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We propose colors light detection and ranging (LiDAR) using visible laser diodes (LD) of red, green, and blue (RGB) colors to identify colors as well as obtain position information of surrounding objects. To verify the principle, we performed round-trip time-of-flight (TOF) measurements by irradiating a target of different colors with pulsed light from a LD of RGB colors. It is clarified that accurate distance measurements of up to 12 m can be realized in any RGB LD, and the received signal in each LD has different intensity characteristics depending on the target color. From a judgment table created from reception intensity characteristics for three types of LD and seven types of color target, the color of each target is successfully identified.

A new concept of integrated systems, named “IoT station”, using laser scan technology with visible laser diodes (LDs) common to smart lighting and LiDAR is proposed. It is applicable not only for smart lighting but also for image projection, power supply, and optical communications. As a fundamental verification of this system, a LiDAR using a LD emitting at red wavelength with two-axis scanning mechanism is fabricated for the first time. 3D image caption with detectable distance up to 10 m is achieved by the visible LiDAR. Spot lighting, projections, space signal transmissions and wireless power supply using light beam scanning are also verified as multi-purpose extended system. Additionally, spot lighting of which illumination area is controlled by visible LiDAR, has been successfully demonstrated.

We have proposed a new electro-optic Bragg-diffraction type spatial modulator/deflector using multi-stage polarization-reversed structures, which can deflect a laser beam with a high speed over GHz. In this paper, the operational principle and deflection characteristics of the proto-type device are reported.

We propose a thin and compact concentrator photovoltaic (CPV) module, about 20mm in thickness, one tenth thinner than those of conventional CPVs, to enlarge CPV application scenarios, and achieved an energy conversion efficiency of 34.7%.

Clarification of anomalous photoluminescence (PL) characteristics for InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures is studied to realize highly strained SL-MQW lasers with a large number of well layers. PL characteristics such as an increase in PL linewidth and a small temperature dependence of the PL peak wavelength are observed in the SL-MQW structures in which a structure of CuPt-type atomic ordering is observed. Elimination of the ordered structure as well as reduction of the PL linewidth have been confirmed with increasing growth temperature. Although formation of an interfacial undulation (lateral modulation) between SL-MQW layers is also suppressed by the increase in growth temperature, the formation has ultimately limited the maximum strain in SL-MQW. We suggest that the anomalous PL characteristics result from generation of ordering, dominant when the growth temperature is lower, as well as from interfacial undulation, dominant in highly strained SL-MQW when the growth temperature is increased.

Clarification of the degradation mechanism of photoluminescence (PL) charac-teristics of InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures on an InP substrate is studied to realize highly strained SL-MQW lasers with a large number of well layers. An unusual temperature-dependence of the PL peak wavelength is observed in the SL-MQW structure: the shift of the PL peak wavelength is reduced with change in measurement temperature. The degradation of PL characteristics is evaluated by the reduc-tion in the PL shift as well as an increase in PL linewidth and a decrease in PL peak intensity. The extent of the PL degradation increases with an increase in the number of well layers and an increase in strain. In the SL-MQW structure with degraded PL characteristics, the structure of CuPt-type atomic ordering is clearly observed for the first time in each barrier layer by high-resolution transmission electron microscope (HR-TEM) measurements. In the SL-MQW structure, neither dislocation nor three-dimensional nucleation is observed by TEM measurements. By increasing the growth temperature, elimination of the ordering structure as well as improvement in the PL characteristics have been confirmed even in the SL-MQW structure with a large amount of strain and a large number of well layers.

We have investigated the temperature dependencies of the slope efficiency and the threshold current for strained multiquantum well (MQW) lasers as a parameter of the well number. Smaller well numbers mean larger temperature dependencies of the slope efficiency and the threshold current, while larger well numbers mean larger internal loss and broadening of the photoluminescence linewidth of the MQW structure. Furthermore, the change in the slope efficiency with temperature change is related to the change in internal loss. In this work, the 1.3-μm strained MQW laser with a compressive strain of 1.0% and 7 wells shows the highest output power of 6.8 mW for an injection current of 50 mA and the lowest threshold current of 5.5 mA at 85°C, and the lowest variation in output power of 2.0 dB from 25–85°C at injection current of 50 mA.

