User talk:Bangalibabu1234

Abhijit Chakravarty received his Bachelor of Technology degree in electronics and telecommunication from the Institute of Engineering and Management, India, 2000. He worked as a network engineer from 2000 to 2002 in HCL, India. In 2002 he joined the Florida Institute of Technology for his MS in electrical engineering and worked as a research assistant in the optronics laboratory.In 2005 he received his MS in electrical engineering.He has worked at BEAM Company,Orlando, Florida, as a research scientist on nonlinear optics of liquid crystals. Currently he is pursuing his PhD degree in electrical engineering and working on optical communication and sensor projects.

Society member

SPIE Member, IEEE member, LEOS member.

Research Interests:

Fiber optics communication and sensor Semiconductor based wireless optical sensor Semiconductor characterization (specially SiC, Si, Germanium, GaAs, InP) Photo lithography Wireless Communication Laser doping, laser-microstructuring (Nd: YAG Laser) Thin film coating and optical fabrication methods Design and device implementation of diode pumped solid state lsers, Q-switching, Mode locking etc.

Current Research Work

1) Silicon Carbide (SiC) based Wireless optical sensor for high temperature and pressure measurement (CREOL & FPCE-The College of Optics & Photonics, Orlando, Florida) (US Department of Energy)

Single crystal silicon carbide is a chemically inert transparent material with superior oxidation-resistant properties at elevated temperatures compared to black polycrystalline silicon carbide substrates. These improved properties make crystalline silicon carbide a good optical sensor material for harsh environments such as combustion chambers and turbine systems. Interferometric optical sensors are orders of magnitude more sensitive than electrical sensors and are proposed for these applications. Silicon carbide itself behaves as a Fabry-Pérot etalon eliminating the need for an external interferometer for any measurement using this silicon carbide as a sensor. The principle of the optical sensor in this study is the temperature- and pressure-dependent refractive index of silicon carbide, which can be used to determine the temperatures and pressures of gases that are in contact with silicon carbide. Interference patterns produced by a silicon carbide (4H-SiC) wafer due to multiple reflections of a helium-neon laser beam of wavelength of 632.8 nm have been obtained at temperatures up to 500 °C and pressures up to 600 psi. The pattern changes for the same gas at different temperatures and pressures and for different gases at the same temperature and pressure. The refractive index at the wafer-gas interface is calculated from the interference pattern and the refractive index gradients with respect to temperature and pressure, respectively, are also determined. Decoupling temperature and pressure using these gradients and the measured reflectivity data are discussed in this paper. ©2007 American Institute of Physics

2) Temperature-dependent refractive index of semiconductors such as Si,GaAs,InP,Ge

A single oscillator Lorentz model is applied to four different semiconductors having diamond-like crystal structure to describe the temperature dependence of their refractive index between 300 and 600 K. Theoretical results are compared to previous experiments and to experiments carried out in this study for Si, Ge, GaAs and InP. An efficient experimental method is also presented, enabling fast measurements of the refractive index of materials. Using the Yu-Brooks formalism and the energy bandgap at the X-point of the Brillouin zone, the temperature-dependent refractive indices are calculated and they agree well with experiments, particularly, considering the simplicity of the Lorentz model. However, there are discrepancies between the theory and experiment at high temperatures (near 600 K) in certain cases. This discrepancy may be due to the single oscillator approximation. Additionally the effect of “self-energy” on the temperature dependence of the energy bandgap, such as the temperature-dependent damping of the oscillation of electrons can be significant at higher temperatures

3) Fiber Optic Communication:

Transmission and Detection of Two Spatially Multiplexed Channels on a Standard Silica Based 62.5/125µm Multimode Fiber. Concept: A novel and revolutionary spatial domain multiplexing technique for optical fibers has been developed. This technique provides a method to launch, transport and detect two or more optical channels operating at exactly the same wavelength inside an optical fiber. Hence the bandwidth of existing and new optical fiber systems can be doubled, tripled, or increased by multiple folds. It adds a new dimension to existing multiplexing techniques and complements time division multiplexing (TDM) as well as wavelength/dense wavelength division-multiplexing (WDM/DWDM) techniques. (Spatial Domain Multiplexing / SDM) (United States Patent 7174067)

4) Fiber optic liquid level detection sensor:

