Emerging Optoelectronic Technologies and Applications

The following sections are included:

• PREFACE

• CONTENTS

It is clear that to meet the new demands of wireless customers, conventional cellular service providers and upcoming Personal Communication Service (PCS) providers for conventional phone service and high bandwidth wireless LAN must upgrade their networks to provide complete radio coverage. This evolution has motivated the need for low-cost systems that transport radio signals to and from areas of poor signal coverage. The most important area where this problem must be solved is inside of buildings, since this is where people spend most of their time. Unfortunately, the in-building environment is also the most challenging area to provide radio coverage due to severe attenuation and multi-path effects. The problem must be tackled from the viewpoint of optimization of performance/cost ratio of the network. In this paper, we describe a system-level approach to tackle this problem. We demonstrate how one can trade-off hardware performance, which represent cost, with proper choice of system architecture which includes, among other factors, in-building radio environment, to arrive at an optimum network solution technically and economically.

Recently, organic light emitting diodes have received a lot of attention in different research laboratories world-wide. Red, green and blue emitting devices are readily available. Devices with luminous efficiencies greater than 15 lm/W and lifetimes longer than 10,000 hours have been demonstrated. In this article, we will discuss the basic devices used in physics, materials used in organic light emitting diodes, device degradation mechanisms, and the opportunities of using this technology for commercial display applications.

In this article we review the key technologies for GaN based materials and devices. Developments in the methods for thin film deposition by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) and resulting film properties are highlighted. Breakthroughs in materials growth has enabled extremely high efficiency blue and green GaN LEDs to be achieved for the first time. GaN LEDs complete the primary color spectrum and have enabled bright and reliable full-color solid state displays to be realized. Recently, room temperature operation of pulsed current injection blue-violet lasers emitting at 417 nm has further increased possible applications for GaN based optoelectronic devices.

A surface-micromachined free-space micro-optical bench (FS-MOB) technology has been proposed to monolithically integrate micro-optical elements, optomechanical structures, micropositioners, and microactuators on the same substrate. Novel three-dimensional micro-optical elements have been fabricated by surface-micromachining techniques. The optical axes of these optical elements are parallel to the substrate, which enables the entire free-space optical system to be integrated on a single substrate. Micro-scale Fresnel lenses, refractive microlenses, mirrors, beam-splitters, gratings, and precision optical mounts have been successfully fabricated and characterized. Integration of micro-optical elements with translation or rotation stages provides on-chip optical alignment or optomechanical switching. This new free-space micro-optical bench technology could significantly reduce the size, weight, and cost of most optical systems, and could have a significant impact on optical switching, optical sensing and optical data storage systems as well as packaging of optoelectronic components.

Recent progress on micromachined micro-optic and optoelectronic devices is discussed. We describe a low temperature (240°C) surface micromachining process that can be used to fabricate a variety of micro-optic components on micromachined membranes integrated with microactuators. The devices discussed in this paper include Fabry-Pérot tunable filters with a 341 nm tuning range, wavelength tunable transmitters at 1.55 micron wavelength, high-sensitivity integrated sensors using optical Moiré patterns, and movable microlenses. Such devices represent a new class of micro-optic circuits that will find important applications in many areas including optical communication and sensing.

The following sections are included:

• Introduction

• Thin Film Device Formation and Bonding

• Characterization and Materials Applications of Thin Film Materials

• Thin Film Devices and Bonding to Host Substrates

• Thin Film Devices Integrated with Silicon Circuits and Micromachines

• Conclusions

• Acknowledgements

• References

This paper discusses the issues connected with the application of fusion bonding technology for surface-normal optoelectronic devices (III-V semiconductors). The InP/GaAs fusion bonding technology employed in the development of long-wavelength vertical-cavity lasers is described.