Detection Wavelength Range Research Articles

Characteristics of non-annealed λ = 1.35 μm closely lattice-matched GaInNAs/GaAs p-i-n photodetector structures grown by solid-source molecular beam epitaxy

The electrical and optical characteristics of planar non-annealed GaInNAs/GaAs p-i-n photodetector structures with 0.5 μm thick GaInNAs i-layer with nitrogen composition higher than 3% and detection wavelength up to 1.35 μm are reported. Soft-breakdown behavior in the reverse biased characteristic was observed under non-illuminated condition. Analysis of the reverse biased current dependence on detector diameter under non-illuminated condition shows a more significant contribution from the bulk generation current compared to surface recombination current. Under forward bias, the ideality factor value of 1.35 is found to be temperature independent. This suggests that the recombination current in the depletion region contributes significantly to the forward biased current besides the diffusion current. Low-temperature (4 K) photoluminescence (PL) from the GaInNAs layer shows an emission peak at λ = 1.29 μm. From curve fitting of the photoresponsivity spectrum, the room-temperature bandgap of E g,RT = 0.92 eV (or λ = 1.35 μm) is deduced. The room-temperature photoresponsivity spectrum shows a broad wavelength detection range of up to λ = 1.4 μm.

B(2)A(')-X(2)A(') detection of vibrationally excited HCO produced by the O((3)P)+C(2)H(4) reaction.

The distribution of rotational and vibrational energy in HCO produced by the O((3)P)+C(2)H(4) reaction has been measured using laser-induced fluorescence detection via the B(2)A(')-X(2)A(') transition. Over a detection wavelength range of 248-290 nm, our experiments have shown that HCO is formed in both the ground state and in at least six vibrationally excited states with up to two quanta of energy in the C-O stretch and the bending mode. Dispersed fluorescence experiments were conducted to positively assign all of the HCO vibrational bands. The experiments confirmed that many bands, including the B(000)-X(000) band, are affected by overlap with other HCO bands. Spectral modeling was used to separate the contributions of overlapping HCO B-X bands and to determine a nascent HCO rotational temperature of approximately 600 K, corresponding to approximately 6% of the total energy from the O((3)P)+C(2)H(4) reaction. HCO vibrational distributions were determined for two different average collision energies and were fit with vibrational temperatures of 1850+/-80 K and 2000+/-100 K, corresponding to approximately 15% of the total energy. The observed Boltzmann distribution of vibrational energy in HCO indicates that HCO and CH(3) are formed by the dissociation of an energized intermediate complex.

Thermal imaging system applying two‐color thermometry

AbstractThis study proposes a new thermal imaging system using the principle of two‐color thermometry to determine the temperature of objects. The system can provide a thermal image of objects without being assigned their emissivity. Applying two‐color thermometry to a thermograph is performed by dividing the detectable wavelength range of a radiation detector into two different ranges using respective bandpass filters. A thermal image is constructed from the two energy distributions of radiation which are measured after passing through each filter. In this study, in order to evaluate the accuracy of imaged temperature in the present system, an error analysis for imaged temperature is carried out and the accuracy of the imaged temperature in the present system is compared with those in a conventional thermograph. This study also demonstrates the performance of the present system by imaging the temperature of objects with different emissivities and at different temperatures. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(6): 473–488, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10104

Characterization of III-nitride Based Schottky UV Detectors with Wide Detectable Wavelength Range (360–10 nm) using Synchrotron Radiation

ABSTRACTCharacterizations of transparent Schottky barrier GaN and AlGaN UV detectors in the vacuum UV (VUV) and soft X-ray (SX) region using synchrotron radiation are described. In the GaN UV detectors, the responsivity achieved about 0.05 A/W at 95 eV (13 nm). Thus, their device performance is shown between 3.4 and 100 eV (10 and 360 nm). Furthermore, the high responsivity spectra were realized by using AlGaN Schottky UV detectors consisting of Al0.5Ga0.5N on AlN epitaxial layer.

