Multichannel Fourier Transform Spectrometer Research Articles

High-resolution and high-throughput multichannel Fourier transform spectrometer with two-dimensional interferogram warping compensation

The resolution of multichannel Fourier transform (McFT) spectroscopy is insufficient for many applications despite its extreme advantage of high throughput. We propose an improved configuration to realise both performance using a two-dimensional area sensor. For the spectral resolution, we obtained the interferogram of a larger optical path difference by shifting the area sensor without altering any optical components. The non-linear phase error of the interferometer was successfully corrected using a phase-compensation calculation. Warping compensation was also applied to realise a higher throughput to accumulate the signal between vertical pixels. Our approach significantly improved the resolution and signal-to-noise ratio by factors of 1.7 and 34, respectively. This high-resolution and high-sensitivity McFT spectrometer will be useful for detecting weak light signals such as those in non-invasive diagnosis.

Optical-rotatory-dispersion measurement approach using the nonlinear behavior of the geometric phase.

We propose a method for high-sensitivity optical rotatory dispersion (ORD) measurement of optically active samples that takes advantage of the nonlinear behavior of the geometric phase (GP). To measure the GP as a function of wavelength, we use a multichannel Fourier transform spectrometer (MC-FTS) that is based on Savart plate birefringent-polarization interference, into which we newly insert a zeroth-order quarter-wave plate (QWP). The modified MC-FTS allows us to measure the wavelength dependence of the GP and thus that of the optical rotation angle due to the sample. In this paper, we describe the proposed approach and demonstrate proof-of-principle experiments.

Principle of FT spectrometer based on a lateral effect position sensitive detector and multi channel Fabry–Perot interferometer

The principle of a new type of multi channel Fourier-Transform spectrometer based on a multi channel wedge Fabry–Perot interferometer using a one dimensional lateral effect Position Sensitive Detector and a scanning slit for interferogram readout have been shown. The design of this spectrometer is very compact and the readout electronics very simple. The drawback of using a scanning slit system is minimized by the use of a position sensitive detector where the position is inherently known for each measurement. Experiments show that the position can be resolved with high accuracy and the summation of the two photocurrents gives the interferogram distribution after scanning the slit between the wedge interferometer and the position sensitive detector. The spectral resolution obtained with a 25 mm wedge interferometer together with a 45 mm position sensitive detector and a 25 μm slit is about 5 nm around 600 nm wavelength range, which is close to the theoretically anticipated resolution. The evaluated spectrometer setup show promising results and could be used in applications where compact and low cost spectrometers are required.

Development of a multichannel Fourier-transform spectrometer to measure weak chemiluminescence: Application to the emission of singlet-oxygen dimol in the decomposition of hydrogen peroxide with gallic acid and K 3[Fe(CN) 6

A Fourier-transform spectrometer equipped with a Savart-plate polarization interferometer was developed for observation of weak chemiluminescence and applied to a measurement of emission spectra in the decomposition of hydrogen peroxide with gallic acid and K 3[Fe(CN) 6]. The band appearing at ∼580 nm in the chemiluminescence spectrum was assigned to the emission of singlet-oxygen dimol, the peak wavelength being shifted from that observed in the reaction of hydrogen peroxide with sodium hypochlorite, ∼633 nm. The band intensity was increased with the increasing concentration of K 3[Fe(CN) 6] up to ∼100 mM, and thereafter the peak wavelength was shifted from 580 to 700 nm with a decrease in the intensity.

A New Multichannel Fourier Transform Spectrometer

AbstractStellar spectra have been obtained using a multichannel Fourier Transform Spectrometer (FTS) which incorporates components of the Navy Prototype Optical Interferometer. It is well known that a FTS can provide superior wavelength stability as compared to traditional spectrometers. Unfortunately the FTS traditionally suffers from exceptionally poor sensitivity, which until now has limited its uses to sources with high fluxes and/or those with narrow band emission (e.g. the Sun, nebulae, and laboratory samples). We present stellar observations using a new FTS design which overcomes this sensitivity limitation by using a conventional multichannel spectrometer in conjunction with the FTS system. The signal-to-noise ratio of spectra from our test-bed observations are consistent with the theoretical prediction and show that for N channels the sensitivity scales like N, while the signal-to-noise ratio scales like . With this type of an instrument on a 3-m telescope and 9 000 channels we expect to be able to detect and measure such exciting astrophysical phenomenon as gravitational redshifts from single, main sequence stars and extrasolar planets of terrestrial mass.

