Integrated cavity acousto-optics for frequency domain optical computing and frequency comb generation
Systems and methods for optical computation and acousto-optic modulation are described. The systems and methods comprise acousto-optic modulators with reflectors and transducers used for actuation and modulation of mechanical waves. The systems further comprise multilayer optical computing systems incorporating arrays of acousto-optic modulators. In an embodiment, the acousto-optic modulator comprises a substrate; an optical layer coupled to a first portion of the substrate, the optical layer comprising: a free-standing portion shaped and positioned to define a gap between the free-standing portion of the optical layer and the substrate; and a rib waveguide comprising a photonic crystal, formed in the free-standing portion; and a piezoelectric transducer mechanically coupled to the free-standing portion, wherein the piezoelectric transducer comprises a piezoelectric material and a plurality of conductive electrodes disposed in electrically conductive contact with the piezoelectric material, the plurality of conductive electrodes extending from a base portion of the piezoelectric transducer.
1 . An optical computation system, the system comprising:
a substrate;
an optical layer coupled to a first portion of the substrate, the optical layer comprising:
a free-standing portion suspended shaped and positioned to define a gap between the free-standing portion of the optical layer and the substrate;
a rib waveguide comprising a photonic crystal formed in the free-standing portion; and
a piezoelectric transducer mechanically coupled to the free-standing portion, wherein an actuation of the piezoelectric transducer generates an acoustic wave localized in the substrate;
a controller comprising a memory and one or more processors, wherein the controller is operably connected to the piezoelectric transducer, wherein the memory comprises computer-executable instructions stored thereon that, if executed by the one or more processors, cause the system to perform:
inputting, with light from a light source, an optical signal to the rib waveguide during the actuation of the piezoelectric transducer; and
outputting an output signal based on an interaction of the optical signal and the acoustic wave in the photonic crystal, wherein the output signal corresponds to a result of a matrix operation applied to one or more frequency-space components of the optical signal.
2 . The system of claim 1 , further comprising an input photodetector, wherein the input photodetector is coupled to an end of the rib waveguide.
3 . The system of claim 2 , wherein the inputting comprises detecting the optical signal via the input photodetector.
4 . The system of claim 1 , further comprising an output photodetector, wherein the output photodetector is coupled to an end of the rib waveguide.
5 . The system of claim 4 , wherein the outputting comprises detecting the interaction between the optical signal and the acoustic wave in the photonic crystal via the output photodetector.
6 . The optical computation system of claim 1 , wherein the piezoelectric transducer comprises an interdigital transducer (IDT) disposed overlying the optical layer.
7 . The optical computation system of claim 6 , further comprising a power source, wherein the IDT is resonantly excited by the power source.
8 . The optical computation system of claim 6 , wherein the plurality of conductive electrodes of the IDT comprises a period, wherein excitation of the plurality of the conductive electrodes occurs at one or more frequencies where an angular frequency (Ω) of the frequencies is greater than a total optical cavity decay rate (K) of the optical layer.
9 . The optical computation system of claim 1 , further comprising a free-edge reflector disposed on a side of the optical layer opposite the rib waveguide.
10 . The optical computation system of claim 9 , wherein the free-edge reflector is configured to be reverberated on a plane relative to the side.
11 . The optical computation system of claim 1 , wherein the piezoelectric transducer comprises an aluminum nitride (AlN) layer disposed overlying the optical layer.
12 . The optical computation system of claim 1 , wherein the photonic crystal defines a plurality of recesses in the rib waveguide, a recess of the plurality of recesses being characterized by a width.
13 . The optical computation system of claim 1 , wherein the photonic crystal defines a plurality of recesses in the rib waveguide, a recess of the plurality of recesses being characterized by a length.
14 . The optical computation system of claim 1 , further defining a gap between the piezoelectric transducer and the rib waveguide, the gap characterized by a width.
15 . The optical computation system of claim 1 , wherein the rib waveguide is characterized by a strip height.
16 . The optical computation system of claim 1 , further comprising a grating coupler optically coupled to an end of the optical layer.
17 . The optical computation system of claim 16 , wherein the grating coupler is a first grating coupler, further comprising a second grating coupler, wherein the end is a first end, and the optical layer further comprises a second end opposite to the first end, wherein the first grating coupler is coupled to the first end, and the second grating coupler is coupled to the second end.
18 . The optical computation system of claim 17 , wherein the first grating coupler is an input coupler coupled to the first end, configured to receive an optical input from a coherent light source, and the second grating coupler is an output coupler coupled to the second end, configured to produce an optical output to an optical collection device.
19 . A method of optical computation, the method comprising:
actuating a piezoelectric transducer of an optical layer coupled to a substrate at a first portion, the optical layer comprising:
a free-standing portion suspended shaped and positioned to define a gap between the free-standing portion of the optical layer and the substrate;
a rib waveguide comprising a photonic crystal formed in the free-standing portion, wherein the actuating the piezoelectric transducer generates an acoustic wave localized in the substrate; and
the piezoelectric transducer mechanically coupled to the free-standing portion;
inputting, with light from a light source, an optical signal during the actuation of the piezoelectric transducer; and
outputting an output signal based on an interaction of the optical signal and the acoustic wave in the photonic crystal, wherein the output signal corresponds to a result of a matrix operation applied to frequency-space components of the optical signal.