Ultra-stable cavity temperature monitoring device, preparation method and application

Abstract

The invention provides an ultra-stable cavity temperature monitoring device, a preparation method and application. The precision of temperature control is further improved. The preparation method comprises the following steps: heating a hollow silicon oxide capillary tube on hydrogen flame, and stretching two ends of the hollow silicon oxide capillary tube in the heating process, so that the hollow silicon oxide capillary tube is thin in the middle and thick on two sides; sealing one end of the hollow silicon oxide capillary tube, and pressurizing the hollow silicon oxide capillary tube from the other end until the atmospheric pressure in the hollow silicon oxide capillary tube is increased to a preset value; irradiating the middle part of the hollow silicon oxide capillary by using a carbon dioxide laser to form a microbubble cavity in the middle of the hollow silicon oxide capillary; placing the optical fiber on hydrogen flame for heating, and stretching the two ends of the optical fiber in the heating process so that the optical fiber is thin in the middle and thick on the two sides; and coupling the treated hollow silicon oxide capillary tube with the microbubble cavity with a treated optical fiber to form a cross structure, thereby obtaining the ultra-stable cavity temperature monitoring device.

Description

Technical Field

[0001] The present application relates to the field of optical metrology technology, and in particular to an ultra-stable cavity temperature monitoring device, a preparation method and an application thereof. Background Art

[0002] Frequency standards are essential for radio, microwave and timing systems, and have a wide range of applications in navigation, communications, remote sensing and basic science. In the past two decades, there has been an optical revolution in time and frequency metrology, and the most accurate clocks and the lowest noise microwave signals are currently based on short-term stable lasers locked to ultrastable cavities. The working principle of ultrastable lasers is to lock the frequency of the laser output to the resonant frequency of the ultrastable cavity through the negative feedback of the servo control circuit. The resonant wavelength of the ultrastable cavity is affected by multiple factors, one of which is the temperature of the cavity.

[0003] However, the temperature control system widely used at present uses thermistors as the original temperature detection components, and their accuracy is usually above 1 milli-Kelvin (mK). Although it can meet general temperature control needs, its accuracy is still not enough to meet the requirements for some high-precision and high-sensitivity application scenarios (such as precision optical experiments, ultra-high-precision manufacturing, and small temperature difference measurement). Especially when extremely fine regulation of temperature changes is required, the accuracy of 1mK may not provide sufficient control accuracy, resulting in the system being unable to achieve the required high-precision temperature management.

[0004] Therefore, there is an urgent need for a new type of temperature monitoring method to further improve the accuracy of temperature control, thereby making the temperature of the ultra-stable cavity more stable and further solving the impact of external temperature fluctuations on the laser frequency. Summary of the invention

[0005] The embodiments of the present application provide an ultra-stable cavity temperature monitoring device, preparation method and application. By using a microbubble cavity to replace an existing thermistor, the accuracy of temperature control can be further improved, thereby making the temperature of the ultra-stable cavity more stable, and further solving the influence of external temperature fluctuations on the laser frequency.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a method for preparing an ultra-stable cavity temperature monitoring device, the method comprising: placing a hollow silica capillary tube on a hydrogen flame for heating, and during the heating process, stretching the hollow silica capillary tube at both ends so that the hollow silica capillary tube is thin in the middle and thick at both sides;

[0008] One end of the hollow silica capillary is sealed, and pressure is applied to the hollow silica capillary from the other end until the atmospheric pressure in the hollow silica capillary increases to a preset value;

[0009] A carbon dioxide laser is used to irradiate the middle part of the hollow silica capillary, so that a microbubble cavity is formed in the middle of the hollow silica capillary;

[0010] The optical fiber is placed on a hydrogen flame to heat it. During the heating process, the optical fiber is stretched at both ends, making the optical fiber thin in the middle and thick on both sides.

[0011] The processed hollow silica capillary tube with the microbubble cavity is coupled with the processed optical fiber to form a cross-shaped structure, thereby obtaining an ultra-stable cavity temperature monitoring device.

