We have discovered conditions for the selective lift‐off of large area epitaxial AlGaAs films fro... more We have discovered conditions for the selective lift‐off of large area epitaxial AlGaAs films from the substrate wafers on which they were grown. A 500‐Å‐thick AlAs release layer is selectivity etched away, leaving behind a high‐quality epilayer and a reusable GaAs substrate. We ...
We discuss the design of uncooled lasers which minimizes the change in both threshold current and... more We discuss the design of uncooled lasers which minimizes the change in both threshold current and slope efficiency over the temperature range from -40 to 85°C. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP material system instead of the conventional GaxIn1-xAsyP1-y/InP material system. Experimentally, the AlxGayIn1-x-y As/InP strained quantum well lasers show superior high temperature performances such as a small drop of 0.3 dB in slope efficiency when the heat sink temperature changes from 25 to 100°C, a maximum CW operation temperature of 185°C, a thermally-limited 3-dB bandwidth of 13.9 GHz at 85°C, and a mean-time-to-failure of 33 years at 100°C and 10 mW output power
We discuss the design of uncooled lasers which minimizes the change in both threshold current and... more We discuss the design of uncooled lasers which minimizes the change in both threshold current and slope efficiency over the temperature range from -40 to 85°C. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP material system instead of the conventional GaxIn1-xAsyP1-y/InP material system. Experimentally, the AlxGayIn1-x-y As/InP strained quantum well lasers show superior high temperature performances such as a small drop of 0.3 dB in slope efficiency when the heat sink temperature changes from 25 to 100°C, a maximum CW operation temperature of 185°C, a thermally-limited 3-dB bandwidth of 13.9 GHz at 85°C, and a mean-time-to-failure of 33 years at 100°C and 10 mW output power
... The small signal modulation response is directly read from the microwave network analyser whi... more ... The small signal modulation response is directly read from the microwave network analyser which compares the electrical signal gener-ated by the photodiode to the electrical ... However, the k factor [7] is between 0.4 and 0.6 ns and does not correlate to the wavelength detuning ...
This paper extensively studies the design and resulting performance of high power EDFA pump laser... more This paper extensively studies the design and resulting performance of high power EDFA pump lasers to increase the operating power with each generation of chip developed while maintaining or improving other critical design features.
Wavelength conversion in wavelength-division multiplexing (WDM) networks offers distributed netwo... more Wavelength conversion in wavelength-division multiplexing (WDM) networks offers distributed network management and reduction in blocking rising from wavelength contentions. Transparent WDM networks can route signals of various formats and protocols, and facilitate network evolution with full interoperability. Wavelength conversion with simultaneous multichannel conversion capability can serve as building blocks for scalable and modular wavelength-interchanging-cross-connects. Wavelength conversion by difference-frequency generation uniquely
We report the integration of a multi-wavelength multi-quantum-well distributed-feedback (DFB) las... more We report the integration of a multi-wavelength multi-quantum-well distributed-feedback (DFB) laser array with a star coupler and optical booster amplifiers on the same chip for future wavelength-division multiplexed lightwave communication systems and multi-wavelength optical networks.
Abstract It is shown that the planar metal-semiconductor-metal photodetectors on InGaAs/InP with ... more Abstract It is shown that the planar metal-semiconductor-metal photodetectors on InGaAs/InP with a strained GaAs top layer are promising candidates for optoelectronic integration of long-wavelength (1.3-1.55 mu m) fiber-optic components, combining speed of response (8.5-GHz bandwidth) with a simple technology (only four processing steps were required for the presented detector). Some low-frequency gain was observed at high bias voltages along with a low-frequency increase in noise above that expected from shot ...
... Optical Fibre Communications, San Jose, CA, USA, 1992, Paper ThA4 5 CAMY, P., ROMAN, JE, HEMP... more ... Optical Fibre Communications, San Jose, CA, USA, 1992, Paper ThA4 5 CAMY, P., ROMAN, JE, HEMPSTEAD, M., LABORDE, P., and PD3-1 ... JBD Soole, MR Amersfoort, HP LeBlanc, NC Andreadakis, A. Rajhel, C. Caneau, MA Koza, R. Bhat, C. Youtsey and I. Adesida ...
Summary form only given. In summary, we have investigated wavelength conversion by quasi-phase-ma... more Summary form only given. In summary, we have investigated wavelength conversion by quasi-phase-matched optical frequency conversion (OFG) in an AlGaAs waveguide. Linear conversion process and spectral inversion properties are demonstrated. The conversion efficiencies are polarization insensitive while the device also shows polarization diversity. Simultaneous conversions of multiple input wavelengths with no cross talk are demonstrated.
