Abstract
Integrated microwave photonics has strongly emerged as a next-generation technology to address limitations of conventional RF electronics for wireless communications. High-resolution RF signal processing still remains a challenge due to limitations in technology that offer sub-GHz spectral resolution, in particular at high carrier frequencies. In this paper, we present an on-chip high-resolution RF signal processor, capable of providing high-suppression spectral filtering, large phase shifts and ns-scale time delays. This was achieved through tailoring of the Brillouin gain profiles using Stokes and anti-Stokes resonances combined with RF interferometry on a low-loss photonic chip with strong opto-acoustic interactions. Using an optical power of <40 mW, reconfigurable filters with a bandwidth of ~20 MHz and an extinction ratio in excess of 30 dB are synthesized. Through the concept of vector addition of RF signals we demonstrate, almost an order of magnitude amplification in the phase and delay compared to devices purely based upon the slow-light effect of Brillouin scattering. This concept allows for versatile and power-efficient manipulation of the amplitude and phase of RF signals on a photonic chip for applications in wireless communications including software defined radios and beam forming.
Highlights
Stimulated Brillouin scattering[7, 8] has become very popular for high-resolution and frequency-agile RF photonic signal processing, providing optical filters with unrivalled resolution in the order of megahertz
Two stimulated Brillouin scattering (SBS) loss resonances resulting from the anti-Stokes waves are superimposed at the tail of the SBS gain response, effectively removing energy from the tail of the Lorentzian gain profile
There is a tradeoff between the bandwidth and the suppression, which are dependent on two degrees of freedom[44] allowing tailoring of the optical filter profile: i) the separation between the loss pumps which controls the location of the anti-Stokes resonance with respect to the center of the gain profile, and ii) the ratio of the gain pump to the loss pumps which controls the relative power of the Stokes resonance and the anti-Stokes resonances[44, 52]
Summary
Received: 13 March 2017 Accepted: 8 June 2017 Published: xx xx xxxx interference. Amol Choudhary1,2,Yang Liu[1,2], Blair Morrison[1,2], Khu Vu3, Duk-Yong Choi 3, Pan Ma3, Stephen Madden[3], David Marpaung1,2 & Benjamin J. We present an on-chip high-resolution RF signal processor, capable of providing high-suppression spectral filtering, large phase shifts and ns-scale time delays This was achieved through tailoring of the Brillouin gain profiles using Stokes and anti-Stokes resonances combined with RF interferometry on a low-loss photonic chip with strong opto-acoustic interactions. By precise control of the individual SBS gain and loss resonances, we achieved a unique high-resolution RF photonic bandpass filtering response with anomalously-high-suppression adjacent stop bands, useful for signal selection in the presence of strong interference This filter response was tunable in central frequency up to 40 GHz. We further study the phase response of the filter which reveals that significant enhancement of the phase slope, and subsequently the group delay, can be achieved in the passband. The unique combination of the amplitude and delay response of this filter could point to practical implementations of the EIT-analogue concept for high-resolution and power-efficient RF signal processing
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