An optical distribution system for providing CATV services to approximately 30,000 subscribers using a fiber-to-the-curb (FTTC) system has been developed. This system distributes the optical signal to 128 paths for 90 carriers with a hybrid 150 channel signal which accommodates 60 AM signals and 90 16 QAM signals to provide both conventional service and future services. The development of low distortion and low chirp MQW 1.55 mm DFB-LD is discussed and the zero distortion conditions for optical fiber amplifiers are verified in the investigation of the main parameters in the design of the system. To satisfy the system specifications, the signal wavelength is chosen to be 1561 nm, the input optical power is set to 6 dBm, and a two-stage optical fiber amplifier structure is used. The results of transmission tests are shown to verify the performance of the system. Lastly, the potential for expansion of the optical distribution system is discussed.

InGaAsP/InP multi-quantum well (MQW) planar buried hetero-structure (PBH) lasers which are grown entirely by metalorganic vapor phase epitaxy (MOVPE) on n-InP substrates are demonstrated. Two types of lasers, which are different in ridge shape (reentrant or non-reentrant), are investigated in respect of regrowth structure and damage at the regrowth interface. A new regrown structure constructed of a uniformly thick n-InP current-blocking layer formed on a reentrant ridge stripe is demonstrated for the first time. This structure is expected to be effective to suppress leakage current in laser operation. Furthermore, it is found that threshold current and reliability are strongly dependent on regrowth conditions. High quality regrowth interfaces are realized by optimizing regrowth thermal procedure and hole concentration of p-InP current-blocking layer. Stable laser characteristics in accelerated aging tests have been confirmed in both types of lasers.

Summary form only given. We present a 1.3-/spl mu/m gain-coupled DFB semiconductor laser with a tapered active stripe. The fabricated laser shows narrow beam divergence of 13-14 degrees and high side-mode suppression ratio (SMSR) of >45 dB. The laser has an InAsP absorptive grating, which is buried between the n-InP buffer layer and the corrugated n-InP substrate.

High output-power and narrow spectral-linewidth operation of 1.3 /spl mu/m gain-coupled distributed feedback (DFB) lasers with InAsP buried absorptive grating are reported. In this report, we have investigated the effect of the thickness of separate-confinement-heterostructure (SCH) layer on the spectral linewidth. As a result, it was clarified that decreasing the thickness of SCH layer is effective to reduce the spectral linewidth. For the fabricated laser, a record high output-power of 230 mW and a minimum spectral-linewidth of 100 kHz was realized.

Characteristics of the InAsP layer formed on a corrugated InP substrate by a mass-transport mechanism have been investigated for use as the buried grating of distributed feedback (DFB) lasers, The size of the InAsP layer can be controlled by the height of the corrugation, and the arsenic composition in the InAsP layer can be controlled by the AsH/sub 3/ partial pressure. The results of TEM, EDS and PL show that InP is suitable as the buffer layer between the InAsP layer and MQW active layer. Fabricated 1.3 /spl mu/m DFB lasers which have an InAsP layer as an absorptive grating have shown low threshold current and high slope efficiency from -40-+85/spl deg/C, and high reliability has been demonstrated.

In conclusion, we have reported on lasing characteristics of a 1.3-/spl mu/m InGaAsP strained-layer MQW lasers for butt-coupling modules, in which the active stripe horizontally tapered over almost the whole cavity. The fabricated lasers show low threshold current of 6.9 mA and high efficiency of 0.62 mW/mA with narrow beam divergence of 12/spl sim/13/spl deg/. These results indicate that the fabricated laser is effective to realize direct-coupling laser modules with high-coupling efficiency.

