Resonant absorption of a chemically sensitive layer based on waveguide gratings

A colorimetric sensor providing a direct visual indication of chemical contamination was developed. The sensor is a combination of a chemically sensitive dye layer and a resonant waveguide grating. Enhancement of the light absorption by the photonic structure can be clearly seen. The detection is based on the color change of the reflected light after exposure to a gas or a liquid. Low-cost fabrication and compatibility with environments where electricity cannot be used make this device very attractive for applications in hospitals, industries, with explosives, and in traffic

Roadmap on holography

From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful.This work was supported by Ministerio de Economía, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015

Samarium doped alkaline earth halide thin films as spectrally selective materials for hole burning

Optical hole burning, a potential technique for spectrally selective Recording, was demonstrated in Sm-doped MBE-grown thin films of CaF2/Si(111). The inhomogeneous broadening of the corresponding Sm2+ 5d(T1u) ↞ 4f(7F0, A1g) transition (690 nm) was investigated as a function of substrate temperature and film thickness. The MBE apparatus is briefly described as well as the thin film growth procedure

Room-temperature persistent spectral hole burning in SrFCl:Sm2+ films: Temporal and spatial response

Persistent spectral hole burning was performed on the 7F0–5D1 transition of Sm2 + in thin films of SrFCl. Depending on the substrate and the growth conditions, a total hole depth between 47% and 70% was reached. The holes were Lorentzians of width 4(±0.3) cm – 1. The time evolution of the hole depth was studied. It is described by two exponentials: a short time decay (t1 = 0.37 days) and a long time decay (t2 = 20.4 days) with a 20% infinite time limit. One- and two-photon burning mechanisms act

Samarium-doped thin films of the Matlockite structure: Design, luminescence, and hole-burning experiments

The growth of thin films made from Samarium-doped alkaline earth fluoro halides (AEFH) of composition SrxCa1 – xFCl:Sm2 + (0 7F0 Sm2 + emission linewidth is thereby increased to 70 cm – 1 full width half maximum. A width of 100 cm – 1 may be obtained within the composition range x = 0, x = 1. This represents an enhancement by a factor of 3–5 in comparison with the largest values obtained in appropriate mixed bulk AEFH of constant composition. A factor > 50 is gained in comparison with pure bulk AEFH hosts. The room temperature (RT) homogeneous linewidths, on the other hand, are similar to those found in bulk mixed crystals of constant composition. The intrafilm host cation diffusion during film growth of the sandwich structures was further studied. A diffusion constant of 2 · 10–19 m2 s – 1 for the Sr and Ca ions was deduced from this observation. These films are among the most promising materials for optical mass data storage through RT hole burning

SrB₄O₇ : Sm²⁺: crystal chemistry, Czochralski growth and optical hole burning

The crystal chemistry of the Sm3z to Sm2z reduction in tetraborate lattices was investigated. In crystalline SrB4O7 in air it is mainly Sm2z that is incorporated from a melt or glass containing predominantly Sm3z. For the process in air, a reduction and pick-up mechanism is assumed to take place at the crystal/nutrient interface. Stabilization of Sm2z in SrB4O7 at high temperature and in an oxidizing atmosphere seems to be a particular property of the system, because no Sm2z inclusion could be observed along the series MB4O7 (M~Ca, Ba, Cd, Pb), if similar reaction conditions were applied. So far, there is only one other oxide lattice (BaB8O13) known where at high temperatures significant amounts of Sm2z are obtained for reactions in the air. Single crystals of SrB4O7 : Sm2z were grown by the Czochralski method (keff for Sm is 0.5). Optical hole burning experiments for the transition 5D1±7F0 were performed at 80 K. A hole with a width of 0.21 cm21 and a depth of 5.25% was formed for the first time for Sm2z in a borate crystal excited by the beam of a single frequency dye laser. A rather small inhomogeneous linewidth of 0.28 cm21 allowed the burning of a single hole only

Defect association, Jahn-Teller or off-center effect in CaF₂:Copper, BaF₂:Silver ?

The results of a detailed optical and paramagnetic-resonance study performed on copper in CaF2 and silver in BaF2 are presented. Two different Ag+ centers were identified in BaF2. One is associated with an interstitial F- ion whereas the other one has a cubic surrounding. The Cu2+ ion in CaF2 was shown to reorient at 4.2 K between 6 equivalent minima of D2h symetry. This fact is interpreted with the aid of a T2gx(T2g+Eg) type Jahn-Teller effect. The nonlinear mixed coupling terms are shown to play an important role. The Cu+ impurity in CaF2 is presumably off-center in the F- sublattice without associated defect or impurity

Thin film materials with Sm(III) far room temperature hole burning: design and photomechanism studies

Multicomponent thin films with spectral hole burning capacity at room temperature were synthesized by using molecular beam and pulsed laser deposition techniques All materials were activated by Sm2+ in low-symmetry alkaline earth sites, the synthesis involved the control of ionic diffiision rate during multilayer growth and special reduction of Samarium. Enhancement of hole burning rate by 1-2 orders is obtained in nanocrystalline films as compared to bulk and microcrystalline materials New hypothetic mechanism involving the creation of Sm-defect (photochromic) centers is proposed for reversible photoburning