Guided wave opto-acoustic device
The various technologies presented herein relate to various hybrid phononic-photonic waveguide structures that can exhibit nonlinear behavior associated with traveling-wave forward stimulated Brillouin scattering (forward-SBS). The various structures can simultaneously guide photons and phonons in a suspended membrane. By utilizing a suspended membrane, a substrate pathway can be eliminated for loss of phonons that suppresses SBS in conventional silicon-on-insulator (SOI) waveguides. Consequently, forward-SBS nonlinear susceptibilities are achievable at about 3000 times greater than achievable with a conventional waveguide system. Owing to the strong phonon-photon coupling achievable with the various embodiments, potential application for the various embodiments presented herein cover a range of radiofrequency (RF) and photonic signal processing applications. Further, the various embodiments presented herein are applicable to applications operating over a wide bandwidth, e.g. 100 MHz to 50 GHz or more.
1. A method for making an acousto-optical device, comprising:
depositing an insulating layer on a substrate;
forming a waveguiding member on the insulating layer;
depositing a membrane layer on the insulating layer and on the waveguiding member such that the deposited membrane layer abuts and overlies the waveguiding member;
removing such of the membrane layer as overlies the waveguiding member;
patterning the membrane layer so as to define therein at least one longitudinally extensive phononic resonator traversed by the waveguiding member; and
removing at least a portion of the insulating layer that underlies the membrane layer, including such portion as underlies the longitudinally extensive phononic resonator or resonators.
2. The method of claim 1 , wherein the substrate is silicon, the insulating layer is silicon dioxide, the waveguiding member is silicon, and the membrane layer is silicon nitride.
3. The method of claim 1 , wherein, in response to a first pulse and a second pulse being injected into the waveguiding member, the membrane layer is conformed so as to convey phonons in a direction transverse to an optical direction of the waveguiding member.
4. The method of claim 3 , wherein the phononic resonator is conformed to reflect phonons through the membrane in a direction toward the waveguiding member.
5. The method of claim 1 , wherein the patterning of the membrane layer is carried out so as to form a first slot and a second slot on opposing sides of the waveguide member.