固体Raman激光器与OPO激光器比较

综述了近5年来固体Raman激光器和光参量振荡(OPO)激光器的发展情况,并对Raman激光器和OPO激光器在工作原理、晶体材料方面进行了比较。Raman激光器在光束质量、光路稳定方面存在优势,而OPO激光器调谐范围大,输出功率高。最后对固体Raman激光器和OPO激光器发展前景进行了简要介绍。     

Novel polarisation phenomena on anisotropic multimoded fibres

The lowest-order modes of multimoded fibres composed of birefringent material can differ radically from the familiar modes of multimoded isotropic fibres. In general, the modal fields are neither uniformly polarised nor circularly symmetric as they would be on circularly symmetric isotropic fibres that are weakly guiding. Thus multimoded anisotropic fibres can exhibit dramatic polarisation effects which may have important practical applications.     

直流交流辨

首先指出现行电路原理教材中对直流和交流存在不同的定义,然后用3个例子说明现行定义的不足.在讨论字面含义和工程定义的优劣之后,给出了适合在电路原理课程中讲授直流和交流概念的方法.     

Comparison between lasers isolated by oxygen implantation and SiO2isolated stripe lasers

GaAs/GaAlAs DH lasers isolated by an SiO2layer on top of the p-contacting layer are compared to DH lasers in which the isolation is maintained by an isolating the O+ -implanted layer within the n+- substrate. Measurements were performed on four O+ isolated lasers and five SiO2isolated lasers with the same composition and thickness of active and upper confinement layers. Threshold currents of both groups were very similar, whereas the O+ -implanted lasers showed superior thermal resistances by a factor of 2. Thermal resistances were measured by the shift of the lasing spectra with power dissipation.     

Interactions between closely coupled GaAs injection lasers

Interaction effects between injection lasers have been experimentally studied at 2°K and 77°K under pulse conditions in a single block configuration which permits close optical coupling between the lasers. This close coupling made previously reported effects an order of magnitude more prominent and revealed a new effect. The reduction of the threshold current of one laser by the influence of the coherent beam of a second laser by as much as a factor five has been observed. With respect to the quenching of one laser by a second laser, a quenching ratio (defined as the ratio of the quenched power to the quenching power) of 0.7 was obtained. A new effect observed was the reduction of the threshold current of one laser by the influence of the spontaneous emission from a second laser. A reduction of 10 per cent is typical for this effect. A qualitative discussion treating the two lasers as one optical cavity is given to incorporate these effects into one coherent picture. Logical device applications are also discussed.     

Optical coupling between single-mode semiconductor lasers and strip waveguides

This analysis describes the optimum conditions for coupling a single-mode semiconductor laser to a single-mode strip waveguide, when both the laser and the waveguide have asymmetric optical beam profiles. The outputs are approximated by two Gaussian fields. Two waveguide cases are treated: 1) the case where the two orthogonal waveguide waists are independent and 2) where the ratio of these waists is fixed. The effect on the coupling efficiency of a spherical surface on the waveguide input face is discussed. The results demonstrate the importance of coupling in the laser far-field and indicate the advantage of having relatively large waveguide modes. An intrinsic minimum in the optimum coupling efficiency was found to exist in the near-field for asymmetric laser/waveguide systems. Expressions describing the optimum waveguide waists and the focal length of the lensed waveguide are given for the waveguide parameters that yield the best coupling conditions.     

激光与分子相互作用制备量子态

激光与三能级分子相互作用时分子的状态依赖于激光的位相和振幅,针对具体模型制备具有确定测量几率的量子态     

Correlation between linewidth rebroadening and low-frequency RIN enhancement in semiconductor lasers

The observed correlation between the linewidth rebroadening and the low-frequency relative-intensity noise (RIN) enhancement at high operating power in nearly-singlemode semiconductor lasers is explained by using the two-mode rate equations which include both the self- and cross-saturation contributions to the nonlinear gain.<>     

Vertical-external-cavity surface-emitting lasers and quantum dot lasers

The use of cavity to manipulate photon emission of quantum dots (QDs) has been opening unprecedented opportunities for realizing quantum functional nanophotonic devices and quantum information devices....     

The relationship between optical guiding and the relative phase infree-electron lasers

The relative phase in this case is defined as the shift in the wavenumber from the vacuum value integrated over the interaction length. The relative phase is studied from the standpoint of the linear stability analysis in both the high- and low-gain regimes, and the qualitative implications in each of these regimes of the relative phase on the refractive guiding of the signal are identical. Specifically, the relative phase is found to be negative at the low-frequency end of the gain band. The relative phase increases with increasing frequency over this band until it turns positive at a frequency approximately 10% below the frequency of peak gain. Thus optical guiding is indicated over a large portion, but not all, of the gain band. The specific example of interest involves the low-gain regime prior to saturation. In this case, it is shown that the analytic result is in substantial agreement with the calculation of the relative phase     

A comparative evaluation between internal and external polarization modulation of lasers

A comparison is made between internal polarization modulation (IPM) (or coupling modulation) and external polarization modulation (EPM). This is done for the case of maximum-available laser signal power output when both bias and drive voltages are optimized, as well as for the case of a small fixed drive voltage but optimized bias conditions. Signal-to-noise ratio and efficiency is also considered. Calculations were made without recourse to small-signal theory. Results reveal the conditions of laser gain and modulator loss under which IPM is advantageous.     

