摘要:
A multi-element grating beam splitter with a reflection grating for use in providing a front facet detector signal in an optical system. The multi-element grating beam splitter includes first, second, third, and fourth grating elements for separating a return beam reflected and diffracted from a data track on an optical storage medium into first, second, third and fourth portions, respectively. The grating beam splitter also includes a fifth grating element, which is preferably a reflection grating, for directing a portion of an incident radiation beam onto a front facet detector. The front facet detector signal may be subtracted from a data signal resulting from detection of the first, second, third and fourth portions of the return beam in order to limit the effect of optical source noise on the data signal.
摘要:
Apparatus and method for amplitude modulation of laser light by means of an electro-optic waveguide having a grating coupler, the length of the grating being short relative to the coupling length and to the waist of the incident laser beam.
摘要:
A waveguide structure includes a substrate, a waveguide film, and an overlay material in contact with the waveguide film. The overlay material may also contact the substrate or the film may be disposed between the overlay and the substrate. The overlay material has a higher refractive index than the waveguide so that the ratio of the effective refractive indexes is substantially constant for all propagating modes supported by the waveguide.
摘要:
Mode-index optical elements comprise an optical waveguide having a optical overlay of substantially uniform thickness. The contour of the overlay in the plane of the overlay controls the direction of propagation of radiation within the waveguide. According to the invention, mode-index optical elements are optimally achromatized (i.e., rendered as insensitive as possible to radiation wavelength changes) over a desired wavelength rqange by properly selecting the respective thicknesses and bulk refractive indices of the overlay and waveguide components. Specifically, such parameters are chosen so that, for a given waveguide substrate (e.g., quartz) and superstrate (e.g., air), the deviation of the ratio of the respective effective refractive indices of the waveguide element (N.sub.E) and waveguide material (N.sub.WG) from a mean or nominal value is minimized over the desired wavelength range of achromatization.