The effect of higher-order dispersion on slow light propagation in photonic crystal waveguides

Abstract

We have studied the dispersion of ultrafast pulses in a photonic crystal waveguide as a function of optical frequency, in both experiment and theory. With phase-sensitive and time-resolved near-field microscopy, the light was probed inside the waveguide in a non-invasive manner. The effect of dispersion on the shape of the pulses was determined. As the optical frequency decreased, the group velocity decreased. Simultaneously, the measured pulses were broadened during propagation, due to an increase in group velocity dispersion. On top of that, the pulses exhibited a strong asymmetric distortion as the propagation distance increased. The asymmetry increased as the group velocity decreased. The asymmetry of the pulses is caused by a strong increase of higher order dispersion. As the group velocity was reduced to 0.116(9) .c, we found group velocity dispersion of -1.1(3) .10(6) ps(2)/km and third order dispersion of up to 1.1(4) .10(5) ps(3)/km. We have modelled our interferometric measurements and included the full dispersion of the photonic crystal waveguide. Our mathematical model and the experimental findings showed a good correspondence. Our findings show that if the most commonly used slow light regime in photonic crystals is to be exploited, great care has to be taken about higher-order dispersion.

Slow light enhancement of nonlinear effects in silicon engineered photonic crystal waveguides

“…It has long been predicted that the slow light enhancement of light-matter interaction should induce a reduction of either the physical length of waveguide or input power needed to observe nonlinear phenomena such as stimulated Raman scattering or harmonic generation [3,4]. However, demonstrations of such enhancement process are still rare [5] and preliminary, partly due to the challenging increase of coupling loss, linear [6] and nonlinear losses as well as the large high order dispersion that typically cause pulse distortion in the slow light regime [7].…”

Photonic crystal waveguides with semi-slow light and tailored dispersion properties

“…Potentially, PhCWs may facilitate delay lines for package synchronization, dispersion compensation, and enhanced light-matter interactions [2,3] in nanophotonic circuits by exploiting slow-light phenomena [4]. However, the practical utilization of ultra-slow light reaching group velocities below ~c 0 /200 [3,5] in PhCWs may be limited due to an inherent small bandwidth [6], impedance mismatch [7,8], intensified loss mechanisms at scattering centers [9], and extreme dispersive pulse broadening [4,10]. Previously, it has been demonstrated that the dispersion properties of PhCWs can be altered via a structural tuning of the waveguide geometry, typically, by changing the waveguide width or by introducing bi-periodicity [11,12,13].…”

Systematic design of loss-engineered slow-light waveguides

“…It has been reported that both material loss and material gain in the PhCWs restrict the attainable group index and degrade slowlight effects [7,8]. Moreover, the benefits of slow light are typically compromised by significant group velocity dispersion (GVD) [9] and concomitant propagation losses [10,11].…”