A Novel Three-Section Self-Pulsating DFB Laser with Hybrid Grating

A 1.55μm InGaAsP-InP three-section DFB laser with hybrid grating is fabricated and self-pulsations (SP) with frequencies around 20GHz are observed. The mechanism of SP generation in this device is researched. Furthermore, the important role of the phase tuning section on the SP is investigated.

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.

Material Growth and Device Fabrication of GaAs Based 1.3μm GaInNAs Quantum Well Laser Diodes

Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.

A Wavelength Tunable DBR Laser Integrated with an Electro Absorption Modulator by a Combined Method of SAG and QWI

We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI. The threshold current is 37mA and the output power at 100mA gain current is 3.5mW. When coupled to a single-mode fiber with a coupling efficiency of 15% ,more than a 20dB extinction ratio is observed over the change of EAM bias from 0 to -2V. The 4.4nm continuous wavelength tuning range covers 6 channels on a 100GHz grid for WDM telecommunications.

A GaAs-Based MOEMS Tunable RCE Photodetector with Single Cantilever Beam

A GaAs-based micro-opto-electro-mech anical-systems(MOEMS) tunable resonant cavity enhanced(RCE)photodetector with a continuous tuning range of 31nm under a 6V tuning voltage is demonstrated. The single cantilever beam structure is adopted for this MOEMS tunable RCE photodetector. The maximum and minimum peak quantum efficiency during the tuning are 36.9 % and 30. 8 %, respectively. The maximum and minimum full-width-at-halfmaximum (FWHM) are 20nm and 14nm,respectively. The dark current density is 7.46A/m2 without bias.

Widely Tunable Sampled-Grating DBR Laser

The 3-section SG-DBR tunable laser is fabricated using an ion implantation quantum-well intermixing process. The over 30nm discontinuous tuning range is achieved with the SMRS greater than 30dB.

An Integratable Distributed Bragg Reflector Laser by Low-Energy Ion Implantation Induced Quantum Well Intermixing

An integratable distributed Bragg reflector laser is fabricated by low-energy ion implantation induced quantum well intermixing. A 4.6nm quasi-continuous wavelength tuning range is achieved by controlling phase current and grating current simultaneously,and side mode suppression ratio maintains over 30dB throughout the tuning range except a few mode jump points.

1.55-μm Si-based MOEMS optical tunable filter

A prototype 1.55-μm Si-based micro-opto-electro-mechanical-systems (MOEMS) tunable filter is fabricated, employing surface micromachining technology. Full-width-at-half-maximum (FWHM) of the transmission spectrum is 23 nm. The tuning range is 30 nm under 50-V applied voltage. The device can be readily integrated with resonant cavity enhanced (RCE) detector and vertical cavity surface emitting laser (VCSEL) to fabricate tunable active devices.

Micromechanical Tunable Optical Filter

A micromachined vertical cavity tunable filter with AlGaAs/GaAs distributed Bragg reflector is presented. This filter can be electrostatic tuning over a range of 28nm with an applied voltage of 7V.

1.55μm Fabry-Perot Thermo-Optical Tunable Filter with amorphous-Si as Cavity

A 1.55μm Fabry-Perot (F-P) thermo-optical tunable filter is fabricated. The cavity is made of amorphous silicon (a-Si) layer grown by electron-beam evaporation technique. Due to the excellent thermo-optical property of a-Si, the refractive index of the F-P cavity will be changed by heating; the transmittance resonant peak will therefore shift substantially. The measured tuning range is 12nm, FWHM (full-width-at-half-maximum) of the transmission peak is 9nm, and heating efficiency is 0.1K/mW. The large FWHM is mainly due to the non-ideal coating deposition and mirror undulation. Possible improvements to increase the efficiency of heating are suggested.

The Incident Angle Dependence of Quantum Efficiency of GaAs Based RCE Photodetectors

The theoretical analysis and experimental measurement on the incident angle dependence of quantum efficiency of GaAs based resonant cavity enhanced (RCE) photodetector is presented. By changing the angle of incoming light, about 40 nm wavelength variation of peak quantum efficiency is obtained. The peak quantum efficiency and optical bandwidth at different mode corresponding to different angle incidence is characterized with different absorption dependence on wavelength. The convenient angle tuning of resonant mode will be helpful to relax the strict constraint of RCE photodetector to light source with narrow emission spectrum such applications in space optical detections and communications.

Analysis for the angle dependence of GaAs based RCE photodetectors

The theoretical analysis and experimental measurement on the angle dependence of quantum efficiency of GaAs based resonant cavity enhanced (RCE) photodetector is presented. By changing the angle of incoming light, about 40mn wavelength variation of peak quantum efficiency has been experimentally obtained. The peak quantum efficiency and optical bandwidth at different mode corresponding to different angle incidence have been characterized with different absorption dependence on wavelength. The convenient angle tuning of resonant mode will be helpful to relax the strict constraint of RCE photodetector to light source with narrow emission spectrum while especially applied in space optical detections and communications.

Tunable MQW-DBR lasers using selective area growth

The tunable ridge waveguide distributed Bragg reflector (DBR) lasers designed for wavelength-division-multiplex (WDM) communication systems at 1.55 um by using selective area growth (SAG) is reported. The threshold current of the DBR laser is 62mA and the output power is more than 8mW. The isolation resistance between the active region and the Bragg region is 30K Ohm. The total tuning range is 6.5nm and this DBR laser can provide 6 continuous standard WDM channels with 100GHz channel spacing; in the tuning range, the single mode suppression ratio (SMSR) is maintained more than 32dB and the maximum output power variation is less than 3dB.

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot. (C) 2004 Elsevier B.V. All rights reserved.

Experimental study on tunable external cavity photodetectors

In this paper, an experiment on tunable resonant cavity enhanced (RCE) photodetector with external cavity is reported. It is the first time to realize a tunable RCE photodetector in China. A tuning range about 10 nm has been obtained and further extension is expected. Corresponding theoretical analysis and discussions are presented. (C) 2000 Elsevier Science B.V. All rights reserved.