Abstract
Signal processing using on-chip nonlinear or linear optical effects has shown tremendous potential for RF photonic applications. Combining nonlinear and linear elements on the same photonic chip can further enable advanced functionality and enhanced system performance in a robust and compact form. However, the integration of nonlinear and linear optical signal processing units remains challenging due to the competing and demanding waveguide requirements, specifically the combination of high optical nonlinearity in single-pass waveguides, which is desirable for broadband signal processing with low linear loss and negligible nonlinear distortions required for linear signal processing. Here, we report the first demonstration of integrating Brillouin-active waveguides and passive ring resonators on the same integrated photonic chip, enabling an integrated microwave photonic notch filter with ultradeep stopband suppressions of >40 dB, a low filter passband loss of <−10 dB, flexible center frequency tuning over 15 GHz, and reconfigurable filter shape. This demonstration paves the way for implementing high-performance integrated photonic processing systems that merge complementary linear and nonlinear properties, for advanced functionality, enhanced performance, and compactness.
Highlights
On-chip nonlinear optical effects have been demonstrated as an attractive candidate to generate, convert, and process optical signals,1 providing the unprecedented capability for manipulating microwave signals with enhanced functionalities and superior performance.2,3 This enabling technology has been the basis of demonstrating low-noise microwave signal generation4,5 and modulation,6,7 broadband microwave signal mixing and measurement,8,9 and compact multitap-based microwave filtering.10,11Stimulated Brillouin Scattering (SBS),12 one of the strongest nonlinear optical effects traditionally investigated in optical fibers, can induce an optical gain resonance with tens-of-MHz linewidth over the broadband frequency range,13,14 which is attractive for microwave signal processing, enabling the desired MHzlevel spectral resolution, and ultrawideband tunability
The integration of nonlinear and linear optical signal processing units remains challenging due to the competing and demanding waveguide requirements, the combination of high optical nonlinearity in single-pass waveguides, which is desirable for broadband signal processing with low linear loss and negligible nonlinear distortions required for linear signal processing
We present high-performance integrated microwave photonic (MWP) (IMWP) signal processing based on a centimeter-scale photonic circuit that pairs the Brillouin processor with passive functional devices
Summary
On-chip nonlinear optical effects have been demonstrated as an attractive candidate to generate, convert, and process optical signals, providing the unprecedented capability for manipulating microwave signals with enhanced functionalities and superior performance. This enabling technology has been the basis of demonstrating low-noise microwave signal generation and modulation, broadband microwave signal mixing and measurement, and compact multitap-based microwave filtering.. We implement an IMWP notch filter scheme using an integrated As2S3 photonic chip that consists of a Brillouin-active element and an overcoupled ring resonator, which can provide separate nonlinear and linear optical signal processing functionalities Using this As2S3 photonic chip, a highly localized π-phase inversion can be formed by cascading the complementary optical responses of the Brillouin gain resonance and the ring resonance, leading to an RF notch response due to the localized RF destructive interference. This on-chip implementation enables a new class of IMWP devices that are compact and robust, while exhibiting desirable advantages of deep filter rejection, high resolution, filter shape tunability, and the compatibility with simple MWP link configuration
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