Generation of Reflected Second Harmonic at Semiconductor Quantum Dots

Generation of the reflected second harmonic has been observed for the first time in a composite material: a glass matrix containing microscopic CdSe crystals, ranging in size from 500 to 50 Å. The violation of polarization selection rules in the second-harmonic generation indicates that the nonlinear sources are of a fluctuational nature. A size effect has also been observed: The intensity of the second harmonic increases by a factor of 102 as the size of the microscopic crystals is reduced. A possible mechanism for this size effect is analyzed.