Abstract: The coupled waveguide structure comprises first and second rectangular waveguides, disposed closely. The aspect ratio of the first waveguide is substantially inverse in number to that of the second waveguide.

Abstract: A functional semiconductor element, which is designed to perform an ultrafast amplifying, bistable, similar functional operation by initiating and stopping an avalanche multiplication in one of i-type layers of what is called a triangular barrier diode (TBD) structure having an n-i-p-i-n, p-i-n-i-p, n-i-p-i-p, n-i-n-i-p, n-i-n-i-n, p-i-n-i-n, p-i-p-i-p, or p-i-p-i-n configuration. By forming a light absorbing layer and a light emitting layer or light modulating layer in this structure, it is possible to function the element as an optical functional element. Furthermore, the addition of a resonant tunneling diode implements a novel function.

Abstract: An optical functional semiconductor element which performs ultrafast, high-contrast logic operation through utilization of the high speed of light velocity. A resonant-tunneling diode having a negative resistance characteristic is provided apart from a light absorbing layer formed by one of i-type layers of what is called a triangular barrier diode of an nipin or pinip structure, by which as the quantity of incident light increases, the quantity of transmitted current is switched from increase to decrease, the amount of change is made high-contrast and an ultrafast logic operation can be performed.

Abstract: An optical logic element is disclosed which performs an XOR operation through utilization of the high-speed property of light. On each branched waveguide of a Mach-Zehnder interference type optical waveguide there is provided a phase modulating element whose refractive index undergoes a change when it is irradiated by light. The interference type optical waveguide is adapted to provide different optical output levels when the refractive index changes of the phase modulating elements are both zero or a predetermined value and when they differ from each other. Thus, the optical logic element is capable of performing the XOR or XNOR operation at an ultrahigh speed.

Abstract: A semiconductor optical element comprises a semiconductor substrate, a waveguide, an active layer and a clad layer mounted on said substrate; said active layer comprising first region and second region coupled optically with each other, and having opposite signs of .alpha. parameters with each other, where said parameter is ratio of change of refractive index to change of gain following change of carrier density; a first electrode common to all regions attached on one side of said substrate; and second electrodes for each region attached on the other side of said substrate. The invention is used for an AM modulation laser, or an FM modulation laser.

Abstract: A wavelength-tunable semiconductor laser of distributed feedback (DFB) type wherein a diffraction grating having periodic corrugations along the direction of travel of light is formed on an active layer of at least one of layers adjacent thereto. An electrode on one side is separated into four or more electrodes in the direction of the cavity of the laser. Nonadjoining ones of them are electrically connected to form two electrode groups. The total length of first regions corresponding to a first one of the two electrode groups is larger than the total length of second regions corresponding to the second electrode group. The refractive indexes of the first regions are changed through current injection change to the first electrode group to vary the lasing wavelength and the gain of the second regions is controlled through current injection to the second electrode group, thereby generating output light of a constant output power and a variable single wavelength.

Abstract: A quantum well structure is disclosed, which is comprised of a quantum well layer of a thickness substantially equal to the de Broglie wavelength of electrons and carrier confinement layers of an energy gap greater than that of the quantum well layer. A second material of a lattice constant different from that of a first material primarily for the quantum well layer is disposed in the quantum well layer to provide a phase shift in the period of the crystal lattice of the first material, thereby forming energy levels in the forbidden band of the quantum well layer. A semiconductor device which employs such a quantum well structure and is so constructed as to utilize its physical phenomenon which is caused by the energy levels in the forbidden band. In concrete terms, the present invention has its feature in allowing ease in the fabrication of an intermediate infrared or blue light emitting device, for instance.

Abstract: An optical semiconductor device manufacturing method is disclosed which involves an ion implantation step of implanting ions into a compound semiconductor wafer through an ion implantation mask and an annealing step of activating atoms in the compound semiconductor wafer through an annealing mask film. The ion implantation step and the annealing step are performed in succession after laminating mono- or multi-layered compound semiconductor layers as the ion implantation mask and the annealing mask film on the compound semiconductor wafer.

Abstract: An optical modulation element is disclosed which has, on a substrate directly or through a lower clad layer, an optical waveguide layer of a low impurity concentration, an upper clad layer of a refractive index smaller than that of the optical waveguide layer, and electrodes, and in which light of a constant intensity incident on a light incident end face of the optical waveguide layer is intensity-modulated by changing the absorption coefficient of the optical waveguide layer by means of an electric field applied thereto across the electrodes so that the thus modulated light is emitted from a light emitting end face of the optical waveguide layer.

Abstract: A light triggering switch is disclosed for switching the optical path of an input optical signal to a desired output optical path. A portion of an optical control signal of a predetermined wavelength is branched by a branching filter. An electrically-controlled optical switch is provided for converting the branched optical control signal into an electrical signal and for switching the optical signal to the desired output optical path in accordance with the intensity of the converted electrical signal. In place of the electrically-controlled optical switch, a nonlinear reflector type optical switch may be provided for switching the optical signal to the desired output optical path in accordance with the intensity of the branched optical control signal.

