RU2046480C1 - Gas laser tunable by wave lengths - Google Patents

Abstract

FIELD: laser equipment. SUBSTANCE: distance L between reflecting surfaces of two parallel plates 6 and 7 forming Fabry-Perot interferometer installed inside laser resonator is chosen for each wave length from relation L=L_d.m.b.+ ΔX,, where L_d.m.b. is datum mark base of Fabry-Perot interferometer; ΔX is increment of interferometer base chosen from specified conditions. Accurate setting of interferometer base excludes necessity of scanning the entire range of wave lengths to select specified one. EFFECT: improved precision and timeliness of tuning. 3 dwg

Description

 The invention relates to quantum electronics and can be used for the design and development of gas lasers tunable to wavelengths.

 A known gas laser tunable according to wavelengths, the resonator of which contains an inclined Fabry-Perot reference with an angular selection mechanism as a selector [1] Tuning according to wavelengths is carried out by changing the angle of inclination of the optical surfaces of the reference to the optical axis of the laser resonator.

 The disadvantage of the laser is the reduced efficiency of controlling the frequency of radiation, due to the inertia inherent in mechanical components.

 Also known is a wavelength tunable gas laser containing an optical resonator, the working medium of which provides the generation of laser radiation, and the selection element is an inclined Fabry-Perot standard with an air gap placed in an airtight container with gas [2] The gas density in the container can vary , which leads to a change in the optical refractive index and, consequently, to a restructuring of the radiation wavelength.

 The disadvantage of this laser is the structural complexity due to the presence of gas cylinders, an air inlet and pressure control system, which does not provide the necessary speed for tuning to the required wavelengths and increases the mass-dimensional parameters.

 The closest in technical essence to the claimed laser is a gas laser tunable by wavelength, selected as a prototype, containing an optical resonator, inside which a discharge channel is installed, and a Fabry-Perot standard with an air gap between parallel reflecting surfaces that is adjustable in length along the optical axis [3] The Fabry-Perot etalon is adjusted by changing the distance (base) between the internal reflective surfaces.

 The disadvantages of this laser are the low efficiency of the tuning process due to the fact that the exact value of the reference base is unknown (accurate to λ / 2) and there is no reference to the reference frequency, as well as the inability to tune to vibrational-rotational transitions in an arbitrary order, including the given the program.

 The objective of the invention is the creation of a gas laser, quickly tunable to wavelengths.

 The technical result is an increase in control efficiency and the possibility of automating the tuning process can be obtained by accurately setting the interferometer base for a specific wavelength in an arbitrary order without scanning the entire range, as well as tuning according to a given program.

3

где ν_i центральная частота выделяемого перехода;
ν_к центральные частоты переходов, близко расположенные к выделяемому;
с скорость света в вакууме;
δ наименьшее контролируемое изменение базы интерферометра, равное 0,02 мкм;
ν_p реперная частота.The specified technical result in the implementation of the invention is achieved by the fact that in a wavelength tunable gas laser containing an optical resonator, inside which a discharge channel is installed and a Fabry-Perot interferometer with an air gap adjustable along the length between its parallel reflecting surfaces, at an angle to its optical axis, the distance between the latter is selected for each wavelength from the relation
LL _p + ΔX, (1) where L _{p is the} reference base of the Fabry-Perot interferometer;
ΔX increment of the base of the interferometer, selected from the conditions
ΔX =

3

where ν _{i is the} central frequency of the allocated transition;
ν _{to the} central frequencies of the transitions, close to the allocated;
c is the speed of light in vacuum;
δ the smallest controlled change in the base of the interferometer, equal to 0.02 μm;
ν _p reference frequency.

 Efficiency of the process of tuning according to wavelengths and its automation was achieved due to the fact that the interferometer base is changed to a value known in advance for each wavelength relative to the reference value, selected as the initial one. The settings for each device are determined during the certification process. Thus, there is no need to scan the entire range and there is the possibility of tuning according to a given program.

 A comparative analysis of the claimed technical solution with the prototype shows that the claimed laser provides an increase in the efficiency of the process of tuning according to wavelengths and its automation. Thus, the claimed device meets the requirement of "novelty."

 Other sources of information in which the distinguishing features of the invention would be known were not identified. This allows us to conclude that it meets the requirement of "inventive step".

