AgGaS2 nonlineer kristali ile fark frekans spektrometresi ve molekül spektroskopisindeki uygulaması
Başlık çevirisi mevcut değil.
- Tez No: 55722
- Danışmanlar: PROF.DR. TEPEHAN GALİP
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 105
Özet
ÖZET Nonlineer bir kristal olan AgGaS2 ile fark frekansi jenerasyonu temelli, taranabilir, sürekli dalga kızılötesi spektrometresi kuruldu. AlGaAs“index-guided”mono-mod diod lazer ve bir dairesel boya lazeri (boya: DCM) kullanarak bu spektrometre ile 1920 cm“1 ile 2020 cm'1 dalgasayısı aralığında çalışılabilir duruma getirildi. NO gazı ile temel band'taki dönme-titreşim çizgileri ile 'ölçümler yapılarak spektrometrenin sistem parametreleri incelendi. Bu spektrometre ile bir uygulama olarak NO gazının temel bandında II3/2 R(25,5) A-çiftinin kendiliğinden ve N2 gazı ile basınç genişleme katsayıları belirlendi ve bugüne kadar J”'nun daha küçük değerleri için bulunmuş olan genişleme katsayıları ile karşılaştırıldı. Bu A-çiftinin bileşenleri arasındaki spektral aralık belirlendi. Ayrıca ilk defa NO gazının aynı A-çifti için asal gazlarla (He, Ne, Ar, Kr) olan çizgi genişleme katsayıları belirlendi.
Özet (Çeviri)
SUMMARY Difference Frequency Spectrometer With Nonlinear Kristal AgGaSî and An Application In The Molecular Spectroscopy After the invention of the laser, several applications have been found both in industry and research. Although there are various lasers from UV (Ultra Violet) to IR (Infrared), some spectral regions could not be covered. With the use of optical mixing of the lasers in nonlinear cyrstals these spectral region could be considerably widend for both sides. Since most of the molecules have infrared active rotational-vibrational bands in the wavelength range from 2 to 20 urn it is of great interest to develope high resolution tunable laser sources for this spectral region. Up to now lead-salt diode laser, color- center lasers, CO and CO2 side band lasers are well established in high resolution spectroscopy in the mid-infrared region. However, their applicability is restricted to laboratory applications due to some disadvantages such as cryogenic cooling, lack of portability. On the other hand these lasers have a limited spectral ranges. In this work a cw high resolution laser spectrometer based on DFG (Difference Frequency Generation) was constructed using an AlGaAs diode laser and a ring-dye laser as pump sources which are mixed in a 25 mm long nonlinear crystal AgGaS2. A schema of the spectrometer is shown in Fig.l. The diode laser was placed in a compact self- constructed mount including grin collimating lens with commercial positioner, prism pairs and peltier elements in which the temperature of the diode laser can be changed. The frequency of the diod laser was controlled by using a commercial current and a temperatur controller. Further the frequency of the diode laser was stabilized on a slope of an interferens fringe of a self-constructed confokal Fabry-Perot interferometer. The overall stability achieved was better than 10 MHz. All the dielectric mirror coatings in the spectrometer have been prepared in the laboratory of“Optisches Institut, TU Berlin”. The main part of the spectrometer was mounted on a 2 cm thick aluminium plate which placed on a vibration isolated table. An infrared radiation in the nonlinear crystal AgGaS2 was produced by difference frequency of two visible lasers. To maximize the DFG output power non-critical type I 90°° phase matching was employed. VItemperature diode laser controller driver lock-in grating spectrometer HgCaTe driver detector 1f -“-' L3 ^^HsL SM Ge absorption- cell dye laser 699-29 autoscan to Lock-In Fig. 1: A scheme of the experimental setup An Infrared output power of typically 15 nW could be achieved with pump powers at the cyrstal surface of about 150 mW and 5 mW for the dye and the diode laser, respectively. With several AlGaAs index-guided single mode diode laser in the wavelength range from 770 nm to 785 nm (X2) and a ring dye laser with the dye DCM (Xi) could be covered an output wavenumber range (v3) from 1920-2020 cm1. The wavenumber range of the spectrometer is shown in Fig.2. The wavelegth of the diode laser was measured with a 2 m-graiting spectrometer within 0 015 nm (~ 0.25 cm1 at 770 nm) absolute accuracy. The diode laser beam was transported to the grating spectrometer using a fiber. The wavelength of the dye laser is controlled by an integrated wavemeter with an absolute accuracy of better than 6.7. 10 cm1. Therefore, the determination of the absolute wavenumber in the mid-mfrared is better than 0.26 cm”1 without further calibration. vn*^^^ ^(25.5) 4.987 10* cm P» ^rvs-1 JUJUIJULLJUjJ^ _.111 JLLJUUUULLJIt LLJUI 1953.24 1953.28 1953.32 1953.36 Fig.4: High resolution spectrum of the A-doublet 2Il3/2 RÇ255) of NO The spectra were scanned either for a 0.48 cm“1 or for a 0.18 cm”1 in a pressure range from 3 Torr to 346 Torr. For each case five measurements were made. The spectra were linearized with fringes from FPI 1 and then the absorption profiles were determined. Voigt profiles as given by whiting with the modified Voigt width by Olivero and Longbothum were fitted to the absorption profiles where the Doppler widths were fixed to the theoretical value. be The spacing of the A-doublet was determined from the fits for the low pressures to Av = 165±3MHz. This value is about 20 MHz smaller than the A-doubling given in the HTTRAN 92 database. Recently Spencer reported a similar deviation for their experimental values for R branch 2 TL3/2 with J“ up to 24.5. XAll of the line broadening coefficients for the NO A-doublet 2TLm R(255) in the fundamental band determined in this work are given in Tab. I. The errors (3 a) are given in paranthesis. Tab. I: The line broadening coefficients for the NO A-doublet 2n3/2 R(255) in the fundamental band. Although there are scattery results of the self and nitrogen induced broadening coefficients in the literature (up to 20%), the coefficients derived in this work are in good agreement with the former values for lines with smaller quantum number J”. XI
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