The clamped electrooptic coefficient r
11was measured at 1.15 microns for a selenium crystal grown from an aqueous sulfide solution. The value obtained for

is

m/V and, depending on the value used for n
1, the value for r
11ranges between 5.7 and

m/V. These data indicate modulating efficiencies that may be more than double those calculated from earlier infrared measurements on selenium.