Blackbody Radiation Source Research Articles

Radiation detectors based on PbSnTe:In films, sensitive in the terahertz range of the spectrum

This paper presents a review of studies of the photoelectric properties of PbSnTe:In films obtained by molecular beam epitaxy and photosensitive structures in the far infrared and submillimeter ranges based on these films. The parameters of photodetector arrays of this type and detectors based on doped semiconductors and superconductors are compared. One-dimensional (2×128 elements) and two-dimensional (128 × 128 elements) PbSnTe:In based arrays with a sensitivity threshold of ~22 μm and an operating temperature of T ≤ 16 K are implemented. Under background-free conditions, the noise equivalent power (NEP) was NEP ≤ 10−18 W/Hz0.5 at T = 7 K for a black body radiation source at TBB = 77 K. In the submillimeter range of the spectrum, sensitivity to laser radiation with a wavelength λ ≤ 205 μm and a value NEP ≤ 10−12 W/Hz0.5 was observed without optimization of the design of the photosensitive element and minimization of the measurement circuit noise. The directions of the development of PbSnTe:In based radiation detectors are considered..

$$-30\,^{\circ }\hbox {C}$$ - 30 ∘ C to $$960\,^{\circ }\hbox {C}$$ 960 ∘ C Variable Temperature Blackbody (VTBB) Radiance Temperature Calibration Facility

A blackbody radiance temperature calibration facility (RTCF) has recently been established at the National Institute of Metrology, China, offering calibration and verification services for variable temperature blackbody (VTBB) radiation sources. The RTCF includes reference VTBBs in the range of \(-30\,^{\circ }\hbox {C}\) to \(960\,^{\circ }\hbox {C}\) and consists of a stirred liquid bath blackbody of \(-30\,^{\circ }\hbox {C}\) to \(80\,^{\circ }\hbox {C}\) and water, cesium, and sodium heat-pipe blackbodies spanning \(50\,^{\circ }\hbox {C}\) to \(960\,^{\circ }\hbox {C}\). In addition, the facility is equipped with a set of radiation thermometers with different working wavelengths (or wavebands); these thermometers are used to transfer radiance temperatures from the reference to customers’ VTBBs. Cavities with V-notch grooves in the inner surface have an estimated emissivity from 0.99986 to 0.99994. The temperature control stability and temperature uniformity of VTBBs are characterized. Furthermore, we test the difference between a cavity and thermometer well temperatures and compare the radiance temperatures of the Cs and Na heat-pipe blackbodies. The expanded uncertainty \((k = 2)\) of VTBBs’ radiance temperatures at \(10~\upmu \hbox {m}\) (\(8~\upmu \hbox {m}\) to \(14~\upmu \hbox {m}\)) is evaluated from \(0.016\,^{\circ }\hbox {C}\) to \(0.23\,^{\circ }\hbox {C}\). The facility has been used to calibrate and characterize customers’ VTBBs.

Comparison of Blackbody Sources for Low-Temperature IR Calibration

Radiation thermometers are traditionally mostly used in high-temperature applications. They are, however, becoming more common in different applications at room temperature or below, in applications such as monitoring frozen food and evaluating heat leakage in buildings. To measure temperature accurately with a pyrometer, calibration is essential. A problem with traditional, commercially available, blackbody sources is that ice is often formed on the surface when measuring temperatures below $$0\,{}^{\circ }\hbox {C}$$ . This is due to the humidity of the surrounding air and, as ice does not have the same emissivity as the blackbody source, it biases the measurements. An alternative to a traditional blackbody source has been tested by SP Technical Research Institute of Sweden. The objective is to find a cost-efficient method of calibrating pyrometers by comparison at the level of accuracy required for the intended use. A disc-shaped blackbody with a surface pyramid pattern is placed in a climatic chamber with an opening for field of view of the pyrometer. The temperature of the climatic chamber is measured with two platinum resistance thermometers in the air in the vicinity of the disc. As a rule, frost will form only if the deposition surface is colder than the surrounding air, and, as this is not the case when the air of the climatic chamber is cooled, there should be no frost or ice formed on the blackbody surface. To test the disc-shaped blackbody source, a blackbody cavity immersed in a conventional stirred liquid bath was used as a reference blackbody source. Two different pyrometers were calibrated by comparison using the two different blackbody sources, and the results were compared. The results of the measurements show that the disc works as intended and is suitable as a blackbody radiation source.

