Biography
Biography: D V G L N Rao
Abstract
We have been working on basic nonlinear optics of the protein complex Bacteriorhodopsin (bR) thin polymer films with milliwatt cw lasers. The unique feature of this material is its flexibility. Absorption of a visible photon by bR triggers the photo cycle, starting from the initial B state to the relatively long lived M state via short lived intermediate states. It can revert to the initial B state thermally in milliseconds via short lived intermediate states or can go back directly to B state within nanoseconds by shining blue light. Both life times can be altered by orders of magnitude using chemical methods or genetic mutation. The process of switching between B and M states (chemical isomers) can go in both directions depending on wavelength, intensity and polarization of the incident light offering a variety of possibilities for manipulating amplitude, phase and polarization. Over the years we studied the basic nonlinear optics-four wave mixing, phase conjugation, photo induced anisotropy, etc. We successfully exploited the unique properties for many applications like: All optical switching, modulation, computing, information processing, power limiting for laser eye protection, medical image processing, transient Fourier holography, etc. More recently, we are focusing on optical Fourier techniques for early detection of micro calcifications in mammograms for breast cancer diagnostics. We also developed an innovative technique of Fourier phase contrast microscopy and multimodal optical microscopy for live cell imaging of biological samples. I will present some highlights of our work with particular reference to development of inexpensive biomedical devices.