Continuous-Wave, All-Solid-State, Single-Frequency 400-mW Source at 589 nm Based on Doubly Resonant Sum-Frequency Mixing in a Monolithic Lithium Niobate Resonator

Sum-frequency mixing of two cw single-mode Nd:YAG lasers in a doubly resonant congruent lithium niobate resonator generated two TEM(00) beams of single-frequency 589-nm radiation. The primary beam had a power of 400 mW and the secondary beam of approximately 15 mW by use of 320 mW of 1319-nm and 660 mW of 1064-nm Nd:YAG radiation incident on the lithium niobate resonator. This corresponds to an optical power conversion efficiency of more than 40%.     

Broadly Tunable, Mode-Hop-Tuned cw Optical Parametric Oscillator Based on Periodically Poled Lithium Niobate

We describe a broadly tunable, cw optical parametric oscillator (OPO) based on periodically poled lithium niobate. The OPO can be tuned over a broad region in the mid IR (2900-3100 cm(-1)) covering the important C-H stretch region while a high spectral resolution (<0.1 cm(-1)) is maintained. The OPO is the light source for a field-portable photoacoustic spectrometer for gas-phase monitoring of volatile organic compounds.     

Optical properties of apple skin and flesh in the wavelength range from 350 to 2200 nm

Optical measurement of fruit quality is challenging due to the presence of a skin around the fruit flesh and the multiple scattering by the structured tissues. To gain insight in the light-tissue interaction, the optical properties of apple skin and flesh tissue are estimated in the 350-2200 nm range for three cultivars. For this purpose, single integrating sphere measurements are combined with inverse adding-doubling. The observed absorption coefficient spectra are dominated by water in the near infrared and by pigments and chlorophyll in the visible region, whose concentrations are much higher in skin tissue. The scattering coefficient spectra show the monotonic decrease with increasing wavelength typical for biological tissues with skin tissue being approximately three times more scattering than flesh tissue. Comparison to the values from time-resolved spectroscopy reported in literature showed comparable profiles for the optical properties, but overestimation of the absorption coefficient values, due to light losses.     

Transfer of Frequency Stability from an Atomic Frequency Reference to a Quartz-Crystal Oscillator

This paper presents a study of the transfer of frequency stability from an atomic reference to a quartz-crystal oscillator. The study is done for the cases of active and passive atomic frequency standards in which one makes use of a phase-lock loop and of a frequency-lock loop, respectively. The analysis is made in both the frequency and time domains and covers the cases of the hydrogen and rubidium masers and the passive cesium-and rubidium-frequency standards. The results obtained from numerical calculations are presented under the form of graphs. These results include the fractional frequency spectral density Sy(f) as a function of the Fourier frequency f, and the two sample variance ?2(?) as a function of ?, the sampling time.     

Optical frequency standard by using a 1560 nm diode laser locked to saturated absorption lines of rubidium vapor

A robust, compact, highly accurate rubidium optical frequency standard module was developed to overcome the delicate performance of conventional frequency stabilized lasers. A frequency doubled 1560 nm distributed feedback diode laser locked to a rubidium D(2) saturated absorption line without using an optical amplifier was demonstrated, and dithering-free optical output was obtained. In addition, the sensitivity of the developed optical frequency standard to magnetic fields was investigated. We confirmed that the influence of the magnetic fields on the optical frequency standard can be almost negligible when using appropriate magnetic-shield films. As a result, the magnetic-field-insensitive optical frequency standard, which can be embedded in optical systems, exhibiting uncertainty less than at least 100 kHz, was successfully realized for the first time to the best of our knowledge.     

Optical calibration from tens to hundreds of meters for a neutrino telescope

A critical review of the available optical calibration techniques is given in the context of the Neutrino Burst Experiment. We will discuss the effects of the optical properties of water on different candidate light sources and the challenges from an engineering point of view. The merits of candidate light sources will be compared.     

Useful Algorithms to Derive the Optical Properties of Clouds from a Back-scatter Lidar Return

Abstract

The main algorithms for back-scatter lidar equation inversion have been studied and compared in order to find the most appropriate methods for cloud optical parameter determination. Two efficient and complementary methods have been selected: Platt's method is used for optically thick clouds, while a new method, named the back-slope method, is used for optically thin clouds. The two methods can determine an average back-scatter-to-extinction ratio, the optical depth, and the back-scatter and extinction coefficients for clouds.     