Design considerations for fabricating highly efficient uncooled semiconductor lasers are discusse... more Design considerations for fabricating highly efficient uncooled semiconductor lasers are discussed. The parameters investigated include the temperature characteristics of threshold current, quantum efficiency, and modulation speed. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP material system instead of the conventional GaxIn1-x AsyP1-y/InP material system. To reduce the transparency current and the carrier-density-dependent loss due to the intervalence-band absorption, strained-layer quantum wells are chosen as the active layer. Experimentally, 1.3-μm compressive-strained five-quantum-well lasers and tensile-strained three-quantum-well lasers were fabricated using a 3-μm wide ridge-waveguide laser structure. For both types of lasers, the intrinsic material parameters are found to be similar in magnitude and in temperature dependence if they are normalized to each well. Specifically, the compressive-strained five-quantum-well lasers show excellent extrinsic temperature characteristics, such as small drop of 0.3 dB in differential quantum efficiency when the heat sink temperature changes from 25 to 100°C, and a large small-signal modulation bandwidth of 8.6 GHz at 85°C. The maximum 3 dB modulation bandwidth was measured to be 19.6 GHz for compressive-strained lasers and 17 GHz for tensile-strained-lasers by an optical modulation technique. The strong carrier confinement also results in a small k-factor (0.25 ns) which indicates the potential for high-speed modulation up to 35 GHz. In spite of the aluminum-containing active layer, no catastrophic optical damage was observed at room temperature up to 218 mW for compressive-strained five-quantum-well lasers and 103 mW for tensile-strained three-quantum-well lasers. For operating the compressive-strained five-quantum-well lasers at 85°C with more than 5 mW output power, a mean-time-to-failure (MTTF) of 9.4 years is projected from a preliminary life test. These lasers are highly attractive for uncooled, potentially low-cost applications in the subscriber loop
IEEE Journal of Selected Topics in Quantum Electronics, 1997
We demonstrate GaAs-based 0.98-μm multiple-quantum-well (MQW) tunneling injection lasers with ult... more We demonstrate GaAs-based 0.98-μm multiple-quantum-well (MQW) tunneling injection lasers with ultrahigh-modulation bandwidths. Electrons are injected into the active region via tunneling, leading to a “cold” carrier distribution in the quantum wells (QWs). The tunneling time (2 pS) measured by time resolved differential transmission spectroscopy agrees with the capture time extracted form the electrical impedance measurement. The tunneling barrier prevents electrons
In the Optical Network Technology Consortium, we have improved the design and fabrication of InP ... more In the Optical Network Technology Consortium, we have improved the design and fabrication of InP multiwavelength laser arrays with integrated combiners for the opical transmitters of WDM network access modules. Here we report our recent progress
We have discovered conditions for the selective lift‐off of large area epitaxial AlGaAs films fro... more We have discovered conditions for the selective lift‐off of large area epitaxial AlGaAs films from the substrate wafers on which they were grown. A 500‐Å‐thick AlAs release layer is selectivity etched away, leaving behind a high‐quality epilayer and a reusable GaAs substrate. We ...
We discuss the design of uncooled lasers which minimizes the change in both threshold current and... more We discuss the design of uncooled lasers which minimizes the change in both threshold current and slope efficiency over the temperature range from -40 to 85°C. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP material system instead of the conventional GaxIn1-xAsyP1-y/InP material system. Experimentally, the AlxGayIn1-x-y As/InP strained quantum well lasers show superior high temperature performances such as a small drop of 0.3 dB in slope efficiency when the heat sink temperature changes from 25 to 100°C, a maximum CW operation temperature of 185°C, a thermally-limited 3-dB bandwidth of 13.9 GHz at 85°C, and a mean-time-to-failure of 33 years at 100°C and 10 mW output power
We discuss the design of uncooled lasers which minimizes the change in both threshold current and... more We discuss the design of uncooled lasers which minimizes the change in both threshold current and slope efficiency over the temperature range from -40 to 85°C. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP material system instead of the conventional GaxIn1-xAsyP1-y/InP material system. Experimentally, the AlxGayIn1-x-y As/InP strained quantum well lasers show superior high temperature performances such as a small drop of 0.3 dB in slope efficiency when the heat sink temperature changes from 25 to 100°C, a maximum CW operation temperature of 185°C, a thermally-limited 3-dB bandwidth of 13.9 GHz at 85°C, and a mean-time-to-failure of 33 years at 100°C and 10 mW output power
... The small signal modulation response is directly read from the microwave network analyser whi... more ... The small signal modulation response is directly read from the microwave network analyser which compares the electrical signal gener-ated by the photodiode to the electrical ... However, the k factor [7] is between 0.4 and 0.6 ns and does not correlate to the wavelength detuning ...
This paper extensively studies the design and resulting performance of high power EDFA pump laser... more This paper extensively studies the design and resulting performance of high power EDFA pump lasers to increase the operating power with each generation of chip developed while maintaining or improving other critical design features.
