Electrooptic thin-film modulator

Claim 2

An electrooptic modulator comprising: a light waveguide of an electrooptic crystalline composite structure including a substrate having a surface of a plane defined by rectangular coordinate first and second axes, a light transmissible thin-film per se having an electrooptic property and deposited on said surface of the substrate, and a buffer layer deposited on said thin-film; a light source emitting a coherent light beam; an input light coupler coupling said coherent light beam into said thin-film as a mode of guided wave propagating in the direction of said first axis; interdigital electrodes engraved from a deposited metal layer on said light waveguide to cause therein an electric field which has spatial periodicity larger than the total thickness of said thin-film and buffer layers in the direction of said second axis and uniform in the direction of said first axis; a voltage source connected to said electrodes to apply thereto a modulating signal voltage; and an output light coupler coupling the propagated light wave out of said waveguide, the coupled out light being diffracted into orders.

Claim 3

An electrooptic modulator as claimed in claim 1, wherein said substrate is of a bulk single crystal and said thin-film is of a single crystal grown epitaxially on said substrate.

Claim 4

An electrooptic modulator as claimed in claim 1, wherein said substrate is of a glass and said thin-film is of an aggregation of fine crystals formed on said substrate.

Claim 5

An electrooptic modulator as claimed in claim 1, which further comprises: means to selectively pass one of the diffracted orders.

Claim 6

An electrooptic modulator as claimed in claim 4, which further comprises: a photo-detector receiving an original pulsed light beam and generating a voltage responsive thereto, which voltage, once applied to said electrodes, produces a pulsed change in the output beam in said selected order which is larger than the change of said original pulsed light beam.

Claim 7

A combination of a first modulator as claimed in claim 5 and a second modulator as claimed in claim 5, which combination includes a construction wherein the photodetector in said first modulator receives the selected order of light from said second modulator and the photo-detector in said second modulator receives the selected order of light from said first modulator, to form an optical analogy of a flip-flop circuit having two stable states, either of said first and said second modulator passing through said selected order of light.

Claim 8

An electrooptic modulator as claimed in claim 2, wherein said bulk single crystal and said epitaxially grown single crystal are ferroelectric crystals of 3m crystal symmetry.

Claim 9

An electrooptic modulator comprising: a light waveguide of an electrooptic crystalline composite structure including a substrate of an electrooptic crystal having a refractive index n s and having a surface of a plane defined by rectangular coordinate first and second axes, a light transmissible thin-film of a thickness d per se not having electrooptic property deposited on said surface of the substrate and a buffer layer deposited on said thin-film; a light source emitting light beam; an input light coupler coupling said coherent light beam into said thin-film as a definite mode of guided wave propagating in the direction of said first axis with a wave vector k g ; interdigital electrodes engraved from a deposited metal layer on said light waveguide to cause therein an electric field which has spatial periodicity larger than the total thickness of said thin-film and said buffer layer in the direction of said second axis and uniform in the direction of said first axis; a voltage source connected to said electrodes to apply thereto a modulating signal voltage; an output light coupler coupling the propagated light wave of said mode out of said waveguide, the coupled out light beam being diffracted into orders; and wherein said thickness d of the thin-film is larger but not so much than the cutoff value corresponding to said mode that the derivative of said wave vector k g of said mode with regard to said refractive index n s is not much less than the wave vector in the free space.

Claim 10

An electrooptic modulator comprising: a light waveguide of an electrooptic crystalline composite structure including a substrate of an electrooptic crystal having a refractive index n s and having a surface of a plane defined by rectangular coordinate first and second axes, a light transmissible thin-film of a thickness d per se not having electrooptic property deposited on said surface of the substrate and a buffer layer deposited on said thin-film; a light source emitting light beam; an input light coupler coupling said coherent light beam into said thin-film as a definite mode of guided wave propagating in the direction of said first axis with a wave vector k g ; interdigital electrodes engraved from a deposited metal layer on said light waveguide to cause therein an electric field which has spatial periodicity larger than the total thickness of said thin-film and said buffer layer in the direction of said second axis and uniform in the direction of said first axis; a voltage source connected to said electrodes to apply thereto a modulating signal voltage; an output light coupler coupling the propagated light wave of said mode out of said waveguide, the coupled out light beam being diffracted into orders; and wherein said thickness d of the thin-film is larger but not so much than the cutoff value corresponding to said mode that the derivative of said wave vector k g of said mode with regard to said refractive index n s is not much less than the wave vector in the free space.

Claim 11

An electrooptic modulator as claimed in claim 8 which further comprises: means to selectively pass one of said diffracted orders.

Claim 12

An electrooptic modulator as claimed in claim 9, a photo-detector receiving an original pulsed light beam and generating a voltage responsive thereto, which voltage, once applied to said electrodes, produces a pulsed change in the output beam in said selected order which is larger than the change of said original pulsed light beam.

Claim 13

A combination of a first modulator as claimed in claim 10 and a second modulator as claimed in claim 10, which combination includes a construction wherein the photo-detector in said first modulator receives the selected order of light from said second modulator and the photo-detector in said second modulator receives the selected order of light from said first modulator, to form an optical analogy of a flip-flop circuit having two stable states, either of said first and said second modulator passing through said selected order of light.