By controlling the thickness of the grating depth with chemical beam epitaxy (CBE) growth time, w... more By controlling the thickness of the grating depth with chemical beam epitaxy (CBE) growth time, we report in this letter the design and performance of an integrated tunable detector. A carefully designed tunable active filter, which allows only one below threshold Fabry–Perot mode for operation, is integrated with a waveguide detector. The full tuning range of this kind of tunable device can now be utilized for system applications.
The current era is notably characterized by the major advances in communication technologies. The... more The current era is notably characterized by the major advances in communication technologies. The increased connectivity has been transformative in terrestrial, space, and undersea applications. Nonetheless, the water medium imposes unique constraints on the signals that can be pursued for establishing wireless links. While numerous studies have been dedicated to tackling the challenges for underwater communication, little attention has been paid to effectively interfacing the underwater networks to remote entities. Particularly it has been conventionally assumed that a surface node will be deployed to act as a relay using acoustic links for underwater nodes and radio links for air-based communication. Yet, such an assumption could be, in fact, a hindrance in practice. The paper discusses alternative means by allowing communication across the air–water interface. Specifically, the optoacoustic effect, also referred to as photoacoustic effect, is being exploited as a means for achiev...
There is a rise in the study of functional connectivity among various cortical regions and invest... more There is a rise in the study of functional connectivity among various cortical regions and investigations to uncover causal links between a stimulus and the corresponding neural dynamics through electrophysiological imaging of the human brain. Animal model that exhibit simplistic representations of such networks open a doorway for such investigations and are gaining rapid popularity. In this study, we investigate and compare resting state network and auditory stimulus related activity with minimal invasive technology along computational spectral analysis on a C57/BL6 based mouse model. Somatosensory, motor and visual cortex are observed to be highly active and significantly correlated (p-value<0.05). Moreover, given the spatial limitation due to small size of the mouse head, we also describe a low-cost and effective fabrication process for the mouse EEG Polyimide Based Microelectrodes (PBM) array. The easy-to-implement fabrication process involves transfer of the pattern on a cop...
ABSTRACT We report in this work the near-Infrared optical quenching effects on mid-Infrared Quant... more ABSTRACT We report in this work the near-Infrared optical quenching effects on mid-Infrared Quantum Cascade Lasers (QCLs). The quenching effect is both intensity and wavelength dependent. A group of strain-compensated InGaAs/InAlAs, 4.8mum mid-IR QCLs, were used in the experiment. The pump lasers are near-IR lasers with wavelengths ranging from 1550nm to visible wavelength around 500nm. When the pump lasers have their lasing wavelengths shorter than 950 nm, it seems that majority of the generated electrons are excited above the conduction band edge of the InAlAs material and be swept off as photoconductive current without significantly affecting the QCL intersubband operations. So their quenching effect is weaker. We also observe that a near-IR laser with good quenching ability can modulate the mid-IR laser with speeds way above 100 MHz, which excludes the possibility of a thermal origin of these results.
Low threshold quantum cascade lasers (QCLs) are important for low-power chemical sensor applicati... more Low threshold quantum cascade lasers (QCLs) are important for low-power chemical sensor applications. We report a low-threshold high-period-number 4.8mum strain-balanced InGaAs/InAlAs quantum cascade laser. By growing more periods (up to 60 periods) of QCL stages, shortening the QCL cavity length, and applying high-reflectivity coatings on both facets of the laser cavity, low threshold QCLs can be obtained. At current stage a QCL threshold of <30mA at 20K, <50mA at 80K, and <120mA near room temperature were achieved. Low current threshold QCLs will have significant impacts to future chemical sensing systems.
Conference on Lasers and Electro-Optics 2012, 2012
ABSTRACT Heat dissipation issues are critical for quantum-cascade-laser (QCL) high-power operatio... more ABSTRACT Heat dissipation issues are critical for quantum-cascade-laser (QCL) high-power operations. Simulation shows multi-emitter array can better dissipate heat than broad area laser does. QCL arrays with 5 and 16 elements are fabricated and results are presented.
Conference on Lasers and Electro-Optics 2012, 2012
ABSTRACT Using quantum-cascade-lasers (QCL) as resonant optical amplifiers, active filters, and d... more ABSTRACT Using quantum-cascade-lasers (QCL) as resonant optical amplifiers, active filters, and detectors with gain, we demonstrated signal amplification in the mid-IR wavelength range. Optical gain of &gt;10dB and electrical gain of &gt;28dB were achieved.
Neuron optical excitations are important for brain-circuitry explorations and sensory-neuron-stim... more Neuron optical excitations are important for brain-circuitry explorations and sensory-neuron-stimulation applications. To optimize the stimulation, we identify neuron mid-IR absorption peaks in this study and discuss their meanings and delivery methods of mid-IR photons.
Amplification and detection characteristics of mid-infrared quantum cascade lasers (QCLs) are stu... more Amplification and detection characteristics of mid-infrared quantum cascade lasers (QCLs) are studied. The QCL amplifier has an adjustable bandwidth and tunable gain peak to function as a tunable mid-IR filter. By biasing the QCL slightly below its threshold, we demonstrated more than 11dB optical gain and over 28dB electrical gain at specified wavelengths. In the electrical gain measurement process, the resonant amplifier also functioned as a detector. Mid-IR amplification and detection can be achieved using the same material for the laser source. This indicates that intersubband based gain materials can be ideal candidates for mid-IR photonic integrations.
