Daisuke Kondo

Lateral current injection GaInAsP/InP laser on semi-insulating substrate for membrane-based photonic circuits

A room-temperature pulsed operation was demonstrated using lateral current injection-type lasers composed of a 400-nm-thick GaInAsP core layer with compressively strained 5 quantum wells. A threshold current of 105 mA and corresponding density of 1.3 kA/cm(2) (260 A/cm(2) per well) were obtained with the stripe width of 5.4 microm and the cavity length of 1.47 mm. A fundamental transverse mode operation was obtained with the narrower stripe device of 2.0 microm and the cavity length of 805 microm, while the threshold current and corresponding density were 49 mA and 3.0 kA/cm(2), respectively.

Continuous Wave Operation of Thin Film Lateral Current Injection Lasers Grown on Semi-Insulating InP Substrate

New structural designs are adopted to reduce the waveguide loss and increase the internal quantum efficiency of lateral current injection lasers consisting of a thin GaInAsP core layer grown on a semi-insulating InP substrate. This led to a drastic reduction in the threshold current. Room temperature continuous-wave operation has been successfully realized with a threshold current of 11 mA and an external differential quantum efficiency of 33% for a stripe width of 1.7 µm and a cavity length of 720 µm.

Lateral Junction Waveguide-Type Photodiode Grown on Semi-Insulating InP Substrate

A lateral junction waveguide-type GaInAsP/InP photodetector was fabricated on a semi-insulating InP substrate by two-step organometallic vapor-phase epitaxy (OMVPE) regrowth. Responsivities of 0.9 A/W at 1500 nm and 0.27 A/W at 1550 nm were obtained. A 3-dB bandwidth of 6 GHz and 6-Gbps error-free operation under non-bias conditions were achieved with a stripe width of 1.4 µm and a device length of 220 µm.

Catalytic Asymmetric Synthesis of Tertiary Alcohols and Oxetenes Bearing a Difluoromethyl Group

The catalytic asymmetric ene reaction with difluoropyruvate as an electrophile in the presence of a dicationic palladium complex is shown. This is the reliable and practical catalytic asymmetric synthesis for various α-CF2H tertiary alcohols in high yields and enantioselectivities. The reaction with isobutene can be catalyzed efficiently under solvent-free conditions with low catalyst loading (up to S/C 2000). Furthermore, difluoropyruvate is applicable to the [2 + 2] cycloaddition reaction in high yields and enantioselectivities.

Lewis Acid Catalyzed Asymmetric Three‐Component Coupling Reaction: Facile Synthesis of α‐Fluoromethylated Tertiary Alcohols

A chiral dicationic palladium complex is found to be an efficient Lewis acid catalyst for the synthesis of α-fluoromethyl-substituted tertiary alcohols using a three-component coupling reaction. The reaction transforms three simple and readily available components (terminal alkyne, arene, and fluoromethylpyruvate) to valuable chiral organofluorine compounds. This strategy is completely atom-economical and results in perfect regioselectivities and high enantioselectivities of the corresponding tertiary allylic alcohols in good to excellent yields.

Lateral current injection type GaInAsP/InP DFB lasers on SI-InP substrate

Toward injection type GaInAsP/InP membrane lasers consisting of high index contrast waveguide structure, lateral current injection type distributed-feedback lasers on a semi-insulating InP substrate were realized by an electron-beam lithography and organo-metallic vapor-phase-epitaxial regrowth. Single mode operation with a threshold current of 27 mA and a side-mode suppression ratio of 35dB at a bias current of two times the threshold was obtained at room temperature pulsed condition.

Room-temperature CW operation of lateral current injection lasers with thin film lateral cladding layers

Semiconductor membrane laser with high index-contrast waveguide is promising for achiving low power consumption operation. As a step to realize a current injection (LCI) type membrane laser, GaInAsP/InP lateral current injection type Fabry-Perot lasers with 400 nm thin core layer, including compressively-strained 5 quantum-wells were realized by 2-step OMVPE regrowth on a semi-insulating InP substrate. A RT-CW operation with a threshold current of 12 mA, which corresponds to a threshold current density of 1.7 kA/cm2, was obtained for a sample with a stripe width of 1.4 µm and a cavity length of 490 µm. This LCI structure can be attractive for membrane photonic devices for optical interconnections and on-chip optical wiring.

Lateral junction waveguide type photodiode for membrane photonic circuits

A lateral junction type photodiode grown on a semi-insulating InP substrate was realized by 3-step OMVPE growth. The responsivity of 0.27 A/W, 3 dB bandwidth of 6 GHz and 7.5 GHz at a bias voltage of 0 V and −2 V, respectively, were obtained for the stripe width of 1.4 µm and device length of 220µm. An error free transmissions up to 6 Gbps at 0 V were confirmed.

Electrolytic deposition of calcium phosphates films on nitinol stents

Calcium phosphates films were deposited onto pipes and stents of nitinol alloys by an electrolytic deposition (ELD) method. Monocalcium phosphate (Ca (H2PO4)2·H2O) solutions were used as the electrolyte, and electric depositions were carried out at the constant cathode current of 1.59 mA/cm2 at 65°C for 60 min. From the deposition on nitinol pipes, deposition rates were changed in 15 minutes and the precipitates were identified to be octacalcium phosphate (Ca8H2(PO4)6·5H2O) and dicalcium phosphate anhydrous (CaHPO4). The electrolytic depositions on the nitinol alloys were useful for the formation of calcium phosphates films on the complex shape of stents.

Thin-film GaInAsP/InP lateral current injection type Fabry-Perot laser — Improved quantum efficiency operation

Based on a theoretical analysis of internal quantum efficiency of a thin-film GaInAsP/InP lateral current injection type Fabry-Perot laser prepared on the semi-insulating InP substrate, its fabrication process was modified. As the results, the internal quantum efficiency was improved by a factor of 2 and the waveguide loss was reduced to 2/3 in comparison with previously reported devices. A threshold current of 11 mA and an external differential quantum efficiency of 33% were obtained for the device with 720 µm-long cavity and 1.7 µm-wide stripe under a room temperature continuous-wave condition.