A fiber optic liquid level detector uses optical fibers to detect the presence or absence of liquids. The waveguide properties of optical fibers tend to deviate from the normal at dielectric interfaces so that a fiber optic probe whose tip is immersed in a liquid has a reflection coefficient smaller than when surrounded by air or vacuum. This is caused by the differences in refractive indices of liquid and air and is used to measure the amount of light transmitted or reflected by the fiber in the presence or absence of a liquid. A fiber optic coupler is connected to a light source from a first fiber optic line and is connected to a light detector from a second fiber optic line. A fiber optic probe is connected to the fiber optic coupler for insertion into a liquid to be detected, where only the unconnected end of the probe is sensitive to the presence or absence of fluid. A signal processor is connected to the light detector for determining the deviation of the reflected light at the dielectric interface between the liquid being detected and the atmosphere adjacent the liquid. Liquid level is measured by detecting the presence or absence of liquid, resulting from a chancre in reflective coefficient(s), using one or more fiber optic probes positioned at specific levels

Publications

1) S. Murshid and A. Chakravarty, Experimental results from co-propagating analog channels of same wavelength over 600 meter long standard step index multimode fiber, Journal of Optical Engineering, vol 47, Issue 10, pp. 1005002(1)-1005002(4), 2008.

2) A. Chakravarty, N. Quick, A. Kar, ‘Decoupling of silicon carbide optical sensor response for temperature and pressure measurements’,Journal of Applied Physics, Vol 102, Issue 7, pp.073111, 2007.

3) Nicolas Cherroret, Abhijit Chakravarty, and Aravinda Kar,'Temperature-dependent refractive index of semiconductors',Journal of Material Scinece, Vol 43, Issue 6, pp.1795-1801, 2008.

4) A.Chakravarty, N. Quick, A. Kar, ‘ Wireless optical sensor for smart thin film coating’.Advanced coating material and technology, Pennstate University, 2006.

5) A.Chakravarty, N. Quick, A. Kar, ‘ SiC Based Wireless Optical Sensor for Combustion Chemical Species',Industrial affiliates, CREOL & FPCE, UCF,2005.

6) A.Chakravarty, S. Bet, N. Quick, A. Kar, Laser Doping of Wide Bandgap Semiconductors: Fabrication of Laser Diodes and Wireless Optical Sensors, (Industrial affiliates, CREOL & FPCE, UCF, ,pp. 16, issue 11,2006).

7) A.Chakravarty‘ Application of laser metallization and doping to improve the accuracy of silicon carbide based wireless optical temperature and pressure sensor’. (Submitted to Journal of Material Science2007).

8) S. Murshid, A. Chakravarty, R. Biswas, Simultaneous transmission of two channels operating at the same wavelength in standard multimode fibers, JWA 107, Proceedings of The Conference on Lasers and Electro-Optics (CLEO), San Jose, CA, May 4-9, 2008.

9) S. Murshid, A. Chakravarty, R. Biswas, Spatially Multiplexed Beam Combining and Beam Separator Modules for Optical Communication Bandwidth Enhancement, WOC 621-133, Proceedings of The Eighth IASTED International Conferences on Wireless and Optical Communications (WOC 2008), Quebec City, Canada, May 26-28, 2008.

10) S. Murshid and A. Chakravarty, R. Biswas,and Ebad Zahir,"Co-propagation of six spatially separated helical channels over a single strand of standard plastic optical fibers using spatial domain multiplexing", Proceedings of The 17th International Conference on Plastic Optical Fibers, (POF), August 25 - 28, Santa Clara, CA, Aug. 2008 IEEE, Piscataway, NJ (2008).

11) A. Chakravarty, "Crystalline Silicon based remote optical sensor for temperature measurement",Proceedings of The 17th International Conference on Plastic Optical Fibers, (POF), August 25 - 28, Santa Clara, CA, Aug. 2008 IEEE, Piscataway, NJ (2008).

12) A. Chakravarty, "Gallium Arsenide Based Wireless Optical Sensor for High Temperature Measurement", Proceedings of The 17th International Conference on Plastic Optical Fibers, (POF), August 25 - 28, Santa Clara, CA, Aug. 2008 IEEE, Piscataway, NJ (2008).

13) A. Chakravarty and R. Biswas, “Optical Fiber Based Extrinsic Fabry-Perot Interferometric Sensor for Temperature Measurement”, Proceedings of The 17th International Conference on Plastic Optical Fibers, (POF), August 25 - 28, Santa Clara, CA, Aug. 2008 IEEE, Piscataway, NJ (2008).

14) R. Biswas and A. Chakravarty, “Liquid Level Detection Sensor Using Plastic Optical Fiber”, Proceedings of The 17th International Conference on Plastic Optical Fibers, (POF), August 25 - 28, Santa Clara, CA, Aug. 2008 IEEE, Piscataway, NJ (2008).

15) S. Murshid, A. Chakravarty, R. Biswas, "Beam Profile of Two Simultaneously Propagating Channels of Same Wavelength in Step Index Multimode Fibers", Proceedings at Frontiers in Optics (FiO) 2008/Laser Science XXIV (LS) Conf. FiO/LS, October 2008, Rochester,New York, Laurin Publishing, Pittsfield, MA, 2008.