[0012] A possible design scheme, the method of the first aspect also includes that the inner diameter of the hollow silica capillary is 100 microns and the outer diameter is 140 microns. During the heating process, the hollow silica capillary is stretched at both ends so that the inner diameter of the hollow silica capillary is 9 microns and the outer diameter becomes 10 microns.

[0013] In a possible design scheme, the method of the first aspect further includes, during the heating process, stretching the hollow silica capillary at both ends, including:

[0014] Fix both ends of the hollow silica capillary with a clamp, and place the clamp on a stepper motor to drive the stepper motor to stretch the hollow silica capillary.

[0015] A possible design scheme, the method of the first aspect also includes that the preset value is three times the normal atmospheric pressure.

[0016] In a possible design scheme, the method of the first aspect also includes that the diameter of the microbubble cavity formed in the middle of the hollow silica capillary is 30 microns and the side wall thickness is 500 nanometers.

[0017] A possible design scheme, the method of the first aspect also includes that the optical fiber has a diameter of 125 microns, and during the heating process, the optical fiber is stretched at both ends so that the diameter of the thinnest part of the optical fiber is no more than 1 micron.

[0018] In a possible design scheme, the method of the first aspect further includes, during the heating process, stretching the optical fiber at both ends, including:

[0019] Use a clamp to fix the two ends of the optical fiber, and place the clamp on a stepper motor to drive the stepper motor to stretch the optical fiber.

[0020] In a second aspect, the present application provides an ultra-stable cavity temperature monitoring device, which is prepared according to the preparation method of the ultra-stable cavity temperature monitoring device of the first aspect.

[0021] In a third aspect, the present application provides an application of an ultra-stable cavity temperature monitoring device for temperature monitoring, the application method comprising: fixing the ultra-stable cavity temperature monitoring device on the outer surface of a copper shell of the ultra-stable cavity;

[0022] The laser is input from one end of the optical fiber to interact with the microbubble cavity formed in the middle of the hollow silica capillary. The laser is received at the other end of the optical fiber, and the intensity of the laser transmission signal is measured to obtain a Lorentz line transmission spectrum, in which the initial wavelength of the laser is known.

[0023] The position of the peak of the transmission spectrum of the Lorentz line shape is measured to obtain the resonant wavelength of the laser, and then the difference between the resonant wavelength and the initial wavelength is obtained;

[0024] According to the resonance condition of the microbubble cavity and the thermo-optic coefficient of the microbubble cavity, the relationship between the difference, the initial wavelength and the temperature change is obtained, and then the temperature change is determined.

[0025] A possible design scheme, the method of the third aspect also includes fixing the ultra-stable cavity temperature monitoring device on the surface of the object whose temperature change needs to be measured by using ultraviolet curing glue.

[0026] In the embodiments of the present application, the microbubble cavity has the advantages of small model volume, low production cost, easy integration and miniaturization. Using the microbubble cavity to replace the existing thermistor can significantly improve the accuracy of temperature control, thereby making the temperature of the ultra-stable cavity more stable.

[0027] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A schematic flow chart of a method for preparing an ultra-stable cavity temperature monitoring device provided in an embodiment of the present application;

[0030] Figure 2 A flow chart for preparing a microbubble cavity formed in the middle of a hollow silica capillary provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of the structure of an ultra-stable cavity temperature monitoring device provided in an embodiment of the present application;

[0032] Figure 4Schematic diagram of the application of the ultra-stable cavity temperature monitoring device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. At the same time, in the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0034] Figure 1 A schematic flow chart of a method for preparing an ultra-stable cavity temperature monitoring device provided in an embodiment of the present application is shown below.

[0035] Step S101, placing the hollow silica capillary on a hydrogen flame for heating, during the heating process, stretching the hollow silica capillary at both ends, so that the hollow silica capillary is thin in the middle and thick at both sides.

[0036] The hollow silica capillary is placed on a hydrogen flame for heating, and the flow rate of hydrogen can be freely adjusted, for example, the hydrogen flow rate is 120 ml / s, and there is no specific restriction.

[0037] During the heating process, when the hollow silica capillary is stretched at both ends, a clamp can be used to fix the two ends of the hollow silica capillary, and the clamp is placed on a stepper motor to drive the stepper motor to stretch the hollow silica capillary. During the specific stretching process, the displacement speed of the stepper motor can be freely adjusted, for example, the displacement speed of the stepper motor is 10 microns / second.

