Polarization-independent waveguides based on the complete band gap of the two-dimensional photonic crystal slabs

Abstract

Twodimensional photonic crystal (PC) slabs exhibiting photonic band gaps (PBGs) in both TE and TM polarizations are of particular interest for a better control of light propagation and easy experimental fabrication. Through reducing the symmetry of the PC lattice, simultaneous realization of PBGs in both TE and TM polarizations within a certain frequency region can be achieved. Based on the air holes immersed in the silicon background, two kinds of two dimensional PC slab structures are proposed. These are a honeycomb lattice of circular air holes with different sizes and larger circles, and smaller triangles alternately arranged, respectively. The light transmittances show that these two structures offer large complete band gaps. Different kinds of straight waveguides are designed, and their abilities of localizing the incident beam are studied by analysing the light transmittances and spatial field distributions, where the light energy is localized perfectly in the optimized waveguide structure. Our proposed PC slab waveguides are convenient for fabrication, and could be applied in future alloptical integrated circuits.

Complete photonic bandgap in silicon nitride slab assisted by effective index difference between polarizations

“…Because of the small mode volumes and high quality factors [1], silicon-based photonic bandgap (PBG) devices have been regarded as the essential elements for miniaturization and integration [2]. Compared with PBG for one single polarization, the complete photonic bandgap (CPBG), which has PBGs for both transverse-electric (TE) and transverse-magnetic (TM) polarizations, is of particular interest for reduced loss of light propagation [3] and the ability to polarize multiplex [4]. Therefore, various powerful silicon photonic devices based on CPBG have been demonstrated theoretically and experimentally, such as high-Q microcavity [1], polarization beam splitter [2,5,6], polarizationindependent waveguide [7,8], etc.…”

“…Therefore, various powerful silicon photonic devices based on CPBG have been demonstrated theoretically and experimentally, such as high-Q microcavity [1], polarization beam splitter [2,5,6], polarizationindependent waveguide [7,8], etc. However, currently most of these devices are based on the SOI platform which has a high refractive index contrast (RIC) [2,3,[5][6][7][8][9]. Unfortunately, bulk crystalline silicon has non-negligible twophoton absorption [10] in all telecommunication bands with wavelengths shorter than about 2000 nm, which seriously affects the efficiency of nonlinear photonic chips in generating and processing all-optical signals [11,12].…”