Koichi Naniwae

First demonstration of novel active multi-mode interferometer (MMI) LDs integrated with 1st order-mode permitted waveguides

Here we propose novel active multi-mode-interferometer (MMI) laser diodes (LDs) for 14XXnm fiber amplifier pump applications. The waveguide of the LDs is consisted from 1x1-MMI couplers integrated with 1st order-mode permitted waveguides to enhance the total active area. Although there is no single-mode waveguide region inside the cavity, the novel active MMI-LDs emitted in stable single-transverse-mode output up to maximum output power. Moreover, they achieved high output power of 1.46W, and low driving voltage of only 1.75V at 1W output power.

MBE growth of ZnCdSe and MgZnCdSe alloys on InP substrates with a GaInAs buffer-layer

Abstract Molecular beam epitaxy growth of ZnCdSe and MgZnCdSe systems on (001) InP substrates were investigated. These films were grown on a lattice-matched GaInAs buffer-layer which was ex-situ grown on (001) InP by metalorganic vapor phase epitaxy. During the thermal cleaning process prior to II–VI film growth, group-V molecular beams were not used. By introducing this buffer-layer and lowering the initial growth temperature, the surface morphology of ZnCdSe films changed from rough to specular and the full width at half maximum (FWHM) of the double-crystal (004) X-ray rocking curves of the films decreased from more than 400 arcseconds to 60 arcseconds. The ZnCdSe film showed a very sharp excitonic emission in the 5 K photoluminescence spectra with a FWHM as narrow as 5.5 meV. No emission through deep levels was observed. High-quality MgZnCdSe films were also obtained using a GaInAs buffer-layer.

Wideband External Cavity Wavelength-Tunable Laser Utilizing a Liquid-Crystal-Based Mirror and an Intracavity Etalon

In this paper, high-performance full-band external cavity wavelength-tunable lasers (ECTLs) are detailed. Our approach utilizes an external cavity configuration, which makes use of a liquid-crystal tunable mirror and a wavelength reference etalon. This ECTL module shows a tuning range of 45 nm, fiber-coupled output power of more than 14 dBm with a side-mode suppression ratio better than 59 dB, wavelength accuracy of 0.6 GHz, relative intensity noise better than -150 dB/Hz, and linewidth narrower than 1 MHz.

Epitaxial growth of n- and p-type ZnCdSe on InP

Abstract Chlorine doping and nitrogen doping of lattice-matched ZnCdSe on InP were investigated. High-quality ZnCdSe films were successfully grown on a GaInAs buffer layer using a dual-growth-chamber molecular-beam epitaxy system. The reflection high-energy diffraction oscillations on the ZnCdSe surface persisted for about 80 periods after the ZnCdSe layer growth was started. The full-width at half-maximum of the double-crystal X-ray (0 0 4) diffraction curve was as narrow as 42 arcsec. Epitaxial chlorine doping and epitaxial nitrogen doping were performed using ZnCl 2 and a radio-frequency nitrogen-plasma source, respectively. In the ZnCdSe: Cl layer, free-electron concentrations up to 7×10 18 cm −3 were obtained. In the ZnCdSe: N layer, p-type conductivity was observed for the first time with a maximum net acceptor concentration of 3.5 × 10 16 cm −3 .

High-power operation of inner-stripe GaN-based blue-violet laser diodes

We review our recent progress in novel planar blue-violet laser diodes (BV-LDs). The planar BV-LDs are characterized by an inner-stripe waveguide formed with a buried AlN current-blocking layer and a wide regrown cladding layer that also acts as a current and heat spreader. These features enable high-power operation for BV-LDs thanks to their low electrical and low thermal resistance even with a narrow-stripe waveguide. In this paper, we report successful demonstration of the planar inner-stripe BV-LDs by utilizing low-temperature-grown AlN and the regrown cladding layer. Low electrical resistance of the regrown cladding layer was confirmed by scanning spread resistance microscopy. Heat spreading characteristics were also investigated by 2-dimensional thermal simulation. The fabricated BV-LDs with a 1.4-&mgr;m-wide stripe achieved a low threshold current of 32 mA, a low threshold voltage of 4.1 V and greater than 200- mW kink-free output power under CW operation. Moreover, the kink-free output level surpassed 1,000 mW for the 1.0- &mgr;m stripe BV-LDs under 0.03%-duty-pulsed operation. The BV-LDs operated stably for more than 1,000 hours at a high output power of 200 mW at 80oC under a 50%-duty-pulsed condition. After the reliability test, transmission electron microscopy revealed no defect near the regrown interface of the tested LDs.

Wavelength-selectable microarray light sources for S-, C-, and L-bands WDM applications

We have developed eight-DFB-LD-array WSLs having a novel integration structure that uses a selectively-grown microarray active waveguides directly connected to dry-etched passive waveguides. We have first demonstrated an entire coverage of 100-GHz-spaced 135 ITU-T grids over the S-, C-, and L-bands by using only six WSLs fabricated on two wafers. High device performances such as more than 15-nm /spl Delta//spl lambda/, P/sub f/ of over 9 mW, and an SMSR of more than 42 dB were also shown. The practical properties of the WSLs over the three bands will increase the transmission capability of multi band DWDM systems.

Molecular beam epitaxial growth and optical properties of lattice-matched MgxZn1−xSeyTe1−y alloys on InP substrates

Molecular beam epitaxial growth and the optical properties of lattice-matched MgxZn1−xSeyTe1−y alloys on InP were investigated. Two-dimensional growth and high crystalline quality were achieved by forming an InP buffer layer and a Zn0.48Cd0.52Se buffer layer before the MgxZn1−xSeyTe1−y layer growth. The band-gap energy (Eg) of the MgxZn1−xSeyTe1−y films, measured by optical-reflection measurements, increased with the Mg content and is expressed by the quadratic equation Eg=0.90x2+0.83x+2.37. We found that the Stokes shifts of MgxZn1−xSeyTe1−y quaternary alloys, which seemed to originate from deep trap levels related to Te clusters, were larger than those of ZnSeTe ternary alloys. The refractive index of MgxZn1−xSeyTe1−y at a wavelength of 600 nm decreased as the Mg content rose, as expressed by the linear equation n600(x)=−1.09x+2.99.

94-channel wavelength-selectable light source module with integrated multiwavelength locker

We have first reported on a 94-channel wide-band WSL installed in a 22-pin butterfly package with a multi-wavelength locker. We could realize 40-nm operation in the L-band for an 8-DFB arrayed monolithic WSL by covering 5 nm per DF3-LD. By using a monolithically integrated WSL and minimizing the number of components on the wavelength locker we could install all function in a 12.7-mm /spl times/ 20.8-mm standard butterfly package. This WSL module with a stable-wavelength operation and uniform locking performance is a promising development to provide a large degree of flexibility in DWDM system design.

Low wall-plug consumption laser diodes by using active multi-mode interferometer (MMI)

We demonstrate low wall-plug consumption principle by using active multi-mode interferometer (MMI) with over 1 W output. It shows larger in the area of the active MMI contributes lower in the wall-plug consumption.

1 V and Stable Dynamic Operation of Laser Diode Using Active Multi-Mode Interferometer

A low operation voltage of only 1 V at 10 mW was achieved for 1.5 µm wavelength active multi-mode-interferometer laser diodes (MMI-LDs) due to a significant reduction in resistance of 60% compared with that of conventional LDs. We also investigated the dynamic characteristics of the MMI-LDs. Although there was concern that current modulation might cause changes in refractive index, thus, deteriorating self-imaging properties, stable 1 Gbps operation without jitter and improved roll-off frequency due to the low resistance were confirmed experimentally.