Analysis of the frequency noise of tunable multisection DBR lasers

A theoretical analysis is performed of the frequency noise in tunable two- and three-section distributed Bragg reflector (DBR) laser diodes (LDs), taking into account the nonlinear gain compression effect. For a two-section DBR LD the frequency noise is shown to depend significantly on the tuning current, particularly at low frequencies (below the gigahertz range) and for low and moderate values of the grating coupling coefficient. For high values of this coefficient the tuning dependence is generally negligible when the tuning is performed only through the DBR section, but it becomes significant when using the phase control current in a three-section device. It is shown that the enhancement factor for the spontaneous emission rate due to the longitudinal field dependence increases significantly with tuning for low values of the grating coupling coefficient     

RIN in multisection MQW-DBR lasers

The relative intensity noise (RIN) of both a two-section and a three-section tunable multiple-quantum-well distributed-Bragg-reflector (MQW-DBR) laser operating at 1.53 μm is discussed. It is found that the RIN can be modeled using a single-mode rate equation, which neglects the frequency dependence of the Bragg reflector, and that the RIN is independent of tuning current for fixed output power     

Tunability of multisection DFB lasers

Using a comprehensive multisection model taking into account spatial hole burning, we study the stability and tunability of various multielectrode DFB lasers. For each structure, we determine the emission wavelength, the output power and the spectrum as a function of the injected currents and find a good agreement with experimental results. For the first time, different structures are examined with the same model, leading to fruitful comparisons     

1.55 ?m multisection ridge lasers

A new 1.55 ?m wavelength GaInAsP laser is described: the multisection ridge laser. Pulsed thresholds were typically 40?80 mA. CW thresholds were comparable. The lowest measured CW threshold was 38 mA at 12°C. The laser operated stably in a single longitudinal mode (spurious modes down by ?16 dB) under fast pulse modulation with a prebias below threshold. Theoretical results based on a waveguide scattering theory are in qualitative agreement with the experimental results.     

Theory of spontaneous emission noise in multisection semiconductor lasers

Calculations of spontaneous emission noise in semiconductor lasers are mainly based on a fundamental theory developed by Henry in 1986, which is useful for simple systems, together with a formulation in terms of transfer matrices by Makino and others, which facilitates application of the theory to more complicated multisection systems. The aim of this review is to present a unified account of this theoretical work in a transparent form intended to encourage its further use in complex systems. The opportunity is taken to strengthen the existing theory by including the effects of differing optical wave vectors in different sections and the consequent reflections at interfaces, which are important in some applications. Sample calculations are presented for a range of systems with one, two, three, and four sections and the predictions compared with other theoretical and experimental results.     

Single-frequency tunable semiconductor lasers

Work on single-frequency tunable-wavelength semiconductor lasers with an external cavity based on fiber Bragg gratings formed in a single-mode optical fiber is reported. Methods for discrete and continuous tuning of the emission wavelength are considered. The described lasers emit dynamically stable radiation with a narrow linewidth (10 kHz) in the wavelength range of 635–1650 nm.     

A correct single-mode photon rate equation for multisection lasers

It is shown that not the photon number but photon number divided by the square root of the excess factor of spontaneous emission must be used in the photon rate equation for single-mode lasers when the longitudinal field distribution changes with time. The importance of using the correct dynamic quantity is illustrated with two examples.     

可调谐激光器波长控制

文章介绍了可调谐激光器的波长调节及稳定控制的设计方法,并通过试验验证了其可行性.该设计由温度控制、偏置电流控制及锁波电路3部分组成,温度控制粗调波长,偏置电流控制微调波长,而锁波电路主要是针对外界温度发生变化时提供反馈.它适用于温度控制型分布反馈式 (DFB)可调谐激光器的外围电路设计.     

可调谐电子振动的固体激光器

离子晶体中掺入过镀金属离子的电子振动激光器，是一类新型的可调谐高功率红外固体激光器，其激光波段可望复盖0．5μm-5μm的光谱区。本文综述了这类激光器的发展近况，分析讨论了这类激光器及激光晶体材料的光电特性，并对今后发展的可能趋向作一评述。     

Synchronization properties of two coupled multisection semiconductor lasers emitting chaotic light

We present numerical simulations describing the dynamics of two multisection semiconductor lasers emitting in a chaotic regime coupled in a master-slave configuration. By changing the current of the passive section of the master laser, we observe a change in the maximum correlation between the outputs of the two systems. These devices are promising candidates for on-off phase-shift keying encryption.     

