Generation of optical-beam induced current via two-color (two-photon) excitation

Optical-beam induced current (OBIC) is generated in blue light-emitting diode samples (peak emission wavelength = 480 nm) via two-color (two-photon) excitation using the second- (502.9 nm) and third-order (635.9 nm) Stokes beam outputs of a hydrogen Raman shifter that is pumped by the 355 nm pulsed output (5.4 ns pulsewidth) of a 10 Hz Nd:YAG laser. Two-color OBIC generation happens only in sample regions where the two focused Stokes beams overlap in both space and time. We have verified the direct proportionality of the two-color OBIC signal with the product of the individual Stokes beam intensities as well as the localized nature of two-color OBIC generation in the common focal volume of the two confocal excitation beams.