Paraxial energy transport of a focused Gaussian beam in ruby with nondegenerate two-wave couplinglike mechanism

Abstract

Paraxial energy transport of an intensity-modulated and focused Gaussian beam is studied in ruby. Deformations of the temporal profiles are observed under different conditions and explained by the interplay among a nondegenerate two-wave couplinglike mechanism, the population oscillations, and the Fraunhofer diffraction. Experimental evidence is provided for the existence of a nondegenerate two-wave couplinglike mechanism. The self-superluminal can be observed under proper conditions. A group velocity of −83m∕s is achieved with a Gaussian-like-modulated pulse of 30ms with background illumination. Based on these results, a method to control the group velocity of a single beam in such media is proposed.

Nonlinear optical properties and superluminal propagation in the ruby

“…Shifting the driving voltage from the upward ramps to the downward ramps, we could control the frequency shift δ to be positive or negative between the two frequency components while keeping the intensity modulation and the experimental configuration the same. The transmitted pulse profiles are shown in Figure 3 [21]. Because the modulation of the intensity is the same, the Fraunhofer diffraction and the population oscillations are unchanged.…”

“…The temporal profiles of the transmitted signal pulses at different Z s near the focal spot of the lens are presented in Figure 2 [21]. The dashed curve shows the pulse profile of the reference and the vertical line indicates its peak position.…”

“…Large group velocity delay with easy operation in solid-state medium at the room temperature is the aim of the current research. According to the recent research, the group velocity could be slowed down very much and speed up in the ruby crystal by the only signal beam itself [15,21]. In this article, the investigations on weak light nonlinear property of population oscillations, self-phase modulation together with Fraunhofer diffractions and nondegenerate two-wave coupling in the ruby are reviewed and our published results of the self-induced superluminal and subluminal group velocity propagation in the ruby are specially introduced.…”

“…The experiment configuration is presented in Figure 1 [21]. A 532 nm TEM 00 laser beam was temporally modulated by an electro-optic modulator EO to generate a 30-ms Gaussian pulse with the peak power of 490 mW and a background power 100 mW.…”

“…Together with the slow light, the superluminal pulse propagation was also found [6][7][8][9][10]. The researches are developing very fast on this topic in both theories and experiments [11][12][13][14][15][16][17][18][19][20][21]. Large group velocity delay with easy operation in solid-state medium at the room temperature is the aim of the current research.…”