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Ho2O3 transparent ceramics were fabricated by vacuum pre-sintering combined with hot isostatic pressing (HIP) post-treatment at relatively low temperature from high-purity Ho2O3 powder calcined at 1000 °C for 4 h. The optimal Ho2O3 ceramic sample prepared by vacuum pre-sintering at 1250 °C and HIP post-treating at 1450 °C has a dense microstructure with average grain size of 0.77 μm, and the in-line transmittances reach 80.7 % at 1550 nm and 76.7 % at 1064 nm. The effect of air annealing on the optical quality of Ho2O3 ceramics was studied, and the existence of compressed pores in the HIP-ed Ho2O3 ceramics was confirmed. The Verdet constants of Ho2O3 ceramics were measured to be -47.4 rad/(T m at 1064 nm and -15.4 rad/(T m at 1561 nm. High transmittance and large Verdet constant in the wavelength regions 1–1.07 μm, 1.3–1.5 μm make Ho2O3 transparent ceramics promising for magneto-optical devices for lasers based on Yb-, Nd-doped materials and telecom lasers. © 2020 Elsevier Ltd 19-52-53014; Chinese Academy of Sciences, CAS: QYZDB-SSW-JSC022; Russian Science Foundation, RSF: 18-13-00355; National Key Research and Development Program of China, NKRDPC: 2017YFB0310500 This work was supported by the National Key R&D Program of China (Grant No. 2017YFB0310500 ), the Special Exchange Program of Chinese Academy of Sciences (Plan B) , the key research project of the frontier science of the Chinese Academy of Sciences (No. QYZDB-SSW-JSC022 ), partially by the Research Project of the Russian Science Foundation (No. 18-13-00355 ) and Verdet constant measurements was done under NSFC-RFBR Cooperative Research Projects Grant 19-52-53014.

The paper presents results of a research on fabrication of magneto-optical ceramics based on Ho2O3 and Dy2O3 sesquioxides. The ceramics were made by hot pressing of powders prepared by self-propagating high-temperature synthesis. The methods and modes of the powder treatment developed made it possible to significantly increase the thickness of the ceramics without deterioration in optical quality in comparison with the samples obtained by vacuum sintering. The characteristics of the ceramics, such as transmission spectrum, thermal conductivity, linear thermal expansion coefficient, microhardness, elastic modulus, and crack resistance have been investigated. © 2021 The Author(s). The study was funded by the Russian Science Foundation, research project No. 18-13-00355, https://rscf.ru/en/project/18-13-00355.

In solar tower plants, thousands of heliostats reflect sunlight into a central receiver. Heliostats consist of a subset of mirrors called facets that must be perfectly oriented (i.e., canted) to concentrate as much solar radiation as possible. This study presents and validates the so-called flux map fitting technique to detect and correct canting errors. The computed distributions were matched to a series of images through an optimization algorithm. According to the sensitivity analysis, three images spread along a single day provide sufficient information for the algorithm to succeed. Using this methodology, four heliostats at the THEMIS research facility were recanted, thereby substantially increasing the optical quality in three of them. The procedure to infer the heliostat aimpoint was assessed. Universidad Carlos III de Madrid (2020/00051); European Commission (823802); Horizon 2020 Framework Programme (727762). We thank the CNRS-PROMES laboratory, UPR 8521, belonging to the French National Center for Scientific Research (CNRS), for providing access to its facilities, the support of its scientific and technical staff, and the financial support of the SFERA-III project (Grant Agreement No. 823802). We thank the technical help provided by Yann Volut, William Baltus, and Antoine Pérez. The research project VISHELIO-CM-UC3M has been funded by the call "Programa de apoyo a la realización de proyectos interdisciplinares de I+D para jóvenes investigadores de la Universidad Carlos III de Madrid 2019-2020" under the framework of the "Convenio Plurianual Comunidad de Madrid-Universidad Carlos III de Madrid". This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 727762, project acronym NEXT-CSP. Publicado

