Green light emission in silicon through slow-light enhanced third-harmonic generation in photonic-crystal waveguides

Abstract

Slow light has attracted significant interest recently as a potential solution for optical delay lines and time-domain optical signal processing 1,2. Perhaps even more significant is the possibility of dramatically enhancing nonlinear optical effects 3,4 due to the spatial compression of optical energy 5,6,7. Two-dimensional (2D) silicon photonic crystal (PhC) waveguides have proven to be a powerful platform for realizing slow light, being compatible with on-chip integration and offering wide-bandwidth and dispersion-free propagation 2. Here, we report the slow light enhancement of a nonlinear optical process in a 2D silicon PhC waveguide. We observe visible third-harmonic generation (THG) at a wavelength of 520nm with only a few watts of peak power, and demonstrate strong THG enhancement due to the reduced group velocity of the near-infrared pump signal. This demonstrates yet another unexpected nonlinear function realized in a CMOS-compatible silicon waveguide. Main text Although silicon has been the material of choice for the CMOS industry and more recently for integrated photonics, its optical properties-e.g light emission-still provide major challenges. In addition to an indirect band-gap and inversion symmetry,

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.…”

Advanced photonic filters based on cascaded Sagnac loop reflector resonators in silicon-on-insulator nanowires

“…With enhanced light trapping, there are increased time delays and enhanced light-matter interactions, which are useful in nonlinear optics and laser excitation. 10,11,27,28 In Fig. 5(c), one can see that there are central transmission peaks induced by an additional phase shift along L 4 , which correspond to a group delay 2.1 times higher than that of the CSLR resonator without the additional phase shift in Fig.…”

“…[7][8][9] Moreover, the resulting group delay response and mode interaction are useful for enhancing light-material interaction and dispersion engineering in nonlinear optics. [10][11][12][13][14] Photonic resonators can be classified into two categories-travelling-wave (TW) resonators, exemplified by ring resonators, and standing-wave (SW) resonators represented by photonic crystal cavities, distributed feedback cavities, and Fabry-Pérot (FP) cavities. 3 The majority of work on mode splitting in photonic resonators has been based on TW resonators [15][16][17][18][19] although some recent work has investigated device structures consisting of both TW and SW resonators.…”

Coherent Fano resonances in a plasmonic nanocluster enhance optical four-wave mixing

“…It has recently been shown that certain plasmonic nanostructures can produce an enhanced nonlinear response when excited at their resonant frequency (1,2). Phase-matching requirements (3)(4)(5) for nonlinear optics in macroscopic media are usually optimally fulfilled at nanoscale dimensions [sinc 2 (Δk z/2) ∼1 for small z, where z is the propagation distance through the medium]. For plasmonic nanostructures, the most important property for the enhancement of nonlinear properties is their increased local fields at resonance, which can provide larger effective susceptibilities than their intrinsic material susceptibility.…”