Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon

Abstract

The growing demand for bandwidth makes photonic systems a leading candidate for future telecommunication and radar technologies. Integrated photonic systems offer ultra-wideband performance within a small footprint, which can naturally interface with fiber-optic networks for signal transmission. However, it remains challenging to realize narrowband (∼MHz) filters needed for high-performance communications systems using integrated photonics. In this paper, we demonstrate all-silicon microwave-photonic notch filters with 50× higher spectral resolution than previously realized in silicon photonics. This enhanced performance is achieved by utilizing optomechanical interactions to access long-lived phonons, greatly extending available coherence times in silicon. We use a multi-port Brillouin-based optomechanical system to demonstrate ultra-narrowband (2.7 MHz) notch filters with high rejection (57 dB) and frequency tunability over a wide spectral band (6 GHz) within a microwave-photonic link. We accomplish this with an all-silicon waveguide system, using CMOS-compatible fabrication techniques.

Chip-Based Brillouin Processing for Microwave Photonic Phased Array Antennas

“…This generates an acoustic wave through forward Brillouin scattering [66], which modulates the phase of the optical signal in the adjacent, receiver waveguide through photoelastic coupling [66]. The signatures of acoustic waves with narrow linewidths as low as 2.4 MHz [110] have been observed, facilitating MWP filters with fine frequency resolution, as we discuss later in this section.…”

“…Using this technique, an RF notch filter, as shown in Fig. 10 (e), with rejection of up to 57 dB has been observed with bandwidth as narrow as 2.7 MHz [110].…”

“…Figure 10 (b-c) from [120]; licensed under a Creative Commons Attribution (CC BY) license. Figure 10 (d-e) from [110]; licensed under a Creative Commons Attribution (CC BY) license.) shift at its resonant frequency.…”

“…PPER waveguides, as outlined in Section IV, offer an alternate approach for implementing MWP bandpass [120], [121] and notch filters [110], which circumvent the need to filter the high-power Brillouin pump, as demonstrated by Gertler et al. An MWP filter with a passband centred at the BFS, Ω B , is realised by encoding the RF input signal onto the pump laser through intensity modulation [120], as shown in Fig.…”

“…10 (c). MWP notch filters have been demonstrated using PPER waveguides [110], as shown in 10 (d). In this scheme, the PPER waveguides select a narrow region of the RF spectrum, which is subsequently subtracted from the original input signal, forming a notch filter through destructive interference.…”