Nonlinear compression of high-power laser pulses: compression after compressor approach

Abstract

The peak power of present-day lasers is limited by the pulse energy that the diffraction gratings of an optical compressor can withstand. A promising method to overcome this limitation is reviewed: the pulse power is increased by shortening its duration rather than increasing the pulse energy, the pulse being shortened after passing a compressor (Compression after Compressor Approach (CafCA)). For this purpose, the pulse spectrum is broadened as a result of self-phase modulation, and the pulse is then compressed by dispersion mirrors. Application of this idea, known since the 1960s, to lasers whose power is over 1 TW has been restrained until recently by a number of physical problems. These problems and possible methods to solve them are discussed in detail. The experimental results obtained over the past few years demonstrate the efficiency of the technique (compression by a factor of 5) in the range up to 250 TW. CafCA features three undisputed merits: simplicity and low cost, negligible loss of pulse energy, and applicability to any high-power laser.

Use of KDP crystal as a Kerr nonlinear medium for compressing PW laser pulses down to 10 fs

“…All the aspects of nonlinear compression (spectrum broadening, pulse shortening, and peak intensity increase) were considered in detail in [3] as a function of two key parametersthe В-integral (1) and the dimensionless parameter of nonlinear medium dispersion D…”

“…An alternative recently developing approach, within the framework of which power is enhanced due to reduced pulse duration after the compressor, rather than due to energy increase, is free from these drawbacks. This approach has different names/acronyms: TFC (Thin Film Compression) [2], CafCA (Compression after Compressor Approach) [3], or post-compression [4]. The corresponding technique is as follows: pulse spectrum is broadened as a result of self-phase modulation (SPM) during propagation in a medium with Kerr nonlinearity and is then compressed due to reflection from chirped mirrors (CM) with negative dispersion.…”

“…Later, nonlinear compression was obtained in the femtosecond range in a fiber [7], in hollow waveguides filled with gas [7], and in bulk material bounded in the transverse direction [8]. Despite a huge number of works (see, for example, references in the review paper [3]), pulses were compressed only with mJ energy, and the energy efficiency was less than 50%. In the recent years, quite a few experimental results were obtained [9][10][11][12][13][14][15][16], in which CafCA was successfully implemented for pulses with an energy of 1-18 J and energy efficiency close to 100%.…”

“…In experiments, different materials were used as a nonlinear medium, e.g., glass [9], polyethylene terephthalate [10], but in the majority of works it was silica [11][12][13][14][15][16]. As shown in [3], a compressed pulse will be shorter at a minimal ratio of the group velocity dispersion k 2 to the nonlinear index of refraction n 2 . A decrease in k 2 /n 2 is especially important for large Bintegral values at which pulse spectrum is broadened markedly by SPM.…”

High-energy few-cycle pulses: post-compression techniques

“…Using the so-called Thin Film Compression (TFC) G. Mourou et al envisioned the generation of single-cycle 100 J-level pulses focused to ultra-relativistic intensities of 10 24 W/cm 2 on the basis of simulations [49]. Currently, the reach of these goals is still far away, nevertheless substantial steps in energy scaling are achieved at moderate compression factors [50]. Especially, the fivefold compression of a part of a 17 J, 250 TW laser beam down to 14 fs (4.6 optical cycles) is promising [51].…”