Abstract: An infrared emitting device for use in the 2 to 3 .mu.m region, which is low in the threshold current and operates over a wide temperature range. In accordance with the present invention, an InP substrate is employed in place of GaSb substrate and InAs substrate heretofore employed for the 2 to 3 .mu.m infrared semiconductor lasers. Moreover, as active layers or clad layers, one of more semiconductor layers are employed which differ in lattice constant from the InP substrate.

Abstract: An optical modulation device is disclosed in which a difference between the photon energy of incident light and the band-gap energy of the modulation waveguide layer is set to a value greater than 50 meV to thereby suppress the degradation of the modulation voltage and the modulation band width which is caused by an increase in the intensity of incident light and in that the optical modulation device is formed in a predetermined length to thereby decrease the modulation voltage.

Abstract: A semiconductor optical amplifying element is disclosed which has a semiconductor multilayer structure including at least a first semiconductor layer for providing an optical gain in response to the injection of carriers thereinto, and a p-side electrode and an n-side electrode for the carrier injection. A first reflecting surface and a second reflecting surface are disposed thickwisely of the semiconductor multilayer structure and opposite to each other thereacross. The element is designed so that light incident thereon from the thickwise direction of the semiconductor multilayer structure is amplified by propagating through the element perpendicularly to the thickwise direction of the semiconductor multilayer structure while being multiple-reflected between the first reflecting surface and the second reflecting surface.

Abstract: An optical packet switching system is disclosed in which a routing signal is composed of a wavelength-multiplexed optical signal and an information part and a packet end code are also composed of optical signals. In accordance with the present invention, a switching network is formed by a multi-stage combination of light triggering switches which are closed depending on the presence or absence of a particular wavelength in the wavelength-multiplexed optical signal.

Abstract: A variable-waveguide optical branching filter is disclosed, in which a diffraction grating is formed in the cross region of two crossing waveguides, only light of a particular wavelength which is determined by the period of the diffraction grating is branched to a desired one of the waveguides, and the refractive index of the cross region is changed by control of a voltage or a current, or by way of irradiation with light, thereby changing the wavelength of light to be branched.

Abstract: A semiconductor laser is disclosed in which a light emitting region having a light emitting layer and a waveguide region having a waveguide layer which is coupled to at least one side of the light emitting layer with a high efficiency are integrated on the same substrate; the light emitting region includes an active filter section having a diffraction grating equipped with a band-pass filter function; the light emitting region and the waveguide region are electrically isolated and are each provided with an electrode; and the oscillation wavelength of the semiconductor lase is changed by changing the refractive indices of at least the waveguide region and the active filter section through voltage application or current injection to the electrodes, thereby producing a narrow-linewidth, single-wavelength oscillation output light of a wavelength which corresponds to the transmission wavelength of the active filter section determined by the preset refractive indices of the waveguide region and the active filter se

Abstract: A variable wavelength semiconductor laser is disclosed, in which light emitting regions, waveguide regions and an active filter region including a diffraction grating equipped with a filter function are integrated on a single substrate, whereby only one resonance wavelength is selected to ensure a stable laser operation at a single wavelength of a small oscillation line-width. Further, both light emitting and waveguide regions are disposed on both sides of the active filter region substantially symmetrically with respect thereto, thereby allowing ease in adjusting the refractive indices of the respective regions.

Abstract: A method is disclosed for manufacturing a diffraction grating formed by corrugations reversed in phase between a first region and a second region through use of two kinds of photoresists of opposite photosensitive characteristics. An isolation film is introduced for preventing the photoresists from getting mixed with each other, permitting the combined use of any photoresists. A step may be further included in which the isolation film is deposited on one of two kinds of photoresist films in at least one of a first region and a second region, is subjected to two-beam interference exposure, is removed and then a degraded layer, which is formed in the surface of the above said one kind of photoresist film during the deposition of the isolation film, is removed.

Abstract: A distributed feedback semiconductor laser with monitor is disclosed, in which the energy gap of a light absorbing layer provided on the window region alone is smaller than the energy gap of the light emitting layer, and in which an independent pn junction isolated from the pn junction in the laser region is provided in or at one edge of the light absorbing layer on the window region.

Abstract: An optical waveguide switch is disclosed in which at least two optical waveguides intersect at a predetermined angle to each other to provide, on both sides of the intersection region, input side optical waveguide regions for receiving incident light and output side optical waveguide regions for outputting guided light, and in which the incident light is input into one of the input side optical waveguide regions and is output from a desired one of the output side optical waveguide regions. In accordance with the present invention, an optically nonlinear material whose refractive index undergoes a substantial variation, depending on the intensity of incident light, is disposed in the intersection region. A loop is provided in association with a corresponding one of the input side optical waveguide regions for essentially branching the guided light in the corresponding waveguide output side optical waveguide region for feedback to the corresponding input side optical waveguide region.