Miniature, accurate, and cost-effective functional photonic/optoelectronic devices/circuits are at high demands now-a-days for applications in the area of computation, communication, biomedical, space and defense environments. Optical grade silicon-on-insulator (SOI) substrate has been established to be an attractive platform for a photonic/optoelectronic integrated circuit (PIC/OEIC). Compact, light-weight, cost-effective, multifunctional and efficient PIC/OEIC can be realized in SOI platform by integrating various photonic and electronic components via low-loss, broad-band and high-speed optical interconnects. Thus, completely a new research area namely, "Silicon Photonics" had been introduced. Very recently, it has been excellently shown how SOI based CMOS technologies can be exploited to integrate both electronic and photonic devices monolithically.
Realizing the trend and prospects, we at IIT Madras have been intensively engaged in silicon photonics research since 2007. We have already succeeded to fabricate and characterize the single-mode (λ ~ 1550 nm) SOI rib waveguides, integrated optical polarizer, compact directional coupler, 1X2 & 1X8 power splitters, 100 GHz ITU channel interleaver exploiting the 2μm silicon technology available in our Integrated Optoelectronics / Microelectronics Labs, Dept. of Electrical Engineering, IIT Madras. The rib waveguides used to develop these devices are single-moded (for λ ~ 1550 nm) and have large mode-size (~10 μm x 5 μm) comparable to that of standard single-mode telecommunication fiber. As a consequence of large cross-sectional area and weakly guiding fundamental mode, typical size of an integrated optical device is very large (μ~ 1 cm²). Major bottleneck in size reduction is the bend induced waveguide losses. We observed that the bending radius of our large cross-section symmetrically etched rib waveguide should be as large as ~ 10 mm to limit the bend induced waveguide loss to a tolerable level of 1 dB. The bending radius could be reduced to ~ 2 mm by introducing a novel asymmetric slab design of ribs at the bend regions. However, it is still quite large and this large bending radius is the bottleneck for the development of any novel and compact multifunctional IO chip. As we have already acquired the expertise in silicon photonics technology for 2- μm feature size, we are now to explore further for more challenging silicon nanophotonics research with a futuristic goal of 3D integration of optics and electronics. Very recently, we have already undertaken following research projects in our laboratory:

Realization of large bandwidth, high-speed and polarization insensitive optical interconnects

Photonic wire (PhW) waveguide embedded with dispersive photonic crystal (PhC) structures

Distributed grating structures for light coupling and wavelength filtering

Tunable microring resonators with predictable Q-values

ITU channel transmitter using PhW/PhC waveguide based integrated optical components

Sponsored Projects

Silicon Nanophotonics - Technology developement, novel device design, Fabrication and Characterization
  (Sponsored by DRDO, Govt. of India, Initiated in August 2012)

Silicon Photonics - Photonic wire waveguide devices, Center for NEMS and Nanophotonics
  (Sponsored by DeiTY, Govt. of India, Initiated in 2011)

SOI integrated optical chip for sensor applications
  (Sponsored by RCI, Hyderabad, Initiated in 2008)

Development of integrated optical single channel add-drop multiplexer (SCADM) in SOI platform for fiber optic communication systems
  (Sponsored by DIT, Govt. of India, Initiated in 2008)

Development of passive integrated photonic components in SOI platform
  (Sponsored by DST Govt. of India, Initiated in 2008)

Fabrication of Integrated Optical Polarizer for Fiber Optic Gyro Applications
  (Sponsored by RCI, Hyderabad, Initiated in 2007)

Development of Photonic Integrated Circuit Technology on SOI Platform
  (Sponsored by IIT Madras, Initiated in 2006)

National & International Collaborators

Optoelectronics Division, SAMEER, Mumbai, India

Integrated Optics Group, RCI, Hyderabad, India

Photonics Division, IRDE, Dehradun, India

Integrated Optics Group, University of Paderborn, Germany

Photonics Research Group, Ghent University, Belgium