Power Load and Temperature Dependence of Cold-Electron Bolometer Optical Response at 350 GHz

Cold-electron bolometers (CEBs) integrated with twin-slot antennas have been designed and fabricated. Optical response was measured at bath temperatures of 0.06 to 3 K using blackbody radiation source at temperatures of 3 to 15 K. The responsivity of 0.3 * 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> V/W was measured at 2.7-K blackbody temperature that is close to the temperature of the cosmic microwave background. Optical measurements indicate quasi-optical coupling efficiency of up to 60% at low phonon temperature and low signal level. Estimations for bolometer responsivity were made for practical range of bath temperatures and blackbody radiation temperatures. The estimated ultimate dark responsivity at 100-mK bath temperature can approach S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub> = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> V/W and reduces down to 1.1 * 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> V/W at 300 mK for a device with absorber volume of 5 * 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-20</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Challenges in using an analog uncooled microbolometer thermal camera to measure crop temperature

Abstract: It has been long known that thermal imaging may be used to detect stress (e.g. water and nutrient deficiency) in growing crops. Developments in microbolometer thermal cameras, such as the introduction of imaging arrays that may operate without costly active temperature stabilization, have vitalized the interest in thermal imaging for crop measurements. In this study, we have focused on the challenges occurring when temperature stabilization is omitted, including the effects of focal-plane-array (FPA) temperature, camera settings and the environment in which the measurements are performed. Further, we have designed and tested models for providing thermal response from an analog LWIR video signal (typical output from low-cost microbolometer thermal cameras). Finally, we have illustrated and discussed challenges which typically occur under practical use of thermal imaging of crops, by means of three cereal showcases, including proximal and remotely based (UAV) data acquisition. The results showed that changing FPA temperature greatly affected the measurements, and that wind and irradiance also appeared to affect the temperature dynamics considerably. Further, we found that adequate settings of camera gain and offset were crucial for obtaining a reliable result. The model which was considered best in terms of transforming video signals into thermal response data included information on camera FPA temperature, and was based on a priori calibrations using a black-body radiation source under controlled conditions. Very good calibration (r2>0.99, RMSE=0.32°C, n=96) was obtained for a target temperature range of 15-35°C, covering typical daytime crop temperatures in the growing season. However, the three showcases illustrated, that under practical conditions, more factors than FPA temperature may need to be corrected for. In conclusion, this study shows that thermal data acquisition by means of an analog, uncooled thermal camera may represent a possible, cost-efficient method for the detection of crop stress, but appropriate corrections of disturbing factors are required in order to obtain sufficient accuracy. Keywords: analog thermal camera, uncooled microbolometer, canopy temperature, cereals, UAV DOI: 10.3965/j.ijabe.20140704.007 Citation: Kusnierek K, Korsaeth A. Challenges in using an analog uncooled microbolometer thermal camera to measure crop temperature. Int J Agric & Biol Eng, 2014; 7(4): 60－74.

EURAMET Project to Examine Underlying Parameters in Radiance Temperature Scale Realization, $$156\,^{\circ }\mathrm{C}$$ 156 ∘ C to $$1000\,^{\circ }\mathrm{C}$$ 1000 ∘ C

Over the medium temperature range (from \(156\,^{\circ }\mathrm{C}\) to \(1000\,^{\circ }\mathrm{C}\)), radiation thermometry is usually established within a national metrology institute (NMI) by means of variable temperature blackbody radiation sources, whose temperature is determined using a platinum resistance thermometer or thermocouple, calibrated in terms of the International Temperature Scale of 1990 (ITS-90), positioned in close proximity to the back radiating surface of the blackbody. It is also reasonably common to establish a scale using a suitable radiation thermometer, such as an indium gallium arsenide (InGaAs) detector-based narrow band radiation thermometer, calibrated using a number of fixed-point blackbody sources from the indium (In) to silver (Ag) (or copper (Cu)) points, with the calibration results fitted using a parameterized Planckian interpolation function. During 2007 and 2008, two InGaAs-based radiation thermometers were circulated around seven NMIs within the European Association of National Metrology Institutes (EURAMET) region in order to undertake a comparison of parameters necessary for radiation thermometry over the medium temperature range. Measurements were made of the size-of-source effect and gain (range) ratios of the two thermometers along with an assessment of the effect of changes in the ambient temperature and humidity on the thermometer output. The thermometers were also calibrated using fixed-point and/or variable temperature blackbody sources at each institute. A brief overview of the results obtained by this project is presented in this paper.

