Linewidth broadening in a distributed feedback laser integrated with a semiconductor optical amplifier

The problem of the linewidth degradation in systems using distributed-feedback lasers together with strained-layer multi-quantum-well semiconductor optical amplifiers (SOAs) is examined. A modified expression for the linewidth in the case of anti reflection-coated SOA output facets is derived and simulation results are given in the case of output facets with a nonvanishing reflectivity. A numerical model combining finite-element calculations in the transverse x-y plane and a longitudinal model based on the Green's function method is used for that purpose.     

Quantum well interferometric modulator monolithically integrated with 1.55 mu m tunable distributed Bragg reflector laser

The first monolithically integrated laser/interferometric modulator is reported. The total chip length of 2.5 mm includes a 970 mu m-long strained InGaAs-InGaAsP quantum well gain section, a 230 mu m-long wavelength tuning section containing a distributed Bragg reflector grating, and an 800 mu m-long active length Mach-Zehnder modulator based on electrorefractive InGaAsP-InP quantum wells. 4 V push-pull drive voltage produces 12.5 dB modulation depth with -9 dBm optical power coupled into a cleaved fibre.<>     

Thermal effects in monolithically integrated tunable laser transmitters

We investigate thermal effects in widely tunable laser transmitters based on an integrated single chip design. The chip contains a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption modulator (EAM). The thermal impedance of the ridge structure is evaluated through simulation and experiment, and thermal crosstalk between sections is examined. Heating of the mirrors by neighboring sections is found to result in unintentional offsets in wavelength tuning. Thermal effects in the EAM are examined in depth. A positive feedback mechanism causes local temperature rise at the modulator input, with the potential to trigger catastrophic thermal runaway. A self-consistent finite-element model is developed to simulate the EAM temperature profile and device performance. This model is used to optimize the device, resulting in integrated EAMs that achieve a dissipated power limit in excess of 300mW.     

Widely tunable complex-coupled distributed feedback laser with photonic Crystal mirrors and integrated optical amplifier

We report the development of a current-controlled widely tunable laser diode based on InP with photonic crystal mirrors and an integrated amplifier section for stabilized power output. The laser consists of three longitudinally coupled ridge waveguide cavities that are coupled through photonic crystal mirror segments. A laterally defined binary superimposed grating provides complex-coupled distributed feedback into two of the laser cavities. The wavelength can be switched over a range of 26 nm. Through adjustment of the current into a third amplifier section, the output power can be stabilized over the tuning range of the laser.     

Monolithically integrated external cavity wavelength tunable laser using beam steering controller

A Littrow-configured grating-coupled external cavity wavelength tunable laser monolithically integrated with a semiconductor optical amplifier, an etched grating, and a beam steering controller (BSC) is demonstrated. Using incidence angle variation induced by current injection into the BSC region, 7 nm of wavelength tuning range and over 35 dB side-mode suppression ratio is obtained.     

Transmission performance of monolithically integrated Y-branch tunable laser with zero-chirp Mach-Zehnder modulator

A zero-chirp Mach-Zehnder modulator monolithically integrated with a widely tunable modulated grating Y laser and SOA, operating at 10 Gbit/s, is demonstrated. The device is hermetically packaged with a wavelength locker within a 12.7times15.24 mm module. With a fixed receiver threshold and fixed voltage modulation depth, the extinction ratio exceeds 12 dB and the receiver penalty for dispersion in the range plusmn800 ps/nm is below 1.5 dB on all channels     

紧凑型光栅外腔可调谐半导体激光器

研制了一台结构紧凑的窄线宽、可调谐半导体激光器.采用光栅外腔Littrow结构,将光栅和平面反射镜置于同一个旋转平台上,并使光栅衍射平面和平面镜反射平面的交线与平台旋转轴重合,通过旋转平台实现光栅外腔选取单纵模、压窄线宽和波长调谐,并保证输出光的方位不发生改变,同时用棱镜将输出光斑压缩成为类方形.该激光器的尺寸为110 mm×80 mm×35 mm,中心输出波长为653 nm,谱宽0.07 nm,调谐范围4.6 nm,可连续稳定运转4小时以上.     

Singlemode tapered quantum dot laser diodes with monolithically integrated feedback gratings

Based on a single InGaAs/GaAs quantum dot layer as active region, tapered laser diodes with laterally complex coupled grating emitting near 920 nm were fabricated for wavelength controlled optical pump applications. Output powers > 500 mW at room temperature and side- mode suppression ratios >35 dB are demonstrated.     

Wideband tuning of tunable distributed amplification distributed feedback laser array

A wide continuous tuning range of 6.7 nm was achieved with a tunable distributed amplification distributed feedback (TDA-DFB) laser by employing an asymmetric periodic structure. A 36-channel operation with a 100 GHz grid was realised for an array of six TDA-DFB lasers integrated monolithically with a coupler and an amplifier.     

40 Gbit/s RZ wavelength converter in a monolithically integrated chip with a tunable laser

An all-optical wavelength-switch module with 40 Gbit/s capacity is integrated monolithically in InP. The device combines an SOA-based wavelength converter and a fast-tunable 8-channel multi-frequency laser. Error-free operation is demonstrated.     