[0038] In the embodiment of the present application, the inner diameter of the selected hollow silica capillary is 100 microns and the outer diameter is 140 microns. During the heating process, the hollow silica capillary is stretched at both ends so that the inner diameter of the hollow silica capillary is 9 microns and the outer diameter becomes 10 microns. The hollow silica capillary before stretching can be referred to Figure 2 (1) in the figure, the stretched hollow silica capillary can be referred to Figure 2 in (2).

[0039] In addition, hollow silica capillaries of other sizes may also be selected, which are not limited here and are selected based on the temperature accuracy that needs to be measured.

[0040] Step S102, sealing one end of the hollow silica capillary tube, and applying pressure to the hollow silica capillary tube from the other end until the atmospheric pressure in the hollow silica capillary tube increases to a preset value.

[0041] In the embodiment of the present application, the preset value may be three times the normal atmospheric pressure (ie, three atmospheric pressures, 3.03×105Pa). The preset value may also be selected according to the temperature accuracy to be measured, and is not limited here. The pressurization method may refer to Figure 2 in (3).

[0042] Step S103, using a carbon dioxide laser to irradiate the middle portion of the hollow silica capillary, so that a microbubble cavity is formed in the middle of the hollow silica capillary.

[0043] The hollow silica capillary tube pressurized by carbon dioxide laser irradiation causes the silica to heat, soften, and swell to form a microbubble cavity. The microbubble cavity formed in the middle of the hollow silica capillary tube has a diameter of 30 microns and a side wall thickness of 500 nanometers. Figure 2 (3) in the figure, the irradiated hollow silica capillary can be referred to Figure 2 in (4).

[0044] Among them, the microbubble cavity has a circular outer edge structure, so it can form a whispering gallery optical mode and can be used as a whispering gallery optical microcavity.

[0045] Step S104, placing the optical fiber on a hydrogen flame for heating, during which the optical fiber is stretched at both ends so that the optical fiber is thin in the middle and thick at both sides.

[0046] The optical fiber is placed on a hydrogen flame for heating, and the flow rate of hydrogen can be freely adjusted, for example, the hydrogen flow rate is 120 ml / s, and there is no specific restriction.

[0047] During the heating process, when the optical fiber is stretched at both ends, a clamp can be used to fix the two ends of the optical fiber, and the clamp is placed on a stepper motor to drive the stepper motor to stretch the optical fiber. During the specific stretching process, the displacement speed of the stepper motor can be freely adjusted, for example, the displacement speed of the stepper motor is 10 microns / second.

[0048] In the embodiment of the present application, the selected optical fiber has a diameter of 125 microns. During the heating process, the optical fiber is stretched at both ends so that the diameter of the thinnest part of the optical fiber is no more than 1 micron. The optical fiber before stretching can refer to the hollow silica capillary before stretching, and the optical fiber after stretching can refer to the hollow silica capillary after stretching, which will not be described in detail. In addition, since the stretched optical fiber has a geometric structure that is thin in the middle and thick on both sides, it is similar to a cone and can also be called an optical fiber cone, or other possible names, which are not limited here.

[0049] Step S105, coupling the processed hollow silica capillary having the microbubble cavity with the processed optical fiber to form a cross-shaped structure to obtain an ultra-stable cavity temperature monitoring device.

[0050] The treated hollow silica capillary and the treated optical fiber are sealed at both ends and coupled to form a cross-shaped structure. For details, please refer to Figure 3 , and then place the device on the outer surface of the copper shell of the ultra-stable cavity that needs temperature monitoring, or on other objects that need temperature monitoring, to achieve temperature monitoring.

[0051] In summary, the microbubble cavity has the advantages of small model volume, low production cost, easy integration and miniaturization. Using the microbubble cavity to replace the existing thermistor can significantly improve the accuracy of temperature control, thereby making the temperature of the ultra-stable cavity more stable.

