Electromechanical Brillouin scattering in integrated optomechanical waveguides

Abstract

In the well-known stimulated Brillouin scattering (SBS) process, spontaneous acoustic phonons in materials are stimulated by laser light and scatter the latter into a Stokes sideband. SBS becomes more pronounced in optical fibers and has been harnessed to amplify optical signals and even achieve lasing. Exploitation of SBS has recently surged on integrated photonics platforms as simultaneous confinement of photons and phonons in waveguides leads to drastically enhanced interaction. Instead of being optically stimulated, coherent phonons can also be electromechanically excited with very high efficiency as has been exploited in radiofrequency acoustic filters. Here, we demonstrate electromechanically excited Brillouin scattering in integrated optomechanical waveguides made of piezoelectric material aluminum nitride (AlN). Acoustic phonons of 16 GHz in frequency are excited with nanofabricated electromechanical transducers to scatter counter-propagating photons in the waveguide into a single anti-Stokes sideband. We show that phase-matching conditions of Brillouin scattering can be tuned by varying both the optical wavelength and the acoustic frequency to realize tunable single-sideband modulation. Combining Brillouin scattering photonics with nanoelectromechanical systems, our approach provides an efficient interface between microwave and optical photons that will be important for microwave photonics and potentially quantum transduction.

CMOS-compatible, piezo-optomechanically tunable photonics for visible wavelengths and cryogenic temperatures

“…There have been attempts to use aluminum nitride to piezoelectrically strain optical waveguides to achieve modulation. This form of modulation allows a larger range of waveguide materials, with previous demonstrations of AlN piezoelectrically modulating AlN waveguides directly [15][16][17][18][19][20][21], and silicon nitride waveguides [22][23][24]. Demonstrations of directly piezoelectrically modulating AlN waveguides suffer from the same high losses at near-visible and shorter wavelengths as mentioned above.…”

Circulator‐Free Brillouin Photonic Planar Circuit

“…[ 1 ] SBS has been widely investigated in bulk media [ 2,3 ] and optical fibers, [ 4–6 ] and has underpinned a wide range of important applications, based on the unique nature of high‐efficiency parametric (de)amplification and the ultra‐fine spectral selectivity. [ 7 ] Recent advances in inducing and harnessing Brillouin scattering in centimeter‐scale photonic chips [ 8–15 ] have enabled enhanced functionalities and advanced signal processing capability [ 16–18 ] for signal synthesis, [ 19,20 ] microwave photonic processing, [ 21–23 ] optical communication carrier regeneration, [ 24 ] signal storage, [ 25,26 ] and ultra‐sensitive detection. [ 27 ] New hybrid integration approaches allow for the co‐integration of lasers, [ 28 ] modulators, [ 29 ] detectors [ 30 ] and functional processing units, [ 22,31 ] providing the basis of a fully integrated Brillouin photonic chip that incorporates Brillouin‐active elements with functional photonic circuits, essential for enabling compact and robust signal processing systems.…”

Integrated microwave acousto-optic frequency shifter on thin-film lithium niobate

“…Integrated acousto-optic or Brillouin scattering devices [1] have enabled a wide range of applications including frequency shifting [2][3][4][5], microwave-to-optical conversion (modulation) [6][7][8][9][10][11], microwave photonic filtering [12], frequency comb generation [13], pulse shaping [14], ultra-narrow-linewidth lasing [15,16], and nonreciprocal transmission [17][18][19][20][21][22][23]. Such integrated devices employ photoelasticity and optical confinement of thin-film materials such as silicon [16,17,[19][20][21], silicon nitride [15], aluminum nitride [4,5,14,22,23], gallium arsenide [6], arsenic trisulfide [12], lithium tantalate [13], and lithium niobate (LN) [7][8][9][10][11]. Acousto-optic frequency shifters (AOFSs) deflect the light into a different spatial mode and shift its optical frequency by the acoustic frequency.…”

“…To develop integrated AOFSs, surface acoustic waves have been employed to deflect light confined by an ion diffused layer [2], but its relatively large optical mode size (a few microns) limits interactions with sub-micron-wavelength gigahertz acoustic waves. Recently, electromechanically driven suspended acousto-optic waveguides have been utilized to achieve frequency shifts exceeding 10 GHz [4,5] but suffer from low efficiencies of ∼ 10 −5 and weak carrier suppression. In additional to AOFSs, electro-optic devices can achieve optical frequency shifting by destructive interference between Mach-Zehnder modulators [25,26], by serrodyne frequency shifting [27][28][29], and by employing electro-optic cavities [30][31][32].…”