Zhang Ruikang

Fabrication and Characterization of High Power 1064-nm DFB Lasers

A ridge waveguide distributed-feedback laser emitting at 1064 nm is demonstrated. Two low-temperature-grown In0.21Ga0.79As/GaAs quantum wells are employed as the active layer. A second-order grating is formed by holographic photolithography and wet-etching. The laser operates at a single-mode up to 255 mA, corresponding to an output power of 90 mW.

GaInNAs/GaAs Multiple-Quantum Well Resonant-Cavity-Enhanced Photodetectors at 1.3 µm

A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced photodetector (RCF-PD) operated at a wavelength of 1.3 mum with the full width at half maximum of 4nm has been demonstrated. The GaInNAs RCE - PD was grown by molecular beam epitaxy using a homemade ion-removed dc plasma cell as a nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature, which is very beneficial for applications in long-wavelength absorption devices. For a 100 mum diameter RCE-PD, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is - 18 V. The measured 3 dB bandwidth is 308 MHz, which is limited by the resistance of p-type distributed Bragg reflector mirror. The tunable wavelength in a range of 18 nm with the angle of incident light was observed.

Design and Fabrication of a 400GHz InP-Based Arrayed Waveguide Grating with Flattened Spectral Response*

A four-channel 400 GHz channel spacing InP-based arrayed waveguide grating with a flattened wavelength response by employing a multimode interference coupler at the input waveguide of the filter is prepared. The fabricated devices show a flattened spectral response with a broadened 3-dB bandwidth up to 3.5 nm, interchannel non-uniformity of <0.7 dB and excellent match to the simulation results.

Fabrication and optimization of 1.55-μm InGaAsP/InP high-power semiconductor diode laser*

A comprehensive design optimization of 1.55-μm high power InGaAsP/InP board area lasers is performed aiming at increasing the internal quantum efficiency (ηi) while maintaining the low internal loss (αi) of the device, thereby achieving high power operation. Four different waveguide structures of broad area lasers were fabricated and characterized in depth. Through theoretical analysis and experiment verifications, we show that laser structures with stepped waveguide and thin upper separate confinement layer will result in high ηi and overall slope efficiency. A continuous wave (CW) single side output power of 160 mW was obtained for an uncoated laser with a 50-μm active area width and 1 mm cavity length.

Optimization of 1.3-µm InGaAsP/InP Electro-Absorption Modulator

We report the simulation and experimental results of 1.3-μm InGaAsP/InP multiple quantum well (MQW) electro-absorption modulators (EAMs). In this work, the quantum confined Stark effect of the EAM is systematically analyzed through the finite element method. An optimized structure of the 1.3-μm InGaAsP/InP QW EAM is proposed for applications in 100 G ethernet. Then 1.3-μm InGaAsP/InP EAMs with f−3 dB bandwidth of over 20 GHz and extinction ratio over 20 dB at 3 V bias voltage are demonstrated.

High Power 1060 nm Distributed Feedback Semiconductor Laser

A GaAs based high power distributed feedback (DFB) semiconductor laser with a second-order grating has been demonstrated. An output power of 150 mW at an injection current of 350 mA is realized with a 1-mm cavity length. With a new design of the waveguide structure, the DFB laser maintains a stable single longitudinal mode around 1060 nm with a side mode suppression ratio of larger than 50 dB.

Optimization of High Power 1.55-μm Single Lateral Mode Fabry—Perot Ridge Waveguide Lasers*

Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different waveguide structures of Fabry—Perot lasers emitting at a wavelength of 1.55 μm are fabricated. The influence of an effective lateral refractive index step on the maximum output power is investigated. A cw single mode output power of 165 mW is obtained for a 1-mm-long uncoated laser.

Graded doping low internal loss 1060-nm InGaAs/AlGaAs quantum well semiconductor lasers*

Internal loss is a key internal parameter for high power 1060-nm InGaAs/AlGaAs semiconductor laser. In this paper, we discuss the origin of internal loss of 1060-nm InGaAs/GaAs quantum well (QW) AlGaAs separate confinement heterostructure semiconductor laser, and the method to reduce internal loss. By light doping the n-cladding layer, and stepwise doping the p-cladding layer combined with the expanded waveguide layer, a broad area laser with internal loss of 1/cm is designed and fabricated. Ridge waveguide laser with an output power of 350 mW is obtained. The threshold current and slope efficiency near the threshold current are 20 mA and 0.8 W/A, respectively.

Polarization Dependent Characteristics of a Resonant Cavity Enbanced Photodetector

In this paper, polarization dependent characteristics of resonant cavity enhanced (RCE) photodetector (PD) with respect to the incident light angle were analyzed in detail. The simulations carry out on a 1.3μm GaInNAs quantum wells RCE PD, which is fabricated in our group. Analysis results show that the influence of polarization can only be neglected at small angle of incidence.