[0052] Combination of the above Figure 1-Figure 3 The preparation method of the ultra-stable cavity temperature monitoring device provided in the embodiment of the present application is described in detail. Figure 4 The application of the ultra-stable cavity temperature monitoring device provided in the embodiment of the present application is described.

[0053] The specific application steps are as follows:

[0054] Step S201, fixing the ultra-stable cavity temperature monitoring device on the outer surface of the copper shell of the ultra-stable cavity.

[0055] Among them, the ultra-stable cavity temperature monitoring device is fixed on the surface of the object whose temperature change needs to be measured by using UV curing glue. Figure 4 The ultra-stable cavity temperature monitoring device is fixed on the outer surface of the copper shell of the ultra-stable cavity.

[0056] It should be noted that UV-curing adhesive can cure quickly, has high bonding strength, and has the advantages of low-temperature curing. It is suitable for applications that require high precision, such as packaging of electronic components and optical devices, and surface mount technology (SMT).

[0057] In step S202, the laser inputs laser light from one end of the optical fiber, interacts with the microbubble cavity formed in the middle of the hollow silica capillary, receives the laser light at the other end of the optical fiber, measures the intensity of the laser transmission signal, and obtains a Lorentz line transmission spectrum, wherein the initial wavelength of the laser light is known.

[0058] That is to say, the laser is input through one end of the optical fiber, and after entering the hollow silica capillary, it interacts with the microbubble cavity formed therein. That is, after the laser passes through the microbubble cavity, it will be affected by the change in the refractive index in the cavity, causing the frequency and intensity of the laser to change. At this time, by receiving the transmitted laser signal at the other end of the optical fiber, the transmission intensity of the laser can be measured to obtain the transmission spectrum of the Lorentz line. Among them, the optical fiber is a channel for transmitting laser signals, which can ensure the transmission of lasers over long distances and reduce losses.

[0059] In the embodiment of the present application, the initial wavelength λ0 of the laser is taken as 780 nm as an example.

[0060] Step S203, measuring the position of the peak value of the transmission spectrum of the Lorentz line shape to obtain the resonant wavelength of the laser, and then obtaining the difference between the resonant wavelength and the initial wavelength;

[0061] That is to say, the peak position of the transmission spectrum is measured, that is, the resonance wavelength (λ res ). This wavelength corresponds to the resonant frequency of the microbubble cavity and is the wavelength at which light propagates most efficiently in the cavity.

[0062] The difference between the resonant wavelength and the initial wavelength is Δλ = λ res -λ0.

[0063] Step S204, according to the resonance condition of the microbubble cavity and the thermo-optic coefficient of the microbubble cavity, the relationship between the difference, the initial wavelength and the temperature change is obtained, and then the temperature change is determined.

[0064] According to the resonance condition of the microbubble cavity, we can get Where n is the refractive index of silicon oxide, and Δn represents the change in the refractive index of silicon oxide at different temperatures.

[0065] According to the thermo-optic effect, the refractive index of silicon oxide has a certain dependence on temperature changes. Specifically, the relationship between the refractive index of silicon oxide and temperature can be expressed by a thermo-optic coefficient (α), and the relationship between the thermo-optic coefficient and the refractive index can be expressed as: Therefore, the relationship between the refractive index change Δn and the temperature change ΔT is:

[0066] When the microbubble cavity is made of silicon oxide, the thermo-optic coefficient is 6×10 -6 ,so

[0067] The laser wavelength is set to 780 nm (i.e., λ0 = 780 nm), and the quality factor of the microcavity is greater than 10 9 , and the line width of the resonant mode (i.e., Δλ) is less than 7.8×10 -7 nm.

[0068] The temperature measurement accuracy can be estimated by the above formula Substitute λ0=780nm, Δλ=7.8×10 -7 nm, ΔT = 0.16 mK. That is to say, through the resonance condition of the microbubble cavity, the temperature measurement accuracy of about 0.16 mK can be achieved, which is an order of magnitude higher than the temperature measurement sensitivity of existing thermistors.

[0069] From the above, the temperature change of the copper shell of the ultra-stable cavity can be obtained, and the change can be displayed on an oscilloscope or other program software, which is not limited here.

[0070] The various embodiments in the present application are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences between it and other embodiments.

