Determination of excitation profile and dielectric function spatial nonuniformity in porous silicon by using WKB approach

We develop an analytical model based on the WKB approach to evaluate the experimental results of the femtosecond pump-probe measurements of the transmittance and reflectance obtained on thin membranes of porous silicon. The model allows us to retrieve a pump-induced nonuniform complex dielectric function change along the membrane depth. We show that the model fitting to the experimental data requires a minimal number of fitting parameters while still complying with the restriction imposed by the Kramers-Kronig relation. The developed model has a broad range of applications for experimental data analysis and practical implementation in the design of devices involving a spatially nonuniform dielectric function, such as in biosensing, wave-guiding, solar energy harvesting, photonics and electro-optical devices.

Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

The properties of fiber Bragg gratings in hydrogenated fibers under conditions of ultraviolet overexposure were investigated. Abnormal spectral evolution of the regenerated grating following erasure of the initial type I grating was observed in the hydrogenated fibers. The regenerated grating also exhibited less temperature sensitivity and an 18 nm shift in the Bragg wavelength.

Effect of dopants on the fracture toughness of silicon

Fracture experiments were conducted on p-type and n-type Si in the presence and absence of hydrogen. It was found that fracture toughness is slightly less than the fracture toughness of n-type silicon. Annealing silicon in an Ar/H atmosphere gave a hydrogen concentration of less than 0.1 ppm, which did not have any measurable effect on fracture toughness. Likewise, the exposure of pre-cracked specimens to H did not cause any measurable change in fracture toughness.

Molecular dynamics simulation of brittle fracture in silicon

The fracture process involves converting potential energy from a strained body into surface energy, thermal energy, and the energy needed to create lattice defects. In dynamic fracture, energy is also initially converted into kinetic energy. This paper uses molecular dynamics (MD) to simulate brittle frcture in silicon and determine how energy is converted from potential energy (strain energy) into other forms.

Kerr nonlinear switching in a core-shell microspherical resonator fabricated from the silicon fiber platform

We investigate the Kerr nonlinearity in a core-shell microspherical resonator fabricated from a silicon fiber. By exploiting the ultrafast wavelength shifting, sub-picosecond modulation is demonstrated. © OSA 2015.

Tunable coaxial resonators based on silicon optical fibers

Thermal tuning of a coaxial fiber resonator with a silica cladding surrounding an inner silicon core is investigated. By pumping the silicon with below bandgap light, it is possible to redshift the WGM resonances. © 2014 OSA.

Superior gas-sensing performance of amorphous CdO nanoflake arrays prepared at room temperature

Highly sensitive and selective detection of volatile organic compounds (VOCs) with fast response time is imperative based on safety requirements, yet often remains a challenge. Herein, we propose an effective solution, preparing a novel gas sensor comprised of amorphous nanoflake arrays (a-NFAs) with specific surface groups. The sensor was produced via an extremely simple process in which a-NFAs of CdO were deposited directly onto an interdigital electrode immersed in a chemical bath under ambient conditions. Upon exposure to a widely used VOC, diethyl ether (DEE), the sensor exhibits excellent performance, more specifically, the quickest response, lowest detection limit and highest selectivity ever reported for DEE as a target gas. The superior gas-sensing properties of the prepared a-NFAs are found to arise from their open trumpet-shaped morphology, defect-rich amorphous nature, and surface CO groups.

A comparative analysis of the characterization methods for submicron silicon waveguide propagation loss

An important parameter in integrated optical device is the propagation loss of the waveguide. Its characterization gives the information of the fabrication quality as well as the information of other passive devices on the chip as it is the basic building block of the passive devices. Although, over the last three decades many methods have been developed, there is not a single standard present yet. This paper presents a comparative analysis of the methods existing from the past as well as methods developed very recently in order to provide a complete picture of the pros and cons of different types of methods and from this comparison the best method is suggested according to the authors opinion. To support the claim, apart from the analytical comparison, this paper also presents a comparison performed with the experimental results between the suggested best method which is recently proposed by Massachusetts Institute of Technology (MIT) researchers based on undercoupled all-pass microring structure and the popular cut-back method.