Photonic integrated circuit and characterization method

Inventors

Brown, Thomas G. • SAULNIER, Debra • Howard, Tyler

Assignees

University of Rochester

Abstract

A method for characterizing a photonic integrated circuit comprising includes coupling an evanescent field into a scattering element adjacent to a guiding layer of the photonic integrated circuit. The evanescent field is of an optical mode of light propagating in the guiding layer, and has an in-medium wavelength in the guiding layer. A maximum spatial dimension of the scattering element is less than the in-medium wavelength. The method includes scattering, with the scattering element, the coupled evanescent field as a reference scattered-signal. The method also includes detecting one of the reference scattered-signal and a signal derived therefrom.

Core Innovation

The invention provides a photonic integrated circuit having a substrate, a cladding layer, and a guiding layer, where the guiding layer supports an optical mode that extends to a decay-range into the cladding. The optical mode decay into the cladding enables a nearby scattering element to interact with the evanescent field in the decay-range while remaining separated from the guiding layer by a gap-distance less than the decay-range.

The scattering element has a maximum spatial dimension less than the in-medium wavelength of the optical mode, and the scattering element has a scattering refractive index exceeding the cladding refractive index. This structural relationship places a subwavelength scattering element within the evanescent decay-range at a controlled gap-distance, and the scattering is treated as a dipole-like radiator aligned to the guided-mode polarization.

The invention also characterizes the photonic integrated circuit by coupling an evanescent field into the scattering element and using the resulting scattered light as a reference scattered-signal. Detection includes detecting the reference scattered-signal or a signal derived therefrom, and interferometric processing forms an interference signal. The document describes using Fourier or spatial-frequency domain representation to locate defect scatterers and extracting an effective refractive index from phase differences between reference signals from multiple scatterers.

Claims Coverage

This document includes two independent claims that cover a photonic integrated circuit architecture with a guiding layer supporting an optical-mode decay into a cladding and a subwavelength scattering element positioned within that decay-range, and a method for characterizing the photonic integrated circuit by evanescent-field coupling into the scattering element, treating the coupled scattered light as a reference scattered-signal, and detecting that signal or a derived signal. Across the independent claims and their dependents, the inventive features emphasize the relative placement, size, and refractive-index constraints of the scattering element and the use of interferometric reference/scattered-signal processing for localization and parameter extraction.

Overall, the claim set ties together a guided optical mode with decay into a cladding and a nearby subwavelength scattering element constrained by gap-distance, size relative to in-medium wavelength, and refractive-index contrast, and then uses evanescent-field coupling to generate a reference scattered-signal that is detected and can be further processed for localization of defects and extraction of guiding-layer parameters.

Stated Advantages

Documented Applications