Optimization design of an electroabsorption modulator integrated with spot-size converter

A novel 1.55 μm spot-size converter integrated with electroabsorption modulator is designed and fabricated with conventional photolithography and chemical wet etching process.For the modulator,we employed a deeply-etched ridge waveguide structure with polyimide on each side of its walls.For the spot-size converter,we employed a buried double-core structure in which a ridge-based passive waveguide is incorporated.The wide and thin passive waveguide is optically combined with a laterally tapered active waveguide to control the mode size.By simulation,the figure of merit is 4.17(dB/V/(100 μm)) and the beam divergence angles in the horizontal and vertical directions are as small as 11.2°×13.0°,respectively.

Growth of GaAs on Si by Using a Thin Si Film as Buffer Layer

We report a novel technique for growing high-quality GaAs on Si substrate.The process involves deposition of a thin amorphous Si film prior to the conventional two-step growth.The GaAs layers grown on Si by this technique using metalorganic chemical vapor deposition exhibit a better surface morphology and higher crystallinity as compared to the samples grown by conventional two-step method.The full width at half maximum(FWHM)of the x-ray(004)rocking curve for 2.2 μm thick GaAs/Si epilayer grown by using this new method is 160 arcsec.The FWHM of the photoluminescence spectrum main peak for this sample is 2.1 meV.These are among the best results reported so far.In addition,the mechanism of this new growth method was studied using high-resolution transmission electron microscopy.

Optical Transitions in Cubic GaN Grown by Metalorganic Chemical Vapor Deposition on GaAs (100) Substrate

Photoluminescence measurements have been performed on cubic GaN films with carrier concentration as low as 3×10^(13) cm^(-3).From the temperature and excitation intensity dependence,the emission lines at 3.268,3.150 and 3.081 eV were assigned to the excitonic,donor-acceptor pair,and free-to-acceptor transitions,respectively.Additionally,we observed two additional emission lines at 2.926 and 2.821 eV,and suggested that they belong to donor-acceptor pair transitions.Furthermore,from the temperature dependence of integral intensities,we confirmed that three donor-acceptor pair transitions(3.150,2.926,and 2.821 eV)are from a common shallow donor to three different acceptors.The excitonic emission at 3.216 eV has a full-width-at-half-maximum value of 41 meV at room temperature,which indicates a good optical quality of our sample.

Offset quantum-well method for tunable distributed Bragg reflector lasers and electro-absorption modulated distributed feedback lasers

A two-section offset quantum-well structure tunable laser with a tuning range of 7 nm was fabricated using offset quantum-well inethod. The distributed Bragg reflector （DBR） was realized just by selectively wet etching the multiquantum-well （MQW） layer above the quaternary lower waveguide. A threshold current of 32 mA and an output power of 9 mW at 100 mA were achieved. Furthermore, with this offset structure method, a distributed feedback （DFB） laser was integrated with an electro-absorption modulator （EAM）, which was capable of producing 20 dB of optical extinction.

Structures of an asymmetrically coupled double-well superlattice by double-crystal X-ray diffraction

An asymmetrically coupled ( GaAs/AlAs/GaAs/AlAs)/GaAs(001) double-well supperlattice isstudied by HRDCD (high resolution double-crystal X-ray diffractometry).The intensity of satellite peaks is modulated by wave packet of different sublayers.In the course of simulation,the satellite peaks in the vicinity of the node points of wave packet are very informative for precise determination of sublayer thickness and for improving accuracy.

Novel electroabsorption modulator monolithically integrated with spot-size converter

A novel 1.55-μm spot-size converter integrated electroabsorption modulator was designed with conventional photolithography and chemical wet etching process. A ridge double-core structure was employed for the modulator, and a buried ridge double-core structure was incorporated for the spot-size converter. The passive waveguide was optically combined with a laterally tapered active waveguide to control the mode size. The figure of merit is 4.1667 dB/V(/100 μm) and the beam divergence angles in the horizontal and vertical directions were as small as 11.2°and 13.0°, respectively.

Narrow-beam divergence 1.55μm laser diodes with integrated self-aligned spotsize converter

This paper describes the high performance of narrow-beam divergence spot size converter (SSC) integrated separately confined heterostructure (SCH) LD. The upper optical confinement layer (OCL) and the butt-coupled tapered thickness waveguide were regrown simultaneously, which not only offered the separated optimization of the active region and the integrated spotsize converter, but also reduced the difficulty of the butt-joint selective regrowth. The threshold current was as low as 5.4 mA, the output power at 55 mA was 10.1 mW, the vertical and horizontal far field divergence angles were as low as 9° and 15°, and the 1-dB misalignment tolerances were 3.6 and 3.4 μm, respectively.