| In
many applications the presence of interfering gases calls for better spectral resolution
than simply achieved by detecting the average absorption of the sample over the whole
emission band of an LED source. Previously [1] we described 7-channel miniature grating
spectrometer module utilizing infrared LED array with a resolution of about 2(FWHM)~120 nm
at wavelengths around 3.3 mm designed at VTT Electronics. Here
we present preliminary data on LED spectrometer performance consisting of 15-element
monolithic InGaAs LED array with the element sizes of 0.45?0.45 mm2 and the
whole length of 7.5 mm emitting at 3.3 mm, spherical concave
mirror (f=220 mm) and flat grating with 200 lines/mm (see Fig. 1 and [2]).
Fig. 2 presents pure methane (optical path ~2 cm), acetone and ethanol
(thickness of appr. 20-40 mm for both liquids) transmission
spectra obtained through sequential activation of LED array elements and recording the
transmitted radiation by a PbSe detector. Absence of fine methane absorption structure is
attributed to the "cross-talk" of elements in array. Nevertheless, as seen from
Fig. 2, the above substances are easily distinguished one from another when using LED
array spectrometer transmission data. It is believed that by using nonmonolitic LED array
[1] it would be possible to improve device spectral resolution and performance in the
promising mid-infrared analytical region.
References
1. J. Malinen , T. Hannula , N.V. Zotova, S.A.
Karandashov, I.I. Markov, B.A. Matveev, N.M. Stus', G.N. Talalakin, "Nondispersive
and multichannel analyzers based on mid-IR LEDs and arrays", SPIE vol.2069, Optical
Methods for Chemical Process Control, Boston 7-10 September, 1993, pp.95-101.
2. B.A. Matveev, G.A. Gavrilov, V.V.
Evstropov, N.V. Zotova, S.A. Karandashov, G.Yu. Sotnikova , N.M. Stus', G.N. Talalakin and
J. Malinen, "Mid-infrared (3-5 mm) LEDs as sources for gas
and liquid sensors", Sensors and Actuators, B 38-39, (1997) 339-343.
B.A. Matveev, Yu.M. Zadiranov, A. L. Zakgeim, N.D. Il'inskaya, S.A. Karandashev,
M.A. Remennyy, N.M. Stus', A. A. Usikova, A. E. Cherniakov, “InGaAsSb LED
arrays (λ = 3.7 um) with Photonic Crystals” Photonic and Phononic Crystal
Materials and Devices X, edited by Ali Adibi, Shawn-Yu Lin, Axel Scherer, Proc.
of SPIE Vol. 7609, 76090I-1 -5 © 2010 SPIE · CCC code: 0277-786X/10/$18 · doi:
10.1117/12.841689
N. D. Il’inskaya, S. A. Karandashev, N. G. Karpukhina, A. A.
Lavrov, B. A. Matveev, M. A. Remennyi, N. M. Stus' and
A. A. Usikova,
“Photodiode 1x64
Linear Array Based on a Double
p-InAsSbP/n-InAs0.92Sb0.08/n+-InAs
Heterostructure”,
Semiconductors, 2016, Vol. 50, No. 5, pp. 646–651. DOI:
10.1134/S1063782616050122
P.N.
Brunkov, N.D. Il’inskaya, S.A. Karandashev, A.A. Lavrov, B.A. Matveev, M.A.
Remennyi, N.M. Stus’ a, A.A. Usikova,
“P-InAsSbP/n-InAs
single heterostructure back-side illuminated 8 x 8 photodiode array»,
Infrared Physics & Technology 78 (2016) 249–253,
http://dx.doi.org/10.1016/j.infrared.2016.08.013 |
|
Fig. 1. Spectrometer schematic. 1 - LED/PD array
(only 4 elements are shown), 2 - photodetector/LED,
3 - flat grating,
4 - spherical concave mirror, 5- gas cell/filter
Fig. 2. Relative transmission of methane (optical path 25
mm), acetone and alcohol (~0.03 mm path for both of them) recorded by the 15-element LED array
spectrometer. |