Widely tunable Y-coupled cavity integrated interferometric injection laser

A novel tunable single mode light source has been developed in the InGaAsP/InP material system. The Y-coupled cavity (YCC) type integrated interferometric injection (I/sup 3/) wavelength tunable laser operates in the 1300 nm wavelength region with a sidemode suppression of about 20 dB. By adjusting the currents through the four all active sections of this YCC-I/sup 3/-laser, a total tuning range of more than 14 nm and continuous tuning of 1.15 nm was obtained from non-optimised first devices.<>     

Simple model for a distributed feedback laser integrated with a Mach-Zehnder modulator

Presents a time-domain traveling-wave algorithm for the modeling of the large-signal dynamic response of a distributed feedback laser integrated with a Mach-Zehnder (MZ) modulator. The influence of residual optical feedback from the output of the modulator facet on the dynamic frequency chirp is studied. It is found that the difference in frequency chirp between the turn-on and -off states (i.e., adiabatic chirp) of a /spl pi//2-shifted 2 /spl times/2 MZ modulator is minimal and is independent of-the residual optical feedback. In addition, it can be shown that the presence of chirped frequency spikes (i.e., transient chirp), due to the change in refractive index as a result of the rapid variation of the bias voltage, can broaden the linewidth and distort the spectrum of the modulated optical signal. Furthermore, the possibility of doubling the modulation frequency of MZ modulators using a dual-arm dual-signal modulation format is investigated.     

Linewidth reduction of cleaved-coupled-cavity lasers by optical feedback from a single-mode polarisation-preserving fibre external cavity

Linewidth characteristics of a cleaved-coupled-cavity laser with a single-mode polarisation-preserving fibre external cavity have been investigated as a function of feedback power level and side-mode suppression ratio. The optimum power feedback ratio is near 2×10?4 for a minimum linewidth of about 30 kHz. A weak dependence of linewidth on side-mode suppression ratio is observed as long as the suppression ratio is greater than 500:1.     

Two-section gain-levered tunable distributed feedback laser withactive tuning section

A composite cavity semiconductor laser structure that consists of two active (gain) sections is analyzed. One of the sections has a grating corrugation, while the other is flat. The operation of the device is enhanced by utilizing the gain-lever effect. A round-trip analysis is combined with the rate equations pertinent for this structure to study the characteristics of the device. The performance of the device is compared to that of a similar case without the gain lever. It is shown that, utilizing the gain-lever effect, improved operation in terms of tuning range, modulation efficiency, and output power control can be obtained     

Linewidth of monolithic external cavity DFB lasers

An expression for the linewidth of DFB lasers with lossy external cavities is derived. The influence of facet reflectivity and high feedback levels is discussed     

低阈值短腔随机分布反馈光纤激光器

设计了一种低阈值短腔随机分布反馈光纤激光器,采用1455 nm的激光二极管泵浦一段色散补偿光纤,采用正向反馈和反向反馈两种结构分别将一阶随机激光阈值降至760 mW和520 mW,且反向反馈结构的二阶阈值与一阶阈值相同,分析了色散补偿光纤长度对阈值的影响,实验证明优化色散补偿光纤长度是降低一阶与二阶随机激光阈值的有效方法。     

Broadly tunable external cavity laser diodes with staggered thickness multiple quantum wells

Widely tunable low-threshold current laser diodes fabricated from an engineered multiple-quantum-well (MQW) gain structure consisting of three compressively strained In/sub 0.2/Ga/sub 0.8/As wells of different thicknesses are reported. Using a grating in an external cavity, a continuous-wave tuning range of 70 nm (911-981 nm) is measured for a 155-/spl mu/m semiconductor cavity length device at a current of 32 mA. This is the lowest reported bias current for a semiconductor laser with this broad a tuning range. A maximum continuous wave tuning of 80 nm (901-981 nm) has been measured at a bias current of 95 mA. At long wavelengths, a suppression of amplified spontaneous emission and preferential population of the lowest energy well were observed.     

Tunable single-mode output of a multimode laser in a tunable fibre grating external cavity

Tunable single-mode oscillation has been obtained from a 1.3?m multimode laser using a tunable fibre grating reflector in a fibre external cavity. The output was tuned over a 26 nm range with a secondary mode suppression greater than 25 dB at the centre of the gain profile.     

Linewidth and offset frequency locking of external cavity GaAlAslasers

Stable external cavity GaAlAs lasers operated with full-width-at-half-maximum (FWHM) linewidths of less than 3 kHz are discussed. Offset frequency locking has been demonstrated over long periods to within the 10-Hz resolution bandwidth of the experiment. The spectral characteristics of these devices are presented graphically     

Linewidth reduction of a semiconductor laser by electrical feedback

An electrical feedback technique was proposed to stably reduce the linewidth of a semiconductor laser without changing its cavity structure. Calculations and experiments were carried out to reduce the linewidth of a 1.5 μm InGaAsP laser (DFB type) according to the following procedure. A compact Fabry-Perot interferometer was used as a freqeuncy discriminator. The minimum attainable linewidth, limited by the detector noise, was estimated as being narrower than 1 kHz when the reflectance of the interferometer used was higher than 0.9. The minimum linewidth obtained in the experiment was 330 kHz, which was 15 times as narrow as in the case of a free-running laser. The improvements of this experimental result can be expected by simultaneously reducing the AM noise of the laser.