Monolayer transition metal dichalcogenides (TMDC) grown by chemical vapor deposition (CVD) are plagued by a significantly lower optical quality compared to exfoliated TMDC. In this work we show that the optical quality of CVD-grown MoSe$_2$ is completely recovered if the material is sandwiched in MoS$_2$/MoSe$_2$/MoS$_2$ trilayer van der Waals heterostructures. We show by means of density-functional theory that this remarkable and unexpected result is due to defect healing: S atoms of the more reactive MoS$_2$ layers are donated to heal Se vacancy defects in the middle MoSe$_2$ layer. In addition, the trilayer structure exhibits a considerable charge-transfer mediated valley polarization of MoSe$_2$ without the need for resonant excitation. Our fabrication approach, relying solely on simple flake transfer technique, paves the way for the scalable production of large-area TMDC materials with excellent optical quality., Comment: Just accepted for publication in Nano Letters (http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b00904)

A novel formulation and synthesis method to overcome the thickness limitations in samples of photopolymerizable glasses with high refractive index species is presented. The reported method allows the recording of volume holographic diffraction gratings in samples of similar to 500 mu m thickness with a high optical quality and low scattering. Holographic grating recording is performed in a single coherent light exposure step, resulting in volume gratings of high optical quality. A holographic notch filter implemented in a 500 mu m thick photopolymerizable glass with a spectral bandwidth below 0.3 nm and an excellent filter extinction ratio of

Disposable microfluidic systems are used to avoid sample contamination in a variety of medical and environmental monitoring applications. A contactless hot intrusion (HI) process for fabricating reusable polymer micromolds with near "optical quality" surface finishes is described in this paper. A metallic hot intrusion mask with the desired microchannels and related passive components is first machined using a tightly focused beam from a diode-pumped solid-state (DPSS) laser. The polymer mold master is then created by pressing the 2D metallic mask onto a polymethylmethacrylate (PMMA) substrate. Since it is a contactless fabrication process the resultant 3D micro-reliefs have near optical quality surface finishes. Unfortunately, the desired micro-relief dimensions (height and width) are not easily related to the hot intrusion process parameters of pressure, temperature, and time exposure profile. A finite element model is introduced to assist the manufacturing engineer in predicting the behavior of the PMMA substrate material as it deforms under heat and pressure during micromold manufacture. The FEM model assumes that thermo-plastics like PMMA become "rubber like" when heated to a temperature slightly above the glass transition temperature. By controlling the material temperature and maintaining its malleable state, it is possible to use the stress-strain relationship to predict the profile dimensions of the imprinted microfeature. Examples of curved microchannels fabricated using PMMA mold masters are presented to illustrate the proposed methodology and verify the finite element model. In addition, the non-contact formation of the micro-reliefs simplifies the demolding process and helps to preserve the high quality surface finishes. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Microfluidics, BioMEMS, and Medical Microsystems X, January 23-24, 2012, San Francisco, CA, USA, Series: Proceedings of SPIE; no. 8251

cited By 26; International audience; Transparent 9.8. at% Yb:YAG ceramic samples were prepared by reactive sintering of commercial oxides and using 0 or 1. wt% polyethylene glycol (PEG) as dispersant. The optical quality of the samples turns out to be improved by using a dispersant and optical transmittance close to the commercial samples has been obtained. On the other hand the laser characterization evidenced the activation of a non-linear loss mechanism occurring only in the sample containing PEG and despite its better optical quality, at high excitation level. A SEM analysis of material microstructure could not explain this behavior. A state of the art TEM analysis at nanometric scale was performed providing high resolution chemical spectroscopic results that indicate the presence of amorphous and crystalline silicate phases playing different roles in the two samples. © 2012 Elsevier Ltd.

Date of Conference: 23-27 September 2012 Colloidal semiconductor quantum dots (QDs) have been extensively explored for numerous applications ranging from optoelectronics to biotechnology. This strong demand for the colloidal QDs arises because of their favorable optical and electronic properties. From the application points of view, QDs typically need to be used in their solid form, as opposed to their as-synthesized dispersion form. For immobilization of QDs and homogeneity of their films, various polymers have been used to host QDs within solid media. However, the integration of QDs into a polymeric medium is commonly complex, which requires a high level of understanding to provide optical quality. © 2012 IEEE.

