Air and dielectric bands photonic crystal microringresonator for refractive index sensing.

We present the experimental and numerical analysis of a microring resonator with an integrated one-dimensional photonic crystal fabricated on a silicon-on-insulator platform and show its applicability in bulk refractive index sensing. The photonic crystal is formed by periodically patterned, partially etched cylindrical perforations, whose induced photonic bandgap is narrower than the range of measurable wavelengths (1520-1620 nm). Of particular interest is that the microring operates in both air and dielectric bands, and the sensitivities of the resonances on both edges of the bandgap were investigated. We showed that a higher field localization inside the volume of the perforations for the air band mode leads to an increase in sensitivity.

Ultra-wide free spectral range, enhanced sensitivity, and removed mode splitting SOI optical ring resonator with dispersive metal nanodisks.

A refractive index sensor with a free spectral range that is unlimited by neighboring mode spacing (10 fold increase with respect to 20 nm of an unmodified ring), based on an optical silicon-on-insulator microring resonator patterned with periodically arranged set of gold nanodisks, is presented and numerically verified. It is shown that the particular periodic arrangement of nanodisks selects a single resonance from a wide set of ring resonator modes and removes mode splitting. Extraction of the waveguided electromagnetic energy into evanescent plasmonic modes enhances light-analyte interaction and increases device sensitivity to variation of refractive index up to 176 nm/RIU (about 2-fold increase compared to the unmodified ring), which is useful for sensor applications. Proof of the concept is presented by finite-difference time-domain simulations of a design readily practicable by means of modern nanotechnology.

Numerical and experimental analysis of optical response of sub-wavelength period structure in carbonaceous film for refractive index sensing.

The resonance structure coupling the light into the leaky guided modes, which are visible in the reflection spectra as sharp peaks (Wood's anomalies), is analyzed experimentally and numerically. The guided mode resonance structure of 428 nm period patterned in a carbonaceous film demonstrated sensitivity of 70 nm/RIU. The calculated mode diagram explained the nature and positions of the peaks registered experimentally. The reflection spectra, near/far field distributions and field penetration depth for the analyzed structure were simulated employing three numerical solvers. The set of weak Rayleigh's anomalies was indentified from the simulations and the experimental data.

Aberrations induced by anti-ASE cap on thin-disk active element.

Optical aberrations induced in thin-disk laser elements with an undoped layer, performing as an anti-ASE cap, are analyzed. A numerical model, used for calculations of the optical path difference (OPD) induced by temperature distribution inside the laser element and by deformation of surfaces, was confirmed experimentally. Results of numerical modeling manifest that adding an undoped layer on the thin-disk has detrimental effect on the reflected laser beam brightness and scaling. It is also shown that brightness of a thin-disk laser may be enhanced by the use of the Gaussian pump beam profile.