Simple interferometric setup enabling sub-Fourier-scale ultra-short laser pulses

In this work, we describe an interferometric method to generate ultra-short pulses below the Fourier limit. It is done by extending concepts first developed in the spatial domain to achieve sub-diffractive beams through the addition of a spatial chirp in one of the arms of a Michelson interferometer using a spherical mirror. To experimentally synthesize sub-Fourier pulses, we replace the spherical mirror with a water cell, since it produces chirp in the temporal domain. We also present an alternative procedure, based on asymmetrical interference between the widened pulse and the original pulse where the peaks of both pulses exhibit a temporal delay achieving the narrowing of ultra-short pulses with sub-Fourier scales. To characterize the performance of the system, we performed a preliminary assessment considering the percentage of FWHM shrinking obtained for each scheme. By means of a symmetrical configuration 7 and 12 \% pulse reductions were verified, both experimentally and analytically, while for the non-symmetrical configuration 10 and 24\% reductions were achieved corresponding to main lobe to side-lobes ratios of 10 and 30\% . The experimental setup scheme is simple, versatile and able to work with high-power laser sources and ultra-short pulses with a broad bandwidth at any central wavelength. The results presented in this work are promising and help to enlighten new routes and strategies in the design of coherent control systems. We envision that they will become broadly useful in different areas from strong field domain to quantum information.

Investigation of Spatial Chirp Induced by Misalignments in a Parallel Grating Pair Pulse Stretcher

Spatial chirp induced by the misaligned gratings and mirrors in a parallel grating pair pulse stretcher can significantly affect the performance of the output pulses. Firstly, a detailed analysis about the spatial chirp of the stretched pulses caused by the misalignments has been carried out using the ray tracing simulation method. According to the simulation results, an adjustment procedure has been summarized to accurately calibrate these misalignments. The proposed method has been successfully applied in a home-made chirped pulse stretcher. By measuring the output pulse with an imaging spectrometer, the results show the stretched pulse has a good linear temporal chirp and little spatial chirp, which demonstrates the good adjustment of the stretcher.

Spatial Chirp of Agate Bands

Agate bandwidths are analyzed and shown to consist of spatial chirps. It is shown that (a) bands are created by following an equal volume mode and (b) the spatial chirps are approximately spherical and concentrated at different “disturbance” locations in the individual agate sectors. Results indicate that the sequence of formation started with banding under a nonlinear process in a gel matrix and were secondarily deformed by external forces.