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May 2000

Volume 71, Issue 5, pp. 1929-2249

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Instrumental noise and detectivity analysis of photopyroelectric destructive thermal-wave interferometry

Chinhua Wang and Andreas Mandelis

Rev. Sci. Instrum. 71, 1961 (2000); http://dx.doi.org/10.1063/1.1150562 (10 pages) | Cited 2 times

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A complete noise analysis of a two-beam photopyroelectric (thermal-wave) destructive interferometric sensor instrument is presented and compared to its single-beam, noninterferometric counterpart. The noise analysis is performed using a Green-function formalism applied to experimental observations. The instrumental background noise contribution from the detector and the amplifier is separated from the laser noise and the instrumental noise due to amplification associated with different sensitivity scales. The latter serves as the source of comparison between the two sensor configurations. It is found that the dc laser drift noise and low-frequency fluctuation noise, which are dominant in the single-beam mode, are greatly reduced to the same order of magnitude as the instrumental background noise in the two-beam mode. The system white noise resulting from the incident laser beam and from the sensitivity scale (amplification) of the demodulating lock-in amplifier are also examined in light of the experimental data. It is found that the detectivity D∗ (the inverse of the noise equivalent power), of the instrument is enhanced by at least 1 order of magnitude in the interferometric mode. © 2000 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.60.Ly Interferometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Measurements of the velocity and temperature in a turbulent flow by the laser photothermal effect with the new compulsorily phase locked interferometer

Noboru Nakatani

Rev. Sci. Instrum. 71, 1971 (2000); http://dx.doi.org/10.1063/1.1150563 (4 pages) | Cited 1 time

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This article describes measurements of the velocity and temperature in a turbulent flow by means of a photothermal effect. We developed a new differential interferometer for detecting small phase variation caused by the photothermal effect without influence of turbulent phase fluctuation. The detected fringe point of the interferometer is scanned repeatedly by moving a photomultiplier. An electric system is constructed for compulsorily operating the interferometer at the maximum inclination point of the fringe intensity curve. Using a turbulent jet of nitrogen gas mixed with ethylene gas, we confirmed that this measurement system is useful to measure the velocity and temperature in the turbulent flow. © 2000 American Institute of Physics.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
47.27.-i Turbulent flows
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
07.60.Ly Interferometers
07.20.Dt Thermometers

A highly sensitive photoacoustic spectrometer for near infrared overtone

Lu-yuan Hao, Jia-xiang Han, Qiang Shi, Jin-hui Zhang, Jin-jin Zheng, and Qing-shi Zhu

Rev. Sci. Instrum. 71, 1975 (2000); http://dx.doi.org/10.1063/1.1150564 (6 pages) | Cited 4 times

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By optimizing the size of a photoacoustic cell for decreasing acoustic loss and noise, and using a proper multipass arrangement for increasing light power in the cell and optical coupling to the acoustic wave, a high-resolution external laser photoacoustic spectrometer with a detection sensitivity of 6.35×10−9 cm−1 (1:1 signal to noise level) has been developed. Using this apparatus, the high quality Doppler-limited overtone spectra of AsH3 (600) and H2Se (60) have been observed at room temperature in the wave number regions 11 500–11 650 and 12 600–12 925 cm−1, respectively. Results are presented which highlight the applicability of this apparatus to the spectroscopy of weak optical transitions. © 2000 American Institute of Physics.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
43.58.-e Acoustical measurements and instrumentation
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Multiple-reflection interferometer for high accuracy measurement of small vibration displacement

Doo Hee Lee and Byoung Yoon Kim

Rev. Sci. Instrum. 71, 1981 (2000); http://dx.doi.org/10.1063/1.1150565 (6 pages) | Cited 4 times

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A novel multiple-reflection interferometer is developed for the accurate measurement of sinusoidal vibration amplitudes, and its characteristics are analyzed theoretically and experimentally. The multiple-reflection system employs a right-angle prism and a convex lens, which is located in the probe beam path of a Michelson interferometer. The performance of the multiple reflection interferometer as a function of reflection number was assessed at the vibration frequency of 1250 Hz using Bessel function null method. © 2000 American Institute of Physics.
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07.60.Ly Interferometers
42.79.Bh Lenses, prisms and mirrors
06.30.Gv Velocity, acceleration, and rotation
06.20.F- Units and standards

Optimization of operating conditions for a fast-axial-flow, radio frequency discharge-excited, room-temperature CO laser

