Non-degenerate signal pulse compression and amplification using DFG-based nonlinear interaction via controlling pump pulse power and shape

Abstract

This study investigates the simultaneous amplification and compression of signal and idler pulses through the nonlinear difference-frequency generation (DFG) process in quasi-phase-matched Ti in-diffused LiNbO${}_3$ (LNB) nonlinear optical waveguides. Using the split-step Fourier transform numerical method, we demonstrate that pulsed pump sources can achieve simultaneous amplification and compression of signal and idler pulses, provided the slope of the idler pulse peak growth (${\eta }_2$) relative to the idler energy conversion efficiency (${\eta }_1^i$) remains positive. Under optimized conditions, signal energy conversion efficiency (${\eta }_1^s$) reaches up to $22.7dB$, with the full width at half maximum (FWHM) of the resultant signal pulses reduced from $10ps$ to $4.9ps$ ps at a propagation length of $20mm$. Furthermore, employing pump pulses with shorter FWHM (FWHM = $5ps$) than the initial signal pulses, enhances compression and amplification, achieving an FWHM of $3.32ps$ for the signal pulses with initial FWHM of $10ps$. Also, ${\eta }_1^s$ reaches to $12.8dB$. In a realistic scenario involving a 50 km conventional single-mode fiber (CSF), severely distorted pulses with an FWHM of $300ps$ and $>90\text{\%}$ energy loss are successfully amplified to ${\eta }_1^s=10.9dB$ and compressed to an FWHM of $1.5ps$ using a super-Gaussian pump pulse (order $m=5$) over a $20mm$ nonlinear waveguide. Compared to conventional methods requiring a few meters of erbium-doped fiber amplifiers (EDFAs) and kilometers of dispersion-compensating fibers, this work proposes a compact and efficient approach utilizing DFG in Ti:LNB waveguides, achieving simultaneous amplification and compression within a few centimeters. This novel method holds significant potential for advancing compact photonic devices and high-efficiency pulse processing systems.