Multi-λ ridge waveguide gain-coupled DFB laser array

Multi-wavelength gain-coupled quantum well DFB laser array has been fabricated on an InP substrate by simply varying the ridge waveguide width of the element lasers. Owing to the gain-coupling effect, seven singlemode lasing wavelengths around 1.55 μm with ~2 nm spacing were obtained simultaneously. The lasers had low threshold currents and small beam divergence     

A two-dimensional DFB laser model accounting for carrier transporteffects

A two-dimensional numerical model for DFB semiconductor laser simulation is developed and presented. In this model the transverse carrier transport and longitudinal spatial/spectral hole-burning effects in a bulk DFB laser are accounted for rigorously. Comparison with simplified models is made. Methods for improving the accuracy of steady-state and small-signal analyses by the simplified models are proposed and verified     

A wavelength-tunable curved waveguide DFB laser with an integratedmodulator

A distributed-feedback (DFB) laser with a curved waveguide in the active region integrated with an electroabsorption modulator is studied experimentally and theoretically. The modulator controls the lasing wavelength of the DFB laser by acting as an optical phase shifter. Our model, which is based on the transfer matrix method, is used to simulate this multisection device with the curved waveguide, self-consistently including the effects of spatial hole burning (SHB). The model explains the features and wavelength-tuning behavior of the spectrum and shows good agreement with experimentally measured spectra. We also show theoretically that the curved waveguide suppresses the longitudinal photon density profile of the device compared with a straight waveguide case, which implies reduced SHB effects     

565 Mbaud 100 km optical system trial using a ridge waveguide DFB laser at 1.478 ?m

565 Mbaud transmission over 100 km of step-index mono-mode fibre using a new ridge waveguide distributed feedback (DFB) laser structure operating at 1.478 ?m and a Ge APD receiver has been demonstrated. No residual dispersion penalty was observed.     

Dynamic single-transverse-mode properties of varying ridge width DFB laser arrays

Controlling the lasing wavelength by varying the ridge width is a simple and versatile technique for realizing practical WDM laser arrays. The purpose of this letter is to report the dynamic transverse mode properties of such laser arrays. We show that it is possible to maintain single-mode lasing even for ridges wide enough to support multiple transverse modes. As a result, we were able to increase the tuning range in the array without introducing any detrimental effects on their single-mode properties.     

Planar GaAs-AlGaAs MQW transverse junction ridge waveguide lasersusing shallow zinc diffusion

A new transverse-junction ridge waveguide AlGaAs-GaAs multiple-quantum-well laser is demonstrated. The combination of the ridge structure and transverse junction yields advantages of stable index guiding, and a greatly simplified fabrication process with a rapid thermal diffusion time as short as three minutes     

Low threshold ridge waveguide laser at 1.55 ?m

Fundamental-transverse-mode ridge waveguide lasers have been operated at 1.55 ?m with threshold current as low as 42 mA. The threshold of fabrication and performance are similar to that of 1.3 ?m ridge lasers, including the large modulation bandwidth.     

Gain saturation in traveling-wave ridge waveguide semiconductor laser amplifiers

The saturation behavior of traveling-wave ridge waveguide diode amplifiers is studied both numerically and analytically. It is shown that an 'effective saturation power' can be used to characterize the saturation of these devices by up to 4 dB. The effective saturation power, which is sensitive to device geometry, carrier density, and operating wavelength, is useful in the design of the ridge waveguide optical amplifiers.<>     

High-power 980-nm ridge waveguide laser diodes including an asymmetrically expanded optical field normal to the active layer

We propose a new ridge waveguide laser diode (LD) which supports an asymmetrically expanded optical field normal to the active layer in order to increase the maximum kink-free output power and reduce the aspect ratio of output beams. The dependence of maximum kink-free output power on facet reflectivity was analyzed from the viewpoint of the total optical power in the cavity. It was clarified that the maximum kink-free output power is influenced by the facet reflectivity which affects the refractive index changes of the ridge region via the total optical power in the cavity. More than 600 mW of maximum kink-free output power and an aspect ratio of less than 2.5 were achieved in experiments with 980-nm ridge waveguide LDs by means of this proposed new structure.     

Multiwavelengths DFB waveguide laser arrays in Yb-Er codoped phosphate glass substrate

The realization of arrays of 15 distributed feedback lasers integrated on an Er-Yb-doped phosphate glass substrate is reported. A submicronic corrugated grating has been etched on a comb of Ag/sup +/-Na/sup +/ ion exchanged waveguides with varying diffusion aperture width. Robust single frequency emission spectrum are shown, closely gauged on the 25- and 100-GHz International Telecommunications Union grids around 1.535 /spl mu/m with a pump-power threshold of 14 mW and a slope efficiency of 5.7%.     

