Ii-vi Delaware, Inc.

Guomin Jiang

Helen Chen

Haiji J Yuan

Jack Robert Kelly

Yimin Ji

Qingyu Li

Qingyu (Tom) Li

Tom Li

Jim Yuan

Lawrence Wang

Kun Gao

Lixin (Lawrence) Wang

Xuewen Lu

Xinran Wang

Lixin Wang

Wenyi Cao

In a wavelength selective switch, an input port transmits an input beam, and diffraction grating disperses the input beam into optical channels. A liquid-crystal-on-silicon (LCoS) switch assembly has a phase grating profile and has addressable pixels, which are liquid crystal based. The LCoS switch assembly can selectively direct first-order diffracted beams of the optical channels for output to selected output ports. A tunable optical wedge adjacent the LCoS switch assembly can direct higher-order diffraction beams in the space between the output ports to reduce crosstalk. The wedge is a liquid crystal cell having spaced-apart resistive layers and having liquid crystal material disposed between the layers. In the wedge, the liquid crystal material can produce a phase profile in response to bias voltages applied to the resistive layers, and a beam steering angle of the phase profile can direct at least the second-order diffracted beams towards the port spacing between the ports.

Tunable optical wedge for reducing crosstalk in wavelength selective switch

A reconfigurable polarization rotator is formed of an array of very small liquid crystal (LC) cells (e.g., cells of less than 10 μm in width, termed 'microcells'), referred to hereinafter as “microcells”. Each LC microcell is addressable by a separate electrical voltage input that independently controls the polarization rotation performed by the associated LC microcell. By defining a set of adjacent microcells to be held at the same voltage level, that group may be used to form a polarization rotator window of a proper size for a first fiber array configuration. When a fiber array of a different configuration (say, an array with twice the pitch) is used, a different-sized group of adjacent LC microcells is held at a common voltage level so as to form a reconfigured “window” of a new dimension.

Reconfigurable port arrays for wavelength selectable switch

A voltage-controlled optical wedge is formed by creating an adjustable voltage gradient along the length of a relatively large-sized LC cell. A pair of bias voltages (AC voltages) are applied at the opposing side terminations of the LC cell, their RMS values selected to create a continuous phase variation along the length of the cell, where a defined phase variation is associated with a specific beam steering angle. Adjustments in the applied bias voltages (specifically, changes in the RMS values of the bias voltages) result in changing the beam steering angle, providing for active, controllable beam steering as a function of time. The LC cell may be configured to provide either a linear or nonlinear continuous phase variation, as preferred for different beam steering applications.

Tunable optical wedge for beam steering

A two-step optimization process is utilized to define an optimal phase profile for a LCoS spatial light modulator. The two-step optimization process first utilizes a nonlinear constrained optimization (NCO) program to determine the specific parameters required to obtain an optimal phase profile (hologram), where the 'optimal phase profile' is typically defined as that profile which achieves maximum diffraction efficiency for optical switching. Following this first step, phase scaling (and perhaps an adjustment in the number of pixels per period) is employed to slightly modify the values of the optimal phase profile to effectively suppress crosstalk peaks. If any orders still exhibit an unacceptable level of crosstalk, these orders are then subtracted from the phase profile to create the final design.

Optimization of wavelength selective switch using phase control of liquid crystal spatial light modulator

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Fremont, CA, United States of America

Guomin Jiang