Dynamic-grating-assisted energy transfer between ultrashort laser pulses in lithium niobate.

Energy redistribution between two subpicosecond laser pulses of 2.5 eV photon energy is observed and studied in congruent, nominally undoped LiNbO ₃ , aiming to reveal the underlying coupling mechanisms. The dependences of pulse amplification on intensity, frequency detuning and pulse duration point to two different contributions of coupling, both based on self-diffraction from a recorded dynamic grating. The first one is caused by a difference in pulse intensities (transient energy transfer) while the second one originates from a difference in pulse frequencies. The latter appears when chirped pulses are mutually delayed in time. A quite high coupling efficiency has been observed in a 280 µm thin crystal: one order of magnitude energy amplification of a weak pulse and nearly 10% net energy enhancement of one pulse for the case of equal input intensities.