[0071] The above describes a specific embodiment of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the specific order or continuous order shown in the process depicted in the drawings is not necessarily required to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0072] The above is only the embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for preparing an ultra-stable cavity temperature monitoring device, characterized in that: The preparation method comprises: The hollow silica capillary is placed on a hydrogen flame for heating, and during the heating process, the two ends of the hollow silica capillary are stretched so that the hollow silica capillary is thin in the middle and thick at both sides; Sealing one end of the hollow silica capillary, and applying pressure to the hollow silica capillary from the other end until the atmospheric pressure in the hollow silica capillary increases to a preset value; Using a carbon dioxide laser to irradiate the middle portion of the hollow silica capillary, so that a microbubble cavity is formed in the middle of the hollow silica capillary; The optical fiber is placed on a hydrogen flame for heating, and during the heating process, the optical fiber is stretched at both ends so that the optical fiber is thin in the middle and thick at both sides; The processed hollow silica capillary tube with the microbubble cavity is coupled with the processed optical fiber to form a cross-shaped structure, thereby obtaining an ultra-stable cavity temperature monitoring device.

2. The method for preparing the ultra-stable cavity temperature monitoring device according to claim 1, characterized in that: The inner diameter of the hollow silica capillary is 100 microns and the outer diameter is 140 microns. During the heating process, the hollow silica capillary is stretched at both ends so that the inner diameter of the hollow silica capillary is 9 microns and the outer diameter becomes 10 microns.

3. The method for preparing the ultra-stable cavity temperature monitoring device according to claim 1 or 2, characterized in that: During the heating process, the hollow silica capillary is stretched at both ends, comprising: A clamp is used to fix the two ends of the hollow silica capillary, and the clamp is placed on a stepper motor, and the stepper motor is driven to stretch the hollow silica capillary.

4. The method for preparing the ultra-stable cavity temperature monitoring device according to claim 1, characterized in that: The preset value is three times the normal atmospheric pressure.

5. The method for preparing the ultra-stable cavity temperature monitoring device according to claim 2, characterized in that: The diameter of the microbubble cavity formed in the middle of the hollow silica capillary is 30 micrometers, and the thickness of the side wall is 500 nanometers.

6. The method for preparing the ultra-stable cavity temperature monitoring device according to claim 1, characterized in that: The optical fiber has a diameter of 125 microns. During the heating process, the optical fiber is stretched at both ends so that the diameter of the thinnest part of the optical fiber is no more than 1 micron.

7. The method for preparing the ultra-stable cavity temperature monitoring device according to claim 1 or 6, characterized in that: During the heating process, the optical fiber is stretched at both ends, including: A clamp is used to fix the two ends of the optical fiber, and the clamp is placed on a stepper motor, and the stepper motor is driven to stretch the optical fiber.

8. An ultra-stable cavity temperature monitoring device, characterized in that: The ultra-stable cavity temperature monitoring device is prepared by the preparation method of the ultra-stable cavity temperature monitoring device according to any one of claims 1 to 7.

9. An application of an ultra-stable cavity temperature monitoring device for temperature monitoring, characterized in that: include: Fixing the ultra-stable cavity temperature monitoring device on the outer surface of the copper shell of the ultra-stable cavity; Inputting laser light from one end of an optical fiber to interact with a microbubble cavity formed in the middle of a hollow silica capillary, receiving the laser light at the other end of the optical fiber, measuring the intensity of the laser transmission signal, and obtaining a Lorentz line transmission spectrum, wherein the initial wavelength of the laser light is known; Measuring the position of the peak value of the transmission spectrum of the Lorentz line shape to obtain the resonant wavelength of the laser, and then obtaining the difference between the resonant wavelength and the initial wavelength; According to the resonance condition of the microbubble cavity and the thermo-optic coefficient of the microbubble cavity, the relationship between the difference, the initial wavelength and the temperature change is obtained, and then the temperature change is determined.

10. The application of the temperature chamber temperature monitoring device according to claim 9, characterized in that: The ultra-stable cavity temperature monitoring device is fixed on the surface of the object whose temperature change needs to be measured by using ultraviolet curing glue.

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