The dependence of photoluminescence (PL) characteristics on both SL-MQW structure and epitaxial growth condition is studied. The degradation of PL characteristics in the SL-MQW is confirmed as a broadening of PL linewidth and an unusual temperature-dependence of PL peak wavelength. By using a high-resolution transmission electron microscope (HRTEM), the structure of atomic ordering is demonstrated over entire barrier layers of the SL-MQW structure with degraded PL characteristics. By increasing growth temperature, elimination of the ordering structure as well as improvement of the PL characteristics have been confirmed even in a SL-MQW structure a with large amount of strain.

We have investigated the temperature dependencies of the output power and the threshold current for compressively strained InGaAsP MQW lasers on well number. Smaller well number means larger temperature dependencies of the slope efficiency as well as the threshold current due to enhanced carrier overflow, while greater well number means degradation in crystalline quality that lowers the reliability of the laser. The 1.3 /spl mu/m strained MQW laser with a compressive strain of 1.0% and 7 wells shows the highest output power of 6.8 mW and the lowest threshold current of 5.5 mA at 85/spl deg/C, and the lowest variation in output power of 2.0 dB from 25/spl deg/C to 85/spl deg/C at the injection current of 50 mA. These characteristics show that the optimized lasers are suitable for light sources of the optical access networks.

Distributed feedback laser diodes (DFB-LDs) with low distortion characteristics, lasing at 1.55-μm wavelength, are in strong demand as light sources for analog multichannel transmission systems using Er+3-doped fiber amplifiers (EDFA).1 To achieve high quality multichannel transmission, low distortion characteristics over a wide modulation frequency range are required. However, conventional DFB-LDs for analog transmission exhibit low distortion characteristics only up to several hundred MHz.

Amplitude-modulated frequency-division multiplexed (AM-FDM) optical transmission systems are strongly demanded for cable television (CATV) networks because of their compatibility with current coaxial systems.1 In these systems, 1.3-μm-wavelenth low-distortion distributed-feedback (DFB) laser diodes (LD’s) with high fiber-output are important light sources for long-distance high-density multiple-channel transmission. Multiple-quantum-well (MQW) DFB lasers are expected to implrove on these characteristics as compared with conventional DFB lasers. In a MQW LD, a smaller spatial hole-burning effect and higher resonant relaxation frequency owing to the quantum-size effect favor low-distortion operation,2 and low internal loss owing to a smaller confinement factor facilitates high output power.3 We report on a 1.3-μm-wavelength MQW-DFB LD and its analog multichannel transmission characteristics for the first time.

High output power and narrow spectral linewidth operation of 1.3 µm gain-coupled distributed feedback (DFB) lasers with InAsP buried absorptive grating is reported. In this study, we have investigated the effect of the thickness of a separate-confinement-heterostructure (SCH) layer on the single-mode stability and the spectral-linewidth property of 1.3 µm gain-coupled DFB lasers. As a result, we clarified that decreasing the thickness of the SCH layer led to stable single-mode operation at high output power and the reduction of the product of the spectral linewidth and the output power. For the fabricated gain-coupled DFB laser, a record high output power of 230 mW and a minimum spectral linewidth of 100 kHz at an output power of 150 mW were realized.

A new structure of 1.3 µm strained-layer multi-quantum well (MQW) complex-coupled distributed feedback lasers having an InAsP absorptive grating is demonstrated. In this structure, the InAsP absorptive grating and the strained-layer MQW active layer can be fabricated by a metalorganic vapor phase epitaxy process involving only one step. Furthermore, the fabricated laser has a low threshold current (16.8 mA) and a high efficiency (0.45 mW/mA).

