摘要:
A optical medium, such as an angled distributed reflector, e.g., an angular grating, or .alpha.-DFB laser diode or a waveguide wavelength selective filter, has a mean optical axis defining an optical cavity for substantially confined light propagation within the device. An angular grating is provided in at least a portion of the optical cavity forming a grating region permitting light to propagate along the optical cavity in two coupled waves or modes incident along the angular grating, a first incident propagating wave substantially parallel with respect to the mean optical axis and a second incident propagating wave at an angle with respect to the mean optical axis. At least one preferential coupling region in the optical cavity at an interface or boundary with the grating region to receive both propagating waves and provide for preferential treatment to the first incident propagating wave by coupling propagating light in the second incident propagating wave into the first incident propagating wave prior to light output from the medium via the non-grating region, forming a boundary with the grating region. The angle of the boundary at the interface of these respective regions is chosen to be substantially collinear with a propagation direction of the second incident propagating wave so that propagating light in the second incident propagating wave will substantially enter the preferential coupling region from the grating region via the boundary in a propagation direction substantially parallel with the mean optical axis.
摘要:
A buried heterostructure (BH) laser source with a narrow active region is disclosed for use in close proximity with optically-addressed data storage media for read/write functionality in a relatively high data density format. The BH laser source is formed on a pregrooved or prepatterned substrate to form mesas upon which epitaxial layers are formed to form laser source active regions that have small emission apertures at the laser source facet output. Selective removal of semiconductor cladding material and replacement of this material with lower refractive index materials provides a way of obtaining further mode size-reduction at the output facet of the laser source. Each mesa has a top surface and adjacent sidewalls such that in the growth of the epitaxial layers above the active region doped with a first conductivity type, the above active region epitaxial layers depositing on the top surface deposit as a first conductivity type and depositing on said sidewalls deposit as a second conductivity type. This growth construction provides for a naturally formed p-n junction at the laser source active region and eliminates the need to perform a subsequent diffusion process to form such a junction. The optical cavities of the laser sources may be tapered so that die cleaving a predetermined point along the length of the optical cavity will provide the desired emission aperture size at the laser source output facet.