Simultaneous Optical Tuning of Hole and Electron Transport in Ambipolar WSe2 Interfaced with a Bicomponent Photochromic Layer: From High-Mobility Transistors to Flexible Multilevel Memories

The interfacing of 2D materials (2DMs) with photochromic molecules provides an efficient solution to reversibly modulate their outstanding electronic properties and offers a versatile platform for the development of multifunctional field-effect transistors (FETs). Herein, optically switchable multilevel high-mobility FETs based on few-layer ambipolar WSe₂ are realized by applying on its surface a suitably designed bicomponent diarylethene (DAE) blend, in which both hole and electron transport can be simultaneously modulated for over 20 cycles. The high output current modulation efficiency (97% for holes and 52% for electrons) ensures 128 distinct current levels, corresponding to a data storage capacity of 7 bit. The device is also implemented on a flexible and transparent poly(ethylene terephthalate) substrate, rendering 2DM/DAE hybrid structures promising candidates for flexible multilevel nonvolatile memories.     

A method for the measurement of thin film optical constants with a spectral photometer from 230 nm to 850 nm and its application to plasma silicon (oxy) nitride

A technique to measure the complex index of refraction of thin solid films in the visible and near-UV range with a spectral photometer using polarized light is introduced. The complex index of refraction of amorphous silicon (oxy)nitride films deposited in a glow discharge with different gas flow ratios of NH₃:SiH₄ and N₂O:SiH₄ at 270°C was measured as a function of wavelength. The real part of the index of refraction at 632.8 nm of the films investigated varies from 1.5 to 2.5. The results could be confirmed by scanning ellipsometry.     

Optical properties and size distribution of aerosols derived from simultaneous measurements with lidar, a sunphotometer, and an aureolemeter

A new method is proposed to derive the optical properties and size distribution of aerosol in an air column from simultaneous measurements of the backscattering coefficient, the optical thickness, and the solar aureole intensity with lidar, a sunphotometer, and an aureolemeter. Inasmuch as the backscattering properties and the optical thickness depend on both the complex refractive index and the size distribution, whereas the forward-scattering properties depend mainly on the size distribution, real and imaginary indices of refraction and size distributions of aerosol are retrieved from these measurements. The real and the imaginary parts of the complex refractive index of an aerosol at a wavelength of 500 nm during the period from November 1991 to March 1992 obtained in Tsukuba, Japan, were estimated to be 1.46-1.48 and 0.005-0.014, respectively. It is inferred from the size distribution and an optical thickness fraction of stratospheric aerosols in the total columnar aerosols that these results reflect the influences of stratospheric aerosols that originated from the Mt. Pinatubo eruption.     

Continuous calibration of a vacuum ultraviolet system from 65 to 125 nm by a cascade arc and comparison with the calibrated line radiation of a hollow cathode

A high-power stationary helium cascade arc has been developed as a standard source for continuum radiation in the VUV spectral range from 65 to 125 nm. The calibration of the VUV system response was based on the calculated and measured continuum radiation of a 2-mmphi pure He arc. Diagnostics of the arc plasma in partial thermal equilibrium yielded the electron density and the temperature that were inserted in the calculations of the continuous radiation. The results were compared with the helium, argon, and krypton radiation lines of a high-current hollow cathode lamp. This lamp was built according to the construction drawings of a hollow cathode, which was calibrated by means of the electron synchrotron radiation at the Physikalisch Technische Bundesanstalt Berlin.     

High-accuracy measurements of the refractive index and its temperature coefficient of calcium fluoride in a wide wavelength range from 138 to 2326 nm

The refractive indices of synthetic calcium fluoride for 69 wavelengths from 138 nm in the deep ultraviolet to 2326 nm in the near infrared were measured by the minimum-deviation method in a nitrogen environment. We made these measurements at 20 degrees and 25 degrees C, respectively, to determine the thermal coefficients of the refractive index over this wide-wavelength region. These refractive indices were fitted to a four-term Sellmeier dispersion formula. The temperature coefficients of the refractive index were fitted to a Hoffman-type dispersion formula. The standard deviation of the residual between the observed values and the calculated values was 0.6 x 10(-6) for the refractive index and was 0.13 x 10(-6)/degrees C for the temperature coefficient of the refractive index.     

Correction to: Optical and photovoltaic properties of vacuum evaporated CZTSe,CAZTSe and AZTSe thin films: a comparative study

Journal of Materials Science: Materials in Electronics - The original version of this article unfortunately contained mistakes.     

