Tunable narrowband microwave photonic filter created by stimulated Brillouin scattering from a silicon nanowire

Abstract

We demonstrate the first functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip SBS gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high performance RF photonic filter.Brillouin scattering is a light-sound interaction process that occurs when photons are scattered from a medium by induced acoustic waves. 1 Stimulated Brillouin scattering (SBS) is the strongest nonlinear process and manifest optically in ultra-narrow resonances, which have been harnessed in optical fibers for slow light, sensing, and laser applications.

Thermal Brillouin noise observed in silicon optomechanical waveguide

“…Within the field of silicon photonics this effect was first seen in silicon/silicon-nitride hybrid suspended waveguides [26] and in silicon pedestal wires [27]. These observations soon led to reconfigurable microwave filters [22,23]. Cascades of suspended wires enabled gain exceeding the propagation losses last year [28], which was improved recently in suspended silicon rib waveguides [29].…”

Net on-chip Brillouin gain based on suspended silicon nanowires

“…Nevertheless, the removal of the optical bandwidth restriction and the accompanying versatility has motivated a great deal of SBS work in small-core waveguides, from photonic crystal [16][17][18], dual-web [19] and subwavelength [20] fibres to chalcogenide [21][22][23][24] and silicon waveguides [3,4,25]. It may provide new integrated signal processing capabilities such as tunable RF notch filters [25,26] and true time delays [27]. The prospect is especially appealing in silicon photonic wires, whose strong confinement enhances the light-matter coupling.…”

Compact Brillouin devices through hybrid integration on silicon

“…Highly coherent lasers are used in optical communication, LIDAR and producing pure microwave sources 15 among other applications. While the majority of previous works have traditionally utilised SBS in optical fiber, a number of these applications have been demonstrated in integrated form factors [16][17][18][19][20] . Most recently, the demonstration of 52 dB Brillouin gain 21 in centimeter length scale As 2 S 3 rib waveguides proves that performance equivalent to kilometers of optical fiber is achievable in integrated devices.The capability to embed SBS as a functional component in active photonic circuits will enable the creation of a new class of opto-electronic devices, in particular for integrated microwave photonics 22 .…”