Wavelength conversion in wavelength-division multiplexing (WDM) networks offers distributed netwo... more Wavelength conversion in wavelength-division multiplexing (WDM) networks offers distributed network management and reduction in blocking rising from wavelength contentions. Transparent WDM networks can route signals of various formats and protocols, and facilitate network evolution with full interoperability. Wavelength conversion with simultaneous multichannel conversion capability can serve as building blocks for scalable and modular wavelength-interchanging-cross-connects. Wavelength conversion by difference-frequency generation uniquely
We report the integration of a multi-wavelength multi-quantum-well distributed-feedback (DFB) las... more We report the integration of a multi-wavelength multi-quantum-well distributed-feedback (DFB) laser array with a star coupler and optical booster amplifiers on the same chip for future wavelength-division multiplexed lightwave communication systems and multi-wavelength optical networks.
Abstract It is shown that the planar metal-semiconductor-metal photodetectors on InGaAs/InP with ... more Abstract It is shown that the planar metal-semiconductor-metal photodetectors on InGaAs/InP with a strained GaAs top layer are promising candidates for optoelectronic integration of long-wavelength (1.3-1.55 mu m) fiber-optic components, combining speed of response (8.5-GHz bandwidth) with a simple technology (only four processing steps were required for the presented detector). Some low-frequency gain was observed at high bias voltages along with a low-frequency increase in noise above that expected from shot ...
... Optical Fibre Communications, San Jose, CA, USA, 1992, Paper ThA4 5 CAMY, P., ROMAN, JE, HEMP... more ... Optical Fibre Communications, San Jose, CA, USA, 1992, Paper ThA4 5 CAMY, P., ROMAN, JE, HEMPSTEAD, M., LABORDE, P., and PD3-1 ... JBD Soole, MR Amersfoort, HP LeBlanc, NC Andreadakis, A. Rajhel, C. Caneau, MA Koza, R. Bhat, C. Youtsey and I. Adesida ...
Summary form only given. In summary, we have investigated wavelength conversion by quasi-phase-ma... more Summary form only given. In summary, we have investigated wavelength conversion by quasi-phase-matched optical frequency conversion (OFG) in an AlGaAs waveguide. Linear conversion process and spectral inversion properties are demonstrated. The conversion efficiencies are polarization insensitive while the device also shows polarization diversity. Simultaneous conversions of multiple input wavelengths with no cross talk are demonstrated.
Design considerations for fabricating highly efficient uncooled semiconductor lasers are discusse... more Design considerations for fabricating highly efficient uncooled semiconductor lasers are discussed. The parameters investigated include the temperature characteristics of threshold current, quantum efficiency, and modulation speed. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP material system instead of the conventional GaxIn1-x AsyP1-y/InP material system. To reduce the transparency current and the carrier-density-dependent loss due to the intervalence-band absorption, strained-layer quantum wells are chosen as the active layer. Experimentally, 1.3-μm compressive-strained five-quantum-well lasers and tensile-strained three-quantum-well lasers were fabricated using a 3-μm wide ridge-waveguide laser structure. For both types of lasers, the intrinsic material parameters are found to be similar in magnitude and in temperature dependence if they are normalized to each well. Specifically, the compressive-strained five-quantum-well lasers show excellent extrinsic temperature characteristics, such as small drop of 0.3 dB in differential quantum efficiency when the heat sink temperature changes from 25 to 100°C, and a large small-signal modulation bandwidth of 8.6 GHz at 85°C. The maximum 3 dB modulation bandwidth was measured to be 19.6 GHz for compressive-strained lasers and 17 GHz for tensile-strained-lasers by an optical modulation technique. The strong carrier confinement also results in a small k-factor (0.25 ns) which indicates the potential for high-speed modulation up to 35 GHz. In spite of the aluminum-containing active layer, no catastrophic optical damage was observed at room temperature up to 218 mW for compressive-strained five-quantum-well lasers and 103 mW for tensile-strained three-quantum-well lasers. For operating the compressive-strained five-quantum-well lasers at 85°C with more than 5 mW output power, a mean-time-to-failure (MTTF) of 9.4 years is projected from a preliminary life test. These lasers are highly attractive for uncooled, potentially low-cost applications in the subscriber loop
IEEE Journal of Selected Topics in Quantum Electronics, 1997
We demonstrate GaAs-based 0.98-μm multiple-quantum-well (MQW) tunneling injection lasers with ult... more We demonstrate GaAs-based 0.98-μm multiple-quantum-well (MQW) tunneling injection lasers with ultrahigh-modulation bandwidths. Electrons are injected into the active region via tunneling, leading to a “cold” carrier distribution in the quantum wells (QWs). The tunneling time (2 pS) measured by time resolved differential transmission spectroscopy agrees with the capture time extracted form the electrical impedance measurement. The tunneling barrier prevents electrons
In the Optical Network Technology Consortium, we have improved the design and fabrication of InP ... more In the Optical Network Technology Consortium, we have improved the design and fabrication of InP multiwavelength laser arrays with integrated combiners for the opical transmitters of WDM network access modules. Here we report our recent progress
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Papers by Rajaram Bhat