R. Barber

Gating demultiplexer integrated with MSM detector array in InGaAs/AlGaAs/GaAs for WDM

The authors demonstrate the integration of a grating demultiplexer with curved output waveguides and a MSM photodetector array in InGaAs/AlGaAs/GaAs operating in the 1- mu m wavelength region. The structure provides 38 channels with 1-nm channel spacing. The total loss, including scattering from the unmetallized grating, is about 17 dB. A channel crosstalk of -11 dB is obtained. The FWHM of the channel pass band is 0.5 nm.<<ETX>>

Electrically pumped circular-grating surface-emitting DBR laser on InGaAs strained single-quantum-well structure

The authors demonstrate the fabrication and room temperature operation of an electrically pumped circular-grating surface-emitting distributed-Bragg-reflector laser. An InGaAs/GaAs single quantum well (SQW) graded-index separate confinement heterostructure (GRINSCH) structure was grown by one-step molecular beam epitaxy (MBE). Circular gratings were defined by focused ion beam lithography. The lasing wavelength was 942 nm, and the threshold current was 280 mA. This is the first demonstration of these lasers with no epitaxial regrowth.<<ETX>>

Circular-grating surface-emitting distributed Bragg reflector lasers on an InGaAs-GaAs structure for 0.48-/spl mu/m applications

In this paper, we report on the design and fabrication of electrically-pumped circular-grating surface-emitting DBR lasers for operation in the 0.98-/spl mu/m wavelength range. The layer structure with InGaAs-GaAs-AlGaAs strained multiquantum-wells was obtained by one-step epitaxial growth. Circular gratings are defined by electron-beam lithography around circular gain sections of different diameters. Low threshold CW operation as low as 26 mA for a 60-/spl mu/m diameter gain section, and high-power pulsed operation of over 120 mW for a 100-/spl mu/m diameter gain region are demonstrated. A quasi-circular far-field pattern with a divergence of about 1/spl deg/ is obtained. >

High-speed photodetection in a reverse biased GaAs/AlGaAs GRINSCH SQW laser structure

The authors report extremely efficient ( approximately 100% internal quantum efficiency) and high-speed ( approximately 25-pS FWHM) photodetection in a reverse-biased GaAs/AlGaAs ridge waveguide single-quantum-well (SQW) graded-index separate confinement heterostructure (GRINSCH) laser structure near lambda =830 nm. The impulse response is limited by device parasitics to 25 pS at large reverse bias voltages, and by photogenerated electron escape closer to flatband conditions.<<ETX>>

Low threshold CW operation of circular-grating surface-emitting DBR lasers using MQW and a self-aligned process

In this letter, we present the first room temperature continuous wave operation of circular-grating surface-emitting DBR lasers. The structure is an InGaAs/GaAs strained multiquantum-well. A modified fabrication process with a better control on the steps is used. A CW threshold current as low as 26 mA at a lasing wavelength of about 977 mm are reported. This is the first demonstration of CW operation for these lasers in any material system.<<ETX>>

Focused ion beam lithography of multiperiod gratings for a wavelength‐division‐multiplexed transmitter laser array

Wavelength‐division multiplexing with closely spaced multiple wavelengths is of great interest for high‐capacity data transmission. One major and very critical requirement of such a system is the fabrication of a laser array with very small wavelength separations (∼2 nm). In this paper, the design, fabrication, and performance of an integrated eight‐channel system is described. Focused ion beam lithography, with the beam deflection sensitivity modified from its calibrated value, is used to write the critical stepped‐period distributed‐Bragg‐reflector gratings required to provide the tightly controlled multiple laser frequencies. The outputs of the lasers are combined via curved waveguides into a single optical output.

High temperature operation of circular-grating surface-emitting DBR lasers fabricated on an InGaAs/GaAs structure

We demonstrate high temperature operation of circular-grating surface-emitting distributed Bragg reflector lasers. The structure is a strained InGaAs/GaAs double quantum well. Circular gratings are defined by electron beam lithography. No epitaxial regrowth is used. A surface emission power of over 40 mW under pulsed operation at temperatures of up to 80/spl deg/C is obtained without saturation. A fixed single mode operation was achieved over a temperature range of 60 degrees.<<ETX>>

Focal Plane Imaging Arrays Based on GaAs/AlGaAs Quantum Well Infrared Photodetectors

We summarize our work on the development of focal plane imaging arrays based on GaAs/AlGaAs quantum well infrared photodetectors. The infrared of interest here is from 3 to 12 μm in wavelength, and detection is based on intersubband excitation of electrons in GaAs/AlGaAs quantum wells and the subsequent photocarrier transport resulting in photoconductivity.

Eight-wavelength distributed-Bragg-reflector (DBR) laser array transmitter for WDM applications

We report on the design, growth, fabrication and characterization of monolithic wavelength division multiplexed (WDM) laser array transmitter and receiver chips produced by the Canadian Solid State Optoelectronics Consortium. The transmitter chip includes multiple, discrete wavelength, distributed Bragg reflector (DBR) laser diodes monolithically integrated with waveguide combiners fabricated using an InGaAs/GaAs heterostructure. The corresponding wavelength demultiplexer unit is based on a Rowland circle grating spectrometer monolithically integrated with a metal-semiconductor-metal (MSM) detector array fabricated on an InGaAs/AlGaAs/GaAs heterostructure. The epitaxial layer wafers for both transmitter and receiver modules were grown in single molecular beam epitaxy (MBE) runs.

Ultrafast electron tunneling times in reverse-biased quantum-well laser structures

We report extremely efficient and fast (approximately 25 pS FWHM) escape times of optically generated carriers in a reverse biased GaAs/AlGaAs graded index separate confined heterostructure single quantum well (GRINSCH-SQW) laser. Room temperature photoconductivity (PC) measurements in a high speed ridge waveguide detector are compared with time resolved photoluminescence (PL) measurements at T equals 20 K, 70 K, and 150 K. By comparing the experimental PL and PC response times and efficiencies as a function of bias voltage and temperature with theory, we show that the results are consistent with a simple model based on electron recombination and escape out of the quantum well. Electron escape occurs by either direct tunneling out of the lower electronic level, by thermally assisted tunneling out of the upper weakly bound state, or by thermionic emission over the barrier, depending on the bias voltage and temperature.