Unambiguous demonstration of soliton evolution in slow-light silicon photonic crystal waveguides with SFG-XFROG

Abstract

We demonstrate the temporal and spectral evolution of picosecond soliton in the slow light silicon photonic crystal waveguides (PhCWs) by sum frequency generation cross-correlation frequency resolved optical grating (SFG-XFROG) and nonlinear Schrödinger equation (NLSE) modeling. The reference pulses for the SFG-XFROG measurements are unambiguously pre-characterized by the second harmonic generation frequency resolved optical gating (SHG-FROG) assisted with the combination of NLSE simulations and optical spectrum analyzer (OSA) measurements. Regardless of the inevitable nonlinear two photon absorption, high order soliton compressions have been observed remarkably owing to the slow light enhanced nonlinear effects in the silicon PhCWs. Both the measurements and the further numerical analyses of the pulse dynamics indicate that, the free carrier dispersion (FCD) enhanced by the slow light effects is mainly responsible for the compression, the acceleration, and the spectral blue shift of the soliton.

Ultra-fast pulse propagation in nonlinear graphene/silicon ridge waveguide

“…We know that free carrier effect, such as free carrier dispersion (FCD) and free carrier absorption could lead the output pulse to be asymmetry, especially FCD effect, it can lead to the refractive index decreasing and thus cause acceleration of the pulse 22 23 24 , and thus lead to the blue shift of the output pulse. FCD has been used to demonstrate soliton compression in silicon photonic crystal waveguides 23 24 . However, the free carrier response in silicon is not an instantaneous response, and picosecond pulses are needed to achieve this effect.…”

Observation of Ultrashort Laser Pulse Evolution in a Silicon Photonic Crystal Waveguide

“…In order to unveil the principles of the pulse broadening and spectrum shift as shown in Figure 2 , we perform the optimized nonlinear Schrödinger equation (NLSE) modeling simulations [ 26 ]. where the group velocity dispersion (GVD) ps /m; The Kerr coefficient is (1⁄W/m); The effective TPA coefficients is m/W; The effective free carrier dispersion and absorption parameters are m and m , respectively.…”

“…A is the slow varying envelope of the propagation pulse electric amplitude; is the density of free carrier; Z is the pulse transmission position inside the waveguide. is the free carrier effective lifetime, which is estimated to s. h and are the Plank constant and light frequency, respectively [ 26 ].…”

“…Actually, the FROG and SFG-XFROG are efficient tools for check the measurements of ultra-short laser pulses [ 18 , 19 , 20 ]. However, up to now, although we had checked the soliton behavior in the Si nanowire and PhCWs [ 21 , 22 , 23 , 24 , 25 , 26 ], there is unclarity about all details of the soliton propagation, especially the evolution dynamics of the low-energy soliton in the Si PhCWs, which are considered to be suitable to manage the solitons for the Si nanowire [ 27 ].…”

Improving Low-Dispersion Bandwidth of the Silicon Photonic Crystal Waveguides for Ultrafast Integrated Photonics

“…With the capabilities in flexible designability, high integration and mature massproduction, the slow-light photonic crystal waveguide (PhCW) [1] has become a versatile element for many applications including integrated lasers [2], microwave photonics [3], optical communications and optical computing [4]. Especially, due to its remarkable slow-light enhanced effects and flexible dispersion engineering properties under the roomtemperature condition, ultrafast nonlinear photonics within the slow-light region of PhCW has emerged as a hot topic recently, with many impressive works including front-induced transitions [5], pulse acceleration [6], pure-quartic solitons [7], pulse compression [8], ultrafast time delay tuning [9], slow-light-induced Doppler shift [10], optical auto-correlator [11] and dynamic control [12] having been demonstrated in PhCW. However, the inherent original small bandwidth, extremely large group velocity dispersion (GVD) and sophisticated linear and nonlinear loss properties distort the ultrashort pulse seriously, which limit the practical ultrafast utilization of slow-light PhCW.…”