman scattering factor in rate equations are deduced in detail for the first time, and the oscillating threshold of the first Stokes inside the resonator is deduced analytically. A sample calculation for an actively Q-switched self-Raman laser is presented to demonstrate the use of the curves and related formulas.     

Theoretical characterization of Raman oscillation with intracavitypumping of fiber lasers

Theoretical results relating to the generation of continuous-wave (CW) output from fiber lasers that are internally pumped with light generated from the stimulated Raman effect are presented. This investigation establishes the important fiber and resonator parameters, such as the fiber length and glass composition, dopant concentration, and pump power required to realize this new form of fiber laser arrangement. Three examples are studied: the Ho³⁺-doped silica fiber laser that is pumped at a wavelength of 1.15 μm, the Er ³⁺-doped silica fiber laser which is pumped at 1.48 μm and, the Tm³⁺-doped silica fiber laser which Is pumped at 1.625 μm. These three examples cover first Stokes pumping, second Stokes pumping, and first Stokes pumping with direct dopant absorption of the pump light, respectively. The simulations involve the use of simple numerical models comprising the spatially dependent field propagation equations (under the slowly varying field approximation) and the rate equations for the population densities. It is established that intracavity Raman pumping of fiber lasers with first Stokes radiation is efficient when the losses at the pump, Stokes and laser wavelengths are kept low (<10 dB/km). It is also established that second Stokes pumping is, even with direct absorption of the pump light, theoretically quite efficient and, as a result, the Er³⁺-doped silica fiber laser which is pumped with second Stokes radiation at 1.48 μm may provide the best demonstration of intracavity Raman pumping     

Injection locking of CW ring dye lasers

An analytical treatment of the injection locking of CW dye lasers, taking into account the Fabry-Perot enhancement of the laser cavity is presented. The analysis, restricted to the case where the injected radiation is resonant within the injected resonator, is based on a set of rate equations for the population densities and photon flux. Analytical solutions are found which allow the injection threshold conditions to be easily determined, and which describe the different intracavity intensities characterizing the system. The dependence of these quantities on various parameters such as input coupler transparency, pump intensity, injected intensity, and wavelength is analyzed. These results correct, in the case of steady-state laser operation, the theoretical predictions obtained by Ganiel et al. from a model where only the field intensities were considered instead of the field amplitudes. The experimental feasibility of CW ring dye laser injection locking is discussed and the conditions for an optimum system, in terms of intracavity power are determined.     

Dynamics of Q-switched and mode-locked intracavity secondharmonic generation in a ring laser

The temporal dependence, spectral characteristics, and efficiency of a multimode Q-switched ring laser containing an intracavity second harmonic generator is described. Numerical studies show that such lasers are stable and efficient. Comparison with Q-switched lasers (not containing a second harmonic generator) demonstrates that the intracavity second harmonic generation lasers can be even more efficient than the fundamental laser due to nonlinear output coupling. General considerations for the operation of such lasers are described. Spectral characteristics of the output as a function of the gain of the active medium and the spectrum of the injected pulse are discussed. Instabilities at very high second harmonic conversion are observed     

全固态黄光激光器研究进展

黄光波段的激光在生物医学、空间目标探测和识别、激光显示、化学等领域有着广泛的应用前景,近年来人们对全固态黄光激光器进行了大量的研究.简述了全固态黄光激光器的发展历史和研究现状.对黄光激光的产生方式进行了讨论,重点介绍两种获得黄光激光的非线性光学方法:和频和受激拉曼散射效应.在和频方式的讨论中,对比分析了腔内和腔外两种和频方式.分析了三种不同技术途径的全固态拉曼黄光激光器.介绍了通过直接倍频红外激光获得黄光激光的研究情况.最后指出了全固态黄光激光器的发展方向.     

High-speed switching of monolithic arrays ofgrating-surface-emitting diode lasers

The electrooptic switching properties of injection-coupled coherent two-dimensional grating-surface-emitting (GSE) laser arrays with multiple gain sections and quantum-well active layers are discussed. Within such an array of injection-coupled GSE lasers, a single gain section can act as an intracavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient subnanosecond switching of high-power GSE laser arrays by operating only one gain section as an intracavity loss modulator     

Multiwavelength Raman fiber-ring laser based on tunable cascaded long-period fiber gratings

Multiwavelength Raman fiber lasers using intracavity tunable cascaded long-period fiber gratings (LPFGs) are discussed. The application of the cascaded LPFGs as a multichannel fiber filter for the multiple-wavelength generation is proposed and experimentally demonstrated. The characteristics of multiwavelength fiber-ring lasers can be controlled by changing the physical parameters of cascaded LPFGs such as the separation distance between the gratings, grating length, and number of gratings. The multiwavelength Raman fiber-ring laser with nine wavelength-division-multiplexing channels with 100-GHz spacing and 19 channels with 50-GHz spacing has been achieved by varying the physical parameters of cascaded LPFGs.     