The distortion characteristics of multiquantum well (MQW) distributed-feedback (DFB) lasers emitting at 1.55 mu m wavelength are investigated over a wide frequency range. The relaxation oscillation frequency f/sub r/ of the MQW DFB laser is 13 GHz at I/sub b/=77 mA, which is about 1.5 times larger than that of a DFB laser with a bulk active layer. Owing to the high relaxation oscillation frequency characteristics and the good linearity of the light-output against injection-current curve of the MQW DFB laser, extremely low distortion characteristics (IM/sub 2/ >

We have constructed a photochemical storage battery with an n-GaP Photoelectrode. A two-compartment cell, n-GaP|aqueous K3[Fe(CN6]–K4[Fe(CN)6||aqueous NiSO4|Pt, is capable of being charged by the irradiation of the photoelectrode. The current efficiency of nickel deposition on the storage electrode was 80%. When we drew electrical energy out of the dattery, the deposited nickel could act as a Ni electrode in the Ni2+ solution. The power efficiency of the storage battery amounted to about 2%. We could recharge the battery more than five times after discharge.

The Zn auto-doping phenomenon of DH structures grown by LPE was evaluated, using photoluminescence (PL) and SIMS analyses. From these analyses, it was found that Zn contamination of an undoped epitaxial film is rather large when a highly Zn-doped melt is adjacent to an undoped melt, and this amount is 5% of the total Zn doping level. But, if the melts are separated, the contamination can be much decreased to only 0.5% and as a result the undoped InGaAsP epi-layer contains much less Zn introduced from the heavily Zn doped InP layer.

Multi‐quantum‐well (MQW) strip‐loaded waveguides, which are composed of liquid‐phase‐epitaxy‐grown InGaAsP/InP systems, have been characterized in detail. Several MQW waveguides with well depths (Lz) ranging from 100 to 240 A have been compared with bulk ones about the electric‐field‐induced absorption effect, considering the zero‐bias propagation loss and the optical confinement factor in the region in which absorption occurs. It has been confirmed that the MQW (Lz∼100 A) waveguides have an absorption change under the electric field more than five times larger than the bulk ones with the same zero‐bias propagation loss.

We propose a new 1.3‐μm wavelength InGaAsP laser—the integrated passive cavity (IPC) laser—and demonstrate its device performances compared with conventional lasers fabricated under similar procedures. The long IPC laser (3.55‐mm‐long passive cavity), as well as the short IPC laser, exhibited single frequency oscillation even just above the threshold, and the maximum ratio of longitudinal main to submode exceeded 30 dB. They also showed favorable effects in the oscillation frequency stabilization.

We have proposed a novel technique to measure loss and facet reflectivity of semiconductor waveguides using Fabry-Perot resonance characterization. In order to obtain stable visibility of the optical transmittance, this technique has for the first time adopted a unique electro-optic effect instead of temperature-dependent Fabry-Perot resonance method. As a result, very accurate measurement has been realized as compared with those of currently available other measurement technique. Also we discussed the relation between spectral characteristics of incident light sources and waveguide parameters, and verified the conditions of this measurement to meet tight requirements of the waveguides.

Mean quantum yields ranging from 0.0053 to 0.16 have been determined for the reduction of Ag+ by irradiation with 365 nm light on a TiO2 single-crystal surface in aqueous solutions containing 1 × 10–5 to 1 × 10–2 mol dm–3 AgNO3. The electrochemical behaviour of the same crystal electrode has been investigated in order to clarify the mechanism of silver reduction. It is proposed that some conduction-band electrons, produced in the TiO2 by irradiation, transfer to the Ag+ adsorbed on the TiO2 surface. A convenient expression for the dependence of the mean quantum yield on the Ag+ concentration is derived from the viewpoint of semiconductor electrochemistry.

Recently considerable attention has been paid to developing narrow spectral linewidth semiconductor lasers for use in various coherent application systems. To obtain a stable and narrow linewidth light source, integrated external cavity configurations were employed, and single-frequency oscillation was achieved.1-3 However, the linewidths were in the range of 1-2 MHz, and further reduction was required for practical use.

The spectral linewidth of 1.3 μm monolithic integrated-passive-cavity (IPC) semiconductor laser is measured by a delayed self-heterodyne technique. It is found that the line-width is narrowed when longitudinal submode is suppressed. The narrowest linewidth obtained so far is 900 kHz at 6 mW output power.