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1,179 results on '"Jayaraman, V."'

108. Design and performance of broadly tunable, narrow line-width, high repetition rate 1310nm VCSELs for swept source optical coherence tomography

Author

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Jayaraman, V., Jiang, J., Potsaid, B., Cole, G., Fujimoto, J., Cable, A., Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Jayaraman, V., Jiang, J., Potsaid, B., Cole, G., Fujimoto, J., and Cable, A.

Abstract

MEMS tunable vertical cavity surface emitting laser (MEMS-VCSEL) development, over the past two decades, has primarily focused on communications and spectroscopic applications. Because of the narrow line-width, single-mode operation, monolithic fabrication, and high-speed capability of these devices, MEMS-VCSELs also present an attractive optical source for emerging swept source optical coherence tomography (SSOCT) systems. In this paper, we describe the design and performance of broadly tunable MEMS-VCSELs targeted for SSOCT, emphasizing 1310nm operation for cancer and vascular imaging. We describe the VCSEL structure and fabrication, employing a fully oxidized GaAs/AlxOy mirrors in conjunction with dielectric mirrors and InP-based multi-quantum well active regions. We also describe the optimization of MEMs speed and frequency response for SSOCT. Key results include 1310 nm VCSELs with >120nm dynamic tuning range and imaging rates near 1MHz, representing the widest VCSEL tuning range and some of the fastest swept source imaging rates thus far obtained. We also describe how low-noise semiconductor optical amplification boosts average optical power to the required levels, while maintaining superior OCT imaging quality and state of the art system sensitivity. Finally, we present measured multi-centimeter dynamic coherence length, and discuss the implications of VCSELs for OCT. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Published
2021

125. NEW GENES AND DISEASES / NGS & RELATED TECHNIQUES

Author

Meyer, A., primary, Cottrell, C., additional, Reshmi, S., additional, Pfau, R., additional, Lee, K., additional, Mathew, M., additional, Corsmeier, D., additional, Jayaraman, V., additional, Dave-Wala, A., additional, Hashimoto, S., additional, Matthews, T., additional, Mouhlas, D., additional, Stein, M., additional, Waldrop, M., additional, and Flanigan, K., additional

Published
2020
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132. Design and Development of Instrumentation for Remote Detection of Hydrogen Using Metal Oxide Sensor.

Author

Keshari, Ajay Kumar, Prabhakar Rao, J., Rama Murthy, A. Sree, and Jayaraman, V.

Subjects
HYDROGEN content of metals, METALLIC oxides, DETECTORS, LOCAL area networks
Abstract

Indigenous instrumentation setup was designed, developed and demonstrated for remote detection of hydrogen using metal oxide (MO) sensors. The metal oxide sensor was developed to sense the low concentration of hydrogen. The hardware developed was based on a function generator configuration and uniquely designed to give low excitation voltage across the sensor to improve the life of the sensor and reduces the number of components. The data acquisition software was developed to collect the sensor response in PC remotely. The hardware was calibrated, tested with standard resistance and found to give an accuracy of ±0.5% and high stability and reliability. The sensor response towards hydrogen was measured by the instrument. Different features of sensor response viz., sensitivity, response time and recovery time were studied towards different concentrations of hydrogen at optimized temperature. [ABSTRACT FROM AUTHOR]

Published
2022
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133. Epoxy-based Light Weight Gamma Ray Shielding Materials.

Author

Joshi, Shailesh, Chandrasekaran, S., Vijayalakshmi, I., Sivasubramanian, K., and Jayaraman, V.

Subjects
COMPOSITE materials, ATTENUATION coefficients, X-rays, CHEMICAL structure, PARAMETER estimation
Abstract

Lightweight epoxy-based X-ray/gamma-ray shielding materials were synthesized by blending epoxy resin with the different weight percent of lead oxide, bismuth oxide, and tungsten oxide powders. The synthesized composites were characterized using FTIR, elemental analyzer, and X-ray radiography for their chemical structure, elemental composition, and filler distribution. The photon interaction parameters such as linear/mass attenuation coefficient, attenuation percentage, and half value layer were determined for all composites at photon energies 59.5, 364, and 661.7 keV. The measured mass attenuation coefficients of epoxy composites matched well with the obtained from XCOM. Moreover, the shielding effectiveness of the composites was analyzed by the half-value layer and heaviness of the composites and was compared with conventional shielding materials (concrete, lead, and steel). [ABSTRACT FROM AUTHOR]

Published
2022

135. Early Results from New Initiatives on SLR Tracking of GNSS and Synchronous Satellites

Author

Perlman, M. R., Appleby, G., Ipatov, A., Jayaraman, V., Noll, C. E., Pavlis, E. C., Shargorodsky, V., and Woo, J.

Abstract

On November 16, 2013, at the 18th International Workshop on Laser Ranging in Fujiyoshida, Japan, the attendees adopted a resolution endorsing expanded ILRS tracking on Global Navigation Satellite System—GNSS satellites with retroreflector arrays of sufficient quality, highlighting the example of the fully populated GLONASS constellation.

Published
2020
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150. Electrical injury in pediatric patients – A case series

Author

Ramakrishnan, KMathangi, primary, Ramachandran, Bala, additional, Ravikumar, KG, additional, Ravikumar, K, additional, Putli, Sulochana, additional, Jayaraman, V, additional, Mathivanan, T, additional, Ravi, R, additional, Gnanamani, S, additional, and Babu, Mary, additional

Published
2020
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