半导体DH条形激光器的瞬态稳定性与稳态稳定性的关系

从实验上研究了GaAs-Al_xGa_(1-x)AsDH条形激光器的稳态束腰、束宽和激光功率随电流变化的规律与瞬态自脉动的关系。随着稳态注入电流的变化,激光器的垂直束腰位置都在镜面上,其束宽不变;不管水平束腰位置是否有变化,水平束腰宽有明显变化时,其瞬态往往出现自脉动,而出现自脉动的电流范围往往在光功率特性的A、B扭折之间。     

半导体激光器阈值条件与横模的关系

本文用平板波导模型的电磁波理论解析地导出了半导体激光器的阈值条件.发现TE模和TM模的阈值条件有不同的表示式.与通常采用的公式相比,这里导出的公式中出现一项修正因子,它可以用锯齿波的观点来解释.     

Comparison of linewidth enhancement factor between p-doped and undoped quantum-dot lasers

The optical linewidth enhancement factor (LEF) of a p-doped quantum-dot (QD) laser is measured below threshold and compared with a theoretical calculation. The optical gain, refractive index, and LEF are well matched with our theoretical model when the thermal effect is isolated by an additional pulse current measurement of the LEF. We also theoretically calculate the LEF of an undoped QD Fabry-Pe/spl acute/rot (FP) laser assuming that the structure of the undoped FP QD laser is the same as that of the p-doped QD FP laser except the p-type doping. The changes in modal gain and refractive index due to the respective QD ground and excited states are calculated. Based on the theoretical results, we show that the LEF of the p-doped QD laser is smaller than that of the undoped QD laser due to the reduced transparency carrier density.     

Relation between the cavity detuning and the output opticalintensity in free-electron lasers

The authors use a simple model of saturation in free-electron lasers operating with pulsed beams to study the intensity growth as a function of the cavity mismatch and of the coupling parameter. In spite of the simplicity of the model, the dependence of the intracavity power, as a function of the cavity detuning, is reproduced remarkably well. It is also pointed out that an enhancement of the optical power is obtained by adjusting the cavity length while the optical signal grows. The problem is analyzed qualitatively and realization schemes are proposed     

Comparison between epi-down and epi-up bonded high-power single-mode 980-nm semiconductor lasers

Epi-down and epi-up bonded high-power single-mode 980-nm lasers have been studied in terms of bonding process, thermal behavior, optical performances, and long-term laser reliability. We demonstrated that epi-down bonding can offer lower thermal resistance and improved optical performance without degrading the long-term laser reliability. An optical power of 630 mW was obtained for the first time from an epi-down bonded 980-nm pump module. Our studies have shown that epi-down bonding of single-mode 980-nm lasers can reduce junction temperature and thermal resistance by up to 30%. Experimental measurements showed over 20% in thermal rollover power improvement and over 25% reduction in wavelength shift versus current in epi-down mounted lasers compared to epi-up mounted lasers. Lifetime test over 14 000 h at 500 mA and 80/spl deg/C of the epi-down bonded lasers is reported for the first time.     

Electrical and optical interactions between integrated InGaAsP/InPDFB lasers and electroabsorption modulators

Electrical and optical interactions occurring in InGaAsP/InP integrated light sources composed of DFB lasers and electroabsorption modulators have been studied. Static measurements indicated that an isolation resistance between the laser and the modulator should be as large as 100 kΩ or more in order to reduce a lasing wavelength shift associated with biasing the modulator. The useful guided light out of the modulator was about 1-2 percent of the laser output. At high frequency modulation, asymmetric sidebands were observed in dynamic spectra measured at the modulator facet, which were caused by additional modulation of the laser part. Such additional modulation was relatively large at the relaxation oscillation frequency of the laser, but it was reduced by connecting an RF bypass condenser in parallel to the laser diode and by depositing an antireflection coating at the modulator facet. After eliminating the additional modulation, an integrated device showed a high frequency response of 5.7-GHz 3-dB bandwidth and a small linewidth enhancement factor of α=0.8     

Electronic control of the difference frequency between two semiconductor lasers

A method for controlling the difference frequency between two semiconductor lasers has been developed. The beat frequency is directly measured and current feedback applied to one laser to control this frequency. Stability to plus or minus 10 MHz was achieved. Applications include coherent optical communication systems.     

Phase correlation between longitudinal modes in semiconductor self-pulsating DBR lasers

Phase correlation leading to self-pulsation (SP) in semiconductor distributed Bragg reflector (DBR) lasers is investigated experimentally and theoretically. Under proper biasing conditions, the laser oscillates with three main modes and we observe that each two-modes beating provides SP with identical spectral linewidth. Under the same operating conditions, the measured spectral linewidths of the beating modes are much larger than the linewidth of the self-pulsating signal. These results demonstrate the natural occurrence of passive mode-locking (PML) and phase correlation in semiconductor DBR lasers. A model based on multimode coupled-wave rate equations, including four-wave mixing (FWM), is developed to describe PML and SP in the gain region of the laser cavity. This model demonstrates that the existence of phase correlation between longitudinal modes is due to FWM.