Optical Cherenkov radiation by cascaded nonlinear interaction: an efficient source of few-cycle energetic near- to mid-IR pulses

TL;DR

This paper demonstrates that cascaded nonlinear interactions in lithium niobate can generate efficient, few-cycle, energetic near- to mid-infrared pulses via optical Cherenkov radiation, with potential applications in ultrafast optics.

Contribution

It introduces a method to produce few-cycle IR pulses using cascaded nonlinearities and optical Cherenkov radiation, supported by numerical simulations and simple filtering techniques.

Findings

Cherenkov waves are generated in the 2.2-4.5 μm range.

Conversion efficiency reaches up to 25%.

Cherenkov pulses are few-cycle and Gaussian-shaped.

Abstract

When ultrafast noncritical cascaded second-harmonic generation of energetic femtosecond pulses occur in a bulk lithium niobate crystal optical Cherenkov waves are formed in the near- to mid-IR. Numerical simulations show that the few-cycle solitons radiate Cherenkov (dispersive) waves in the $\lambda=2.2-4.5\mic$ range when pumping at $\lambda_1=1.2-1.8\mic$. The exact phase-matching point depends on the soliton wavelength, and we show that a simple longpass filter can separate the Cherenkov waves from the solitons. The Cherenkov waves are born few-cycle with an excellent Gaussian pulse shape, and the conversion efficiency is up to 25%. Thus, optical Cherenkov waves formed with cascaded nonlinearities could become an efficient source of energetic near- to mid-IR few-cycle pulses.