Integrated microwave photonic true-time delay with interferometric delay enhancement based on Brillouin scattering and microring resonators

Abstract

True-time delays are important building blocks in modern radio frequency systems that can be implemented using integrated microwave photonics, enabling higher carrier frequencies, improved bandwidths, and a reduction in size, weight, and power. Stimulated Brillouin scattering (SBS) offers optically-induced continuously tunable delays and is thus ideal for applications that require programmable reconfiguration but previous approaches have been limited by large SBS gain requirements. Here, we overcome this limitation by using radio-frequency interferometry to enhance the Brillouin-induced delay applied to the optical sidebands that carry RF signals, while controlling the phase of the optical carrier with integrated silicon nitride microring resonators. We report a delay tunability over 600 ps exploiting an enhancement factor of 30, over a bandwidth of 1 GHz using less than 1 dB of Brillouin gain utilizing a photonic chip architecture based on Brillouin scattering and microring resonators.

Chip-Based Brillouin Processing for Microwave Photonic Phased Array Antennas

“…Beam squint can be eliminated by introducing a TTD between elements to control the beam angle [81] by applying a linear phase shift to the RF signal of interest. The resultant delay, τ, is the derivative of the applied phase shift with respect to frequency [77], [78]. Substituting the relationship between the applied phase shift and frequency into (3), we find that the beam angle no longer directly depends on the PAA operating frequency [5] (4)…”

“…Fig. 3 (b-e) highlight demonstrations of Brillouin-based MWP processing devices that perform the key functions within a beamforming network, including frequency converters [72], low phase noise RF sources [71], filters [69], phase shifters [77] and TTDs [78]; we expand on these examples and conclude with a perspective on how these distinct functionalities can be combined onto a single photonic chip to enable element-level processing for PAAs.…”

“…In this paper, we review the recent advances in MWP processing systems that utilise on-chip SBS. We highlight key functionalities required for optical beamforming networks, including filters [29], [69], RF sources [70], [71], frequency converters [72], [73], phase shifters [74]- [76], and TTDs [77], [78]. We outline the challenges that must be overcome to enable a fully-integrated Brillouin-based beamforming network suitable for element-level processing in PAAs, and provide perspectives on technical improvements that must be made to achieve the long-term performance goals for MWP processors [29], [79].…”

Multi-Band and Frequency-Agile Chip-Based RF Photonic Filter for Ultra-Deep Interference Rejection

“…In this work, we overcome these limitations with a hybrid approach [39], combining tunable and low-loss Si 3 N 4 MRRs (iii)…”

Hybrid Chalcogenide‐Germanosilicate Waveguides for High Performance Stimulated Brillouin Scattering Applications

“…[ 17–23 ] One such platform that has particular promise is the high index contrast arsenic trisulfide glass (As 2 S 3 ) nonlinear waveguide platform. [ 24–38 ] Apart from reducing footprint and cost, the small mode volume enabled by the high index contrast promotes a greater light‐matter interaction, and in the case of As 2 S 3 , higher opto‐acoustic interactions as the acoustic wave is also tightly confined to the waveguide core. This allows compact waveguide devices to achieve equivalent gain to their long fiber length counterparts.…”