Abstract: Apparatus for frequency conversion of light, the apparatus comprises: a light-emitting device for emitting a light having a first frequency, the light-emitting device being an edge-emitting semiconductor light-emitting diode having an extended waveguide selected such that a fundamental transverse mode of the extended waveguide is characterized by a low beam divergence. The apparatus further comprises a light-reflector, constructed and designed so that the light passes a plurality of times through an external cavity, defined between the light-emitting device and the light-reflector, and provides a feedback for generating a laser light having the first frequency. The apparatus further comprises a non-linear optical crystal positioned in the external cavity and selected so that when the laser light having the first frequency passes a plurality of times through the non-linear optical crystal, the first frequency is converted to a second frequency being different from the first frequency.

Abstract: The method produces coherent dislocation-free regions from initially dislocated and/or defect-rich lattice mismatched layer grown on top of the substrate having a different lattice constant, which does not contain any processing steps before of after the lattice-mismatched layer growth. The process preferably uses in situ formation of a cap layer on top of a dislocated layer. The cap layer preferably has a lattice parameter close to that in the underlying substrate, and different from that in the lattice mismatched layer in no strain state. Under these conditions, the cap layer undergoes elastic repulsion from the regions in the vicinity of the dislocations, where the lattice parameter is the most different from that in the substrate. The cap layer is absent in these regions.

Abstract: A wavelength division multiplexing system based on arrays of wavelength tunable lasers and wavelength tunable resonant photodetectors is disclosed. The system allows self-adjusting of the resonance wavelength of the wavelength tunable photodetectors to the wavelengths of the laser light emitted by the lasers. No precise wavelength stabilization of the lasers is required.

Abstract: A method for fabrication of defect-free epitaxial layers on top of a surface of a first defect-containing solid state material includes the steps of selective deposition of a second material, having a high temperature stability, on defect-free regions of the first solid state material, followed by subsequent evaporation of the regions in the vicinity of the defects, and subsequent overgrowth by a third material forming a defect-free layer.

Abstract: A wavelength tunable semiconductor vertical cavity surface emitting laser which includes at least one active element including an active layer generating an optical gain by injection of a current, and at least one phase control element, and mirrors. The phase control element contains a modulator exhibiting a strong narrow optical absorption peak on a short wavelength side from the wavelength of the laser generation. The wavelength control is realized by using a position-dependent electro-optical effect. If a reverse bias is applied, the absorption maximum is shifted to longer wavelengths due to the Stark effect. If a forward bias is applied, a current is injected and results in the bleaching and reduction of the peak absorption. In both cases a strong modulation of the refractive index in the phase control element occurs. The effect tunes the wavelength of the cavity mode, and the sign and the value of the wavelength shift are defined by the position of the modulator.

Abstract: A novel class of semiconductor lasers, or “tilted cavity lasers” includes at least one active element with an active region generating an optical gain by injection of a current and mirrors. The active element is placed into a cavity. The cavity is designed such that the optical path of the resonant optical mode is tilted with respect to both the vertical direction and the lateral plane. Thus, the feedback both in the vertical and in the lateral direction is provided for the resonant optical mode. Depending on the particular embodiment, the laser operates as both a surface emitting laser and an edge-emitting laser. Employing a tilted optical mode allows the use of substantially fewer layers in the bottom and the top interference reflectors than in conventional lasers. This preserves the necessary high reflection coefficients. Also, a wavelength-stabilized laser is realized for edge-emitters.

Abstract: A semiconductor laser having a low beam divergence is disclosed. The laser includes at least one waveguide comprising an active layer generating an optical gain by injection of a current, a photonic band gap crystal having the refractive index modulation in the direction perpendicular to the propagation of the emitted light, and at least one defect. The active layer is preferably placed within the defect. The photonic band gap crystal and the defect are optimized such that the fundamental mode of laser radiation is localized at the defect and decays away from the defect, while the other optical modes are extended over the photonic band gap crystal. Localization of the fundamental mode at the defect results in the relative enhancement of the amplitude of the mode with respect to the other modes. Therefore, there is a larger confinement factor of the fundamental mode as compared to the confinement factor of the other modes. This enables efficient single-mode lasing from the laser having an extended waveguide.

Abstract: A wavelength tunable semiconductor vertical cavity surface emitting laser which includes at least one active element including an active layer generating an optical gain by injection of a current, and at least one phase control element, and mirrors. The phase control element contains a modulator exhibiting a strong narrow optical absorption peak on a short wavelength side from the wavelength of the laser generation. The wavelength control is realized by using a position-dependent electro-optical effect. If a reverse bias is applied, the absorption maximum is shifted to longer wavelengths due to the Stark effect. If a forward bias is applied, a current is injected and results in the bleaching and reduction of the peak absorption. In both cases a strong modulation of the refractive index in the phase control element occurs. The effect tunes the wavelength of the cavity mode, and the sign and the value of the wavelength shift are defined by the position of the modulator.

Abstract: The method produces coherent dislocation-free regions from initially dislocated and/or defect-rich lattice mismatched layer grown on top of the substrate having a different lattice constant, which does not contain any processing steps before of after the lattice-mismatched layer growth. The process preferably uses in situ formation of a cap layer on top of a dislocated layer. The cap layer preferably has a lattice parameter close to that in the underlying substrate, and different from that in the lattice mismatched layer in no strain state. Under these conditions, the cap layer undergoes elastic repulsion from the regions in the vicinity of the dislocations, where the lattice parameter is the most different from that in the substrate. The cap layer is absent in these regions.