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Speckle contrast of single, dual, and triple emitter broad area laser diodes (BA-LDs) with a wavelength of 638 nm was experimentally investigated. Speckle noise was relatively small near the threshold current probably due to the longitudinal mode competition. Higher output power led to smaller speckle noise owing to the spectrum widening. A wide stripe presented an advantage in terms of speckle reduction in the single emitter LDs. It is also found that wider emitter width leads to the smaller the speckle noise. A larger number of emitters decreased speckle noise due to the beam superposition effect, even for multi-emitter LDs in which the emitters are built into one chipa.

Color speckle metrics of an RGB-combined white laser beam emitted from an optical fiber output of two types of RGB laser module are measured. A new method for eliminating the effects of a fiber far field pattern from the measured 2D speckle data is employed to calculate the speckle metrics with a statistical accuracy. In this method, unspeckled 2D data of the far field pattern can be directly measured by opening the iris of the speckle measurement equipment. As a result, white photometric speckle contrast and color speckle distribution in CIE1931 chromaticity diagram are, for the first time, successfully obtained by eliminating the far field pattern effects.

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.

Visual resolution of raster-scan, laser mobile projectors using red, green, blue (RGB) laser diodes was measured using a high-speed 2D speckle measurement equipment, considering the effects of color speckle. Blind evaluation of three laser mobile projectors was carried out. Photometric visual resolution of white point was obtained by calculating contrast modulation CM using a grille pattern of narrowing line-pairs. The color speckle distribution was plotted in CIE 1931 chromaticity diagram and in CIELab color space. The color speckle was found to degrade photometric visual resolution, as well as the color speckle distribution spreading in the color spaces. Color shifts at the edge of the line image were obviously observed by the color speckle plots in the color spaces. The color shifts are found to be generated due to RGB LD switch timing mismatches. As a result, one of them achieved better performance than the others. This 2D color speckle measurement method is indispensable for measuring visual resolution of laser displays, reproducing speckle grain sizes on human retina.

Angular dependence of speckle contrast of speckle pattern projected out of a multi-mode fiber connected to a high-power blue laser module is investigated. The laser module has nine high-power InGaN/GaN blue laser diodes arranged in a three-by-three array. Each of the arrayed laser diodes have slightly different incident angle to the fiber. We have successfully extracted the fine screen speckle pattern from the projected pattern mixed up with the coarse fiber speckle pattern by processing the measured data. It is found that the speckle contrast of the both screen and fiber speckles are larger around the center area where the guided-light component closest to the paraxial direction is projected. This is because the output of the center laser in the array is likely to couple into the paraxial mode more than the rest. Speckle contrast behaviors when applying the speckle reduction methods, fiber vibration, diffuser, and spinning diffuser are also investigated.

Self-sustained-pulsing A1GaInP laser diodes having very low intensity noise characteristics were successfully demonstrated by adopting a novel structure, which has highly doped saturable absorbing layer. Short carrier lifetime, which is indispensable for self-sustained pulsation, was realized by applying highly doped saturable absorbing layer. Self-pulsing laser diodes with the lasing wavelength of 650nm-band were fabricated, resulting in the threshold current of 76mA at 20°C. The relative intensity noise (RIN) was below - 138dB/Hz in the temperature range 20-60°C at the average output power of 5mW.

Accommodation of misfit in the earlier stage of heteroepitaxial growth has been studied for GaP films on GaAs. Raman spectroscopy has been applied to the evaluation of the misfit strain and the distribution of dislocations in GaP films thinner than 1000 A. The crystallographic orientation of the films has been also evaluated. The misfit strain varies with thickness in the range of 20–800 A and is partially relaxed even at a thickness of 20 A. The variation of the misfit strain with thickness has been examined with several models of dislocation nucleation. The analysis has shown that the misfit is accommodated by elastic strains and dislocation introduced in the region near the interface.

Crystal properties of Ga x In 1− x P grown by gas source molecular beam epitaxy using phosphine (PH 3 ) were studied by using double crystal X-ray diffractmetry, Nomarski microscopy and photoluminescence (PL). Smooth surfaces were obtained if the lattice mismatch (Δ d / d ) ⊥ was less than about 5x10 −3 . The full width at half maximum of the PL spectra measured at 300 K was as narrow as 37.3 meV. The radial variations in layer thickness, PL intensity and composition are less than 10%, nearly constant and about 0.4%, respectively, across a 50 mm diameter wafer.

The electrical, optical and structural properties of Al0.5In0.5P and Ga0.5In0.5P layers grown on (001) GaAs substrates by gas source molecular beam epitaxy (GSMBE) using phosphine (PH3) gas have been studied. For heavy Be doping, the electrical activity was found to be unity up to atomic Be concentration of 2 × 1018 cm-3 in Al0.5In0.5P and 3 × 1019 cm-3 in Ga0.5In0.5P. The maximum hole concentrations achieved are 3.5 × 1018 cm-3 in Al0.5In0.5P and 4 × 1019 cm-3 in Ga0.5In0.5P. 20 K photoluminescence (PL) measurements for heavily Be-doped Al0.5In0.5P showed that the decrease in electrical activity is due to deep levels resulting possibly from Al-Be related defects. An ordered structure and a compositional modulated structure were first observed in Ga0.5In0.5P grown by GSMBE. The degree of ordering was found to be less perfect than that for metalorganic vapor phase epitaxy (MOVPE) due to the lower growth temperature. Typical 300 K PL energy was found to be 1.88 eV which was 20 meV lower than the “normal” energy (1.9 eV).

