Tuning of zero group velocity dispersion in infiltrated vertical silicon slot waveguides

Abstract

In this work the design of Si / hybrid waveguides which contain a vertical infiltrated slot is studied. The case of slots infiltrated with a χ³ nonlinear material of relatively high refractive index (e.g. chalcogenide glasses) is specifically discussed. An optimized waveguide geometry with periodic refractive index modulation, a nonlinear figure of merit > 1 and minimum effective mode cross section is presented. Introducing a periodic refractive index variation along the waveguide allows the adjustment of the group velocity dispersion (GVD). Choosing the period accordingly, the phase matching condition for degenerate four wave mixing (GVD = 0) can be fulfilled at virtually any desired frequency and independently from the fixed optimized waveguide cross section.

Nonlinear Group IV photonics based on silicon and germanium: from near-infrared to mid-infrared

“…For example, As 2 S 3 and As 2 Se 3 have bandgap energies around 2.26 eV [150,151] and 1.77 eV [152], and they are transparent up to 12 and 15 µm [153], respectively. Although in this paper chalcogenide glasses are not considered a material for the core of a waveguide, one may use them for waveguide cladding and slot layer [53,58].…”

“…Having a slot, one has an opportunity to fill the slot with highly nonlinear materials into it [49,51,53,55,56,58,59], which can overcome the decrease of the nonlinear coefficient over wavelength. In Figure 5(B), we show the γ value increasing to 306 /(m·W) with wavelength from 1.4 to 2.5 µm.…”

“…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]. A high refractive index is also beneficial to build a slow light element with reduced group velocity of light, which can effectively increase optical length for nonlinear interactions and reduce power requirement [64][65][66].…”

Broadband wavelength conversion in a silicon vertical-dual-slot waveguide

“…In our structure, the field is mainly confined in the silicon core, rather than in the slot as the single-slot structures [19][20][21][22][23][24][25][26][27]33]. Although an ultra-small effective mode area A eff can be achieved when the optical field is mainly confined in the single slot, such a small A eff does not always enable an ultra-high nonlinear coefficient γ, given by γ = ωn 2 /cA eff .…”

“…Previous research has mainly focused on the geometry of the silicon core [4], but this provides only few degrees of freedom, hence it remains a challenge to achieve spectrally-flattened nearzero anomalous GVD. Recently, sandwich structures [8][9][10][11][12][13][14][15][16][17][18] and slot structures [17][18][19][20][21][22][23][24][25][26][27][28] with flexible geometrical dimension have been developed. The basic concept of these structures is to introduce slots between silicon strips, and use other materials to fill the slots.…”