Filament-based, optical detection apparatus

Abstract

Optical detection apparatus comprises a solid state laser having an intracavity optical waveguide that supports a lasing filament and operates in one of two states: (1) in a first state, the filament is fixed in one of two orientations, and (2) in a second state, the filament may be induced to switch or oscillate between the two orientations, or it may be suppressed altogether. At least one feature is located on the output facet off-center with respect to the waveguide cross-section in order to provide a preferred orientation for the filament. In one embodiment, a single feature is located off-center and optical radiation of one intensity is injected through the facet feature, thereby causing the laser to operate in one of its states, whereas injected radiation of another intensity causes the laser to operate in the other of its states. The injected radiation may be radiation emitted by the laser that is reflected by an object (e.g., a bit mark in an optical storage medium or a region of an integrated circuit being viewed under an optical microscope) proximate the facet feature (e.g., in the laser near-field). Alternatively, the injected radiation may originate from a transmitter in an optical communication system. In either case, any change in the state of the laser is detected as change in a parameter of the laser (e.g., a change in its impedance that is detected as a corresponding change in its terminal voltage). In an alternative embodiment, based on a differential mode of detection, a pair of facet features are located on opposite sides of the center of the waveguide's cross-section.