Optimization of strongly pumped fiber lasers

Backreflection of the residual pump power into the cavity, and optimization of the fiber length, may significantly improve the efficiency of a strongly pumped fiber laser. A rate equation model is introduced and studied. Examples for Yb³⁺-doped fiber lasers, with DBR mirrors at either end, show that employing such a geometry results in higher efficiency with shorter optimal fiber length. Approximate analytical and quasi-analytical expressions are shown to be in excellent agreement with the exact numerical solution of the rate equations     

Operation of erbium-doped fiber amplifiers and lasers pumped withfrequency-doubled Nd:YAG lasers

An optical amplifier consisting of an erbium-doped germanosilicate fiber optically pumped at 532 nm is described. Negligible excited-state absorption at 532 nm allows efficient pumping, enabling a gain of 34 dB at 1536 nm to be obtained for only 25 mW of pump power. The pulsed pump source produces negligible noise on the small signal if the pump repetition rate is above 10 kHz. Pulsed laser operation is achieved by pumping a Fabry-Perot erbium-doped fiber laser with a frequency-doubled Q-switched Nd:YAG laser. Pulses of 0.9-W peak power and 280-ns duration at 1.538-μm were obtained     

多点抽运双包层光纤激光器理论及数值分析

大功率双包层光纤激光器采用分布式多点抽运有利于功率扩展和输出特性的优化.采用数值模拟的方法分别计算了正向多点抽运和反向多点抽运,得出了不同抽运光反射限制和不同的光纤长度条件下抽运点数与输出功率的关系,以及不同抽运点数和不同抽运光反射限制下的光纤最佳长度,并进一步得出,多点抽运时,通过在双包层光纤内包层写入光栅的方法对抽运光进行反射限制可以大大改善光纤激光器的输出特性.这些结论对多点抽运双包层光纤激光器的结构优化具有指导意义.     

1064 nm波段泵浦掺铥光纤激光器的理论研究

文章对1064 nm波段泵浦掺铥光纤激光器进行理论分析,以获得到对实际研究有用的结论.先从理论分析计算了1064 nm泵浦掺铥光纤激光器的粒子速率方程和传输方程,并在传输方程中考虑了泵浦光和激光本征吸收影响.利用matlab软件理论模拟不同长度光纤的正反向泵浦光和激光在光纤中的分布.模拟讨论了输出功率与最佳光纤长度的关系,以及激光本征吸收系数和掺铥离子浓度对输出功率的影响.最佳光纤长度时的激光输出功率最高.考虑激光本征吸收是合理的,较小的本征吸收有较高的最大的输出功率.存在一个最佳的掺杂离子浓度使得输出功率最大.     

Optically pumped semiconductor platelet lasers

Tunable CW laser action of platelet semiconductors is reported in both mode-locked and unmode-locked configurations. The gain media are platelets of CdS, CdSe, CdSSe, and InGaAsP cooled to 85 K and longitudinally pumped by an argon-ion laser. Antireflection (AR) coating of the crystal face and external bandwidth restriction have been used to generate pulses as short as 4 ps. The pulses observed are chirped, with nontransform limited time-bandwidth products of about 1.7. The energy conversion efficiency is 20 percent into the TEM00mode, with output powers of over 10 mW from CdS.     

Optically pumped atomic thulium lasers

A thulium vapor column is irradiated with the fourth harmonic of a Nd:YAG laser at 266 nm. The near coincidence with a dipole allowed transition from ground state results in efficient optical pumping yielding 87 simultaneous superfluorescent laser transitions from 300 to 900 nm. Many of the emissions are due to inversions to the ground state of both neutral and singly ionized Tm atoms.     

Optically pumped CW dimer lasers

Bound-bound electronic transitions in simple molecules are generally suited to realize efficient multiline laser oscillation in the visible and ultraviolet spectral region. By means of optical excitation with argon and krypton lasers, CW laser oscillation could be obtained for various homonuclear diatomic (dimer) molecules such as Li2, Na2, K2, Bi2, S2, Te2, and I2, with emission of several hundred laser lines in the spectral range of about 400-1350 nm. The principles of these lasers and the general dependence of threshold and output power on temperature, pressure, length of vapor zone, and some other parameters is discussed. To achieve satisfactory CW operation, low quenching losses for the upper laser level population and a sufficiently fast relaxation of the population of the lower laser level are necessary. Under optimum operation conditions, efficiencies up to 15 percent, multiline output powers up to 400 mW, and single line-single frequency output powers up to 200 mW were achieved. These dimer lasers are three-level laser systems. In case of coherent optical excitation, two-photon or Raman-type processes contribute to the amplification process. Due to these mechanisms the forward direction is strongly favored and in a ring laser system spontaneous unidirectional oscillation is obtained. By means of a suitable three-level model, analytical and numerical calculations of gain profiles are performed and compared with experiments. These optically pumped molecular lasers are suited for various spectroscopic and kinetic investigations, for frequency standards or as simple and efficient systems to convert pump laser radiation into other spectral regions.     

