Mid-infrared continua via spectral broadening and difference frequency generation in a nanophotonic lithium niobate waveguide

TL;DR

This paper demonstrates a novel nanophotonic lithium niobate waveguide that produces a broad mid-infrared spectrum from 3200 to 4800 nm using femtosecond laser pulses, combining spectral broadening and difference frequency generation.

Contribution

It introduces a dual-stage waveguide design that integrates third-order spectral broadening with efficient difference frequency generation in lithium niobate, enabling broadband mid-infrared light generation.

Findings

Mid-infrared spectrum from 3200 to 4800 nm achieved

Cascaded harmonic generation extends spectrum into visible and UV

Efficient broadband generation with sub-100 fs pulses at 200 pJ

Abstract

Periodically poled thin film lithium niobate waveguides provide simultaneous access to efficient second and third order nonlinear processes, enabling broadband generation of coherent laser light. Here, we demonstrate the generation of a broadband mid-infrared continuum in a nanophotonic lithium niobate waveguide pumped by a telecom-wavelength femtosecond source. Specifically, our dual-stage design includes both third-order nonlinear spectral broadening followed by a dedicated periodically poled waveguide section performing efficient broadband intrapulse difference frequency generation. Driven by sub-100 fs pulses with approximately 200 pJ pulse energy, the generated mid-infrared light covers wavelengths from 3200 to 4800 nm. Cascaded harmonic generation also extends the spectrum into the visible and ultraviolet domains, resulting in an overall spectral bandwidth ranging from 350 to 4800 nm.