Professor Utpal Das
Dept. of EE, and Center for Lasers and Photonics
Indian Institute of Technology, Kanpur, 208016, UP, India.
Coupled resonator rings, of one placed inside another is called embedded ring (ER) resonator, and show sharp resonances due to interfering modes of the individual rings. InGaAsP multiple quantum wells (MQWs) have strong electro-optic quantum confined stark effect (QCSE) and nonlinear effects and, can be integrated with diode lasers and photodetectors. InGaAsP MQW ERs can thus work as optical modulators and switches with improved speed, ease of integration and less power dissipation. A model has been developed to predict the linear and quadratic electro-optic coefficients, which in conjunction with transfer matrix model, Bessel function and vector coupled-mode theory, have been used to design the ER devices. New static and dynamic models have been developed, enabling the design of ~5mm radius embedded ring tuneable filters and 60Gbps modulators at >12dB extinction ratio. Electron beam lithography with proximity correction and Al lift-off etch mask for ~100nm feature size in ICP RIE etch process has been optimised, for obtaining 4.5mm tall ER side walls. Temperature and nonlinear tuning of the ER resonance has also been achieved using the fabricated device, which can be explored for future photonic applications.
Utpal Das obtained his PhD degree in EE from the University of Michigan in 1987. He joined the University of Florida as an Assistant Professor in 1988, and then moved to the Indian Institute of Technology (IIT), Kanpur in 1994. He had been the Head of the Center for Laser Technology for two terms and a member of the Working Group on Nanotechnology in the Ministry of Communication and Information Technology. He is currently a professor in the Dept. of EE and Center for Lasers and Photonics at IIT Kanpur. He has over 100 publications. His current interests are in the area of semiconductor optoelectronic devices and optoelectronic integration.