Simultaneous Enhancement of Contrast and Power of Femtosecond Laser Pulses by Nonlinear Interferometer

Yasser Nada,Efim Khazanov

doi:10.3390/photonics8110520

Abstract

We showed that the nonlinear Mach–Zehnder interferometer may be used not only for enhancing temporal contrast, as proposed earlier, but also for increasing pulse power due to efficient pulse compression. The interferometer introduces into the output pulse a nonlinear phase equal to π/2. This allows increasing laser power by a factor of 1.5 only by means of a chirped mirror. Use of an additional nonlinear plate leads to a multi-fold power increase retaining the contrast enhancement.

Highlights

High temporal contrast has an important role in experiments on studying the behavior of matter in extreme light fields
Several new ideas have been proposed for contrast enhancement, by means of a nonlinear phase induced by cubic nonlinearity: spectral filtering [6,7], spatial filtering [8], a nonlinear polarization interferometer [9], as well as a nonlinear Mach–Zehnder interferometer with symmetric arms [10]
We show that a nonlinear Mach–Zehnder interferometer may be used for contrast enhancement, and for multi-fold pulse compression simultaneously

Summary

Introduction

High temporal contrast has an important role in experiments on studying the behavior of matter in extreme light fields. Several new ideas have been proposed for contrast enhancement, by means of a nonlinear phase induced by cubic nonlinearity: spectral filtering [6,7], spatial filtering [8], a nonlinear polarization interferometer [9], as well as a nonlinear Mach–Zehnder interferometer with symmetric arms [10] In the latter case, the phase difference without non-linearity ∆φL equals π, and the radiation of the pedestal does not pass to the dark port (see Figure 1a). We restrict the consideration to the case in which the CM introduced a purely quadratic spectral phase, i.e., group velocity dispersion only Such a type of CMs cannot compress the pulse to a Fourier transform limit, but they are usually commercially available. Using Equations (3) and (4), we found the output pulses both for the setup with (Figure 1a) and without interferometer (Figure 1b)

Results and Discussion

Spectral Broadening

Optimal Chirped Mirror Dispersion αopt

Peak Power Increase

Conclusions