Patent ID: 6847749

Claim:
A method for controlling a light beam, the method comprising: providing a diffraction grating, attached to or part of a piezoelectric substrate, having an initial substrate length and being connected to a controllable voltage source having an initial first voltage difference in a selected direction across the substrate; directing a beam of light, having at least a selected wavelength λ, at the grating at a selected incidence angle and receiving a first diffracted light beam component of a selected diffraction order m containing the wavelength λ at a first light-receiving site; changing the first voltage difference at the first voltage source by a selected first voltage change amount ΔV1 and permitting the substrate length to change by a selected first length change amount ΔL1 in the selected direction, whereby at least one of the following occurs, after the first voltage change; (1) the first diffracted light beam component is received at a selected second light-receiving site, different from the first site, (2) a second diffracted light beam component of order m, containing a second wavelength λ′ but not the wavelength λ, is received at the first site, (3) a third diffracted light beam component of order m′, with m′≠m, containing at least one of the first and second wavelengths, is received at at least one of the first site and the second site, and (4) a fourth diffracted light beam component, having an incidence angle different from the selected incidence angle and containing at least one of the first and second wavelengths, is received at at least one of the first site and the second site; providing a second controllable voltage source having an initial second voltage difference across the substrate in a second selected direction that is transverse or perpendicular to the first direction; and changing the second voltage difference at the second voltage source by a selected voltage change amount ΔV2 that is chosen so that at leas one of the following occurs: (i) the substrate length changes by a selected second length change amount ΔL2 in the second direction, and (2) a selected axis of the grating is rotated by a selected angle change amount Δφ in a selected plane of the substrate.