The in-flight blackbody calibration system for the GLORIA interferometer on board an airborne research platform

Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is a prototype of an imaging Fourier Transform Spectrometer (FTS) for PREMIER, a former candidate mission for ESA's Earth Explorer 7. GLORIA is deployed on board various research aircraft such as the Russian M55 Geophysica or the German HALO. The instrument provides detailed infrared images of the Upper Troposphere/Lower Stratosphere (UTLS) region, which plays a crucial role in the climate system. GLORIA uses a two-dimensional detector array for infrared limb observations in emission and therefore needs large-area blackbody radiation sources (126 mm × 126 mm) for calibration. In order to meet the highly demanding uncertainty requirements for the scientific objectives of the GLORIA missions and due to the sophisticated tomographic evaluation scheme, the spatial distribution of the radiance temperature of the blackbody calibration sources has to be determined with an uncertainty of about 0.1 K. Since GLORIA is exposed to the hostile environment of the UTLS with mutable low temperature and pressure, an in-flight calibration system has to be carefully designed to cope with those adverse circumstances. The GLORIA in-flight calibration system consists of two identical weight-optimised high-precision blackbody radiation sources, which are independently stabilised at two different temperatures. The two point calibration is in the range of the observed atmospheric infrared radiance emissions with 10 K below and 30 K above ambient temperature, respectively. Thermo-Electric Coolers are used to control the temperature of the blackbody radiation sources offering the advantage of avoiding cryogens and mechanical coolers. The design and performance of the GLORIA in-flight calibration system is presented. The blackbody calibration sources have been comprehensively characterised for their spatially (full aperture) and spectrally (7 to 13 μm) resolved radiation properties in terms of radiance temperatures traceable to the International Temperature Scale (ITS-90) at the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany.

Time-dependent calculations of electron energy distribution functions for cold argon gas in the presence of intense black-body radiation

Boltzmann electron kinetic simulations are performed to study the time development of the electron energy distribution in a plasma resulting from a cold argon gas subject to a black-body radiation source (100–300 eV). The study provides insight into the role of ionized electrons on the kinetics during a period of irradiation. The simulations are performed without any assumptions of electron temperature. The distributions are calculated as a function of time through 1 ps using Boltzmann kinetics, including the appropriate processes that alter state populations and electron energy. The processes included in the electron and atomic kinetics are collisional excitation/de-excitation, photo-excitation/decay, photo-ionization/radiative-recombination, collisional ionization and auto-ionization/di-electronic capture. In addition, terms are included in the electron kinetics to account for electron–electron interactions and for free–free radiation absorption and emission. Results are presented that follow the evolution of the ionization state, effective temperature as well as the electron energy distribution function. The role of inelastic electron collisions, photo-ionization, auto-ionization, resonant radiative excitation and electron–electron interactions is discussed.

Numerical Simulation of the Flow of Inflatable Cover Based on FLUENT

The inflatable cover was used in the low-temperature blackbody radiation source; the function of the external gas separation had great influences on blackbody radiation source performances. This paper presents a new way for performing numerical simulation for the three-dimensional inner flow field analysis of new inflatable cover and blackbody radiation source cavity by using the FLUENT software of CFD. By comparison, the simulation results and the acetone tracer particle experiments revealed the reason of the outside air into the cavity caused frost and dew, so we proposed a number of methods to reduce air convection inside and outside of the cavity for the using inflatable cover, and it gave theoretical basis guidance for the next optimal design of the new inflatable cover.

Metal-Grating-Coupled Terahertz Quantum-Well Photodetectors

Three terahertz (THz) GaAs/AlGaAs quantum-well photodetectors with different 1-D metal gratings are fabricated for front-incident detection of THz waves. Photocurrent spectra are acquired and compared with 45° incident facet samples (without grating), and peak responsivities are determined with a calibrated blackbody radiation source. The results show that these gratings can couple THz waves into detectors effectively, resulting in good detector responsivities. The modal method is employed to simulate the light coupling efficiency and the optimization conditions of the gratings.

