Abstract:In this numerical study, we show that by exploiting the advantages of the horizontal silicon slot wave-guide structure the nonlinear interaction can be significantly increased compared to vertical slot waveguides. The deposition of a 20 nm thin optically nonlinear layer with low refractive index sandwiched between two silicon wires of 220 nm width and 205 nm height could enable a nonlinearity coefficient gamma of more than 2 x 10(7) W(-1)km(-1).
“…Figure 11.9 indicates that there is a threshold in the parameter range of our simulation of A eff ¼ 0:032 lm 2 for a slot width of s ¼ 80 nm and a rail width of w ¼ 225 nm. Also in this case our results are in good agreement with literature data [33]. …”
An approach for design optimization of the geometrical parameters of silicon-on-insulator slot-waveguides for electro-optical modulators and biosensors is presented. Theoretical investigations of field confinement factors and effective nonlinear areas for different slot-waveguide structures are critically analyzed and thoroughly calculated. With our simulation results we explain the high efficiency of electro-optical modulators and the enhanced sensitivity of biosensors compared to strip-waveguides. The influence on the effective refractive index, field confinement factor, and effective nonlinear area of the slot width and the silicon rail width were investigated.
“…Figure 11.9 indicates that there is a threshold in the parameter range of our simulation of A eff ¼ 0:032 lm 2 for a slot width of s ¼ 80 nm and a rail width of w ¼ 225 nm. Also in this case our results are in good agreement with literature data [33]. …”
An approach for design optimization of the geometrical parameters of silicon-on-insulator slot-waveguides for electro-optical modulators and biosensors is presented. Theoretical investigations of field confinement factors and effective nonlinear areas for different slot-waveguide structures are critically analyzed and thoroughly calculated. With our simulation results we explain the high efficiency of electro-optical modulators and the enhanced sensitivity of biosensors compared to strip-waveguides. The influence on the effective refractive index, field confinement factor, and effective nonlinear area of the slot width and the silicon rail width were investigated.
“…Due to the discontinuity in the electric field at the high index contrast interfaces, such a structure supports an optical mode which can confine and guide light along the nanometer-size region of low index material, as shown in Figure 1. This unique property of slot waveguides has been exploited in many areas such as sensing (Barrios et al, 2007;Carlborg et al, 2010), non-linear optics (Muellner et al, 2009;Martínez et al, 2010), electro-optic modulation (Baehr-Jones et al, 2008;Chen et al, 2009;Koos et al, 2009), light sources (Guo et al, 2012;Tengattini et al, 2013), etc. However, a major limitation of slot waveguides is their high propagation loss.…”
We demonstrate low-loss slot waveguides on silicon-on-insulator platform. Waveguides oriented along the (11-2) direction on the Si (110) plane were first fabricated by a standard e-beam lithography and dry etching process. A tetramethylammonium hydroxide-based anisotropic wet etching technique was then used to remove any residual side wall roughness. Using this fabrication technique, propagation loss as low as 3.7 dB/cm was realized in silicon slot waveguide for wavelengths near 1550 nm. We also realized low propagation loss of 1 dB/cm for silicon strip waveguides.
“…For example, when a nano-scale low-index layer is sandwiched between two high-index layers, a slot waveguide can be formed [43][44][45][46], with a large fraction of modal power trapped in the thin layer. Relative to many nonlinear materials such as SRO, SRN, chalcogenides, and polymers, silicon has a sufficiently large index to form a slot waveguide [47][48][49][50][51]. Moreover, adding a slot layer provides more design freedom to tailor chromatic dispersion, as reported in standard slot waveguides [51][52][53][54][55][56][57][58] and strip/ slot hybrid waveguides [59][60][61][62][63].…”
Group IV photonics hold great potential for nonlinear applications in the near-and mid-infrared (IR) wavelength ranges, exhibiting strong nonlinearities in bulk materials, high index contrast, CMOS compatibility, and cost-effectiveness. In this paper, we review our recent numerical work on various types of silicon and germanium waveguides for octave-spanning ultrafast nonlinear applications. We discuss the material properties of silicon, silicon nitride, silicon nano-crystals, silica, germanium, and chalcogenide glasses including arsenic sulfide and arsenic selenide to use them for waveguide core, cladding and slot layer. The waveguides are analyzed and improved for four spectrum ranges from visible, near-IR to mid-IR, with material dispersion given by Sellmeier equations and wavelength-dependent nonlinear Kerr index taken into account. Broadband dispersion engineering is emphasized as a critical approach to achieving on-chip octavespanning nonlinear functions. These include octave-wide supercontinuum generation, ultrashort pulse compression to sub-cycle level, and mode-locked Kerr frequency comb generation based on few-cycle cavity solitons, which are potentially useful for next-generation optical communications, signal processing, imaging and sensing applications.
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