Recent progress on semiconductor lasers for Wavelength Division Multiplexed (WDM) optical communication is introduced. WDM systems require the accurate wavelength setting. The lasing wavelength is determined by many factors of stripe width, active layer thickness and composition, etc. New devices are required for WDM networking. Wavelength tuning and semiconductor laser amplifier are newly required. Wavelength tuning is needed in the network for superimposing the signal with the appropriate wavelength. Semiconductor laser amplifiers are for compensating losses. Array lasers are needed for compact light sources with many wavelengths and the substitute of tunable lasers. Array lasers, tunable lasers and semiconductor gate switches with amplifier are discussed here.

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Optical cross connects and optical add-drop multiplexers are expected to be key technologies to realize higher reliability and flexibility in future optical communication networks, where a huge amount of informations are transmitted over many fibers and many wavelengths. Recent progress of semiconductor optical integrated functional devices are reviewed with emphasis on optical matrix switches, semiconductor arrayed waveguide gratings and their combinations from view points of applications to optical cross connects and optical add-drop multiplexers.

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Nonlinear optical parametric devices to generate optical waves from near infrared (IR) wavelength region to far IR region are reviewed. Quasi-phase matching (QPM) is a novel technique to realize the high efficiency in nonlinear optical interactions, and various optical nonlinear devices using QPM are summarized in the near-mid IR region. Furthermore, the high performance THz wave generation based on optical parametric oscillation and its applications are described. A feasibility of each optical devices is briefly discussed.

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This paper reviews a recent device processing technology for photonic functional-devices. Material integration technology using direct wafer bonding for flexible integration of photonic functions on a chip is discussed. Some demonstrations on vertical cavity surface emitting lasers (VCSELs), photodetectors, and integrated optical interconnection are introduced.

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Planar lightwave circuits (PLCs) are waveguide devices that integrate fiber-matched optical waveguides on Silicon or glass substrate to provide an efficient means of interaction for the guided-wave optical signals. The most prominent feature of the silica waveguides is their simple and well defined waveguide structures. This allows us to fabricate multi-beam or multi-stage interference devices such as arrayed-waveguide gratings and lattice-form programmable dispersion equalizers. PLCs provide various important and functional devices for optical wavelength division multiplexing (WDM), time division multiplexing (TDM) systems and subscriber networks. This paper reviews the recent progress and future prospects of PLC technologies including arrayed-waveguide grating multiplexers, optical add/drop multiplexers, programmable dispersion equalizers and hybrid optoelectronics integration technologies.

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A reduction of dimensionality of the electron motions in quantum nano-structures brings new phenomena in semiconductor physics. Moreover, it allows new device concept to be considered and permits improvements in performance of the transistors and lasers. In this paper, we discuss prospect of nanostructure optical devices with emphasis on our recent results on fabrication, nano-scale characterization, and device applications of quantum dots.

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Low threshold vertical cavity surface emitting lasers (VCSELs) have been developed for future parallel optoelectronics, including optical interconnects. The research field of surface emitting lasers is growing up rapidly and micro-amperes low threshold devices have been realized. The operating wavelength region of surface emitting lasers is now ranging from ultraviolet to infrared. In this paper, the recent progress of surface emitting semiconductor lasers is reviewed.

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Research trends of semiconductor lasers as high speed functional device are reviewed. Enhanced nonlinear-optical response in the active region of semiconductor laser offers excellent functionality such as femtosecond pulse source, optical switch and wavelength converter. Specifically the research efforts on broad bandwidth anti-reflection coating for semiconductor laser amplifiers and external cavity mode-locked lasers are summarized. Bandwidth of 100 nm with reflectivity of 10^-4 is expected.

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