Compact Spectrometer based on Concave Grating (original) (raw)
Related papers
Spectrometers consisting of a diffractive lens and a concave diffraction grating
Journal of Modern Optics, 2004
The concave diffraction grating is used in many spectrometers and monochromators. Since it has both dispersion and focusing properties, one does not need a collimator or camera. In a nearly symmetric setup with a small deviation angle, the second-and third-order aberrations of the spherical concave diffraction grating are less then the respective aberrations of the setup with a plane diffraction grating and spherical mirrors. However, the residual defocusing limits the applicability of concave gratings in high resolution devices. This aberration can only be partially compensated by a grating with nonequidistant grooves. The focal distance of the diffractive lens has a linear dependence on the wavelength. This property is used to design hybrid diffractive-refractive lens systems for a wide spectral region. It is both tempting and promising to compensate the residual defocusing of a concave diffraction grating by means of a diffractive lens. The present paper analyses, both analytically and numerically, the effect of such compensation. The use of the diffractive lenses in the concave grating spectrometers is shown for the flat-field spectrometer and the double monochromator.
Holographically recorded gratings on microlenses for a miniaturized spectrometer array
Optical Engineering, 2000
We report on the investigation of refractive microlens arrays with diffractive grating surfaces in the context of a microspectrometer array system. The elements fabricated combine the fairly large dimensions of the refractive microlens (990-m diam, 60-m height) with the submicron features of the diffraction grating (1-m grating period) on one transmitting surface. The fabrication process of these elements was studied, as well as their performance with respect to resolution and stray-light suppression. The maximum resolution was 3 nm, and the stray-light suppression 25 dB. We present a concept for a system of miniaturized spectrometer arrays for chemical analysis.
Comparison with a Grating based Spectrometer
2018
This paper presents the design study, operational principle and mathematical model of a fiber optic based spectrometer (FOS). Such a spectrometer is highly desired by the ever-increasing applications of fiber optic sensors in compared to a grating based spectrometer, where high response frequency is required while advantages of high accuracy and large dynamic range must be maintained. The white light interferometry could provide a solution for high accuracy and large dynamic range measurement without ambiguity because of its absolute measurement nature. However the signal demodulation speed is limited due to the low spectrum acquisition rate of the existing spectrometers. The new (FOS) utilizes time domain dispersion of the sampled incoming light by dispersive fiber rather than the spatial dispersion employed by traditional spectrometers. In additionthe signal that represents the spectrum of the light is naturally a serial signal which can bedetected by a single detector and recorde...
Multifunctional and compact spectrometers based on cylindrical beam volume holograms
Optics Letters, 2007
We propose a new class of slitless spectrometers using cylindrical beam volume holograms. These holograms disperse an input beam in one direction in an output plane while they do not affect the beam in the perpendicular direction. We show that the spectral mapping of the input beam can be obtained in one direction and the beam can be independently modified in the perpendicular direction. Using this unique property, we demonstrate a spectral wrapping technique to considerably increase the operation spectral range of the slitless spectrometers, without sacrificing their resolution.
Divergent groove gratings: wavelength scanning in fixed geometry spectrometers
A new geometric scheme translates a diffraction grating along the straight central groove of an exponentially curved pattern. Lit by a stationary incident beam, the two-dimensional pattern scales isotropically, scanning wavelength without change to any angles, macroscopic distances, curvatures or aberrations. This is exemplified by a new class of self-focused grating monochromator, analyzed by rigorous light-path expansion and numerical raytracing. All spectral aberrations in pure meridional powers (including defocus, coma and spherical aberration) cancel for any angular deviation, magnification and translation range. The residual mixed powers yield Δλ/λ = 〖10〗^(-3) ~ 〖10〗^(-5) in the soft x-ray for plane and concave gratings at grazing incidence. Over the visible spectrum, Δλ/λ ~ 〖10〗^(-4) is shown for plane gratings mounted at Littrow and at normal incidence in reflection or transmission.
International Journal of Astronomy and Astrophysics, 2013
Optical spectrometer of the Guillermo Haro astrophysical observatory (Mexico) realizes investigations in the visible and near-infrared range 350-800 nm and exploits mechanically removable traditional static diffraction gratings as dispersive elements. There is a set of the static gratings with slit-densities 150-600 lines/mm and optical apertures 9 cm × 9 cm that provide the first order spectral resolution from 0.8 to 3.2 Å/pixel, respectively. However, the needed mechanical manipulations, namely, replacing the static diffraction gratings with various resolutions and following recalibration of spectrometer within studying even the same object are practically inconvenient and lead to wasting rather expensive observation time. We suggest exploiting an acousto-optical cell, i.e. the dynamic diffraction grating tunable electronically, as dispersive element in that spectrometer. Involving the acousto-optical technique, which can potentially provide electronic control over the spectral resolution and the range of observations, leads to eliminating the abovementioned demerits and improving the efficiency of analysis.
Holographic spectrograph for space telescope
Techniques and Instrumentation for Detection of Exoplanets VI, 2013
A spectrograph is described which is made with dual Holographic Optical Elements (HOEs) which are identical and parallel to each other. Both optics are collimating transmission HOEs with focal points that are at equal and opposite distances from each other. The identical HOEs are formed by the interference of a plane wave parallel to the grating plane with an off-axis spherical wave originating in the near-field. In playback, a spectrum can be formed from a point source radiator placed at the position of the recording spherical wave. If played back at an arbitrary wavelength other than the recording wavelength, the image exhibits coma. This spectrograph is intended for an unusual configuration where many nearly monochromatic sources of known wavelengths are separately positioned relative to the first HOE. The special application is in a space telescope capable of resolving spectra from habitable planets within 10 pc. HOEs of this type could be fabricated on membrane substrates with a low areal mass and stowable on rolls for insertion into the second Lagrange point. The intended application is for a 50 x 10 meter class primary objective holographic space telescope with 50 x 10 m HOEs in the spectrograph. We present a computer model of the spectrograph.. Experimental results are compared with predictions from theory. A single HOE is shown to perform over a wider bandwidth and is demonstrated.
Miniaturization of Holographic Fourier-Transform Spectrometers
Applied Optics, 2004
Wave propagation equations in the stationary-phase approximation have been used to identify the theoretical bounds of a miniature holographic Fourier-transform spectrometer ͑HFTS͒. It is demonstrated that the HFTS throughput can be larger than for a scanning Fourier-transform spectrometer. Given room-or a higher-temperature constraint, a small HFTS has the potential to outperform a small multichannel dispersive spectrograph with the same resolving power because of the size dependence of the signal-to-noise ratio. These predictions are used to analyze the performance of a miniature HFTS made from simple optical components covering a broad spectral range from the UV to the near IR. The importance of specific primary aberrations in limiting the HFTS performance has been both identified and verified.