Final report on APMP key comparison of local realization of ITS-90 above the silver point using radiation thermometers as transfer standards, APMP-T-K5-97

In key comparison APMP.T-K5, a radiation thermometer was used as a transfer standard for radiance temperature measurements at a blackbody radiation source or a standard lamp at nominal temperatures Tnom from 962 °C to 2800 °C. The transfer standard was hand-carried from the pilot laboratory, NMIJ (Japan), to a participant where it was compared with the participant's standard within the range from 962 °C to 2800 °C and was returned to the pilot laboratory. In the case of the blackbody comparison, a copper-point blackbody was carried along with the thermometer to ensure the thermometer stability. The pilot calibrated the thermometer before and after each transport. Seven institutes joined the comparison: KRISS, NIM, NMIA, NMIJ, A*STAR, KIM-LIPI and CMS/ITRI. Five institutes participated in both key comparisons CCT-K5 and APMP.T-K5, and among them four institutes acted as the linking laboratories: KRISS, NIM, NMIA and NMIJ. The linkage process is described in the Addendum of the APMP-T-K5 Final Report.The degree of equivalence of each laboratory with respect to the CCT-K5 key comparison reference value, TR, is given by a pair of terms: Di = (Ti − TR) and Ui, its expanded uncertainty (at 95% confidence level), both expressed in kelvin. This uncertainty includes the uncertainties in the original laboratory calibrations, the standard deviation of the average difference, the uncertainties of the key comparison reference values and of the link between the APMP and CCT key comparison from 962 °C to 1700 °C. From 1800 °C to 2800 °C the APMP reference value was determined from the average of the participating laboratories including the pilot.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

InAs/GaSb 응력초격자를 이용한 적외선검출소자의 제작 및 특성 연구

150 주기의 InAs/GaSb (8/8-ML) 제2형 응력초격자 (SLS)를 활성층에 탑재한 초격자 적외선검출소자 (SLIP) 구조를 MBE 방법으로 성장하고, 직경 <TEX>$200{\mu}m$</TEX>의 개구면을 가지는 SLIP 개별소자를 시험 제작하였다 고분해능 투과전자현미경 (TEM) 이미지의 휘도분포와 X선회절 (XRD) 곡선의 위성피크의 분석 결과는 SLS 활성층은 균일한 층두께와 주기적 응력변형을 유지하는 급격한 계면의 초격자임을 입증하였다. 흑체복사 적외선 광원을 이용하여 측정한 입사파장 및 인가전압에 따른 반응도 (R)와 검출률 (<TEX>$D^*$</TEX>)로부터, 차단파장은 <TEX>${\sim}5{\mu}m$</TEX>이고 최대 R과 <TEX>$D^*$</TEX> (<TEX>$\lambda=3.25{\mu}m$</TEX>)는 각각 <TEX>${\sim}10^3mA/W$</TEX> (-0.6 V/13 K)와 <TEX>${\sim}10^9cm.Hz^{1/2}/W$</TEX> (0 V/13 K)임을 보였다. 반응도의 온도의존성으로부터 분석한 활성화에너지 275 meV는 광반응 과정에 개입되어 있는 가전대 및 전도대 부준위 사이의 에너지 간격 (HH1-C)과 잘 일치하였다. The superlattice infrared photodetector (SLIP) with an active layer of 8/8-ML InAs/GaSb type-II strained-layer superlattice (SLS) of 150 periods was grown by MBE technique, and the proto-type discrete device was defined with an aperture of <TEX>$200-{\mu}m$</TEX> diameter. The contrast profile of the transmission electron microscope (TEM) image and the satellite peak in the x-ray diffraction (XRD) rocking curve show that the SLS active layer keeps abrupt interfaces with a uniform thickness and a periodic strain. The wavelength and the bias-voltage dependences of responsivity (R) and detectivity (<TEX>$D^*$</TEX>) measured by a blackbody radiation source give that the cutoff wavelength is <TEX>${\sim}5{\mu}m$</TEX>, and the maximum Rand <TEX>$D^*$</TEX> (<TEX>$\lambda=3.25{\mu}m$</TEX>) are <TEX>${\sim}10^3mA/W$</TEX> (-0.6 V/13 K) and <TEX>${\sim}10^9cm.Hz^{1/2}/W$</TEX> (0 V/13 K), respectively. The activation energy of 275 meV analyzed from the temperature dependent responsivity is in good agreement with the energy difference between two SLS subblevels of conduction and valence bands (HH1-C) involving in the photoresponse process.

