GaAs p+n−n+ directional-coupler switch

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Abstract
GaAs p+n−n+ electro‐optic directional‐coupler switches have been successfully fabricated and evaluated at 1.06 μm for use as components in integrated optical circuits. The devices were fabricated from a pair of closely spaced low‐loss [α≈1 cm−1 (4.3 dB/cm) at 1.06 μm] single‐mode p+n−n+ channel‐stop strip guides. They are operable both as passive directional couplers and as electro‐optic switches. The couplers have exhibited 98% power transfer and have an attenuation only about 0.1 dB/cm greater than that of a single guide having the same dimensions as one of the coupled guides. The switch performance was found to depend on the crystallographic direction chosen for light propagation. All devices were in the {100} plane, and 17‐dB (98%) power isolation in both the switched and unswitched states with constant total power output (≲0.2‐dB variation) was achieved for propagation along a [011] direction. These switches were 7.2 mm long, and had an optimum switching voltage of 43 V and a calculated power‐bandwidth ratio in a 50‐Ω system of 110 mW/MHz.