Compact Brillouin devices through hybrid integration on silicon

Abstract

A range of unique capabilities in optical and microwave signal processing have been demonstrated using stimulated Brillouin scattering. The desire to harness Brillouin scattering in mass manufacturable integrated circuits has led to a focus on silicon-based material platforms. Remarkable progress in silicon-based Brillouin waveguides has been made, but results have been hindered by nonlinear losses present at telecommunications wavelengths. Here, we report a new approach to surpass this issue through the integration of a high Brillouin gain material, As2S3, onto a silicon chip. We fabricated a compact spiral device, within a silicon circuit, achieving an order of magnitude improvement in Brillouin amplification. To establish the flexibility of this approach, we fabricated a ring resonator with free spectral range precisely matched to the Brillouin shift, enabling the first demonstration of Brillouin lasing in a silicon integrated circuit. Combining active photonic components with the SBS devices shown here will enable the creation of compact, mass manufacturable optical circuits with enhanced functionality.Stimulated Brillouin Scattering (SBS) has recently emerged as an impressive tool for optical processing and radio-frequency (RF) photonics. SBS is one of the strongest nonlinearities known to optics, and is capable of providing exponential gain over narrow bandwidths of the order of tens of megahertz. This narrowband amplitude response is accompanied with a strong dispersive response, capable of tailoring the phase or group delay of a counter propagating optical signal. In light of these effects a rich body of applications have been explored such as slow light 1 , stored light 2 , narrowband RF photonic filters [3][4][5] , dynamic optical gratings 6,7 , narrowband spectrometers 8 , optical amplifiers 9,10 and RF sources 11 among others. When pumped in a resonator configuration, a narrow linewidth spectrally pure SBS laser can be generated [12][13][14] . 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 . The desire to harness SBS optical processing in CMOS (Complementary metaloxide-semiconductor) compatible platforms has recently culminated in demonstrations of SBS in various silicon on insulator (SOI) device architectures [23][24][25][26] In this work we introduce a hybrid integration approach to generate large Brillouin gain in a sili...

Controlling phonons and photons at the wavelength scale: integrated photonics meets integrated phononics

“…At the transparency condition C = 1 the phonon noise goes down, eventually reaching the mechanical Schawlow-Townes limit. Several such "phonon lasers" have been demonstrated already, relying on very different integration platforms [150,156,[261][262][263]. Further work is needed to determine if these devices can deliver the performance required to compete with existing microwave oscillators.…”

Mid-infrared integrated photonics on silicon: a perspective

“…Compared to Si or Ge, the drawback of this approach is that chalcogenides and halides are generally not considered compatible with CMOS foundry processes. However, the recent report of chalcogenide device integration with silicon waveguides indicates that such a hybrid configuration can enable seamless integration of unconventional materials with the standard silicon photonics platform [39]. Table 1 shows the available passive platforms for mid-IR integrated photonics on Si, including the best reported results on low loss performance obtained in each category.…”

ARRAW: anti-resonant reflecting acoustic waveguides

“…(c) SBS interaction between the acoustic mode identified as corresponding to the maximum of Q m in (a) as A and the HE 17 optical mode. The three panels represent the displacement field separated into S and P components, the axial Poynting vector P z of the optical mode, and the dominant, real part of the overlap functionQ (PE) 1 (r) originating from the PE interaction defined in (13). (d) SBS gain between the acoustic mode marked as A in (a) and the phase-matched HE modes of decreasing order (and increasing effective optical mode index) HE 17 through HE 12 . and the Pockels tensor (p ijkl ).…”

“…In others, both light and sound are guided along line defects of phoxonic crystals [9][10][11]. Finally, a combination of the desired material properties-high refractive index and low stiffness-has been identified in chalcogenides, allowing researchers to revisit step-index architectures for optoacoustic waveguides [12,13].…”