Advanced Photonics and Microscopy Laboratory
Research Areas
The main areas of focus in the group are in: [1] High contrast gratings and metasurface photonics, [2] Nonlinear integrated optics, [3] Nonlinear optical microscopy and [4] Emerging areas of optical communications. A brief description of these topics can be found below:
[1] High contrast gratings and Metsurface photonics
We are interested in exploring innovating platforms for building active photonic devices. Some of the projects we envision are (i) dielectric metasurfaces for resonantly enhanced parametric light generators, (ii) wavefront shapers, (iii) III-V on silicon heterogeneous integration for building nonlinear optical functionalities and (iv) mid-IR photonics using silicon and germanium waveguide devices. The ability to fabricate such active devices on a flat surface offers the added benefit of efficient light coupling in/ out of the device, compact and low-cost photonics etc. In particular, we are focused on resonant enhancement of nonlinear optical effects, fluorescence using resonant sub-wavelength grating structures, beam steering and wavefront shaping using dielectric metasurfaces. SEM images of one such besm steering surface nanofabricated on amorphous silicon film is shown on the side.
[2] Integrated optics and its applications
SEM image of 1D trasnmit-array fabricated on amorphous silicon film on glass substrate. This transmit-array is designed to deflect 1550 nm laser beam by 16 deg.
We are interested in Group IV integrated optical devices (waveguides, grating couplers etc.) for building active photonic devices. In particular, amorphous silicon and germanium platforms are promising for realizing broadband, back-end compatible photonic elements which are most suitable for integration on a pre-fabricated silicon CMOS wafer. We are interested in exploring nonlinear optical effects, such as super-continuum based spectral broadening in such integrated optical platforms. We are interested in understanding deep sub-wavelength patterned structures for building photonic components and active photonic devices. We are also working on enhancing fluorescence and Raman scattering in waveguide-based sensors for building low-cost sensors which work on a silicon based integrated photonic platform.
[3] Nonlinear optical microscopy
We are also interested in the area of nonlinear optical microscopy. Nonlinear optical microscopy helps image samples (biological, chemical and nano/ microstructures) by using the inherent nonlinear optical response of the sample as the contrast mechanism. In addition to being a label-free imaging technique, other benefits include inherent 3D sectioning/ confocality, real-time imaging capability, and high resolution. A multitude of nonlinear optical processes (second-harmonic, third-harmonic, four-wave mixing, sum-frequency, generation coherent anti-stokes Raman scattering and stimulated Raman scattering etc.) have been investigated. Our research interests are in tissue imaging using nonlinear optical microscopy techniques to explore Collagen imaging (see adjacent image) and fast fresh tissue imaging. We are also interested in exploring ways to develop super-resolution in nonlinear optical microscopy. The challenge here is that the technique is label-free and it is not possible to explore fluorophore properties (as in fluorescence). Beam shaping and interferometry would be explored to as options to realize reduced point-spread functions at the focus of the nonlinear microscope.
Second harmonic generation (SHG) microscopy image of synthetic collagen grown on a glass slide
[4] Emerging areas in optical communications
We are also interested in emerging areas of optical communications. Presently we are working on a visible light communication (VLC) project as part of the 5G testbed initiative. We are setting up a VLC testbed which will support light illumination and communication at high data rates to supplement current wireless communication technology. More updates on this soon...