半导体激光器谱宽的测量研究

本文从范德玻尔(van der Pol)方程出发,导出了描述延迟自差拍法谱宽测量的公式。讨论了各结构参数对测量的影响。报道了用该法对单频半导体激光器测量的一些结果。     

Theory of spectral linewidth of external cavity semiconductor lasers

A new formula of the spectral linewidth of external cavity semiconductor lasers is proposed, with which linewidth narrowing with the optical feedback is discussed. It is shown that in the limit of large external cavity length, the linewidth caused by the phase diffusion due to spontaneously emitted photons becomes dominant and the linewidth decreases proportionally to the inverse of the external cavity length.     

Natural linewidth of semiconductor lasers

A formula is given for the natural linewidth of high-gain lasers, which is applicable to arbitrary three-dimensional geometries. This formula agrees with Petermann's result for lasers with transversely inhomogeneous gains (K-factor) and with previous results for the effect of small mirror reflectivities. It does not agree with the Schawlow-Townes (ST) formula used by most authors in evaluating the ?=?nr/?ni factor of conventional semiconductor lasers. The difference between the two formulas is significant when the mirror power reflectivity is less than about 0.6. Furthermore, the modified formula gives directly the linewidth of lasers coupled to long external cavities. Saturation effects, however, are neglected in this letter.     

Narrow spectral linewidth characteristics of monolithic integrated-passive-cavity InGaAsP/InP semiconductor lasers

The spectral linewidth of 1.3 ?m monolithic integrated-passive-cavity (IPC) semiconductor laser is measured by a delayed self-heterodyne technique. It is found that the line-width is narrowed when longitudinal submode is suppressed. The narrowest linewidth obtained so far is 900 kHz at 6 mW output power.     

Reduction of dynamic linewidth in single-frequency semiconductor lasers

Carrier density oscillations and frequency chirping of pulse code modulated single frequency semiconductor lasers are shown to be greatly reduced by use of a small current step in the leading edge of the drive pulse. For a 100 km single mode fibre link the dispersion power penalty at 1.55 ?m resulting from dynamic line broadening is predicted to be reduced from 3.7 to 1.0 dB by use of the modified current pulse.     

Factors limiting the spectral linewidth of CPM-MQW-DFB lasers

A spectral linewidth of 56 kHz is achieved by a CPM-MQW-DFB (corrugation-pitch-modulated multiquantum-well distributed feedback) laser at an output power of 25 mW. To separate effects of the white noise and 1/f noise in limiting the linewidth, the authors measured the delayed-heterodyne lineshape by using a short delay-fiber. The minimum spectral linewidth is shown to be limited by white noise     

Theory for the spectral linewidth of passive-coupled-cavitysemiconductor lasers

A simple expression for the spectral linewidth of passive-coupled-cavity (PCC) semiconductor lasers is presented. Experimentally observed linewidth narrowing and periodic variation of the linewidth as functions of the injection current and the gap between the active cavity (laser) and the passive cavity (graded index, or GRIN rod) can be satisfactorily explained by this formula     

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.     

Measured spectral linewidth of variable-gap cleaved-coupled-cavity lasers

A variable-airgap 1.3 ?m C3 semiconductor laser with the gap width set for optimum mode-suppression ratio (5000:1) has been used to achieve a measured linewidth of only 1 MHz at 3 mW power output and 250 kHz at 10 mW.     

半导体激光器线宽展宽因数的测量

光反馈自混合干涉技术是一种新出现的有别于传统双光束干涉的测试技术.文章基于此技术对半导体激光器进行线宽展宽因数的测量,以激光器HL7851G为对象进行了大量的实验,实验结果与线宽测量法基本一致,相对误差只有3.22%.相比线宽测量法,光反馈自混合法具有成本低、精度高的优点,是一种更加简洁有效的测量方法.     

