The optical absorption coefficients of highly oriented laser-evaporate
d thin films were determined from the measured reflectance R(lambda) a
nd transmittance T(lambda) in the wavelength range 400-1700 nm. The op
tical absorption spectrum of CuInSe2 thin films shows three energy gap
s, which are associated with the fundamental edge and valence band spl
itting by the tetragonal crystal-field and spin-orbit effects, and fou
r optical transitions from the copper d levels to the conduction bands
.