 In FIG. 1 schematically shows the proposed laser, tunable to wavelengths; in Fig.2 node selection element; in FIG. Figure 3 shows the order of passage of the generation lines (autograph) when the interferometer length is changed by λ / 2.

 The gas laser contains a resonator formed by an output mirror 1 connected to a frequency tuning element 2 and a dull mirror 3. A discharge channel 4 is installed inside the resonator and a Fabry-Perot standard made at an angle Θ to its optical axis 5 with an air gap adjustable in length L between parallel plates 6, 7. Plate 6 is stationary relative to the end of the discharge channel 4 at an angle Θ to the optical axis of the resonator. The plate 7 is installed at a distance L parallel to the plate 6 and is rigidly connected with the control elements 8.

 The laser operates as follows.

m где n показатель преломления вещества, заполняющего рабочий промежуток эталона (равен единице для воздушного промежутка);
m число полуволн, укладывающихся на длине h.The active medium and the resonator form optical radiation, the frequency of which is related to the distance L between the plates 6 and 7 by the following relation:
ν

m where n is the refractive index of the substance filling the working interval of the standard (equal to unity for the air gap);
m is the number of half-waves stacked over a length h.

The tuning for the vibrational-rotational transition is determined by the distance L between the plates 6, 7, selected for a given wavelength from the relation
LL _p + ΔX, where L _{p is the} reference base of the interferometer, set by tuning to the "reference" center frequency, selected from comparison with a set of generation autographs;
ΔX, the increment of the base of the interferometer, selected from conditions (2) - (4), and is provided by control elements 8 that linearly move the plate 7 rigidly connected to them relative to the plate 6. The methods for changing the length of the control elements can be different (thermal, using a piezoelectric corrector and etc.).

m где m число полуволн частоты ν_p, укладывающихся на длине L_р.As reference frequencies, the central frequencies of any vibrational-rotational transition can be selected, but for visualization it is convenient to choose the central frequency of one of the closely spaced transitions, combinations of which are calculated for each value of the initial (technological) base of the interferometer L _o , the individuality of which for each of the devices is related with manufacturing accuracy and external conditions (temperature, etc.), differing by λ / 2. Tuning to the reference frequency is done by changing the technological base of the interferometer L _o by Δ. At the same time, the base of the interferometer L _p corresponding to the setting of the interferometer to the frequency ν _p is
L _p = L _o ± Δ

m where m is the number of half-waves of frequency ν _p that fit along the length L _p .

 The connection of the output mirror 1 with the frequency tuning element (piezoelectric corrector) allows you to change the length of the resonator and during operation of the device to tune to the center frequency of the vibrational-rotational transition.

 The installation of the plate 7 parallel to the plate 6 at a distance L selected from relation (1) and when conditions (2) - (4) are satisfied, provides tuning to a given vibrational-rotational transition.

 Due to the fact that tuning to a given vibrational-rotational transition is carried out by linear displacement of the plate 7, which is rigidly connected with the control elements 8 relative to the plate 6 fixedly fixed at the end of the discharge channel, the efficiency of controlling the generation frequency increases and the instability of the output radiation parameters decreases.

 A rigid connection of the plate 7 with the control elements 8 allows the axial movement of the plate 7 relative to the plate 6 fixed at the end of the discharge channel, which ensures the fulfillment of condition (1).

Pre-tuning to the reference frequency allows you to tune to any vibrational-rotational transition by changing the base of the interferometer L relative to the reference length L _p by the value Δ X calculated in advance for all transitions and, thus, to certify the devices.

выбираемую из условий (2)-(4), позволяет производить как последовательную настройку на колебательно-вращательные переходы, так и настройку в произвольном порядке, в том числе по заданной программе, что может существенно расширить область применения прибора.The change in the base of the interferometer L relative to the "reference" length by Δ X, not exceeding

selected from conditions (2) - (4), it allows both sequential tuning to vibrational-rotational transitions and tuning in an arbitrary order, including a given program, which can significantly expand the scope of the device.

 An example of a specific implementation of the invention. The laser design satisfies the relations (1) (4) of the invention.

The design of the laser, tunable according to wavelengths, has a resonator that includes an input and a blind mirror and plane-parallel plates, the reflective surfaces of which form a Fabry-Perot interferometer associated with the control elements. The magnitude of the base of the interferometer L _o 0.99 ± 0.01 mm is determined by the technological accuracy of manufacture.