Minimization of the linewidth enhancement factor in compressivelystrained semiconductor lasers

A comprehensive model for the optical response of a semiconductor quantum well, including valence subband mixing and many-body effects, is used to theoretically investigate means of minimizing the linewidth enhancement factor. The effects of well width and compressive strain are analyzed, and the contribution of many-body effects evaluated. Compressive strain in narrow quantum wells generally leads to reduction of the linewidth enhancement factor at gain peak. In addition, many-body effects, particularly bandgap renormalization, admit the possibility that by small detuning to below the gain peak position, a zero value is possible     

Tunable DFB lasers with ultra-narrow spectral linewidth

A spectral linewidth of less than 98 kHz was achieved in three-section corrugation-pitch-modulated multiquantum-well distributed feedback (CPM-MQW-DFB) lasers over a tuning range of 1.3 nm, while maintaining a constant output power of 10 mW.<>     

Coupled phase-shift distributed-feedback semiconductor lasers fornarrow linewidth operation

Mode properties of a coupled phase-shift distributed-feedback (DFB) structure are analyzed and the feasibility of narrow-linewidth emission is shown theoretically. The structure consists of a multiple number of phase-shift DFB laser units which are arranged in tandem and coupled with each other through additional phase shift of corrugation. Optimum structure parameters were determined for two coupled laser units so that the frequency detuning is zero and the mode pattern is the flattest. The mode analysis shows that the intensity distribution is flatter and the normalized coupling constant can be larger than those for the conventional DFB laser with a single phase shift. This indicates that the cavity length can be extended with less influence from the longitudinal spatial hole burning effect     

A tool to calculate the linewidth of complicated semiconductor lasers

A theory of the low-frequency phase fluctuations in the output of a semiconductor laser due to spontaneous emission is developed. The theory can be used as a tool to numerically calculate the linewidth of complicated laser structures, e.g., by use of the transfer matrix formulation. The results for the single Fabry-Perot laser are shown to be in exact agreement with the most accurate treatments published so far. Results are then presented for both DFB and F-P lasers with external optical feedback showing how the linewidth varies with the threshold gain, with the coupling coefficient, and with the external feedback conditions.     

Multimode synchronization and communication using unidirectionally coupled semiconductor lasers

We study numerically the synchronization of two multimode semiconductor lasers unidirectionally coupled in an open-loop configuration, focusing on the comparison with the results obtained in the single-mode case. Anticipative and isochronous synchronization, and their range of validity, are analyzed from the point of view of the total lasing output, and the synchronization between individual modes is studied. Selective injection is also examined and compared with global injection. In light of these results, message encoding and decoding via multimode synchronization is analyzed.     

An analysis of the linewidth and spectral behavior of DBR lasers

Using recently developed techniques for calculating the linewidths of lasers with arbitrary external feedback, we demonstrate that DBR lasers with long grating lengths can exhibit sharply reduced linewidths. We also discuss several effects of the dependence of the refractive index on carrier density such as the large sensitivity of the linewidth and threshold current to the roundtrip phase change in the active region. Such linewidth and threshold variations are especially pronounced for long grating lengths.     

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.<>     

The influence of resonator structure on the linewidth enhancementfactor of semiconductor lasers

The phenomenon of intensity-phase coupling in semiconductor lasers is studied in the linear regime in terms of an effective linewidth enhancement factor. The circumstances under which the longitudinal laser structure of a distributed feedback laser may influence this coupling are determined. For the case of uniform gain and carrier density no effect is expected from a periodic or quasi-periodic corrugation. However, when the gain layer is corrugated or a periodic gain is otherwise implemented, the influence may be considerable. It is shown that the degree of gain coupling between right- and left-travelling waves and the specific mechanism by which variations in the carrier density influence this coupling are of key importance. It is found that depending on the degree and nature of the gain coupling the effective linewidth enhancement factor may be considerably reduced or enhanced     

Intensity dependence of the linewidth enhancement factor and itsimplications for semiconductor lasers

The linewidth enhancement factor is shown to become intensity dependent when the intraband relaxation effects responsible for nonlinear gain and index changes are incorporated in the theory of semiconductor lasers. The intensity dependence of the linewidth enhancement factor influences many laser characteristics such as the frequency chirp, the modulation response, the injection-locking range, and the phase noise. In particular, it leads to a power-independent contribution to the laser linewidth. Furthermore, for semiconductor lasers detuned to operate away from the gain peak, the nonlinear index changes can even lead to a rebroadening of the laser linewidth at high-output powers