New optically pumped far-infrared lasers

Ninety-seven new far-infrared (FIR) laser transitions have been observed in optically pumped ethylene glycol, dimethyl ether, formic acid, and monomethyl amine, all excited by a pulsed CO2laser.     

Optically pumped semiconductor nanowire lasers

This paper reviews our recent work on fabrication,optical characterization and lasing application of semiconductor nanowires,with brief introduction of related work from many other groups.     

LD泵浦掺镱的双包层光纤激光器的研究

本文通过数值分析对线形腔LD泵浦掺镱的双包层光纤激光器进行研究,分析了不同泵浦方式下的泵浦光、激光输出功率和增益特性在光纤中的分布。结果表明,双端非对称泵浦比较适合高功率光纤激光器。进一步又研究双端非对称泵浦输出功率与光纤长度及腔镜反射率的影响,为提高光纤激光器的输出功率提供了理论和实验依据。     

Small electrically pumped index-guided vertical-cavity lasers

High-yield, reliable electrically pumped index-guided vertical cavity lasers with diameters less than 4 microns have been fabricated using low resistance, alloyed, ring contact metallization. Existing metallization schemes used for bottom emitting vertical cavity lasers (VCLs) tend to be highly resistive, since the top metallization layer serves the dual purpose of mirror and electrical contact. This results in acceptable performance for large diameter devices, but poor performance for smaller devices that operate at higher current densities. Low resistance alloyed ring contacts have been developed for small bottom emitting VCLs that maintain the required optical properties while dramatically improving the electrical properties     

Tunable optically pumped GaAs-GaAlAs distributed-feedback lasers

A new wavelength tuning effect in optically pumped GaAs-GaAlAs distributed-feedback lasers is presented. It is shown that it is possible to tune the emitted wavelength of the laser by changing the angle between the direction of the pumping line and the normal to the grooves of the periodic structure. The results could be applied to injection DFB lasers to achieve frequency multiplexing for optical communications.     

LD泵浦全固态紫外激光器

研究总结了激光二极管泵浦全固态紫外激光器的最新进展,为紫外激光器的研究提供了参考依据.主要从工作物质,非线性频率变换晶体和腔型结构等三个方面对激光二极管泵浦全固态紫外激光产生的关键技术进行了讨论,并简述其发展历史、现状及未来发展方向.     

Optically pumped submillimeter wave semiconductor lasers

An optically pumped multiple quantum well (MQW) submillimeter wave (SMMW) laser is proposed and designed. The laser can potentially generate significant power in the far-infrared regime. It is based on pumping of a series of InGaAs-GaAs quantum wells with a CO₂ laser. The excited electrons created by the pumping process tunnel into the upper of two subband states in an AlGaAs-GaAs quantum well grown in series with the absorption wells, and thereby give rise to a population inversion between these two states which are tuned to the SMMW frequency desired. The authors present the key concepts of the new device and some designed device structures     

Radio frequency pumped mid-infrared waveguide lasers

RF discharge waveguide laser technology has been extended from the 10.6 μm CO2laser to include 2.7 μm HF, 3.8 μm DF, and several rare gas mid-infrared lasers. The maximum achieved electrical efficiencies of 5.3 and 4.0 percent were demonstrated in pulsed HF and DF systems, respectively. These, as well as several low efficiency rare gas lasers were demonstrated in a 20 cm gain length device. The output power and spectral distribution were determined as a function of the gas composition, pressure, velocity, and the RF power, pulse length, and repetition rate.     

Instabilities in optically pumped infrared lasers

The unstable emission of an optically pumped FIR gas laser is theoretically analysed through numerical resolution of the associated Maxwell-Bloch equations. The instability domain in the main control parameters space is determined and an example of chaotic behaviour is examined.     

Theory of optically pumped submillimeter lasers

Theoretical models of the operating characteristics of both pulsed and CW optically pumped submillimeter (SMM) lasers are reviewed. The SMM laser gain is discussed for both pressure and Doppler broadened transitions. A review is given of expressions for SMM laser gain based on quantum mechanical calculations in a three-level molecular system.     

XeCl激光泵浦的ns染料激光器

报道了以XeCl准分子激光作泵浦源,通过所谓的“控制腔瞬态过程”的方法,直接获得ns染料激光脉冲的实验结果。与N_2光泵浦比较,XeCl激光泵浦可得到更短波长和更高阈值系统的激光振荡。     

Stability of single-mode optically pumped lasers

We study mode competition in optically pumped lasers with one active laser line. The stability of single-mode operation under one mode pumping (both fields arbitrarily intense) is determined by calculating the saturated laser gain using either a mono- or bichromatic probe. The probe spectra differ dramatically from the single-mode, intense field gain curves occasionally exploited in this context in earlier works. Some features in the spectra are interpreted with the dressed atom picture. The mathematically simpler single probe gain is shown to be a good approximation for large mode spacings. When the strong field induced Rabi flipping is comparable to the mode spacing, however, a bichromatic probe containing two frequencies which are symmetric with respect to the intense mode is usually needed. Typical mono- and bichromatic probe spectra are discussed and parameter regions are explored which give stable single-mode operation. The results are also relevant in general laser instability studies: some aspects due to the strong field induced coherences will be pointed out.