In this work we analyze the optical quality, performance, and recording mechanism of holographic diffraction gratings recorded in photopolymerizable sol-gel glasses. These classes of holographic photomaterials have various compositions, one of which incorporates a High Refractive Index Species (HRIS), already developed in our group GICO-UCM. The new types of photopolymerizable glasses under study incorporate ionic liquid (IL). We present a comparative study, showing distinctive behaviors for each photopolymerizable glass class, and determining particular features for various ranges of applications. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., International Conference on Applications of Optics and Photonics, May 3-7, 2011, Braga, Portugal, Series: Proceedings of SPIE; no. 8001

We report on optically pumped lasing at 500 nm on InGaN laser structures grown by plasma assisted molecular beam epitaxy. The InGaN laser structures were grown under group III-rich conditions on bulk (0001) GaN substrates. The influence of the nitrogen flux and growth temperature on the indium content of InGaN layers was studied. We demonstrate that at elevated growth temperatures, where appreciable dissociation rate for In-N bonds is observed, the indium content of InGaN layers increases with increasing nitrogen flux. We show that growth of InGaN at higher temperatures improves optical quality of InGaN quantum wells, which is crucial for green emitters. The influence of piezoelectric fields on the lasing wavelength is also discussed. In particular, the controversial issue of partial versus complete screening of built-in electric field at lasing conditions is examined, supporting the former case. © 2011 American Institute of Physics.

Fabrication of ultraviolet light emitting devices using ZnO nanostructures is still difficult due to the high cost synthesis for high quality ZnO. It is important to suppress the visible emission. In this paper, we report the effective low cost in-situ preparation of high quality monodispersed and non-agglomerate ZnO nanoparticles in nanofibrous PVA matrix derived from electrospinning method. The final product was investigated by SEM, EDAX, XRD, FTIR, TEM, and SAED. The XRD analysis proved the successful preparation of ZnO with wurtzite hexagonal phase. FTIR spectroscopic measurements showed the interaction between ZnO and PVA. The purity of the sample was studied using PL. The result showed that the obtained sample exhibits intense ultraviolet emissions at 369 nm while the absence of deep level emission confirms the high quality sample. PVA matrix and electrospinning method are found to have a vital role to the preparation of defect free ZnO. Experimental results have proven that the prepared ZnO by this method have excellent optical quality. � 2011 Elsevier B.V. All Rights Reserved.

An AlN buffer layer and a thick-GaN layer for high-electron-mobility transistors (HEMTs) were grown on sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The structural and morphological properties of the layers were investigated by high resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) techniques. The optical quality of the thick-GaN layer was also evaluated in detail by a photoluminescence (PL) measurement. It was found that the AlN buffer layer possesses high crystal quality and an atomically flat surface with a root-mean-square (rms) roughness of 0.16 nm. The screw-and edge-type dislocation densities of the thick-GaN layer were determined as 5.4 x 10(7) and 5.0 x 10(9) cm(-2) by means of the mosaic crystal model, respectively. It was observed that the GaN layer has a smooth surface with an rms of 0.84 nm. Furthermore, the dark spot density of the GaN surface was estimated as 6.5 x 10(8) cm(-2) over a scan area of 4 mu m(2). Turkish State Planning Organization [2001K120590]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [105E066, 105A005, 106E198, 106A017]; Turkish Academy of SciencesTurkish Academy of Sciences This work was supported by the Turkish State Planning Organization (Project No. 2001K120590). This work is also supported by TUBITAK under Project Nos. 105E066, 105A005, 106E198, and 106A017. One of the authors (E. O.) also acknowledges partial support from the Turkish Academy of Sciences.

An experimental system was designed, built and used to determine the optical constants of matenals in the Vacuum Ultraviolet region of the electromagnetic spectrum. An optical analysis chamber was designed to mount onto the back end of an existing monochromatic VUV imaging beam system, which covers a wavelength range from 30-200nm. The chamber may accommodate three different expenmental configurations, allowing transmission and reflection measurements to be taken separately or at the same time. A versatile computational analysis system was developed to process the data obtained with this experimental system Recorded CCD images are aligned using a novel interpolation method, and reflection or transmission values are calculated from these. A Kramers-Kromg analysis program was developed and used to obtain a complete set of optical constants in the VUV region if reflection data is available over a sufficiently extensive wavelength range. The absorption coefficient of aluminium in the region between 30 and 85 5nm was determined to demonstrate the capabilities of the suite of expenmental and computational analysis systems. The absorption coefficient of aluminium is shrouded in controversy in this region of the spectrum due to two papers with conflicting results ref [19] & [21].