Tunable optical wedge for reducing crosstalk in wavelength selective switch

A wavelength selective switch comprising:

• a plurality of ports at least including at least one input port and two or more output ports, the at least one input port configured to transmit an input beam, the ports being separated by port spacing;
• a dispersion element arranged in optical communication with the input beam from the at least one input port and configured to disperse the input beam into optical channels;
• a switch assembly arranged in optical communication with the optical channels from the dispersion element, the switch assembly being liquid crystal based and having a plurality of pixels, the pixels being individually addressable to create a reconfigurable phase grating profile, the reconfigurable phase grating profile of the pixels being configured to selectively direct a first order of one or more diffracted beams of one or more of the optical channels from the switch assembly for output to selected one or more of the output ports;
• and
• a tunable optical wedge arranged in optical communication with the switch assembly and the plurality of port, the tunable optical wedge being selectably tunable between a plurality of states in which a distance, at the plurality of ports, between the first order of the one or more diffracted beams and an other order of the diffracted beam having a higher order than the first order (a “higher order”) varies between the states, and the tunable optical wedge is configured, in one of the plurality of states, to direct a-the higher order of the one or more diffracted beams towards the port spacing between the ports and the first order of the diffracted beam toward the selected one of the other ports.

A method for processing an input beam, the method comprising:

• transmitting the input beam from at least one input port of a plurality of ports, the plurality of ports at least including the at least one input port and two or more output ports, the plurality of ports being separated by a port spacing;
• dispersing the input beam into optical channels;
• selectively directing a first order of one or more diffracted beams of one or more of the optical channels by individually addressing pixels of a switch assembly to create a reconfigurable phase grating profile, and outputting the first order thereof to selected one or more of the output ports;
• directing an other order of the diffracted beam having a higher order than the first order (a “higher order”) toward the plurality of ports;
• and
• selectably adjusting a distance, at the plurality of ports, between the first order of the diffracted beam and the higher order of the one or more diffracted beams by applying bias voltages to resistive layers within a tunable optical wedge and producing a phase profile in liquid crystal material between the resistive layers in response to the applied bias voltages.