Search results for "Grating"
showing 10 items of 366 documents
Surface relief grating recording in azo polymer films
2013
In this work holographic recording of surface relief grating in organic Poly(Disperse Red 1 – methacrylate) thin films was studied. In this compound azo dye is chemically bonded to monomers making mass transport very efficient in the presence of optical field gradient. Sample preparation was performed using different solvents and coating methods. In the obtained samples holographic recording was performed by solid-state diode pump laser with 532 nm wavelength. Polarization grating and surface relief grating formation was studied by diode laser with 660 nm wavelength. Diffraction efficiency's dependence on read-out laser beam polarization state was investigated. The depth of surface relief g…
Microwave phase shifter based on fibre Bragg grating
1998
A variable delay line is presented for phased array antennas based on a fibre Bragg grating which has a uniform period and operates at constant optical wavelength. The Bragg wavelength of a localised part of the fibre grating is modified by straining the fibre, the optical carrier is reflected by the strained part of the grating and the time delay of the microwave modulating signal is determined by the position where the strain has been applied. In this initial experiment time delay variations up to 330 ps in the frequency range 1 – 14 GHz have been achieved.
Asymmetric transmission of terahertz radiation through a double grating.
2013
We report on experimental evidence of unidirectional transmission of terahertz waves through a pair of metallic gratings with different periods. The gratings are optimized for a broadband transmission in one direction, accompanied with a high extinction rate in the opposite direction. In contrast to previous studies, we show that the zero-order nonreciprocity cannot be achieved. Nonetheless, we confirm that the structure can be used successfully as an asymmetric filter.
Holographic properties of azobenzene oligomers with differently bonded chromophore groups
2007
Holographic properties of two types (I and II, specified in the text) of azobenzene oligomers (ABO) have been experimentally studied in the spectral region of low absorption at 633 nm. In the case of type I ABO the chromophore groups were covalently bonded to either tolyl-polyurethane or hexamethylene-polyurethane matrix. In the case of type II ABO azobenzene chromophores were dispersed in polystyrene matrix, and their concentration was varied from 0.005 to 0.200 mol/l. Samples were in the form of 10 µm thick films. In both cases the diffraction efficiency exposure time dependences were measured for the holographic grating period of 2 (m at 633 nm. The diffraction efficiency of more than 2%…
Upgrading a brightfield optical microscope into a robust numerically advanced interference-based phase imager
2019
The approach to convert a brightfield microscope into an interference-based versatile quantitative phase imaging unit is presented. It employs partially coherent illumination and diffraction grating. Enhanced interferogram bio-phase retrieval is performed by two-shot numerically-robust Hilbert-Huang method.
"Photonic lantern" spectral filters in multi-core fibre
2012
Fiber Bragg gratings are written across all 120 single-mode cores of a multi-core optical Fiber. The Fiber is interfaced to multimode ports by tapering it within a depressed-index glass jacket. The result is a compact multimode "photonic lantern" filter with astrophotonic applications. The tapered structure is also an effective mode scrambler.
Analysis of Fiber Inhomogeneity Using Time-Resolved Acousto-Optic Interaction
2013
Workshop on Specialty Optical Fibers and their Applications 2013, Sigtuna Sweden, 28–30 August 2013
Multicore optical fibres for astrophotonics
2011
We report progress towards multimode (MM) fibre filters for suppressing the OH emission that hinders ground-based observation of the early Universe. Fibre Bragg gratings (FBGs) can filter these narrow spectral lines in single-mode (SM) fibres [1]. Implementing them in MM fibres well-matched to astronomical instruments requires transitions between the MM fibre and several SM fibres [2]. Such hand-crafted “photonic lanterns” require many identical FBGs to be made and spliced in place. Instead we are pursuing the idea in multicore (MC) fibres, Fig. 1(a). The FBG is written at once in all the SM cores. The fibre is jacketed with low-index glass and tapered to form the core and cladding of a MM …
Remote optical monitoring in remotely power assisted passive optical networks
2010
In this paper, the authors present the latest results on a simple and low cost method to achieve a dynamic and flexible network monitoring. By placing several fiber Bragg gratings (FBG) along the passive optical gigabit Ethernet infrastructure (GePON), the proposed modified optical time domain reflectometer (OTDR) is able to monitor the entire system by simply tuning its working wavelength. Furthermore, the optical network terminals (ONT), at the end users premises, have been interconnected to the trunk via an innovative cable able to both carry the optical signal as well as the power supply.
Nonlocal dispersion anomalies of Dyakonov-like surface waves at hyperbolic media interfaces
2016
Dyakonov-like surface waves (DSWs) propagating obliquely on an anisotropic nanostructure have been theoretically proved in a few cases including 2D photonic crystals and metal-insulator (MI) layered metamaterials. Up to now, the long-wavelength approximation has been employed in order to obtain effective parameters to be introduced in the Dyakonov equation, which is largely restricted to material inhomogeneities of a few nanometers when including metallic elements. Here, we explore DSWs propagating obliquely at the interface between an insulator and a hyperbolic metamaterial, the latter consisting of a 1D MI bandgap grating using realistic slab sizes. We found unexpected favorable condition…