Junichiro Shimizu

Selective-area growth of high-crystalline-quality InGaAlAs by metal-organic vapor-phase epitaxy

To improve optical-integrated device characteristics, namely, characteristic temperature and modulation speed, we investigated selective-area growth of InGaAlAs. When the band-gap wavelength is over 1.3 μm, the residual carrier concentration in InGaAlAs is the same order as that in InGaAsP. The photoluminescence spectra of InGaAlAs and InGaAsP multiple-quantum-well structures grown by selective-area growth are similar. Interfaces are abrupt and growth planes are flat, even in the case of the InGaAlAs selective-area growth. Moreover, light-current characteristics of an InGaAlAs 1.55 μm distributed feedback laser with an integrated modulator are also similar to those of an InGaAsP laser. These results indicate that selective-area growth of InGaAlAs will result in superior device properties.

Compact and Low-Power-Consumption 40-Gbit/s, 1.55-µm Electro-Absorption Modulators

This paper describes 40-Gbit/s operation of 1.55-μm electro-absorption (EA) modulators applicable to compact and low-cost transmitters for very-short-reach (VSR) applications. We start by identifying factors that make a multi-quantum-well (MQW) design suitable for high levels of output power and for uncooled operation. From the basic experimental results, we determine that a valence-band discontinuity ΔE 0 at around 80 meV is optimal in terms of combining high-output-power operation and a good extinction ratio. We then apply the above findings in an InGaAsP-MQW EA modulator that is monolithically integrated with a distributed feedback (DFB) laser, and thus obtain operation with high output power (+1.2 dBm), a high ER (10.5 dB), and a low power penalty (0.4 dB after transmission over 2.6 km of single-mode-fiber). These results confirm the applicability of our EA modulator/DFB laser to VSR applications. After that, we theoretically demonstrate the superiority in terms of ER characteristics of the InGaAlAs-MQW over the conventional InGaAsP-MQW. InGaAlAs-MQW EA modulators are fabricated and demonstrate, for the first time, 40-Gbit/s operation over a wide temperature range (0 to 85°C).

InGaAlAs selective-area growth on an InP substrate by metalorganic vapor phase epitaxy

In the case of InGaAlAs selective-area growth (SAG), when the aluminum content is high (Al: 0.48), flatness at the mask edge degrades and compositional change in the selective region increases. On the other hand, when the aluminum content is low (Al: 0.16), a flat growth plane is formed and no spike growth at the mask edge appears. Moreover, for a multiple-quantum-well structure, the PL peak intensity in the selective region is similar to that in the non-selective region.

Recent Trend in High-Speed/Low-Power-Consumption Light Sources for MAN/Ethernet Applications

During the gradual recovery of the telecommunication market seen in these couple of years, the main target field of the market had been changed to MANs, LANs or Ethers from the conventional trunk DWDM networks. This movement has naturally brought about a substantial impact upon the optical component market. The new market require, higher integration density and higher capacity systems with optimized bit cost rather than higher wavelength density and longer link distance with a high reliability demanded in the old trunk market. Driven by these trends, small-form-factor modules that are operated at 10-Gbit/s have been among the essential components in the new market. The data rate of 10-Gbit/s could offer longer link transmission of up to 80 km without loss/dispersion compensation; a key for MAN application. This is why uncooled 10-Gbit/s sources, detectors and related ICs have been studied extensively these days. In this talk, we will describe the recent R&D activities on our uncooled 1310/1550-nm diode-lasers. InGaAlAs multiple-quantum-wells (MQW) and related new hetero-material monolithic integration allow us to fabricate a variety of laser/modulator-related transmitter devices suitable for 10-Gbit/s low power consumption small-form-factor modules. They include 1,310-nm InGaAlAs uncooled directly modulated lasers and 1,550-nm uncooled electro-absorption (EA) modulator integrated with a distributed feedback (DFB) laser (EA/DFB) for 40to 80-km single mode fiber transmission. They can cover link-distances ranging from a few hundred m to 40 km; the link categories of VSR/SR/IR. Here we report on some of the successful 10-Gbit/s operation of these devices. A challenge to achieve a 40-Gbit/s version of the device is also described. Extended Abstracts of the 2005 International Conference on Solid State Devices and Materials, Kobe, 2005,

Optical modulator/DFB laser using an InGaAlAs MQW structure

We have fabricated an optical modulator/DFB laser using an InGaAlAs MQW structure. The device has demonstrated 10-Gbit/s operation. An InGaAlAs-based optical modulator/DFB laser is a promising candidate for a DWDM light source.