Thermal Imaging System Applying Two-Color Thermometry.

This study proposes a new thermal imaging system using the principle of two-color thermometry to determine the temperature of objects. The system can provide a thermal image of objects without being assigned their emissivity. Applying two-color thermometry to thermography is performed by dividing the detectable wavelength range of a radiation detector into two different ranges using respective band-pass filters. A thermal image is constructed from the two distributions of radiation energy which are measured after passing through each filter. In this study, in order to evaluate the accuracy of imaged temperature in the present system, an error analysis for imaged temperature are carried out and the accuracy in the present system is compared with those in a conventional thermography. This study also demonstrates the performance of the present system by imaging the temperature of objects with different emissivities and at different temperatures.

Proposal for a new electron temperature diagnostic for fusion reactors

The possibility of determining the plasma electron temperature by measuring the depolarization of the radiation scattered by the high temperature fusion reactor plasma is explored in this article. A numerical calculation based on the theory of the article [Sov. J. Plasma Phys. 7, 669 (1981)] in the case of 90° scattering, with the incident radiation linearly polarized and the polarization plane at 45° with respect to the scattering plane, is carried out. The result is that there is a one to one relationship between plasma electron temperature and depolarization, being independent from the detection wavelength. As an example electron density and temperature of 1020 m−3 and 20 keV, respectively, are taken, a wavelength and energy of the incident radiation pulse of 1064 nm and 8 J, respectively, and for a wavelength detection range of 1050–660 nm, a depolarization value of 0.19 and an estimated error on it of 1.7% are found, if the scattering volume is 2 cm long and the collection solid angle is 7.85×10−3 sr. A prototype of the diagnostic apparatus based on beamsplitting Thompson prism is proposed.

The influence of the spectral emissivity on the signal phase at photothermal radiometry

Photothermal radiometric (PTR) measurements from paint coated samples are compared with calculations taking into account the real ir spectrum of the coating. The photothermal signal phase was found to depend sensitively on the detected wavelength range. This fact has to be taken into consideration for the interpretation of PTR measurements.

Optical devices from AlGaAs-GaAs HBTs heavily doped with amphoteric Si

A new optoelectronic multifunctional device, having triple function of light emission, detection and amplification have been developed and some preliminary integrated circuits are demonstrated. The devices consist of N-p-n or N-P-n AlGaAs-GaAs HBT utilizing amphoteric Si heavily-doped GaAs or AlGaAs p-type base layer. Maximum current gain of 3600, and light output power of about 0.17 /spl mu/W with 100 /spl mu/A base current (I/sub b/) in transistor mode operation and of about 10 /spl mu/W with I/sub b/=40 mA in diode mode operation are obtained. The optical emission wavelengths in both are about 0.85-0.86 /spl mu/m. Optical gain of about 130 was obtained near the 0.86 /spl mu/m wavelength as a detection transistor. Spectrum matching between emission and detection wavelength range is achieved. Some monolithic integrated circuits constituted of the transistors are proposed and demonstrated successfully. The relationship between current gain and radiative quantum efficiency at the transistor operation is also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spectral-luminosity functions, scalar linearity, and chromatic adaptation

