Integrated Lithium Niobate Acousto-optic Frequency Shifter
Acousto-optic devices that provide optical frequency shifting have various applications from heterodyne detection
to optical frequency comb generation. Commercially available acousto-optic modulators utilize bulk acoustic modes
and thus operate at low frequencies (at 10 – 100s of MHz) and require up to tens of Watts radio frequency (RF) powers.
An alternative approach utilizes surface acoustic waves to deflect light confined by an ion diffused layer . However,
relatively large optical mode size of such an optical waveguide (a few microns) limits the interactions with sub-micronwavelength GHz acoustic waves. Electromechanical Brillouin scattering has been utilized to achieve frequency shifts
exceeding 10 GHz but this approach suffers from low efficiencies of ~10-5
and sub-optimal carrier suppression.
Here, we demonstrate a 3-GHz integrated acousto-optic frequency shifter (AOFS) on the thin-film lithium niobate
(LN) platform. In our approach, the traveling acoustic wave deflects 1.5-µm wavelength optical beam at the Bragg
angle of 18 degrees resulting in the carrier suppression > 30 dB
All-Fiber Frequency Shifter Based on an Acousto-Optic Tunable
Filter Cascaded with a Tapered Fiber-Coupled Microcavity
Abstract: An all-fiber acousto-optic frequency shifter (AOFS) based on an acousto-optic tunable filter (AOTF) cascaded with a packaged tapered fiber (TF)-coupled microsphere was proposed and demonstrated in both theory and experiment. The configuration has the advantages of easy alignment, robustness, compact size, and low cost, which will improve its further application, such as in the optical heterodyne detection technique (OHDT).