RU1307995C - Method of intraresonator laser spectroscopy - Google Patents

Abstract

The invention relates to the field of quantum electronics and FDI spectroscopy, namely to intracavity laser spectroscopy. An object of the invention is to increase sensitivity to non-selective attenuation. The test substance is placed inside a multimode laser and the emission spectrum is recorded in the presence and absence of the test substance. A part is emitted from the laser-generated radiation inside the resonator, the spectrum of which is in the form of one 1SHI of several bands, the spectral width of which is ten or more times less than the total spectral width of the laser radiation, the uniform amplification width of the active medium of the same laser, and the spectral interval between the bands. The emitted part of the radiation is directed through its own channel, leaving it inside the laser cavity. In this case, the condition is met that, in the absence of the test, de-. The laser emission spectrum was structureless. The concentrated part of the radiation is passed through the test substance, and the magnitude of the dips in the spectrum of the laser generation at the frequencies of the radiation transmitted through the test substance indicates the value of the non-selective attenuated. 3 ill. with about s4

Description

The invention relates specifically to the spectral analysis of substances and can be used to measure the absorption spectra of substances in the solid, liquid, and gas phases to determine the content of contaminants in the test samples, as well as to determine a slight attenuation by the medium.

The aim of the invention is to increase the sensitivity of intracavity laser spectroscopy to non-selective attenuation.

In Fig. 1, a block diagram of an installation operating according to the proposed method is shown; 2 and 3 are signal diagrams explaining osu. a method.

The apparatus contains a spectral device 1, which analyzes the laser radiation spectrum, an output mirror 2 of the laser resonator, an active medium 3 of the laser, a dividing mirror 4, a cuvette 5 with the test substance, blind mirrors 6 and 7, and an equalizing filter 8.

Test substance, for example. NjH, in the liquid phase, having an absorption in the 200 cm band, is placed in a cell 5 mounted in a resonator of a multi-path neodymium-glass laser with a total width of the gain band of X 500 cm and a uniform width of 35 cm. Broadband from a neodymium-glass laser typical values of the parameters are lo / pTo-, J5 / P lO-, which for G / g -12 the laser radiation inside the de-35 resonator leads to the value A from (), equal to

It is divided into two channels by a dividing mirror, which can be used as a mirror with a special image calculated by a dielectric coating, providing transmission in a narrow (3 cm) spectral range and reflection of the rest of the radiation. The width of the interspersed portion of the spectrum is 12 times smaller than the uniform width of the gain loop and 30-100 times smaller than the total width of the generation spectrum, which is 90-300 cm for different pump levels.

Both parts of the radiation (transmitted and reflected) remain in the resonator, for which a mirror is installed in the path of each of them perpendicular to the direction of radiation propagation. Filter 8 attenuates reflected radiation in the same way that an empty cell has passed.

In the absence of attenuation (figure 2) in the test substance is incrusted

radiation (plot 9) and radiation generated inside the resonator (plot 10), when combined, produce radiation with a smooth spectral distribution (plot 11). In the presence of attenuation (Fig. 3), a slight decrease in the intensity of the injected radiation occurs.

The interaction of the propagated radiation with the radiation generated inside the resonator in the active medium of the laser leads to an increase in the change in the spectral pattern and sharp dips appear in the spectrum of the resulting radiation, the magnitude of which is determined by the magnitude of the non-selective attenuation of the investigated substance.

Since the reflection and transmission spectra are complementary, in the absence of the test substance in cell 5, there will be no structure in the laser generation spectrum. When the cuvette 5 is placed, due to the attenuation of the radiation in it in the laser generation spectrum, there is a dip at the frequency of the radiation transmitted through the substance. The spectrum is recorded with spectral instrument 1 and the magnitude of the dip indicates the attenuation coefficient of the test substance.

For a neodymium glass laser, typical values of the parameters are lo / pTo-, J5 / P lO-, which for

leads to the value of A from (), equals the value of A from (), equal to

J-Q way.

mu 1 + 2-10, i.e. in the considered Example, the sensitivity of the proposed method is not worse than the sensitivity of the traditional broadband J-Q method.

The ratio of the threshold sensitivity of the proposed method to the known is determined by

soba.

(- |) aexp (-2p,

()

way.

f, and I (j is the power of spontaneous noise, pumping, and generation

TO is the magnitude of the losses in the laser cavity not related to the test substance;

G homogeneous width

gain circuit of the active medium;

 - peak width F of the emission spectrum, pro5

W

let through is done forever. For a wide class of lasers (lasers based on ruby, neodymium glass, color centers of crystals x), 0 l of different pump levels. With G / j- 10, A "1 + 510-1" - 5-10 2% i.e. threshold sensitivity almost coincide.

The form of expression () is such that with increasing G / threshold the sensitivity remains practically unchanged and remains at the sensitivity level of the broadband radar. A decrease in G / j- leads to an increase in threshold sensitivity, i.e. to the deterioration of the operability of the proposed method. So with G / y 5 exp (-2: // r / j-) -2-3-10 of the generation of multimodosms about the laser, placing the investigated material and cplps inside the cavity of that laser; - no laser radiation spectra in the absence of the studied substance in The laser resonator and in the presence of the test substance there is characterized in that, in order to increase the sensitivity to non-selective attenuation, a part is emitted from the laser radiation inside the resonator, the spectrum of which has the form of one or several bands, whose spectral pyrine is ten or more times least spec the width of the laser radiation j of the uniform width of the amplification of the active medium of the same laser, the spectral interval between the bands,

and A 2-3-U - + 2-10, i.e. at non-20, part of the radiation is directed along its own values of the parameters f, P to the venous channel, leaving it inside the LO sensitivity already more than in the laser cavity and observing at the same time 10 times different from the sensitivity of the broadband BPJTC. Decrease

25

G / leads to a further deterioration in sensitivity.

Estimates show that the G / g ratio should be more than ten. 4) the claims

The method of intracavity laser spectroscopy by excitation

thirty

the condition that, in the absence of the test substance, the laser emission spectrum be structureless, an integral part of the radiation is passed through the test substance and by the magnitude of the dips in the spectrum of the generator laser at frequencies transmitted through; The substance under investigation is evaluated for the amount of non-selective attenuation.

part of the radiation is directed through its own channel, leaving it inside the laser cavity and observing

the condition that, in the absence of the test substance, the laser emission spectrum be structureless, an integral part of the radiation is passed through the test substance and by the magnitude of the dips in the spectrum of the generator laser at frequencies transmitted through; The substance under investigation is evaluated for the amount of non-selective attenuation.

-1

ff

gz;

Compiled by B. Shirokov Editor T. Gor Cheva Tehred M. Khodanich Corrector M. Pozho

Order 1958; Circulation

VNIIIPI of the State Committee of the USSR

for matters of inventions and discoveries 113035, Moscow, Zh-35, Rauska embankment. d. 4/5

Production and printing company, Uzhgorod, st. Project A

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