Mapping of complex optical field patterns in multimode photonic crystal waveguides by near-field scanning optical microscopy

Abstract

We use near-field scanning optical microscopy ͑NSOM͒ operating in collection mode to map the optical field distribution of continuous wave infrared light propagating along an air-bridged W3 silicon photonic crystal ͑PC͒ slab multimode waveguide in a subwavelength resolution. The detected near-field optical intensity distribution patterns show very different longitudinal propagation features and transverse field profiles at different wavelength ranges. We have analyzed the dispersion of the guided modes in the PC waveguide and the corresponding eigenfield profile for each guided mode by means of the three-dimensional plane-wave expansion simulations. It is found that the experimentally observed complex while interesting near-field pattern features can be well explained by the field profiles of the multiple waveguide modes and their superposition at different excitation wavelengths. The detection and analysis of this multimode PC slab waveguide via NSOM could help us to understand complex wave propagation behavior and to further design novel PC devices.

Multilayered Maxwell’s fisheye lens as waveguide crossing

“…However, the simulations, not presented here, show that the MFE lens can support higher modes simply by increasing the waveguides' width and the lens's radius. The multimode photonic crystal waveguides (PhCW) are obtained by removing multiple neighboring rows of rods [18,24,66]. In our simulations, three consecutive rows are removed to form a multimode PhCW.…”

Anomalous transport of light in photonic crystal

“…Integrated optical devices that are built in the platform of silicon 2D PC slab has been extensively investigated in the infrared wavelength because of the superior infrared optical properties of silicon and relative ease of nanofabrication and monolithic integration of various planar optical devices. These structures are usually made from perforating 2D periodic arrays of air holes on a silicon thin membrane suspended in air, so they are also called the air-bridged structure [57][58][59][60][61][62]. As the effective refractive index of the silicon membrane is much larger than the air background, infrared light can be confined within the membrane via the well-known physical mechanism of total internal reflection effect.…”

Mapping the absolute electromagnetic field strength of individual field components inside a photonic crystal

“…So far the only optical method to map local fields is near-field scanning optical microscopy (NSOM) [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The technique relies on scanning a small tip of a tapered optical fiber above the surface of a photonic crystal that collects part of the evanescent field with subwavelength resolution.…”