By controlling the thickness of the grating depth with chemical beam epitaxy (CBE) growth time, w... more By controlling the thickness of the grating depth with chemical beam epitaxy (CBE) growth time, we report in this letter the design and performance of an integrated tunable detector. A carefully designed tunable active filter, which allows only one below threshold Fabry–Perot mode for operation, is integrated with a waveguide detector. The full tuning range of this kind of tunable device can now be utilized for system applications.
The current era is notably characterized by the major advances in communication technologies. The... more The current era is notably characterized by the major advances in communication technologies. The increased connectivity has been transformative in terrestrial, space, and undersea applications. Nonetheless, the water medium imposes unique constraints on the signals that can be pursued for establishing wireless links. While numerous studies have been dedicated to tackling the challenges for underwater communication, little attention has been paid to effectively interfacing the underwater networks to remote entities. Particularly it has been conventionally assumed that a surface node will be deployed to act as a relay using acoustic links for underwater nodes and radio links for air-based communication. Yet, such an assumption could be, in fact, a hindrance in practice. The paper discusses alternative means by allowing communication across the air–water interface. Specifically, the optoacoustic effect, also referred to as photoacoustic effect, is being exploited as a means for achiev...
There is a rise in the study of functional connectivity among various cortical regions and invest... more There is a rise in the study of functional connectivity among various cortical regions and investigations to uncover causal links between a stimulus and the corresponding neural dynamics through electrophysiological imaging of the human brain. Animal model that exhibit simplistic representations of such networks open a doorway for such investigations and are gaining rapid popularity. In this study, we investigate and compare resting state network and auditory stimulus related activity with minimal invasive technology along computational spectral analysis on a C57/BL6 based mouse model. Somatosensory, motor and visual cortex are observed to be highly active and significantly correlated (p-value<0.05). Moreover, given the spatial limitation due to small size of the mouse head, we also describe a low-cost and effective fabrication process for the mouse EEG Polyimide Based Microelectrodes (PBM) array. The easy-to-implement fabrication process involves transfer of the pattern on a cop...
ABSTRACT We report in this work the near-Infrared optical quenching effects on mid-Infrared Quant... more ABSTRACT We report in this work the near-Infrared optical quenching effects on mid-Infrared Quantum Cascade Lasers (QCLs). The quenching effect is both intensity and wavelength dependent. A group of strain-compensated InGaAs/InAlAs, 4.8mum mid-IR QCLs, were used in the experiment. The pump lasers are near-IR lasers with wavelengths ranging from 1550nm to visible wavelength around 500nm. When the pump lasers have their lasing wavelengths shorter than 950 nm, it seems that majority of the generated electrons are excited above the conduction band edge of the InAlAs material and be swept off as photoconductive current without significantly affecting the QCL intersubband operations. So their quenching effect is weaker. We also observe that a near-IR laser with good quenching ability can modulate the mid-IR laser with speeds way above 100 MHz, which excludes the possibility of a thermal origin of these results.
Low threshold quantum cascade lasers (QCLs) are important for low-power chemical sensor applicati... more Low threshold quantum cascade lasers (QCLs) are important for low-power chemical sensor applications. We report a low-threshold high-period-number 4.8mum strain-balanced InGaAs/InAlAs quantum cascade laser. By growing more periods (up to 60 periods) of QCL stages, shortening the QCL cavity length, and applying high-reflectivity coatings on both facets of the laser cavity, low threshold QCLs can be obtained. At current stage a QCL threshold of <30mA at 20K, <50mA at 80K, and <120mA near room temperature were achieved. Low current threshold QCLs will have significant impacts to future chemical sensing systems.
Conference on Lasers and Electro-Optics 2012, 2012
ABSTRACT Heat dissipation issues are critical for quantum-cascade-laser (QCL) high-power operatio... more ABSTRACT Heat dissipation issues are critical for quantum-cascade-laser (QCL) high-power operations. Simulation shows multi-emitter array can better dissipate heat than broad area laser does. QCL arrays with 5 and 16 elements are fabricated and results are presented.
Conference on Lasers and Electro-Optics 2012, 2012
ABSTRACT Using quantum-cascade-lasers (QCL) as resonant optical amplifiers, active filters, and d... more ABSTRACT Using quantum-cascade-lasers (QCL) as resonant optical amplifiers, active filters, and detectors with gain, we demonstrated signal amplification in the mid-IR wavelength range. Optical gain of &gt;10dB and electrical gain of &gt;28dB were achieved.
Neuron optical excitations are important for brain-circuitry explorations and sensory-neuron-stim... more Neuron optical excitations are important for brain-circuitry explorations and sensory-neuron-stimulation applications. To optimize the stimulation, we identify neuron mid-IR absorption peaks in this study and discuss their meanings and delivery methods of mid-IR photons.
Amplification and detection characteristics of mid-infrared quantum cascade lasers (QCLs) are stu... more Amplification and detection characteristics of mid-infrared quantum cascade lasers (QCLs) are studied. The QCL amplifier has an adjustable bandwidth and tunable gain peak to function as a tunable mid-IR filter. By biasing the QCL slightly below its threshold, we demonstrated more than 11dB optical gain and over 28dB electrical gain at specified wavelengths. In the electrical gain measurement process, the resonant amplifier also functioned as a detector. Mid-IR amplification and detection can be achieved using the same material for the laser source. This indicates that intersubband based gain materials can be ideal candidates for mid-IR photonic integrations.
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Papers by Fow-Sen Choa