マルチチャンネルフーリエ変換分光器を使用したラマン散乱スペクトル測定の応用研究

A multi-channel Fourier transform spectrometer (MCFTS) has the merits of both a Fourier transform spectrometer and a multi-channel spectrometer. We tried the application of a MCFTS to Raman scattering measurements. In this study, the emission of Cd spectral lamp was measured by using a birefringence polarizing interferometer with a Savart plate as a calibration of the system.

Proposal for High-Resolution, Wide-Bandwidth, High-Optical-Throughput Spectroscopic System Using a Fabry—Perot Interferometer

We propose a high-resolution, wide-bandwidth, high-optical-throughput spectroscopic system, in which a Fabry–Perot interferometer (FPI) is used in tandem with a second spectrometer. As the second spectrometer, one of the following three instruments can be used: (1) a grating dispersion-type monochromator attached to a multichannel detector (MCD), (2) a conventional Fourier transform spectrometer (FTS), or (3) a multichannel FTS (MFTS). The principle of operation for the three systems is the same. First, we adjust the free spectral range ( FSR) of the FPI to be k (>1) times the data interval DI (or resolved wavenumber) of the second spectrometer. The FSR is divided by N (> k) equally, and the etalon plate spacing of the FPI is changed N times with a step interval of FSR/N in wavenumber. Thereby we gather a total of N spectra from the second spectrometer. Finally, a single high-resolution spectrum is synthesized from the N spectra. To demonstrate the real capabilities of the proposed systems, we present computer simulation results.

Development of a multichannel Fourier transform spectrometer

We devised a novel type of multichannel Fourier transform spectrometer (MCFTS) that incorporates a Wollaston prism, polarizing interferometer combined with two Savart plates and a phase-retarding plate. This original MCFTS produces a number of lines of folded interferograms recorded with a two-dimensional imaging detector such as a CCD detector. In the present type of MCFTS, the total incident light is available except for a small amount of reflection loss. It is possible to enhance the signal-to-noise ratio. The enhancement of the resolving power is also expected by the connection of the interferograms with a newly developed method.

新しい型の２次元マルチチャンネルフーリエ分光計の開発と実用化 干渉縞連結による分解能の向上

A novel type Two Dimensional Multi-channel Fourier Transform Spectrometer (2D-MCFTS) was devised. The spectrometer consists of an Wollaston prism polarizing interferometer, two Savart plates and a phase retarding plate. This spectrometer gives two pairs of interferograms folded within the two dimensional imaging detector. By means of connecting folded interferograms with signal processing method developed by us, nearly twice of resolving power improvement was realized. Another feature of this spectrometer is that almost all the incident light intensity except Fresnel losses at the surfaces of the components can be utilized, since the Savart plates are utilized as a polarizer and an analyzer.

非コリメート光学系を用いたウォラストンプリズム マルチチャンネルフーリエ分光計の試作と光学系の検討

A collimating lens is generally used in the optical system of polarized birefringent interferometer with a Wollaston prism (WP) as a multichannel Fourier transform spec-trometer (MCFTS). In this time, we designed a new optical system of WP interferome-ter without collimating lens. A smaller WP is available as a MCFTS in the system.Interferograms of several discharge lamps were obtained using this system. Line spectra were reproduced after FFT procedures for the interferograms. Various applications are suggested utilizing the merit of this compact and inexpensive MCFTS system.

MULTICHANNEL Fr-IR SPECTROMETER WITH A 4096-ELEMENT INFRARED CCD

A multichannel Fourier-transform spectrometer in infrared was developed with birefringent interferometer with a Savert's plate and a infrared CCD with 4096 elements. The optics and the system configuration are described, and some experimental result of infrared spectrum measurement are shown for standard samples and an infrared radiation source. The resolution attained by the present system is ∼27.6 cm -1 between 5000∼2000 cm -1