Experimental demonstration of the frequency shift of bandgaps in photonic crystal fibers due to refractive index scaling

Abstract

Experimental demonstration of the frequency shift of photonic bandgaps due to refractive index scaling using D2O-filled hollow-core photonic crystal fibers is presented. The results confirm a simple scaling law for bandgaps in fibers in which the low-index medium is varied.

Integration of a 3D hydrogel matrix within a hollow core photonic crystal fibre for DNA probe immobilization

“…This result reveals a bandgap shift to around 700-800 nm, which would indicate a refractive index of about 1.33. The composition of the 25% pre-polymer solution contains 75% water which gives an estimated refractive index for the hydrogel of 1.33, which is close to that of water, for wavelength ~863 nm, as expected [8].…”

“…We believe that techniques to minimise porosity [22] and improve volumetric uniformity throughout the core and microstructure cladding should minimise scattering and cladding propagation and a well-defined bandgap shift should be observed. Assuming the analysis presented in [8] which is represented in figure 8a, it seems that for the spectral dependence of the refractive index shown in figure 7b (~1.46), the bandgap would shift to wavelength below 200 nm for an HC-PCF 1060 and HC-PCF 1550, contrary to the observed wavelength shift in figure 8b. Note that, for this spectrum, a x40 launching-lens was used in order to confine the light at the filled core, unlike figure 4a.…”

“…In a PBG fibre only a restricted band of wavelengths is confined in the core by the photonic bandgap effect induced by a microstructure fabricated within the cladding. Samples which are typically confined to the hollow core of the PBG fibre have improved the interaction between light within the guided wavelength band and the sample under test [8].…”

Long‐distance laser propulsion and deformation‐ monitoring of cells in optofluidic photonic crystal fiber

“…Light is confined to the core by a full or partial photonic bandgap in the periodic cladding structure, allowing single-mode propagation in a low-refractive index core [24]. Importantly, single-mode guidance and low fiber loss are preserved even when all the holes (cladding and core) are filled with liquid [25,26], rendering it an outstanding optofluidic channel.…”

“…The photonic crystal fiber used (see Figure 1B) was fabricated from silica glass capillaries (Suprasil 300, Heraeus) using the stack-and-draw technique described in [32]. It was designed for single-mode guidance at wavelength 1064 nm when entirely filled with D 2 O (see Figure 1C) by following known scaling laws [25,26]. Its core diameter was 17.5 mm -incidentally corresponding to that of smaller blood vessels.…”