We describe the successful operation of a buried heterojunction electroabsorption modulator. This modulator, fabricated from Aly
, is particularly well suited for use with narrow spectral width sources such as the Nd : YAG fiber lasers. The GaAs1−x′
crystal composition can be adjusted to permit operation in the wavelength range 0.9–1.2 μm. At 1.06 μm we have obtained an extinction ratio of 13 dB and a projected insertion loss of 4.0 dB. The low device capacitance permits operation at greater than 900 MHz.