Abstract

Currently, there exists an intensive research effort for practical optical modulators in III–V semiconductors for potential uses in optical interconnections of integrated circuits and information processing.¹ One of the important considerations is low drive power, e.g., low operating voltage swing in electro-optical modulators. Waveguide devices tend to provide low drive voltages (~1 V) because the field is applied perpendicular to the light propagation direction; however, the coupling of the light into the waveguide adds complexity to practical implementations. On the other hand, although coupling is relatively easy, surface-normal devices tend to require high drive voltages ( > 10 V) because of short interaction lengths. Another important device parameter is the amount of input power that is modulated into the output power. Using a figure-of-merit, normalized electro-optic transfer function (M_v), defined as the percentage modulation of the input light per unit driven voltage to relate the transfer function of electro-optic modulators between the electrical and optical signals, previous transverse modulators have M_v values of ~8%/V, and efficient waveguide modulators have a representative value of ≤ 15%/V.¹ Here we report a normally-on electroabsorptive surface-normal Fabry–Perot (FP) reflection modulator with an ~80% top mirror and an active region of 24 quantum wells to achieve a reflection change of >45% for an operating voltage swing of only ~ V, with a contrast ratio of more than 15. The wavelength range over which more than half this reflection change is observed extends as wide as 7 nm. Such devices compete effectively with low-voltage waveguide modulators, with further advantages of easy coupling and compact sizes, i.e., small capacitances.

© 1990 Optical Society of America