ELECTRO-OPTIC VARIABLE PHASE DIFFRACTION GRATING AND MODULATOR

• US 3,813,142 A
• Filed: 12/04/1972
• Issued: 05/28/1974
• Est. Priority Date: 12/04/1972
• Status: Expired due to Term

• Current Assignee: Carl F. Buhrer
• Original Assignee: Carl F. Buhrer
• Inventors: Buhrer, Carl F.
• Primary Examiner(s): Corbin, John K.
• Application Number:
  US05/312,071
• Time in Patent Office: 540 Days
• Field of Search: 350/96WG,16R,161
• US Class Current: 385/10
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: G02F 1/035 in an optical waveguide structure
• CPC Class Codes: G02F 1/2955 by controlled diffraction or phased-array beam steering controlled diffraction for optical waveguide switching G02F1/313
• CPC Class Codes: G02F 2201/124 interdigital
• CPC Class Codes: G02F 2203/22 diffractive

Abstract

An electro-optic variable phase diffraction device is described for varying a phase diffraction grating and modulating an optical wave. A layer of electro-optic material whose index of refraction may be varied with an electric field is placed in interacting relationship with an optical wave passing through a thin-film optical waveguide. An array of parallel spaced electrodes whose widths are substantially more narrow than the width of the optical wave are so located over the optical waveguide to form longitudinal segments in the electro-optical material for interaction with different adjacent components of the optical wave. A controlled electrical energization of the electrodes causes a corresponding change of refractive index of underlying interacting segments to form a diffracted output optical wave whose intensity is modulated in correspondence with the electrical energization. Various embodiments and methods of modulation are described.

Claims

1. A variable electro-optic phase diffraction grating modulator comprising a thin-film optical waveguide sized to propagate an optical wave of predetermined width along a preselected direction;

a layer of electro-optic material placed in proximity to the thin-film optical waveguide for interaction with the optical wave propagating therein;

an array of generally parallel spaced longitudinal electrodes located to control the index of refraction of the electro-optic material which interacts with the optical wave upon the electrical excitement of the electrodes, each of said electrodes having a width dimension which is smaller than the width of the optical wave, with the spacings between electrodes being selected to control the index of refraction of individual segments of the electro-optic material in interaction with the optical wave, selected electrodes being electrically connected to each other to form sets with the electrodes in the sets being interleaved to form pairs of electrodes with adjacent electrodes of different sets; and

means for electrically exciting pairs of electrodes with different electrical signals to induce correspondingly different indices of refraction in the electro-optic material segments and form a diffracted modulated optical output wave along a desired angle with a modulation component related to said electrical signals, said means further producing a plurality of phase related signals connected to respective sets of electrodes to form an apparently moving diffraction grating.

2. The modulator as claimed in claim 1 wherein said phase related signals are applied to electrodes in the sets to form pairs of adjacent electrodes carrying signals which differ in phase by 90* in a polyphase sequence selected to modulate the diffracted optical output wave in a single side band suppressed carrier manner.