Abstract: A semiconductor optical modulator which, with a relatively simple configuration, eliminates phase modulation of output light from the semiconductor optical modulator by applying a voltage to a light absorption layer on the modulator. A nonlinear optical material layer changing refractive index is located in the direction of light propagation and cancels, in the output light, the phase modulation that is generated due to light intensity variations in the light absorption layer.

Abstract: A semiconductor light emitting device includes a double heterojunction structure including an active layer, a cladding layer having a first conductivity type, and a cladding layer having a second conductivity type, which cladding layers sandwich the active layer, and an undoped cladding layer interposed between the first conductivity type cladding layer and the active layer, which undoped cladding layer is the same material as the first conductivity type cladding layer and has a thickness larger than the diffusion length of carriers in the undoped cladding layer. Therefore, carriers are accumulated in the undoped cladding layer and then regularly injected into the active layer by Coulomb repulsion between the carriers, resulting in a semiconductor light emitting device with reduced heat generation, reduced fluctuation of emitted laser light, and reduced noise.

Abstract: A semiconductor laser device includes a semiconductor laser having a pair of facets and disposed on a semiconductor substrate and a photodiode having a light responsive surface on which a laser beam emitted from one of the facets of the semiconductor laser is incident, also disposed on the semiconductor substrate. The pair of facets of the semiconductor laser and the light responsive surface of the photodiode are both perpendicular to the surface of the semiconductor substrate, and the light responsive surface of the photodiode is disposed so that light of the laser beam reflected by the light responsive surface does not return to the emitting point of the laser beam. Therefore, return light noise generated in the semiconductor laser is avoided. In addition, the pair of facets of the semiconductor laser and the light responsive surface of the photodiode can be formed simultaneously by dry etching, thereby shortening the fabricating process.

Abstract: A method of making a semiconductor laser includes forming spaced apart insulating films on a semiconductor substrate of a first conductivity type defining a central groove and two regions transverse to, contiguous to, and continuous with the central groove, the semiconductor substrate being exposed in the groove and the two regions; successively, epitaxially growing a first cladding layer of a first conductivity type, an active layer including a multiple quantum well structure having alternating well and barrier layers, a second cladding layer of a second conductivity type, opposite the first conductivity type, and a contact layer of the second conductivity type on the semiconductor substrate using a process producing thicker well layers in the groove than in the two regions; and forming first and second electrodes on the substrate and the contact layer, respectively.

Abstract: A semiconductor laser includes a p type cladding layer and an n type cladding layer sandwiching an active layer serially disposed on a semiconductor substrate. The p type cladding layer includes a first dopant impurity producing p type conductivity and a smaller quantity of a second impurity that produces n type conductivity and ionically bonds to the first impurity. The first and second dopant impurities attract each other and cannot move individually during a crystal growth step at high temperature whereby the diffusion of those impurities into the active layer is suppressed, preventing formation of a deep impurity level in the active layer, resulting in a semiconductor laser with a reduced threshold current.

Abstract: A semiconductor laser device having an active layer sandwiched by semiconductor layers having larger energy band gaps than that of the active layer, includes a semiconductor absorption layer having an energy band gap no larger than that of the active layer and having a thickness periodically changing in the cavity length direction of the resonator, close to the active layer so that light which is generated at the active layer reaches the absorption layer, and a semiconductor refractive index matching layer, having a larger energy band gap than that of the active layer and a higher refractive index than those of the semiconductor layers sandwiching the active layer, to make the equivalent refractive indices in layer thickness direction substantially equal along the resonator direction.

Abstract: A semiconductor laser device having an active layer sandwiched by semiconductor layers having larger energy band gaps than that of the active layer, includes a semiconductor absorption layer having an energy band gap no larger than that of the active layer and having a thickness periodically changing in the cavity length direction of the resonator close to the active layer so that light which is generated at the active layer reaches the absorption layer, and a semiconductor refractive index matching layer having a larger energy band gap than that of the active layer and a higher refractive index than those of the semiconductor layers sandwiching the active layer to make the equivalent refractive indices in layer thickness direction substantially equal along the resonator direction.

Abstract: A buried stripe semiconductor light emitting device and a method for producing the device in which the buried stripe functions as an internal resonator, and the device has window regions interposed between the resonator and facets on the external surface of the device. A first phase crystal growth is conducted in which a first cladding layer is grown on a doped substrate. Thereafter, a doped stripe of impurities is introduced into the first cladding layer in electrical contact with the doped substrate. The doped stripe extends longitudinally but terminates short of the facets so that later out-diffusion from the doped stripe will form the window regions. A second phase crystal growth is then conducted which buries the doped stripe internal to the semiconductor, i.e., not projecting through any external surface. The second phase crystal growth comprises an active layer, a second cladding layer and a contact layer successively grown on the first cladding layer.

Abstract: A distributed feedback semiconductor laser which achieves a phase shift for stabilizing the longitudinal mode without a substantial increase in reactive current and without introducing dimensional discontinuities in the laser stripe. The active layer of the laser is configured as a multi-quantum well and impurities are selectively diffused into the multi-quantum well to disorder a selected portion of the active layer. The disordered portion has an optical propagation constant which is different than that of the remaining stripe, and the difference in propagation constant coordinated with the length of the phase adjustment section produces a phase shift adequate to stabilize the laser longitudinal mode.

Abstract: A buried stripe semiconductor light emitting device and a method for producing the device in which the buried stripe functions as an internal resonator, and the device has window regions interposed between the resonator and facets on the external surface of the device. A first phase crystal growth is conducted in which a first cladding layer is grown on a doped substrate. Thereafter, a doped stripe of impurities is introduced into the first cladding layer in electrical contact with the doped substrate. The doped stripe extends longitudinally but terminates short of the facets so that later out-diffusion from the doped stripe will form the window regions. A second phase crystal growth is then conducted which buries the doped stripe internal to the semiconductor, i.e., not projecting through any external surface. The second phase crystal growth comprises an active layer, a second cladding layer and a contact layer successively grown on the first cladding layer.