Computation of the Optical Constants of a Thin Dielectric Layer from the Envelopes of the Transmission Spectrum,at Inclined Incidence of the Radiation

Abstract

A mathematical expression for the transmission of a thin dielectric layer on a transmitting substrate is found. The finite dimensions of the substrate and its absorption are taken into account. The cases of inclined incidence of non-polarised, s- and p-polarised radiation to the layer are investigated. A way of determining the optical constants n(λ) and k(λ) of the layer from the envelopes of the transmission spectrum is offered. Computation of n(λ) and k(λ) of a model optical system at different angles of radiation incidence is performed as well as analysis of the results obtained.     

Radiance Temperatures and Normal Spectral Emittances (in the Wavelength Range of 1500 to 5000 nm) of Tin, Zinc, Aluminum, and Silver at Their Melting Points by a Pulse-Heating Technique

The radiance temperatures at four wavelengths (in the range of 1500 to 5000 nm) of tin, zinc, aluminum, and silver at their respective melting points were measured by a pulse-heating technique using a high-speed fiber-coupled four-wavelength infrared pyrometer. The method is based on rapid resistive self-heating of a sample from room temperature to its melting point in less than 1 s while measuring the radiance emitted by it in four wavelength bands as a function of time. A plateau in the recorded radiance-versus-time traces indicates melting of the sample. The melting-point radiance temperatures for a given sample are determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal are, in turn, determined by averaging results for several samples. The normal spectral emittances at the melting transition of each metal are derived from the measured radiances at each wavelength and the published values of the thermodynamic (true) melting temperatures.     

Effect of constituent particle polydispersion on VSSA-based equivalent particle diameter: Theoretical rationale and application to a set of eight powders with constituent particle median diameters ranging from 9 to 130 nm

Volume Specific Surface-Area (VSSA) has been identified as a relevant and alternative method to electron microscopy (EM) to determine whether a material is or not a nanomaterial. VSSA is an integral measurement method that provides an indirect representation of particle size. When this conversion into particle diameter is carried out, constituent particles are supposed to be monodisperse, which can be considered far from reality, materials being composed of polydisperse constituent particles. The way particle polydispersion affects the VSSA of a material, and thus the equivalent particle diameter deduced, is investigated in this paper. In particular, the specific case of normally-distributed, spherical constituent particles, is considered. A theoretical study has led to the introduction of a correction polydispersion-based factor. From experimental VSSA data obtained for eight powders covering a range of constituent particle median diameters from 9 to 130 nm, the VSSA-based constituent particle median diameters were compared to the median constituent particle size obtained from electron microscopy analysis, considered as the reference method. Integrating constituent particle polydispersion through the use of the correction factor improves the accuracy of particle size stemming from the VSSA approach, the relative discrepancies being within ±20% from the reference diameter.     

Method of thermoluminescent measurement of radiation doses from micrograys up to a megagray with a single LiF:Mg,Cu,P detector

On the basis of the newly discovered behaviour of LiF:Mg,Cu,P detectors at high and ultra-high doses, a new method of thermoluminescence (TL) measurement of radiation doses ranging from micrograys up to a megagray, has been recently developed at the Institute of Nuclear Physics (IFJ). The method is based on the relationship between the TL signal, integrated in the given temperature range and dose. It is quantified by a parameter called the 'ultra-high temperature ratio'. It has been demonstrated that this new method can measure radiation doses in the range of about 1 μGy to 1 MGy, using a single LiF:Mg,Cu,P detector. This method was recently successfully blindly tested for 10 MeV electrons up to doses of 200 kGy. It can be used for dosimetry in high-energy accelerators, especially in the Large Hadron Collider at CERN, and has great potential for accident dosimetry in particular.     

Multivariate statistical analysis of the bibliographic output from a research institution,in relation to the measures of scientific policy

The publications produced in a medical research institute in a 16 year interval were classified into five categories (scientific papers in the journals covered byCurrent Contents orScience Citation Index, scientific papers in other journals, books and monographs, technical papers, congress and symposia communications) and counted for each year separately. The number of researchers and yearly budgets were also recorded. The data were analysed by contingency table, correlation and factor-analytical methods. It was shown that, upon introducing quantitative minimal criteria for job promotions, the proportion of scientific papers increased. Principal component analysis indicated that the data can be approximately represented as linear combinations of three mutually independent factors. The approach used is recommended for evaluating the production of scientific information in research institutions and for assessing the effects of the measures of scientific policy.