Abstract

Semiconductor optical waveguides with low propagation loss are essential for integrating guided-wave optical components with other optoelectronic devices. Realization of such low-loss waveguides on InP substrates is of particular importance to optoelectronic circuits for fiber optic communications in the 1.3-1.5 μm wavelength range, for integration with lattice-matched lasers and detectors. While recent progress has resulted in several reports of low-loss waveguides on GaAs substrates, with losses as low as 0.15 dB/cm,¹ there have been few reports of InP-based guides with losses below 1 dB/cm. Losses as low as 0.4±0.1 dB/cm have been reported for double-heterostructure waveguides with InGaAsP guiding layers;^2,3 however, structures with a multiple quantum well (MQW) guiding region, which are especially useful for optical signal processing, have exhibited losses twice as large (0.8 dB/cm).⁴ These loss values refer to the lowest loss waveguides achieved, and were obtained with a small (≤ 10) number of guides. While the lowest achievable loss is an important measure of the quality of crystal growth and guide fabrication, the ability to maintain low-losses over a large area is also of concern for the fabrication of numerous complex guided-wave circuits. In this paper we report MQW waveguides on InP with losses as low as 0.24 dB/cm, significantly lower than previouly achieved losses, and demonstrate that loss ≤ 0.6 dB/cm can be maintained over an appreciable chip area. Our results show that the large number of heteroepitaxial interfaces in MQW guides do not degrade their optical performance.

© 1989 Optical Society of America