The paper presents a novel pressure sensor based on a silicon nitride (SiNx) nanocoated long-period grating (LPG). The high-temperature, radio-frequency plasma-enhanced chemical-vapor-deposited (RF PECVD) SiNx nanocoating was applied to tune the sensitivity of the LPG to the external refractive index. The technique allows for deposition of good quality, hard and wear-resistant nanofilms as requ...

We report on the single-step fabrication of stressed optical waveguides with tubular depressed-refractive-index cladding in phosphate glasses by the use of focused femtosecond hollow laser beams. Tubelike low index regions appear under direct exposure due to material rarefaction following expansion. Strained compacted zones emerged in domains neighboring the tubular track of lower refractive in...

This paper proposes and describes a design of an integrated refractive index sensor for (bio-) chemical sensing applications based on a U-shape bend waveguide structure. The proposed structure is formed by connecting four-bend waveguides and optimized using beam propagation method so that the output power has a function of refractive index of measurand liquid. The results show that the designed...

A simple approach for preparing gradient polymer network liquid crystal (PNLC) with a large refractive index change is demonstrated. To control the effective refractive index at a given cell position, we applied a voltage to a homogeneous cell containing LC/diacrylate monomer mixture to generate the desired tilt angle and then stabilize the LC orientation with UV-induced polymer network. By var...

Tunable acoustic gradient index TAG lenses create tunable multiscale Bessel beams. These lenses are fluid-filled cylindrical cavities within which an acoustic radial standing wave is excited. This standing wave modulates the density, and thereby the refractive index within the lens. Spatial gradients in the refractive index can be used for lensing. A predictive model for the steady-state fluid ...

We report a fabrication method for a gradient refractive-index polymeric object from a binary comonomer system, regardless of the monomers' reactivity ratio and the molar volume criteria of gradient refractive-index development. To fabricate a large gradient refractive-index rod consisting of a methyl methacrylate and 2,2,3,3-tetrafluoropropyl methacrylate comonomer pair that has not been used ...

Bone "stress-whitens," becoming visibly white during mechanical loading, immediately prior to failure. Stress-whitening is known to make materials tougher by dissipating mechanical energy. A greater understanding of stress-whitening, both an optical and mechanical phenomenon, may help explain age-related increases in fracture risk that occur without changes in bone mineralization. In this work,...

Using a non-invasive MRI technique for measuring the refractive index distribution through the crystalline lens, refractive index maps were obtained through 20 intact isolated human lenses (7-82years). Focal length measurements, obtained by simulated light ray propagation through each index map were found to be in agreement with direct measurements performed on a scanning laser apparatus. With ...

A hybrid antireflective coating combining homogeneous layers and linear gradient refractive index layers has been deposited using different techniques. The samples were analyzed optically based on spectrophotometric and spectroscopic ellipsometry measurements under different angles of incidence in order to precisely characterize the coatings. The Lorentz-Lorenz model has been used to calculate ...

A new technique for the refractive index change with high-sensitivity measurements was proposed by the digital image of porous silicon (PSi) microarray utilization in this paper. Under the irradiation of a He-Ne laser, the surface images of the PSi array cells with the microcavity structure were obtained by the digital imaging equipment, whereas the refractive index change of each array cells w...