Theory and operation of high-power CW and long-pulse dye lasers

A complete theoretical model for CW and long-pulse dye lasers is developed. The effects of excited singlet-state absorption of pump and laser fight and triplet absorption of pump and laser light are included. Expressions are derived for gain, actual dye transmission, and output power. Experimental work is presented to verify the theory and to obtain values of excited-state absorption cross sections for rhodamine 6G by matching experimental to theoretical curves.     

Repetition rate enhancement and mode shaping in dual-cavity stretched pulse fiber laser

A novel orthogonally polarized coupled-cavities configuration for stretched pulse fiber lasers, based on tunable birefringence, is presented. By alignment of the birefringence, we achieve envelope modulated mode patterns, which in turn are used to increase the repetition rate of the laser while maintaining the well-profiled femtosecond pulses. Experimental results and a supporting theoretical model are presented.     

Diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO/sub 4//KTP Green laser with a GaAs wafer

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency-doubled c-cut Nd:GdVO/sub 4//KTP green laser with a GaAs saturable absorber is presented. Nearly 100% modulation depth for the mode-locked green pulses has been achieved. By using the hyperbolic secant function methods and considering the influences of continuous pump rate and the stimulated radiation lifetime of the active medium, a modified rate equation model for Q-switched and mode-locked lasers was proposed. With this modified model, the theoretical calculations are in good agreement with the experimental results, and the width of the mode-locked green pulse was estimated to be about 300 ps.     

Theoretical and experimental study on the self-Raman laser with Nd:YVO/sub 4/ crystal

The intracavity photon densities and the initial population inversion density were assumed to be Gaussian distributions in the rate equations of the laser diode end-pumped actively Q-switched intracavity Raman laser. These space-dependent rate equations were solved numerically. In the experiment, an efficient self-Raman laser was realized based on the multifunctional Nd:YVO/sub 4/ laser crystal with the acoustooptic Q-switch. The output, temporal, and spectral characteristics of the self-Raman laser were investigated experimentally in detail. The performance of the self-Raman laser was studied numerically, and the theoretical results showed the main trends of the intracavity Raman laser, which are in agreement with the experimental ones.     

Highly efficient Raman frequency converter with strontium tungstate crystal

A highly efficient extracavity Raman laser pumped by the infrared nanosecond laser pulses is presented utilizing the recently recommended Raman medium-strontium tungstate crystal (SrWO/sub 4/). The maximum conversion efficiency of the first and second Stokes pulses both reached about 50%, and the maximum total conversion efficiency of the first and second Stokes was obtained to be 70% in the experiment. The conversion efficiency dependence on the polarization and the temporal characteristics of the Stokes and pump pulses were also studied. A theoretical model for the solid-state extracavity Raman laser was established based on the radiation transfer equations describing stimulated Raman scattering processes, and solved numerically. This model can accurately predict the energy transfer dynamics observed in extracavity Raman lasers.     

Active harmonic modelocking of an erbium fiber laser withintracavity Fabry-Perot filters

We present both experimental and theoretical investigations of the operation of a harmonically modelocked erbium fiber ring laser stabilized by an intracavity bit-rate etalon. Our model analyzes the effects of cavity components and operating parameters on laser stability and output pulse characteristics. The model predicts the output pulsewidth variation with laser cavity parameters such as cavity length, dispersion, and finesse of intracavity Fabry-Perot etalons. If the laser cavity length is not optimized, a maximum 50% increase in pulsewidth can occur at 5 Gb/s pulse rate. A repetition rate etalon with a finesse of 50 is sufficient to provide a side-mode suppression ratio of over 50 dB in the laser output. We also discuss how detuning from the optimal modulation frequency increases the excess noise that affects the laser stability. The theory predicts a maximum detuning range of ±100 kHz, which agrees with the experimental observations. These theoretical results can guide the design of similar lasers over a wide range of operating parameters     

LD纵向泵浦腔内倍频激光器腔参数的选择

从理论上研究了在一定长ＫＴＰ情况下ＬＤ纵向泵浦Ｎｄ：ＹＶＯ４／ＫＴＰ腔内倍频激光器的绿光输出与腔长、输出镜曲率半径及泵浦光斑半径等参数的关系。根据分析选择了一组实验参数，在入射泵浦功率为６６８．７ｍｗ时获得了１５３．９ｍｗ的绿光输出，光一光转换效率为２３％。将实验结果与理论计算值进行了比较，两者符合较好。