Self‐sustained pulsating 650‐nm‐band AlGaInP visible lasers were fabricated by adopting a new structure, which has a highly doped saturable absorbing (HDSA) layer. Since the doping level and the thickness of the HDSA layer could be controlled accurately by using metalorganic vapor phase epitaxy growth technique, a stable operation of self‐sustained pulsation up to 60 °C was obtained. The lasers operated over 1350 h under the average output power of 5 mW at 60 °C. The relative intensity noise values were below −136 dB/Hz in the temperature ranging from 20–60 °C and remained unchanged after life test.

PT-01 is a newly developed water-soluble controlled-release insert containing ofloxacin (OFLX) as an antibacterial agent. The effect of PT-01 was evaluated by split-mouth application after oral hygiene instruction. No mechanical debridement was carried out during the experiment. PT-01 was applied once a week for 4 weeks in the periodontal pockets of 46 patients with adult periodontitis. The control insert without any antibacterial agent was applied in a selected pocket in a different quadrant for each patient. Clinical findings plaque index, PI; gingival index, GI; bleeding on probing, BOP; pus discharge, pus; and probing depth, PD at both PT-01 and control sites were measured at every visit for 4 weeks. Clinical findings were improved at both PT-01 and control sites, but the improvements were much more significant at PT-01 sites, in particular BOP and PD, than at control sites. PI was also significantly reduced at PT-01 sites. These results suggest that weekly application of PT-01 in the periodontal pocket has a significant effect on the resolution of periodontal inflammation and has an inhibitory effect on supragingival plaque deposition.

650 nm-band self-pulsing lasers which exhibit an extremely low laser beam profile aspect ratio (2.6) and a small astigmatism (2 µm) were successfully demonstrated by optimizing the design of the layer structure. Low-noise self-pulsing lasers have been developed as a light source for optical disc systems. In the case of mounting the lasers on optical systems, a low aspect ratio and a small astigmatism are required in order to realize high optical coupling efficiency and good optical focusing characteristics. In this paper, we report a reduction of the aspect ratio while maintaining a small astigmatism in self-pulsing AlGaInP lasers with a saturable absorbing (SA) layer by optimizing the optical confinement and compressive strain in the SA layer. Simultaneously, a very low intensity noise characteristic up to 50° C was confirmed by stable self-sustained pulsation characteristics.

High-power 650-nm-band AlGaInP visible laser diodes having stable fundamental-transverse-mode at high temperatures were produced using electron cyclotron resonance reactive ion beam etching (ECR-RIBE). Epilayers were etched using a Cl2/N2mixture gas, resulting in very smooth surfaces and symmetric laser mesas. Lasers that are 700-µm-long and 6%/80% coated were fabricated. The typical threshold current of these devices was as low as 46 mA at room temperature, and a stable fundamental-mode operation over 30 mW is obtained up to 70°C. The lasers operated for over 1000 h at 60°C under an output power of 25 mW, and their degradation rate was as low as lasers fabricated by the ordinary wet etching process.

We have developed a microcomputer control system to operate a 100 kV maskless ion implanter for III-V compound semiconductors. The performances of various functions of this computer-controlled ion implanter has been tested. Ion species switching by an E × B mass filter, ion beam diameter monitoring, ion beam mark detection, and ion beam writing by controlling E × B mass separator, electrostatic deflector and sample stage, have been working well, precisely and reproducibly enough to indicate prospects for a production oriented system. Using this technology, we have demonstrated a simple opto-electronic device fabrication process, which cannot be done so easily by any other process technology.

Syrian hamsters were infected with Actinomyces viscosus ATCC 15987 by inoculation into the oral cavity to induce experimental periodontitis. The effect of an antibiotic, ofloxacin (OFLX), on the experimental periodontitis was examined. In Group A, OFLX gel was applied daily to the gingival mucosa, 2 weeks after bacterial inoculation. Groups B and C were an infected control and a noninfected control, respectively. The hamsters in these three groups were fed a powdered high-sucrose diet. The hamsters in Group D, also a noninfected group, were fed an ordinary solid diet. Salivary occult blood test, evaluation of gingival and plaque index, measurement of alveolar bone loss, bacterial examination, and histological observation were performed 11 weeks after infection. Group B exhibited significantly higher levels of gingival index, plaque index, and alveolar bone loss than the noninfected controls. Severe inflammation of the gingivae, formation of gingival pockets, migration of many inflammatory cells, and obvious bone loss were also observed in Group B. However, these inflammatory changes were milder in Group A, which was treated with OFLX.