Search

A report is presented on the transmission electron microscopy of quantum dots formed by cycled submonolayer deposition of InAs/GaAs grown on GaAs substrates.

An analytical model of the dynamic characteristics of a quantum-well (QW) semiconductor optical amplifier (SOA) is developed. Closed-form expressions for the optical gain and cross-gain modulation (XGM) for arbitrary input pulses are derived. The model takes into account the carrier capture and escape transitions between the QW and the continuum states. This model is also used to derive a closed-from expression for interchannel XGM crosstalk in multichannel SOA systems. The model/analysis provides insight into the effect of the SOA parameters on the performance of a wavelength-division multiplexed system. We found that crosstalk in a multichannel SOA system can be reduced by reducing the escape lifetime. [ABSTRACT FROM PUBLISHER]

A low-power, short-wavelength eight-channel monolithically integrated photoreceiver array, based on SiGe/Si heterojunction bipolar transistors, is demonstrated. The photoreceiver consists of a photodiode, three-stage transimpedance amplifier, and passive elements for feedback, biasing and impedance matching. The photodiode and transistors are grown by molecular beam epitaxy in a single step. The p-i-n photodiode exhibits a responsivity of 0.3A/W and a bandwidth of 0.8 GHz at λ=0.88 μm. The three-stage transimpedance amplifier demonstrates a transimpedance gain of 43 dBΩ and a -3 dB bandwidth of 5.5 GHz. A single channel monolithically integrated photoreceiver consumes a power of 6 mW and demonstrates an optical bandwidth of 0.8 GHz. Eight-channel photoreceiver arrays are designed for massively parallel applications where low power dissipation and low crosstalk are required. The array is on a 250-μm pitch and can be easily scaled to much higher density. Large signal operation up to 1 Gb/s is achieved with crosstalk less than -26 dB. A scheme for time-to-space division multiplexing is proposed and demonstrated with the photoreceiver array [ABSTRACT FROM PUBLISHER]

It is possible to grow defect-free strained layers on patterned substrates (mesas or grooves) up to thicknesses far exceeding the critical thickness. Defect nucleation and propagation are inhibited in such growth. We have exploited this property to propose a novel InP-based 1.55-μm vertical cavity surface emitting lasers (VCSEL's). Careful photoluminescence and transmission electron microscopy (TEM) studies have confirmed that there are no propagating defects in the GaAs/AlxGa1-xAs distributed Bragg reflector (DBR) grown on the patterned InP-based heterostructures, specifically in the multiquantum-well (MQW) region. Lasers were designed with InP/InGaAsP bottom mirrors, InAlAs-oxide current confinement and short-stack GaAs/Al xOy top DBR mirrors. An optimal reflectivity and a maximum wall plug efficiency are determined analytically for this structure. In addition, a theoretical analysis of the modulation response of this device is performed using a rate equation model. Both analyzes show the potential of such a device for implementation in practical designs where high power and modulation bandwidth are required. Lasers with 8-40 μm diameter have been fabricated and characterized. A threshold current of 5 mA is observed at 15°C for an 8 μm diameter device; and up to 60 μW of light output is recorded [ABSTRACT FROM PUBLISHER]

A low power GaAs-based monolithically integrated phototransceiver, consisting of a high gain phototransistor and a microcavity light-emitting diode, is demonstrated. The input and output wavelengths are 0.85 and 0.98 μm, respectively. The phototransceiver exhibits an optical gain of 7 dB and power dissipation of 400 μW for an input power of 1.5 μW. The small signal modulation bandwidth is 80 MHz [ABSTRACT FROM PUBLISHER]