Novel semianalytic rib/ridge semiconductor waveguide design including gain and loss

A highly accurate method for rib/ridge waveguides, first put forward for real refractive indices, is extended to structures incorporating gain and loss. The technique is demonstrated by the design of a coupler device with metal-capped ribs, in terms of the fully two-dimensional supermodes.<>     

Large-signal dynamic model of the DFB laser

A computer model is proposed to analyze the characteristics of distributed feedback (DFB) lasers. The model is based on time-dependent coupled wave equations, with spontaneous emission taken into account. In order to avoid uncertain phase factors in spontaneous emission, a method of converting field equations to power equations in a matrix format before computation is introduced. The steady-state LI curve and transient response to the pulse excitation are calculated in the λ/4 phase-shifted DFB lasers. The longitudinal variations of the carrier and photon densities as well as of the refractive index are considered in the model     

High-speed 1.55 ?m single-longitudinal-mode ridge waveguide C3 laser

Fundamental-transverse-mode ridge waveguide laser chips were recleaved to form C3 lasers with a single-longitudinal-mode output stabilised at a fixed wavelength over a wide range of drive currents and temperature. Lasers operated at 1.55 ?m at a bit rate of 2 Gbit/s with on-off ratios greater than 10:1 and side-mode suppression greater than 1200:1. A simple method for mapping the stable operating regime is described.     

AlGaAs/GaAs visible ridge waveguide laser with multicavity structure

Ridge waveguide lasers of two different cavity configurations are described. First is the multisection ridge laser structure in which the longitudinal mode selection due to the coupled-cavity effect was observed and single-frequency operation was achieved. In this structure, stable single-transverse-mode operation was ensured by the central 5 μm wide section, and the beam waist and power output were enlarged by the outer 10 μm wide sections. Output power of more than 13 mW under pulsed excitation was obtained. The second configuration is the shallow groove ridge laser in which the 5 μm wide shallow groove terminates slightly above the active region and provides an index perturbation that contributes to mode selection. All the lasers are designed to emil in the visible range between 7600 and 7900 Å. The shortest observed wavelength is 7570 Å, and can be seen by the naked eye.     

高速脊波导激光器寄生电容的分析

高速调制半导体激光器光源是光纤通信系统、相控阵雷达等的关键器件。高速激光器的寄生电容是影响其调制带宽的因素之一。为了减小寄生电容,针对脊波导结构激光器的电容,采用计算机模拟与实际测试相结合的方法,进行了理论分析和实验验证。结果表明,其寄生电容大小不仅与电极金属化面积有关,还与隔离沟的腐蚀深度有关。当腐蚀至波导层时,寄生电容减小到10pF以下。这一结论对实现激光器的高速调制是非常有意义的。     

Design of ridge waveguide couplers with carrier injection using discrete spectral index method

It is shown that the design of ridge waveguide couplers with a uniformly layered refractive index profile can be extended to include the nonuniformity arising within an active layer as a result of carrier injection. This is analysed using the spectral index method combined with a degenerate perturbation approach. The simplicity of this approach makes it possible to solve design problems in which the correct mixing of the fields beneath the ridges is an essential feature of the modelling, and necessary for accuracy of design.<>     

Simple measurement of carrier induced refractive-index change in InGaAsP PIN ridge waveguide structures

The carrier induced refractive-index change Delta n in integrated InGaAsP 1.30 mu m interferometer structures is evaluated by 1.55 mu m transmission measurements. At carrier concentrations N from 8*10/sup 16//cm/sup 3/ to 3*10/sup 18//cm/sup 3/ a value of Delta n/N=-1*10/sup -20/ cm/sup 3/ is obtained. A good agreement of the experimental results with theoretical predictions on bandfilling, plasma effect and bandgap shrinkage is demonstrated.<>     

Hamiltonian model of a free electron laser including high-density effects

Both the Compton and the Raman regimes of a free electron laser are described by a relativistic Hamiltonian which originates the evolution equations for 2N+2 canonically conjugate electron and field variables, with the space coordinate as the independent variable. Space charge and field contribution to electron transverse velocity are included.     

Low voltage, room temperature, ridge waveguide green-blue diode laser

Ridge waveguide quantum well (QW) diode lasers in the green/blue region have been operated at voltages as low as 7V in ZnCdSe-ZnSSe-ZnMgSSe pseudomorphic confinement heterostructures. These lasers include a p-Zn(Se,Te) graded gap ohmic contact layer to the top metal electrode. Without any attempt at heatsinking, and without reflective facet coatings, these devices have operated at pulsed duty cycles of 20% at room temperature, with average power output of several milliwatts.<>     

Modeling of intensity noise including squeezing in DFB andFabry-Perot semiconductor laser diodes

A new time-domain model using the quantum formalism of the positive-P distribution is used to investigate squeezing in laser diodes, taking into account longitudinal hole burning and distributed noise sources, under steady-state and large-signal modulation. Simulations indicate that the laser structure determines the lowest achievable intensity noise. With losses present or power escaping from the rear facet, this minimum noise may be much higher than expected from the device quantum efficiency. Squeezing appears more difficult in DFB lasers than in Fabry-Perot lasers in our simulations. Mode-partition noise is removed by low-loss passive DBR sections, and such laser diodes are promising sources with low-intensity noise. Intensity noise in the large-signal dynamic regime is also simulated, showing that intensity-squeezed light output is possible