Institute: Indian Institute of Technology (IIT), Madras

Principal Investigator: Prof. Bijoy Krishna Das

Co-Principal Investigator: Prof. Anil Prabhakar

Co-Principal Investigator: Prof. Gopalan Raghavan

The CMOS compatible silicon photonics technology in silicon-on-insulator (SOI) platform is now seen as one of the promising approaches to realize robust and scalable quantum information systems. By integrating various passive and active waveguide components in SOI, it is possible to develop a quantum optical circuit that can generate and manipulate entangled photon pairs which is the key for much needed quantum key distribution (QKD). The major circuit elements are entangled photon source, optical noise filter, beam splitter/combiner, polarization rotator/splitter/combiner, phase-shifter, tunable delay lines, etc. Optical pumping and detection are performed via input/output fiber-optic coupling arrangements. Individual components for the proposed integrated quantum optical circuit (IQOC) are identified as directional coupler (DC), microring resonator (MRR), Mach-Zehnder interferometer (MZI), distributed Bragg reflector (DBR) thermo-optic or electro-optic phase-shifter, variable optical attenuator (VOA), tunable delay lines and wavelength filters, etc. They are all designed with silicon wire waveguide (SWW) with a typical rectangular shaped core dimensions of W ~ 500 nm (width) and H~220 nm (height) in SOI substrate. The passive devices are reconfigured by integrating microheater and/or p-i-n diodes with appropriately modified waveguide cross-sectional geometry. Almost all the above mentioned components were designed and demonstrated individually at IIT Madras in recent years. We need to move one step forward to demonstrate coupled ring optical waveguide (CROW) which has been shown to be an excellent candidate for entangled photon pair generator (via parametric down conversion) and tunable delay-line (achieved via thermo-optic effect by integrating microheaters). The proposed IQOC will be designed, fabricated, and tested for a system level operation.

The major project milestones/deliverables are identified as follows:

• Design of IQOC in SOI which can be fabricated in CMOS compatible silicon photonics foundries for futuristic mass production.
• Fabrication and testing of IQOC prototypes using the process facilities available at the Centre for NEMS & Nanophotonics (CNNP) and characterization facilities available at Integrated Optoelectronics Labs, IIT Madras.
• Fiber pigtailing and packaging of fabricated prototype IQOCs for QKD applications

Publications from this project: