RU202420U1 - Temperature stabilization device for optical resonators - Google Patents

Abstract

The utility model relates to laser technology and can be used in devices for temperature stabilization of optical cavities.

The required technical result, which consists in expanding the arsenal of technical means used to ensure the temperature stability of the optical length of the resonators and improve the quality of stabilization, is achieved in a device containing a compensator for temperature changes in the optical length of the optical resonator, made with the possibility of fixing an optical resonator in it, and the compensator for temperature changes made in the form of an external crimp ring, installed perpendicular to the optical path of the optical resonator, while the width a and thickness b of the outer crimp ring for a given length L ₀ and radius R _{0 of the} optical resonator are selected from the condition

where E and E _M are Young's moduli of the optical resonator and crimp ring, respectively; σ is the Poisson ratio of the optical resonator; n ₀ is the refractive index of the optical resonator at the initial temperature; μ is the thermo-optical coefficient of the material of the optical resonator; α _M and α are the coefficients of linear expansion of the materials of the crimp ring and the optical resonator, respectively. 1 ill.

Description

The utility model relates to laser technology and can be used in devices for temperature stabilization of optical cavities.

For applications in precision spectroscopy, the frequency stability of laser sources is often insufficient, and therefore additional radiation frequency stabilization systems external to the laser are required.

From the existing prior art, many solutions are known in which the laser radiation frequency is stabilized to the eigenmode of an external highly stable optical resonator (US 4451923A publ. 05/29/1984; US 4700150A publ. 10/13/1987; RU 2343611C1, published 01/10/2009; US 8736845B2, publ. 27.05.2014; CA 2690338C, publ. 18.12.2008; US 20090310629A1, publ. 11.01.2011).

The disadvantage of these technical solutions is the relatively narrow functionality and the complexity of the technical implementation.

An analogue of a temperature-independent resonator can be resonators made of materials with an ultra-low coefficient of thermal expansion (DE 102008049367B3 publ. 08.10.2009; WO 2012130199A2 publ. 04.10.2012; US 20070091975, publ. 25.08.2008; J. Alnis et al., Phys. Rev. A, vol. 77, no. 5, pp. 1-9, 2008; DG Matei et al., Phys. Rev. Lett., Vol. 118, no. 26, pp. 1-6, 2017 ).

The disadvantages of these technical solutions are the relatively high complexity of manufacturing such materials, which predetermines their high cost and the need to work in a small neighborhood of a strictly defined value of the temperature of zero thermal expansion.

The closest to the claimed device is [US US 5982488 A, G02B 7/008, 09.11.1999] containing an optically transparent plate through which optical radiation passes along the optical path, and a compensator for temperature changes in the optical length of the optically transparent plate in the form of two compensation plates between which an optically transparent plate is installed and which undergoes thermal expansion and deforms the optically transparent plate by stretching it in directions transverse to the optical path to reduce the thickness of the optically transparent plate in the direction of the optical path in order to compensate for the increase in optical length caused by temperature changes.

With the correct choice of the material of the compensation plates and their thicknesses, it is possible to ensure the constancy of the thickness (optical path length) of the optically transparent plate in a certain temperature range.

The used method of compensating for temperature changes and the corresponding device are good enough for temperature stabilization of thin optically transparent plates, for example, Fabry-Perot plates, but does not provide sufficient stabilization of the optical path length in more complex laser frequency stabilization systems.

Another disadvantage of this method and the corresponding device is the difficulty of optical access to the optically transparent plate due to the compensation plates, which reduces the maintainability and operational reliability of the device.

Thus, the disadvantage of the device is the relatively narrow functionality of the device, which does not allow its use with sufficient stabilization quality for optically transparent resonators of complex shapes, which narrows the arsenal of technical means used as devices for temperature stabilization of optical resonators? and does not provide high quality temperature stabilization.

The task to be solved by the utility model is the creation of a device characterized by an increased quality of stabilization of the optical length of cavity resonators.

The required technical result consists in expanding the arsenal of technical means used to ensure the temperature stability of the optical length of the resonators and improve the quality of stabilization.

The problem is solved, and the required technical result is achieved by the fact that, in a device containing a compensator for temperature changes in the optical length of an optical resonator, made with the possibility of fixing an optical resonator in it, according to the utility model, the compensator for temperature changes is made in the form of an external crimp ring installed perpendicularly the optical path of the optical resonator, in this case, the width a and the thickness b of the outer crimp ring for a given length L ₀ and radius R _{0 of the} optical resonator are selected from the condition

Where:

E and E _M - Young's moduli of the optical resonator and crimp ring, respectively;

σ is the Poisson ratio of the optical resonator;

n ₀ is the refractive index of the optical resonator at the initial temperature;

μ is the thermo-optical coefficient of the material of the optical resonator;

α and α _M are the coefficients of linear expansion of the materials of the crimp ring and the optical resonator, respectively.

The drawing shows an optical Fabry-Perot resonator with a crimp ring, where L is the optical length of the resonator.

The device for temperature stabilization of optical resonators contains a compensator 1 for temperature changes in the optical length of the optical resonator, made with the possibility of fixing the optical resonator 2 in it. In this case, the compensator 1 can be made in the form of a crimp ring, installed perpendicular to the optical path of the optical resonator 2.

The device for temperature stabilization of optical resonators is used as follows.

In the claimed device for temperature stabilization of optical resonators with a change in temperature, the thermal expansion of the optical resonator is compensated by a change in the voltage of the compensator 1, made in the form of a crimp ring.

The resulting (required) zero thermal expansion coefficient (CTE) of the resonator is provided by a quantitative combination of the CTE of the crimp ring and its geometric dimensions.

The optical resonator 2 is compressed with a crimp ring 1 made of a material with a higher CTE than that of the optical resonator in order to increase its working length of the optical resonator, and the size of the crimp ring 1 is selected so that when the temperature rises (changes), the compression force decreases and causes a decrease in the working the size of the optical cavity, which compensates for its own thermal expansion.

To achieve temperature independence of the working size of the optical resonator, the crimp ring is selected from a material with a thermal expansion coefficient that exceeds that of the resonator material, with the effect that the working length is increased. As the temperature rises, the size of the crimp ring increases to a greater extent than the size of the optical cavity, and the compression force weakens, producing a decrease in the working size of the optical cavity, which compensates for its own thermal expansion.

If the body of the optical resonator is compressed with a crimp ring 1 made of material with a high coefficient of thermal expansion (compared to the material of the optical resonator 2, then as the temperature rises, the compression force will decrease and the length of the resonator will receive a negative addition to the length (see drawing). Summing it up with a positive addition due to thermal expansion, we obtain a zero effect of temperature influence on the length of the optical cavity.

- length and radius of the optical resonator before compression L ₀ and R ₀ , temperature T ₀ ;

- the length of the optical resonator after compression L (T ₀ , F ₀ ), the compression force F ₀ ;

- the length of the optical cavity with compression when the temperature changes L (T, F);

- radius of the crimping ring to contact with the body R ₀ - ΔR;

- ring width α, ring thickness b;

- Young's moduli of the body and rings E and E _M ;

- Poisson's ratio of the hull σ;

are the coefficients of linear expansion of the materials of the crimp ring and the optical resonator α _М and α, respectively

Let us calculate the force of compression of the housing by a ring put on the optical resonator at a constant temperature.

The compression force F ₀ reduces the radius of the body:

In this case, the ring increases its radius:

The increase in the radius of the ring is determined by the formula for the dependence of the radius of the pipe under pressure from the inside.

In the initial state, these two radii are equal. From this condition, we determine the relationship between the compression force and the initial diameter of the ring:

In this case, the length of the optical cavity will slightly increase:

This formula assumes that the increase in body length is due to compression of only the cylindrical part of the body within the ring width. To refine this ratio, you can introduce a dimensionless coefficient k:

With an increase in temperature, the dimensions of the optical resonator and the ring increase, the compression force decreases, and we obtain new dimensions:

и

and

from where

which gives the value of the new compression force:

Then the new body length is estimated as

Preservation of the length of the body occurs when equal:

т.е.

those.

Substituting the new force here, we obtain the condition for choosing the size of the ring

and estimation of the optimal ring thickness b:

Hence it follows that the condition of temperature independence is not related to the value of the initial compression force.

The above condition ensures the constancy of the length of the optical resonator at varying temperatures.

In applications, a constant optical length n (T) ⋅L (T, F) is most often required, where n is the refractive index of the material from which the optical resonator is made. Then the condition for the preservation of the optical length of the resonator at varying temperature will have the form:

For example, consider a fused quartz case and a brass ring.

Then the ratio of the thickness of the ring to its radius at the initial temperature will be equal to:

что вполне приемлемо для

which is quite acceptable for

practical implementation.

Thus, in the proposed utility model, the required technical result is achieved, which consists in expanding the arsenal of technical means used to ensure the temperature stability of the optical length of the resonators and improve the stabilization quality.

Claims (8)

A device for temperature stabilization of optical resonators, containing a compensator for temperature changes in the optical length of an optical resonator, made with the possibility of fixing an optical resonator in it, characterized in that the compensator for temperature changes is made in the form of an external crimp ring installed perpendicular to the optical path of the optical resonator, with the width a and the thickness b of the outer crimp ring for a given length L ₀ and radius R _{0 of the} optical resonator is selected from the condition

Where: E and E _M - Young's moduli of the optical resonator and crimp ring, respectively; σ is the Poisson ratio of the optical resonator; n ₀ is the refractive index of the optical resonator at the initial temperature; μ is the thermo-optical coefficient of the material of the optical resonator; α _M and α are the coefficients of linear expansion of the materials of the crimp ring and the optical resonator, respectively.

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