Mitsui-san teached me how to use the spectrophotometer SolidSpec-3700 in the optic shop at ATC.

I measured reflection and transmission at 1064nm of the GaAs sample: S-I axt 8000010699 71

Sample thickness 0.4mm

Reflection = 46.77% (at 12°)

Transmission = 51.16%

Absorption = 100-R-T = 2.07%