We report data for three experiments that assess the effect on the luminosity function of chromatic adaptation arising from the measurement stimuli. First, we report spectral-sensitivity functions (wavelength range, 510-640 nm) measured by heterochromatic flicker photometry for a luminance range of 25-5000 Td. The data were fitted to a linear combination of cone fundamentals. The data narrowed and the fits deteriorated with an increase in luminance level, which indicates that at high luminances chromatic adaptation that is dependent on the spectral composition of the standard and test lights is a factor in spectral-luminosity determination. Second, we report heterochromatic modulation photometry as measured with two spectral lights at constant time-averaged chromaticity and luminance for luminances from 1.6 to 1300 Td. For a time-averaged chromaticity of 570 nm, the red-green ratio of the photometric match was invariant with luminance. For a time-averaged chromaticity of 605 nm, the red-green ratio increased by almost 0.3 log unit for a 2-log-unit increase in luminance, which is indicative of chromatic adaptation to the 605-nm chromaticity. Third, we measured flicker increment detection (wavelength range, 510-640 nm) on 570- and 605-nm backgrounds of 25-5000 Td. The data were fitted to a linear combination of cone fundamentals and showed good fits at all luminances. Fits to the 570-nm-background data set showed little variation in the proportions of the cone fundamentals with luminance. Fits to the 605-nm-background data set required an increased weighting of the middle-wavelength-sensitive cone with luminance. These three experiments indicate that luminance-dependent variation in the spectral-luminosity function as assessed by flicker techniques is caused primarily by chromatic adaptation to the measurement stimuli.

Pigment organization and energy transfer in green bacteria. 3. Picosecond energy transfer kinetics within the B806-866 bacteriochlorophyll a antenna complex isolated from Chloroflexus aurantiacus

The B806-866 antenna protein complex from Chloroflexus aurantiacus has been isolated using the detergents lauryldimethylamine N-oxide (LDAO) and Deriphat-160. These preparations have been characterized spectroscopically. While the B806-866 complex was unstable for longer periods in 0.1% LDAO a high stability was observed when 0.1% Deriphat-160 was used as a detergent. In order to study the energy-transfer processes between the 806 and 866 nm absorbing excited states, fluorescence decays were measured with picosecond resolution in the detection wavelength range from 800 to 910 nm upon excitation at 790 nm. A fast energy transfer from the 806 nm to the 866 nm absorbing states was resolved, and was found to have an equilibration time of 5 ± 1 ps. This equilibration time is in line with previous estimates from steady-state fluorescence. Due to the fast equilibration time, resolution of this energy-transfer process has not been achieved in the past when measuring whole cells of C. aurantiacus.

A new concept silicon homojunction infrared sensor

A new silicon photovoltaic infrared sensor is proposed. Its basic operational principle is demonstrated. The sensor consists of three regions with a homojunction structure, having a flexibly designed barrier height corresponding to the cutoff wavelength. The operation of the sensor is based on infrared absorption and internal photoemission by free electrons in a conduction band in degenerate n/sup ++/-type silicon. The fabricated sensors have verified the basic operational principle and have shown that the detectable wavelength range extends to over 12 mu m.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Picosecond energy transfer kinetics between pigment pools in different preparations of chlorosomes from the green bacterium Chloroflexus aurantiacus Ok-70-fl

Decay-associated (time-resolved) fluorescence spectra of isolated bacteriochlorophyll (BChl) a-containing and BChl a-free chlorosomes were measured using a picosecond single-photon timing apparatus in the detection wavelength range 730 – 820 nm. Two different relaxation steps can be resolved in the energy transfer chain. The first relaxation step occurs within the main BChl c pigment pool and the other is due to the energy transfer from one BChl c pool to the BChl a pool in the so-called baseplate. The corresponding equilibration times are approximately 5 ps and approximately 14 ps respectively.

Picosecond luminescence detection using type-II phase-matched frequency conversion

In order to improve on standard Kerr light gate methods for subnanosecond fluorescence measurements with solid-state lasers, we have used a method for sum and difference frequency generation in a type-11 phase-matched KDP crystal. The result is to generate up- and down-converted radiation from molecular fluorescence with a pulse-correlated time-resolution of less than 10 ps using multiple shots. The wavelength range for fluorescence detection, using KDP alone, is continuous from about 240 nm to greater than 1 micron. The method has a considerably higher signal-to-background ratio than the optical Kerr-cell, easily isolating 5 ps segments of a 10 ns fluorescence profile with high signal-to-noise ratio. Some examples are presented of the application of the method.