微电机械系统使光通讯用可调谐激光器成为可能

动态重组的下一代光纤通讯系统要求配置能将信号传输到任意波分复用通道，并能在通道中实现转换的波长可调谐激光器。目前世界各国科学家积极投入此项研究工作，正在考虑各种方案以实现工作稳定、高效率和廉价的可调谐激光器，其中就包括采用悬臂式微电子机     

Monolithically integrated tunable laterally coupleddistributed-feedback lasers

A new method for fabrication of tunable InGaAsP-InP single-mode lasers without epitaxial overgrowth is reported. These devices show the advantage of a considerably simplified fabrication process compared to conventional tunable laser types. The lasers comprise an active Bragg reflector integrated with an uncorrugated separately pumped gain region. By adjusting the current through the Bragg reflector, the wavelength can be tuned between 1590.8 and 1595.2 nm     

Monolithically integrated grating cavity tunable lasers

A novel grating cavity tunable laser is proposed and experimentally demonstrated. It is realized by monolithically integrating a semiconductor optical amplifier, a dispersive element, a phase-control section, and an etched diffraction grating in a single chip. Tuning operation is based on electrically controlled beam deflection provided by dispersive element and phase matching by phase-control section. With the electrical control, the wavelength tuning of 8.5 nm with a sidemode suppression ratio of about 35 dB has been successfully achieved.     

Widely tunable single-frequency erbium-doped fiber lasers

In this letter, we report on experimental results on a 70-nm-wide quasi-continuously tunable single-frequency erbium-doped fiber (EDF) laser, in which the laser produced a single-longitudinal mode oscillation between 1510-1580 nm, an output power of 0.5 mW, and a tuning step of about 25 MHz. The cavity incorporates three tunable bandpass filters (TBFs): a bulk-grating-based TBF, a fiber-ring-cavity filter, and an autotracking saturable absorption-induced grating filter generated by an unpumped EDF. This laser had a frequency drift of 100 MHz and a signal-to-source spontaneous emission ratio higher than 60 dB.     

Broad-band continuously tunable all-fiber DFB lasers

Up to 27-nm continuous tuning is demonstrated from Er/Yb all-fiber distributed-feedback (DFB) lasers using a simple tuning technique for axial extension and compression. The demonstrated devices operate with powers up to 10 dBm and remain operating in single mode over the full tuning range. Our results represents the broadest tuning-range previously reported in any DFB laser configuration and demonstrate that uniform compression tuning of long Bragg gratings is possible with high reliability     

Coherently tunable mid-infrared distributed feedback lasers

We propose utilization of quantum interference effects in quantum well structures to tune lasing wavelengths of mid-infrared distributed feedback lasers. The interference effects are generated via interaction of an intense laser field with an n-doped quantum well, causing coherent suppression or enhancement of refractive indexes of the conduction intersubband transitions. We show that these processes allow us to shift lasing wavelength to shorter or longer wavelengths by adjusting the intensity and frequency of the intense laser. This study is done for two types of lasers: 1) an electromagnetically induced distributed feedback intersubband laser formed by embedding a longitudinal corrugation of several periods of the quantum well structure within a waveguide structure and 2) a phase-shifted distributed feedback laser where the quantum well is inserted in the middle of an index grating, forming an active phase shift region. In the former the intense laser field is responsible for generation of optical feedback while shifting the coherently induced stop-band. In the latter, however, this field changes the optical length of the phase shift region, tuning the lasing mode within the stop-band. We show that the amount of the wavelength shift, which can reach 17 nm, is controlled by the intensity of the intense laser. The sign of the tuning process (red or blue shift), however, is decided by the frequency of this field, after proper choice of the corrugation periods. We investigate the optical feedback mechanisms in such coherently tunable lasers and discuss how they are related to an electromagnetically induced transparency process that happens in the conduction intersubband transitions.     

可调谐外差式激光偏频锁定

本文提出一种可调谐外差式激光偏频锁定方法,讨论了这种技术在频域内测量激光器瞬稳以及不同频谱振荡的激光器之间进行锁定的可能应用。给出了两台选支CO_2激光器上锁定实验的结果。考虑了本振频率不稳定性对锁定精度的影响。     

Enhanced single-mode operation in multisection DFB lasers with bothlocalized and distributed phase shift

Multisection distributed feedback lasers with both localized (λ/8 phase shift) and distributed phase shift (produced by a phase-adjustment region) are investigated theoretically. It is shown that such a mixed phase shift, combined with a stronger coupling coefficient in the center of the cavity, may enlarge the threshold gain margin as well as the output optical power, enhance the intra cavity field flatness and produce an effective index profile leading to a low sensitivity to spatial-hole burning (SHB) (with respect to conventional λ/4 phase-shifted DFB lasers). As a consequence, the side-mode suppression ratio (SMSR) is improved and single-mode operation up to high bias currents is maintained