NIST Radiance Temperature and Infrared Spectral Radiance Scales at Near-Ambient Temperatures

The realization and the dissemination of spectral radiance and radiance temperature scales in the temperature range of −50 to 250°C and spectral range of 3–13 μm at the National Institute of Standards and Technology are described. The scale is source-based and is established using a suite of blackbody radiation sources, the emissivity and temperature of which have been thoroughly investigated. The blackbody emissivity was measured using the complementary approaches of modeling, reflectometry, and the intercomparison of the spectral radiance of sources with different cavity geometries and coatings. Temperature measurements are based on platinum resistance thermometers and on the direct use of the phase transitions of pure metals. Secondary sources are calibrated using reference blackbody sources, a spectral comparator, a controlled-background plate, and a motion control system. Included experimental data on the performance of transfer standard blackbodies indicate the need for development of a recommended practice for their specification and evaluation. Introduced services help to establish a nationwide uniformity in metrology of near-ambient thermal emission sources, providing traceability in spatially and spectrally resolved radiance temperature, spectral radiance, and background-corrected effective emissivity.

Two-color time-resolved LII applied to soot particle sizing in the cylinder of a Diesel engine

Laser-induced incandescence with time-resolved detection (TR-LII) at two wavelengths was established and applied to the combustion chamber of a single-cylinder two-stroke Diesel engine. The optical system was calibrated by a black-body radiation source. TR-LII signals for different crank angles and varying engine operation conditions were measured. By fitting calculated TR-LII cooling curves to the measured signals, it was possible to determine the mean primary particle diameter and the geometric standard deviation of the in-cylinder particles for an assumed lognormal size distribution. At the beginning of the combustion process the resulting particle sizes increased with increasing crank angle (CA) according to particle formation. This was followed by a subsequent reduction of the particle sizes at later crank angles due to particle oxidation. In all examined cases the mean particle sizes increase with increasing engine load. For validation purposes, soot samples from the exhaust gas were taken onto transmission electron microscopy (TEM) grids for different engine operating conditions and were analyzed by TEM. For the obtained loose agglomerated particle structures, the particle sizes at late crank angles measured by TR-LII are in excellent agreement with the TEM-determined mean primary particle sizes in the exhaust gas. Finally, soot volume fractions were determined from the maximum TR-LII signals via calibration by in-cylinder laser-extinction measurements.

Terahertz magneto-optic generalized ellipsometry using synchrotron and blackbody radiation

We report on the first setup and experimental verification of terahertz frequency domain magneto-optic generalized ellipsometry using a combination of highly brilliant terahertz synchrotron and conventional blackbody radiation sources. The polarizer-sample-rotating-analyzer ellipsometry principle is employed to measure the three normalized Stokes vector elements excluding depolarization information, and the upper left 3×3 block of the normalized 4×4 Mueller matrix accordingly for wave numbers from 30to650cm−1 (0.9–20THz). We discuss setup, measurement, and data analysis procedures specific to the use of synchrotron radiation for terahertz ellipsometry. Two sample systems with different free-charge-carrier properties were studied and are presented here to illustrate terahertz ellipsometry and data analysis. The first example is low-chlorine-doped ZnMnSe, a dilute magnetic semiconductor. Analysis of the normalized Mueller matrix elements using the Drude magneto-optic dielectric function tensor model over the entire spectral range from 30to650cm−1 allowed the independent determination of the free-charge-carrier properties effective mass, concentration, and mobility. We further present and discuss Mueller matrix spectra obtained from highly oriented pyrolytic graphite at low temperatures. The spectra of this second example, a two-dimensionally confined charge carrier system, reveal distinct fingerprints of chiral electronic transitions between Landau levels.

