Wideband Photonic Devices
Broad spectral image sensors are required for various ground-based, air-borne, space-borne military applications, including the atmospheric properties measurement, surface topography and remote sensing. To date, several sensors covering different spectral ranges are used for this purpose. Next generation instruments require single sensor (or its array) that covers multiple spectral bands (0.3 to 2.5 μm of wavelengths) and could be used for different applications. Solid-state image sensors with higher resolution are used in many commercial applications and also for other light imaging uses. As today's CCD and CMOS image sensors technology are based on Si-technology, the detectable spectral ranges are limited to the wavelengths below 1 μm where Si exhibits absorption. Besides, CCD and CMOS image sensors have also other shortcomings such as low frequency response combined with low quantum efficiency over broad spectral response.
InGaAs based detector on InP substrate is used for detecting the light with wavelength range from 0.9 to 1.7 μm which is widely used in the optical communication. Photodiodes especially of InGaAs pin type have been studied extensively over the last decade for its application in optical communication. Now a days, the photodetector speed as high as 40 Gb/s, and quantum efficiency close to 100% are available for optical communication. InGaAs material is usually used as absorption material, and the diode is fabricated on the InP wafer. We design InGaAs photodetectors with enhanced responsivity between 500 and 920 nm. Our calculations show that reasonable responsivities can be achieved in the visible spectrum with this design .
- C. Tam, C-J Chiang, M. Cao, M. Chen, M. Wong, A. Vazquez, J. Poon, K. Aihara, A. Chen, J. Frei, C. D. Johns, Ibrahim Kimukin, Achyut K. Duttaa and M. Saif Islam, "High Speed pin Photodetector with Ultra-Wide Spectral Responses", SPIE Photonics East, 2005.
- K. Dutta and M. S. Islam, "Novel Broadband Photodetector for Optical Communication", The SPIE Conference on Active and Passive Optical Components for WDM Communications Vol. 6014, pp. C-1-10, 2005 (Invited).
- A. K. Dutta, N. K. Dhar, P. Wijewarnasuriya, and M. Saif Islam , "Novel Multi-color Image Sensors for Biochemical, Biomedical, and Security Applications", Proceedings of the SPIE Optics East Conference on Nanosensing Materials and Devices, Vol. 6008, pp 1-15, 2005. (Invited)