Femtosecond pulse collapse in a quadratic nonlinear medium

摘要

Two-dimensional multicolored transverse arrays were generated in a quadratic nonlinear medium under the pump of two crossly overlapped femtosecond beams based on the cascaded non-collinear quadratic nonlinear couplings between the input pulses and quadratic spatial solitary waves originated from spatial breakup of one of the input beams with a small asymmetry. A probing supercontinuum pulse was diffracted and amplified with phase preservation, resulting in the formation of up-converted multicolor two-dimensional transverse arrays. By seeding with weak second harmonic pulses, the two-dimensional multicolored transverse patterns could be suppressed through weak beam control of the induced quadratic spatial solitary waves. At a high-intensity pump, colored conical emissions could be observed as a result of spatiotemporal collapse of femtosecond pulses in a quadratic medium. Seeded amplification of colored conical emission was demonstrated to support ultrabroadband up-conversion with a widely tunable range in wavelength and significantly high energy conversion efficiency.