Conduction-band electron effective mass in Zn0.87Mn0.13Se measured by terahertz and far-infrared magnetooptic ellipsometry

We determine the electron effective mass parameter m*=0.086±0.004m0 of thin-film n-type low-chlorine-doped Zn0.87Mn0.13Se with free-charge-carrier concentration N=4.5×1017cm−3 and optical mobility μ=300±20cm2∕(Vs) using magneto-optic generalized ellipsometry in the terahertz and far-infrared spectral domain for wave numbers from ω=30–650cm−1. The room-temperature measurements were carried out with magnetic fields up to 3 T. We employ synchrotron and black-body radiation sources for the terahertz and far-infrared spectral regions, respectively. Comparison with previous experimental results from samples with considerably higher free electron density and theoretical calculations suggest that our value is sufficiently unaffected by band nonparabolicity and provides a good approximation of the Γ-point conduction band mass in Zn0.87Mn0.13Se. We further provide optical phonon mode parameters and the high-frequency dielectric constant.

Application of the blackbody radiation source for characteristics measurement of submillimeter low-temperature direct detectors

As is well-known characteristics measurement of submillimeter low-temperature direct detectors can be fulfilled using their signal response for the radiation of temperature swept blackbody. We describe a method using the Fredholm integral equation of first kind which solution gives possibility to derive direct detector spectral characteristic from the signal response dependence on temperature with acceptable accuracy. Then a noise equivalent power of detector can be determined as well.

Reference Blackbody Sources in the 100–3500 K Range for Precision Measurements in Radiometry, Photometry, and Optical Thermometry

A wide range of precise blackbody radiation sources that cover the entire optical wavelength range from IR to near-UV at working temperatures from 80 to 3500 K and provide highly stable and uniform radiation has been developed at VNIIOFI. The unique characteristics of blackbody sources have made them the basis of national primary measurement standards and precision calibration facilities in Russia as well as other in world-leading metrology centers in USA, Germany, UK, France, China, and other countries.

The Use of Cathodoluminescence in Gallium Nitride During Growth to Determine Substrate Temperature

AbstractThe Use of Cathodoluminescence in Gallium Nitride During Growth to Determine Substrate Temperature Accurate measurement of the substrate temperature during growth of gallium nitride by molecular beam epitaxy is crucial. Typically, thermocouples are usually used to measure the temperature of the back side of block which is holding the substrate. Alternatively, pyrometers are often used. However, there is a big range of an error. In-situ cathodoluminescence (CL) occurring during reflection high energy electron diffraction is a strong candidate to determine the growth temperature. The electron beam supplied by our RHEED gun has an energy of 13keV which was used for each measurement. CL was easily detected up to and beyond typical growth temperatures. The CL was directed into a monochromator using fiber optics. The final signal was detected with a photomultiplier tube. This technique appears quite useful to accurately and reproducably determine substrate temperature during growth.The CL could also be observed using a ccd camera. Thus, we investigated using the CL to image the sample during growth. This could be used to see temperature inhomogenaities, and potentially to map alloy composition fluctuations. We calibrated the wavelength vs. growth temperature by using narrow band-pass interference filters. Background subtraction with blanking the e-beam could be used to remove black body radiation and other undesired sources of light. For gallium nitride, the photon energy at the growth temperature of 750°C is about 3.0eV. Using different filters, we can take a picture of e-beam on the surface of substrate for each filter and analyze the peak intensity using the line profile. We will present CL images of various samples at differing temperatures.This work was supported by the AFOSR MURI F49620-03-1-0330 monitored by Todd Steiner and Gerald Witt and by ONR Grants N00014-02-1-0974 and N00014-01-1-0571, both monitored by Colin E. C. Wood.

Effects of Periodic Structures on the Coherence Properties of Blackbody Radiation

Radiative properties have been studied for one-dimensional dielectric multilayer structures subjected to blackbody radiation sources. The total hemispherical transmittances are calculated for periodic structures and structures with random variation in layer thickness, using wave-optics and ray-tracing methods. Simulation results show that for periodic structures, the transmittance calculated using wave optics approaches a nonzero constant value with an increasing number of layers, while the transmittance obtained using the ray-tracing method asymptotically approaches zero. For random structures, the transmittance given by wave optics drops to zero at different rates depending on the order of random variations in layer thickness. It is found that the wave interference effect always plays a role when dealing with multilayer structures. The results are explained based on extended and localized waves.