Tunable megahertz bandwidth microwave photonic notch filter based on a silica microsphere cavity

Abstract

We propose and experimentally demonstrate a tunable microwave photonic notch filter with a megahertz order bandwidth based on a silica microsphere cavity coupled by an optical microfiber. The silica microsphere with a quality factor of hundreds of millions offers a full width at half-maximum bandwidth down to the order of megahertz in the transmission spectrum. Due to the coupling flexibility between the microcavity and the optical microfiber, the bandwidth and suppression ratio can be tuned and optimized to get a rejection ratio beyond 30 dB. The tunability of over 15 GHz is also achieved. To the best of our knowledge, this single-stopband microwave photonic filter has the narrowest bandwidth filter that has ever been experimentally demonstrated. This microwave photonic notch filter shows distinct advantages of high selectivity, compactness, flexibility, and low insertion loss.

Advances on silicon-based integrated microwave photonics

“…For a typical MPF system, the key component is the optical resonator, which determines the MPF performance directly. Recently, a few MPF schemes have been proposed by utilizing silica microsphere [42], silicon nitride resonator [43], silicon microring (MRR) [44] or microdisk resonator (MDR) [45], etc. When it comes to integrated platforms, compared to other platforms such as silicon nitride platform [43] and the indium phosphorus platform [14], silicon platform has its own outstanding superiorities such as low cost, small footprint, good tenability, more suitable for the practical applications.…”

Photonic RF and microwave temporal signal processing based on optical Kerr micro-combs

“…There is a very wide range photonic RF approaches including techniques that map the optical filter response in the optical domain onto the RF domain. This is perhaps best represented by integrated devices based on stimulated Brillouin scattering [88][89][90][91][92][93][94][95], which has resulted in extremely high performance for RF resolutionbeing able to resolve features as fine as 32 MHz, at the same time achieving a stopband rejection > 55 dB. A key approach to achieving reconfigurable transfer functions for adaptive signal processing has been based on the transversal filter method [96][97][98][99][100] that operate by generating weighted, progressively delayed replicas of an RF signal imprinted on an optical carrier and then summing them via photo-detection.…”

RF and microwave photonic temporal signal processing with Kerr micro-combs

“…There is a very wide range of photonic RF approaches including techniques that map the optical filter response in the optical domain onto the RF domain. This is perhaps best represented by integrated devices based on stimulated Brillouin scattering [88][89][90][91][92][93][94][95], which has resulted in extremely high performance for RF resolution -being able to resolve features as fine as 32 MHz, at the same time achieving a stopband rejection >55 dB. A key approach to achieving reconfigurable transfer functions for adaptive signal processing has been based on the transversal filter method [96][97][98][99][100] that operate by generating weighted, progressively delayed replicas of an RF signal imprinted on an optical carrier and then summing them via photo-detection.…”