Abstract: The invention relates to a laser with a multi quantum well active layer in which a portion of the quantum well and barrier layers is provided with a compression stress, while another portion is provided with an oppositely directed tensile stress. Said stresses are overcompensated such that the net stress is a tensile stress. Preferably, the laser comprises one or several quantum well layers with a compression stress and a number of barrier layers with an excess tensile stress.

Abstract: A light emitting device for use in lighting and/or display applications includes a UV/blue LED located in a depression having reflecting sidewalls, a light transmitting material surrounding the LED and filling the depression, and a phosphor in the form of particles either dispersed in the light transmitting material or adhered to the surface of the LED. The sidewalls reflect UV as well as visible light, thus enhancing the efficiency of the device. Optical filters located on the top of the LED and/or the bottom of a UV absorbing glass plate covering the depression further enhance efficiency and/or spectral characteristics of the emitted light.

Abstract: A radiation-emitting semiconductor diode, especially a laser having a first and a second cladding layer, an active layer and a mesa which comprises at least the second cladding layer and which lies recessed in a third cladding layer. The second cladding layer comprises a first sub-layer which adjoins the active layer and is comparatively thin, and a second sub-layer which adjoins the first sub-layer and is comparatively thick, while the refractive index of the first sub-layer is lower than that of the second sub-layer. Confinement in the thickness direction of charge carriers and radiation is good in such a diode, while the third cladding layer has a relatively high refractive index (giving a relatively low bandgap). Thus, the third cladding layer has a relatively low aluminium content, while providing good lateral confinement.

Abstract: The invention relates to a radiation-emitting semiconductor diode, in particular a laser diode, whose active layer (3) comprises a II-V mixed crystal in which various elements, for example III elements, may be present in orderly or disorderly arrangement. Such a mixed crystal is InGaP whose emission lies below 1 .mu.m. In the known diode, catastrophic optical degradation is suppressed in that the active layer (3) has an orderly distribution in the active region (3A) and a disorderly distribution of the elements in a passive region (3B) situated near an exit surface (51). The known diode has a low efficiency and a high starting current. In a diode according to the invention, the distribution of the different elements is disorderly in the active region (3A), while the passive region (3B) is formed through local intermixing of the active layer (3).

Abstract: Semiconductor diode lasers are used inter alia in optical disc systems, laser printers, bar code readers, and glass fibre communication systems. Lasers having a so-called (weakly) index-guided structure are very suitable for many applications inter alia because they can be manufactured comparatively simply and reliably. A disadvantage of the known (weakly) index-guided laser is that the so-called P-I (=optical power-current) characteristic thereof exhibits a kink. Such a kink limits the use of the laser to a relatively low optical power. According to the invention, such a (weakly) index-guided laser has a resonance cavity with a length for which the optical power at which a kink occurs in the P-I characteristic is a maximum. It was a surprise to find that the occurrence of a kink in the P-I curve of such a (weakly) index-guided laser depends on the length of the resonance cavity. Very surprising is the appearance of a maximum value in this kink power as a function of the length of the resonance cavity.

Abstract: An optical device includes a phase-locked diodelaser array (10), a collimator lens (17), and behind the collimator lens a prism system (30, 34) of at least one prism to broaden the far field radiation pattern in the lateral plane (XY) and a spatial filter (19) to select a favored mode. The laser radiation is concentrated into a single, round and diffraction limited spot (V).

Abstract: A semiconductor laser/amplifier is disclosed in which the radiation oscillates only in one longitudinal mode. According to the invention this is achieved by a strip-shaped active region which exhibits periodic variations in amplification (and preferably also in the amplification profile) in its longitudinal direction over at least a part of its length. The period of the amplification variation is at least ten times the wavelength of the radiation.

Abstract: The invention relates to a method of manufacturing a semiconductor device in which a compound consisting of at least two semiconductor materials and having an energy gap which is smaller than that of a substrate is deposited epitaxially on the substrate. According to the invention, the composition of the mixture is determined during the deposition by means of measurement of the thermal emission.