≈ 5,3 мкм ≈ 5,3 мкм при фиксированной длине резонатора. Далее производится сравнение полученного автографа с автографами, полученными расчетным путем для значений баз интерферометра, отличающихся на

, и определяется значение базы эталона с точностью до

. После этого производится настройка на реперную частоту, в качестве которой удобно выбрать центральную частоту одного из близкорасположенных в данном автографе колебательно-вращательных переходов.After turning on the laser and warming up, the device is certified. For this, the dependence of the generation power on the change in the value of the base of the interferometer within

≈ 5.3 μm ≈ 5.3 μm with a fixed cavity length. Next, a comparison of the obtained autograph with the autographs obtained by calculation for the values of the interferometer bases that differ by

, and the value of the reference base is determined with an accuracy of

. After that, tuning to the reference frequency is made, for which it is convenient to choose the center frequency of one of the vibrational-rotational transitions located nearby in this autograph.

m 5,36·10^-6·m [M]
Определяют число полуволн, укладывающихся на базовой длине интерферометра,
m

185,4
Поскольку при настройке на реперную частоту между отражающими поверхностями интерферометра должно укладываться целое число полуволн, принимают m 186.For example, comparing the resulting autograph with a set of autographs obtained by calculation (see Fig. 3) gives a value of L _o 0,9938 ± 0,053 mm The center frequency of the vibrational-rotational transition P32 (ν ₃₂ = 27969449, 783 MHz) is chosen as the reference frequency, since the P42 transition is located next to it, which is typical for this autograph. By changing the base of the interferometer, tuning to this frequency is made, while the reference base of the interferometer is
L _p

m 5.36 · 10 ^-6 · m [M]
Determine the number of half-waves that fit on the base length of the interferometer,
m

185.4
Since when tuning to the reference frequency, an integer number of half-waves must fit between the reflecting surfaces of the interferometer, take m 186.

m 5,36·10^-6м·186 0,99683 мм
Для настройки на центральную частоту перехода Р20 необходимо установить величину базы интерферометра, при которой между отражающими поверхностями интерферометра укладывается целое число полуволн, соответствующих линии Р20.Then L _p

m 5.36 · 10 ^-6 m · 186 0.99683 mm
To tune to the central frequency of the P20 transition, it is necessary to set the base value of the interferometer at which an integer number of half-waves corresponding to the P20 line fit between the reflecting surfaces of the interferometer.

0,24015<0,5,
ΔX=

д

я

1,2717·10^-6м
Тогда величина базы интерферометра, обеспечивающая настройку на колебательно-вращательный переход Р20, составляет
L L_р + ΔХ 0,99683 + 0,00127 0,9981 мм.Since the fractional part
Since the fractional part

0.24015 <0.5,
ΔX =

d

I am

1.2717 · 10 ^-6 m
Then the value of the base of the interferometer, which provides tuning to the vibrational-rotational transition P20, is
LL _p + ΔX 0.99683 + 0.00127 0.9981 mm.

5,3 мкм. Этому значению базы интерферометра соответствует свой порядок расположения линий генерации, и близкорасположенные переходы оказываются разнесены.Installation of the specified length is provided by control elements. If you need to tune in to one of the vibrational-rotational transitions located nearby on this autograph, the base of the interferometer is changed by the amount

5.3 microns. This order of the interferometer base corresponds to its own order of arrangement of the generation lines, and the nearby transitions are spaced apart.

 Using the proposed tunable laser, in comparison with the existing ones, it is possible to increase the efficiency and automation of the process of tuning according to wavelengths and significantly expand the scope of applications of devices of this class. The invention can be used in the development of gas lasers tunable by wavelengths, therefore, it meets the requirement of "industrial applicability".

Claims (1)

A GAS LASER tunable by WAVE LENGTHS, containing an optical resonator, inside of which there is a discharge channel and a Fabry Perot interferometer with an air gap between its parallel reflecting surfaces that is adjustable in length, characterized in that the distance L between the reflecting surfaces of the interferometer is selected for each wavelength from the relation
L = L _p + ΔX,
where L _{p the} reference base of the Fabry Perot interferometer;
ΔX increment of the base of the interferometer, selected from the conditions

where c is the speed of light in vacuum;
ν _{i the} central frequency of the allocated transition;
ν _{to the} central frequencies of the transitions, close to the allocated;
ν _p reference frequency;
δ the smallest controlled change in the base of the interferometer, equal to 0.02 μm.

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