Holographically encoded volume phase masks

Abstract

Abstract. We present here a method to create spectrally addressable phase masks by encoding phase profiles into volume Bragg gratings, allowing these holographic elements to be used as phase masks at any wavelength capable of satisfying the Bragg condition of the hologram. Moreover, this approach enables the capability to encode and multiplex several phase masks into a single holographic element without cross-talk while maintaining a high diffraction efficiency. As examples, we demonstrate fiber mode conversion with near-theoretical conversion efficiency as well as simultaneous mode conversion and beam combining at wavelengths far from the original hologram recording wavelength. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Short- and Medium-Range Order in Photothermal Refractive Glass Revealed by Solid-State NMR Techniques

“…The results of the present study provide detailed information about the different types of NMR parameters for the various elemental components in PTR glasses. The standard aluminosilicate framework is partially modified by the NaF component producing F-bearing Al (5) and Al (6) units. Three distinct F species are detectable, which were assigned to Fspecies dominated by Na coordination (F1) and different types of Al-bonded F-species (F2 and F3) with the help of dipolar recoupling experiments.…”

“…The photo-thermo-induced refractive index decrement was explained by precipitation of NaF crystals, and the presence of this crystalline phase in treated glasses was confirmed by X-ray diffraction and nuclear magnetic resonance (NMR) measurements. By applying holographic techniques, optical elements with different spatial profiles of refractive index can be created, including volume Bragg gratings, phase masks, and complex holograms, for example, lenses . Such holographic elements are widely used for narrow band optical filtering and laser design .…”

“…Our conclusions are further strongly confirmed by the 27 Al{ 19 F} REDOR experiments summarized in Figure 3c,d. Four-coordinated Al only shows a very weak REDOR effect (arising from long-range 27 Al− 19 F interactions), while the Al (5) and Al (6) signals are strongly affected by nearby 19 F nuclei. The convergence of the Al (5) { 19 F} REDOR curve to a normalized difference signal of ΔS/S 0 smaller than unity suggests the presence of some {AlO 5/2 2− } as owing to the 100% natural abundance of 19 F, an {AlO 4/2 F 2− } unit should give a close to 100% REDOR effect.…”

“…On the basis of the results of the chemical analysis, we can make some quantitative estimations based on the analytically determined Al contents and the nominal F contents (serving as upper-limit estimates). If all of the Al (5) species were coordinated by one and all Al (6) species by two F species, the 27 Al MAS NMR spectral parameters given in Table 5 would predict about 14−24% of the total amount of F to be Albonded (if only terminal bonds are formed). This number is substantially lower than the area fraction of 43% given in Table 6, summarizing the results from 19 F MAS NMR.…”

Volume Bragg Gratings: Fundamentals and Applications in Laser Beam Combining and Beam Phase Transformations

“…The encoding of a phase profile into a TBG can be carried out by using a holographic setup shown in Figure 10 [26]. In the setup, a standard binary phase mask (see Figure 11) is placed into one of the arms (object beam) of a two-beam-recording system.…”