Etched surface gratings fabricated using computed interference between simulated optical signals and reduction lithography

Abstract

An optical apparatus comprises a set of diffractive elements on a substrate. They are arranged: (i) to receive an input signal propagating from an input port as a diffraction-guided optical beam, (ii) to diffract a portion of the received input signal as an output signal, (iii) to route the output signal to propagate to an output port as a diffraction-guided optical beam, and (iv) to exhibit a positional variation in diffractive amplitude, optical separation, or spatial phase over some portion of the set. The arrangement of the diffractive elements corresponds to an interference pattern derived from computed interference at a surface of the substrate between a simulated design input and output optical signals. Each diffractive element comprises at least one trench segment positioned along a path defined by a constant-phase contour of the interference pattern. Each trench segment is substantially rectangular or trapezoidal in transverse cross section.