Integrated microwave photonic notch filter using a heterogeneously integrated Brillouin and active-silicon photonic circuit

Abstract

Microwave photonics (MWP) has unlocked a new paradigm for Radio Frequency (RF) signal processing by harnessing the inherent broadband and tunable nature of photonic components. Despite numerous efforts made to implement integrated MWP filters, a key RF processing functionality, it remains a long-standing challenge to achieve a fully integrated photonic circuit that can merge the megahertz-level spectral resolution required for RF applications with key electro-optic components. Here, we overcome this challenge by introducing a compact 5 mm × 5 mm chip-scale MWP filter with active E-O components, demonstrating 37 MHz spectral resolution. We achieved this device by heterogeneously integrating chalcogenide waveguides, which provide Brillouin gain, in a complementary metal-oxide-semiconductor (CMOS) foundry-manufactured silicon photonic chip containing integrated modulators and photodetectors. This work paves the way towards a new generation of compact, high-resolution RF photonic filters with wideband frequency tunability demanded by future applications, such as air and spaceborne RF communication payloads.

Cross-polarized stimulated Brillouin scattering empowered photonics

“…For example, by introducing surface acoustic wave in a nano-dimensional waveguide with well-confined optical and acoustic modes, the emergent thin-film LNOI shows strong XP-SBS gain [33][34][35] and the potential of a very promising platform for integrated Brillouin photonic devices and photonic circuits for optical information processing engine with low power consumption. The utilization of on-chip XP-SBS gain, including the optically stimulated Brillouin gain demonstrated here and the electrically driven Brillouin gain, can contribute to more powerful devices, for example onchip isolators [44], fast optical switch [59], tunable notch filter [12,13] and so on.…”

“…Stimulated Brillouin scattering (SBS) is a nonlinear coherent photon-phonon interaction that has been a subject of extensive study since its discovery over a century ago [1][2][3]. This process is characterized by high gain and narrow linewidth, making SBS pivotal in enhancing our understanding of light-matter interactions and has paved the way for innovative technologies including optical atomic clock [4], microwave photonics [5,6], high-resolution spectroscopy [7,8], optical gyroscope [9,10], optical signal processing [11][12][13], SBS microscopy [14][15][16] and quantum sensing [17,18].…”

Anti-resonant acoustic waveguides enabled tailorable Brillouin scattering on chip

“…This versatility is crucial for SBS-based applications with different requirements depending on the use-case. For instance, SBS-based microwave photonic filters 5 – 8 with different center frequencies, bandwidths, and out-of-band suppression ratios demand diverse Brillouin frequency shift, mechanical quality factor Q m , and Brillouin gain coefficient G B . Meanwhile, the innovative loading-effect-based etching technique minimizes the manufacturing cost while maintaining excellent fabrication precision.…”

“…Brillouin nonlinearities arise from the coupling of photons and phonons 1 – 4 . Due to its unique characteristics derived from acoustic phonons, SBS has found widespread applications in the realms of signal generation and processing 5 – 18 , such as narrow linewidth laser 16 , 17 , microwave photonic filters 5 – 8 , slow and fast light 9 – 11 , distributed sensing 13 – 15 , and optical non-reciprocal devices 18 . Recently, integrated photonics has enabled better confinement and manipulation of optical and acoustic modes 19 – 27 , ushering in a new era of photon-phonon interaction.…”