| MS Seminar

Name of the Speaker: Ms. PRATYASHA PRIYADARSHINI (EE18S045)
Guide: Prof. Bijoy Krishna Das
Venue: ESB-244 (Seminar Hall)
Online meeting link: meet.google.com/jsw-uwpj-kgj
Date/Time: 4th October 2024 (Friday), 3:00 PM
Title: Narrowband Resonance Filters using DBR Structures in Silicon Waveguide.

Abstract :

Distributed Bragg reflector (DBR) based Fabry-Pérot resonator is one of the most fundamental device configurations in integrated photonics for various applications like sensing, filtering etc. However, it is yet to reach the ubiquity of a microring resonator or a Mach-Zehnder interferometer when it comes to large-scale integrated photonics. It can be attributed mostly to the fabrication sensitivity of gratings to commercial foundry processes and the gap in design optimization combining both footprint and performance to some extent. There have been multitude of demonstrations on first-order Fabry-Pérot resonators investigated for narrowband transmission and notch filters, sensors, dispersion compensation circuits and few reports on modulator and non-linear photonics-based applications. However, higher order resonators based on DBRs which can be simpler alternatives to coupled ring resonators towards applications such as RF photonic filters, wavelength division (de)multiplexers etc. are relatively very less explored. We will discuss the design and demonstration of 4th and 5th order passive resonant filters in an SOI rib waveguide structure, fabricated with the in-house CMOS compatible silicon photonics technology. These filters exhibit nearly lossless, flat-top response (ripple < 1-dB) and large out-of-band rejection (>40 dB) along with a maximum shape factor of 0.9 without any active tuning operating in the L band of communication.

Next, we will discuss a novel design of a compact tunable resonance filter with a highly extinguished and ultra-broad out-of-band rejection. The proposed device is designed for Fabry-Pérot resonant transmission in an SOI rib waveguide with two identically apodized distributed grating structures. The device design parameters are optimized by CMT-aided-TMM method for a low insertion loss singly-resonant transmission peak at a desired wavelength. A device length of as low as ~ 35 µm exhibits a rejection band as large as ~ 60 nm with an extinction of ~ 40 dB with respect to the resonant wavelength peak at λr ~ 1550 nm (FWHM ~ 80 pm, IL ~ 2 dB). The experimental results have been shown to be closely matching our theoretical simulation and modelling results. The resonance peak has been tuned with the help of integrated metal microheaters near the cavity at a rate of 96 pm per mW of consumed thermal power with switching time ~ 5 µs. As a significant potential application not yet demonstrated in literature to the best of our knowledge, on-chip ASE noise suppression associated with an amplified pump wavelength has been demonstrated which can be investigated further for large-scale integrated quantum photonic circuits. The demonstrated device can also be explored further for many other applications such as modulation, add-drop multiplexing, sensing etc.