Self-compression Of Femtosecond Laser Pulses Research Articles

Self-compression of femtosecond laser pulses in ambient air through conical radiation.

We demonstrate self-compression of 98 fs near-infrared laser pulses down to 8.8 fs in ambient air, utilizing self-phase modulation in air and negative dispersion in the properties of a laser-induced plasma. The blueshifted pulses achieve self-compression through conical radiation, eliminating the need for additional dispersion compensation. The results highlight a simple and compact approach to generate sub-10 fs laser pulses without additional measures for time-resolved applications in ultrafast diagnostics and spectroscopy.

Experimental investigations of nonlinear optical properties of soda-lime glasses and theoretical study of self-compression of fs laser pulses

Nonlinear optical properties of soda-lime glasses irradiated by 100 fs laser pulses with intensities ranging from 80 to 182 GW/cm2 and wavelengths from 780 to 870 nm were investigated by the Z-scan technique. Saturated three photon absorption (3PA) was observed and the dependence of the 3PA coefficient on the intensity and the irradiation wavelengths. The measured value of the nonlinear refractive index was found to be intensity dependent and wavelength independent. The estimated nonlinear optical properties were in good agreement with the experimental results. The self-compression of femtosecond laser pulses in a soda-lime glass was evaluated numerically taken into account the interplay between group velocity dispersion (GVD) and self-phase modulation (SPM) in the soda-lime. A numerical simulation of the transmission of a 200 fs laser pulse through soda-lime glass of 1.2 cm thickness showed that the interplay between anomalous GVD and SPM lead to a significant compression of the pulse to 8.5 fs i.e. by a factor of 23.

Self-compression of soliton-like laser pulses in the process of self-focusing

We study the possibility of efficient self-compression of femtosecond laser pulses in nonlinear media with anomalous dispersion of group velocity during the self-focusing of wave packets with a power several times greater than the critical self-focusing power. The results of qualitative analysis of the evolution of three-dimensional wave packets with the quasi-soliton field distribution are confirmed by the computer simulation. The simulation proves that the considered regime of compression of high-power laser pulses with initial durations of about ten optical cycles is stable relative to filamentation instability, due to the influence of the nonlinear dispersion. We demonstrate the possibility of self-compression of laser pulses at a multi-millijoule energy level and up to one optical cycle with an energy efficiency of more than 50%.

Enhancement of plasma wakefield generation and self-compression of femtosecond laser pulses by ionization gradients

As lasers become progressively higher in power, optical damage thresholds will become a limiting factor. Using the non-linear optics of plasma may be a way to circumvent these limits. In this paper, we report on simulations showing an enhancement to plasma wakefield self-compression of femtosecond laser pulses due to an ionization gradient at the leading edge of the pulse. By operating in a regime where wakefield generation is driven by moderately relativistic (∼1018 W cm−2) laser pulses and proper choice of gas species, the ionization front of the pulse can lead to a frequency shift that enhances the ponderomotive force and therefore both the wakefield generation and subsequent pulse compression.

Direct carrier–envelope phase stabilization of a soliton-effect compressed sub-two-cycle pulse source through nonlinear mixing of solitonic and dispersive waves

We present a carrier–envelope phase (CEP) stabilized sub-two-cycle 5.2 fs pulse source based on soliton-effect self-compression of femtosecond laser pulses in millimetre-long highly nonlinear photonic crystal fibres. We employ a simple and efficient scheme to generate a strong (40–60 dB, configuration dependent) CEP beat signal directly from the pulse source via f-to-2f interferometry where the second harmonic of the main soliton pulse is mixed with the isolated dispersive blue/green radiation peak that is also generated in the compression process, obviating the need for additional spectral broadening mechanisms.

Plasma induced pulse breaking in filamentary self-compression

A plasma induced temporal break-up in filamentary propagation has recently been identified as one of the key events in the temporal self-compression of femtosecond laser pulses. An analysis of the Nonlinear Schrödinger Equation coupled to a noninstantaneous plasma response yields a set of stationary states. This analysis clearly indicates that the emergence of double-hump, characteristically asymmetric temporal on-axis intensity profiles in regimes where plasma defocusing saturates the optical collapse caused by Kerr self-focusing is an inherent property of the underlying dynamical model.

Ionization self-compression of intense femtosecond pulses propagating through gas-filled dielectric capillaries

A mechanism of the ionization-induced self-compression of femtosecond laser pulses propagating in a gas-filled hollow dielectric capillary has been investigated both experimentally and theoretically. In particular, the double self-compression of a laser pulse from 76 to 40 fs has been experimentally demonstrated. A theoretical model that explains the mechanism of such a self-compression and provides a good agreement with the experimental data has been developed. The model also predicts that a laser pulse shorter than 10 fs can be generated in the optimal regime with an energy efficiency exceeding the efficiency of self-compression on a filament widely discussed at present.

Self-compression of femtosecond laser pulses in normally dispersive solid material

We have experimentally demonstrated the self-compression of gegawatt high power femtosecond laser pulses in normally dispersive solid bulk media. It was proved that high-power femtosecond laser pulses can be compressed during the self-focusing propagation in the transparent nonlinear medium. The self-compression behavior was investigated in detail under a variety of experimental conditions, and the temporal and spectral characteristics of resulted pulses are found to be significantly affected by the input pulse intensity, with higher intensity corresponding to shorter compressed pulse. However, the output pulse is split into two peaks when the input intensity is high enough to lead to supercontinuum and conical emission. By the propagation in a piece of BK7 glass, a self-compression from 50fs to 20fs is achieved, with a compression factor of about 2.5. Moreover, we find that pulse self-compression can be achieved with a divergent input laser beam into the glass.