Temporal solitons and pulse compression in photonic crystal waveguides

Abstract

Soliton-effect pulse compression and propagation has been experimentally demonstrated in the temporal domain in fibers [1], fiber Bragg gratings [2], photonic crystal fibers (PhCF) [3][4][5][6], photonic nanowires [7] and in the spectral domain of integrated channel waveguides [8,9].Here we demonstrate the first experimental observations of soliton-effect pulse compression in semiconductor photonic crystal waveguides (PhCWG) in the temporal domain. Pulse compression in the PhCWGs occurs due to the interaction between a strong group-velocity dispersion (GVD) [10] and slow-light enhanced self-phase modulation (SPM) in the periodic dielectric media [11]. Compression of 3 ps input pulses to a minimum pulse duration of 580 fs (~10 pJ) is achieved. The small modal area A eff ~ 10 -13 m 2 combined with a slow-light enhanced optical field allow for ultra-low threshold (~GW/cm 2 ) pulse compression at millimeter length scales. These results open the way for femtosecond and soliton applications on the chip scale.Periodic dielectric structures have long been known to have extremely large dispersion thus enabling observation of soliton effects at centimeter length scales [2,[12][13][14]. The decreased interaction length, however, requires a correspondingly larger intensity-dependent nonlinear effect to match the strength of the dispersion. Increasing the optical intensity inside the waveguide is accomplished through: (a) direct input of larger peak powers; (b) decreasing the effective modal area [7][8][9]; or, most recently, (c) via dispersion-engineered periodic slow-light structures [10,11]. At the so-called slow-light frequencies of PhCWGs, the light experiences a longer effective path length through the lattice via multiple Bragg reflections, leading to an enhanced local field density. The enhanced field scales inversely with the group velocity, thus

Slow-light-enhanced gain in active photonic crystal waveguides

“…The waveguide is terminated by tapers 32 to suppress residual reflections and improve coupling. Similar passive structures have been used for investigating slow-light propagation 3,4 and nonlinearities 7,8 , but in our case an active material is incorporated inside the membrane and the structures are designed such that the slowlight regime spectrally overlaps with the region where positive net material gain can be achieved by optical pumping. A schematic of the setup as well as scanning electron microscopy pictures of fabricated samples are shown in Fig.…”

Statistics of Anderson-localized modes in disordered photonic crystal slab waveguides

“…From Eqs. (12), (15) and (16), the PE factor at the position r and frequency ω, projected in then µ direction, reads…”

“…With regards to waveguide geometries, PC slab waveguides (PCWs) have attracted much attention as a platform for single photon generation 12,13 , optical buffering 14 , and for enhancing non-linear optical processes in the slow-light regime [15][16][17] However, PCWs are known to be extremely sensitive to fabrication disorder [18][19][20] , which becomes relevant for practical applications [21][22][23] . Interestingly, structural disorder in PCs can also induce coherent scattering of light 24 , giving rise to the formation of random cavities where the field can be strongly localized, leading to the quasi-1D Anderson localization regime 2,25 .…”

Giant anomalous self-steepening in photonic crystal waveguides

“…For that purpose we consider typical parameters found in recent nonlinear experiments [12,22,23,31,32]. We take γ eff = 1600 (W m) −1 (n g = 15, n o = 3.17 for GaInP), an anomalous dispersion of β 2 = −7.7 ps 2 /mm, n 2 = 6 × 10 −18 m 2 /W, and modal area A eff = 0.34 μm 2 [6].…”

“…For a typical wavelength of 1550 nm (photon energy of 0.8 eV), silicon (E g = 1.1 eV) is restricted by two-photon absorption (TPA), and the wide-gap material GaInP (E g = 1.9 eV) is limited by three-photon absorption (3PA). While the optical properties of silicon have been widely studied, only over the past few years have we investigated the χ (3) properties of GaInP and established this material as a viable platform for nonlinear optics at 1.5 μm [12,22,32,36]. In simplest terms, nonlinear absorption damps the dynamics similar to linear absorption.…”