Kouki Shimizu, Manabu Taniwaki, Shunichi Sato, Hiroshi Nagano, and Kazuo Maeno

Rev. Sci. Instrum. 71, 1987 (2000); http://dx.doi.org/10.1063/1.1150566 (4 pages)

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To optimize the operating conditions of a fast-axial-flow, rf discharge-excited, room-temperature CO laser, we have investigated the effects of the excitation rf frequency, the diameter of the discharge tube, and the contents of added gases and impurities in the laser gas. The laser output decreased with increasing concentration of H2O, and the laser oscillation ceased at concentrations above 560 ppm. An increase in the excitation rf frequency from 13.56 to 27.12 MHz resulted in an increase in the output power by 35%. The optimum concentrations of added noble gases depended on the diameter of the discharge tube. With the discharge tube at a diameter of 19 mm, the conversion efficiency increased with increasing concentration of added Kr or Xe and the addition of Xe was more effective than that of Kr. For a tube diameter of 30 mm, however, the conversion efficiency decreased with increased concentration of added Kr or Xe and Xe was less effective than Kr. A maximum output of 910 W was obtained at a conversion efficiency of 14.7% at an rf input power of 6.2 kW using a single discharge tube with a diameter of 30 mm with 5% Kr added. © 2000 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
52.80.Pi High-frequency and RF discharges

Divergence effects in monochromatic x-ray microdiffraction using tapered capillary optics

I. C. Noyan, P.-C. Wang, S. K. Kaldor, J. L. Jordan-Sweet, and E. G. Liniger

Rev. Sci. Instrum. 71, 1991 (2000); http://dx.doi.org/10.1063/1.1150567 (10 pages) | Cited 12 times

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Tapered capillaries are frequently used as beam-concentrating optics in microbeam x-ray diffraction experiments. The beams exiting such devices are usually highly divergent and may possess nonuniform intensity distributions. In addition, their alignment poses some special challenges. In this article, the effects of these factors on the precision and accuracy of diffraction data are presented. © 2000 American Institute of Physics.
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41.50.+h X-ray beams and x-ray optics

Small-displacement monochromator for microdiffraction experiments

Gene E. Ice, Jin-Seok Chung, Walter Lowe, Ernest Williams, and Joel Edelman

Rev. Sci. Instrum. 71, 2001 (2000); http://dx.doi.org/10.1063/1.1150568 (6 pages) | Cited 9 times

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We describe the design, construction, and performance of the MHATT-CAT microdiffraction x-ray monochromator. This monochromator is specially engineered for x-ray microdiffraction experiments with a high brilliance undulator source. The monochromator passes a small emittance beam, suitable for focusing to submicron size with submilliradian divergence. Over its energy range of 8–22 keV the absolute energy calibration is better than 2 eV and scans of ± 1 keV show no measurable hysterisis. The monochromator operates with a simple water-cooled first crystal and shows no measurable warm-up time. Horizontal linear bearings allow the monochromator crystals to be rapidly inserted or removed from the beam. Slits before and after the monochromator work to pass broad bandpass or monochromatic x-ray beams at the same vertical height. The monochromatic beam direction is adjusted so the monochromatic and broad bandpass beams are coaxial. The design and performance of the monochromator allows efficient collection of microdiffraction data when coupled to a nondispersive Kirkpatrick–Baez focusing mirror pair. © 2000 American Institute of Physics.
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07.85.Jy Diffractometers

Thomson scattering using an atomic notch filter

L. P. Bakker, J. M. Freriks, F. J. de Hoog, and G. M. W. Kroesen

Rev. Sci. Instrum. 71, 2007 (2000); http://dx.doi.org/10.1063/1.1150569 (8 pages) | Cited 13 times

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One of the biggest problems in performing Thomson scattering experiments in low-density plasmas is the very high stray light intensity in comparison with the Thomson scattering intensity. This problem is especially present in fluorescent lamps because of the proximity of the glass tube. We propose an atomic notch filter in combination with a dye laser and an amplified spontaneous emission (ASE) filter as a way of reducing this stray light level. The dye laser produces 589 nm radiation which is guided through the ASE filter that increases the spectral purity. The beam is then guided in the fluorescent lamp, where the Thomson scattering process takes place. The scattered light is collected and guided through a sodium vapor absorption cell, where the stray light is absorbed because it is resonant to the D2 transition of sodium. The spectral width of the Thomson scattering light is large enough to be transmitted through the absorption cell. In this way we only measure the Thomson scattering light. © 2000 American Institute of Physics.  
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.79.Ci Filters, zone plates, and polarizers
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