Temperature monitoring system of calcium atom furnace

Abstract

The invention discloses a temperature monitoring system of a calcium atom furnace, and relates to the technical field of optical metrology, and a method for monitoring the temperature of the calcium atom furnace by using the monitoring system comprises the following steps: placing a hollow silicon oxide capillary tube on hydrogen flame for heating, stretching two ends while heating, so that the wall thickness of the capillary tube is thinned, and sealing one end of the capillary tube; applying pressure from the other end, irradiating the capillary tube by using a carbon dioxide laser to expand the capillary tube and form a micro-bubble cavity, heating the optical fiber on hydrogen flame, stretching the two ends while heating to thin the optical fiber to form an optical fiber taper with a thin middle and two thick sides, and coupling the optical fiber taper with the micro-bubble cavity to form the micro-bubble optical fiber. The optical fiber taper is sealed and fixed on a ULE light path bottom plate of the calcium atom furnace, and laser is input from one end of the optical fiber taper, interacts with the microbubble cavity and then is received from the other end of the optical fiber taper. According to the invention, the echo wall mode microbubble cavity is used for replacing a commonly-used thermistor at present to realize temperature monitoring of the ULE light path in the calcium atom furnace.

Description

Technical Field

[0001] This invention relates to the field of optical metrology, and in particular to a temperature monitoring system for a calcium atom furnace. Background Technology

[0002] Frequency standards are essential for radio, microwave, and timing systems, and have wide applications in navigation, communication, remote sensing, and basic science. Over the past two decades, an optical revolution has occurred in the field of time and frequency metrology. Currently, optical atomic clocks are trending towards replacing traditional microwave atomic clocks as the next generation of video metrology tools.

[0003] The principle of a calcium atom optical clock is that four parallel laser beams, each propagating in opposite directions, interact with a high-speed jet of calcium atoms to produce Ramsey-Borde interference fringes. The wavelength of the ultrastable laser is then locked at the vertex frequency of the interference fringes. The wavelength of the interference fringes is affected by multiple factors, one of which is the cavity temperature—temperature changes the optical path of the laser, thus altering the phase of the interference fringes. Currently, widely used temperature control systems employ thermistors as the temperature detection element, with an accuracy typically above 1 mK.

[0004] Therefore, a novel temperature monitoring method is proposed. This invention abandons the traditional thermistor as the temperature monitoring element and replaces it with a whispering-gallery mode microbubble cavity, resulting in a temperature measurement accuracy of less than 1 mK.

[0005] It should be noted that the above content falls within the inventor's technical knowledge and does not necessarily constitute prior art. Summary of the Invention

[0006] To address the aforementioned issues, the present invention aims to provide a microcavity with advantages such as small mode volume, low manufacturing cost, and ease of integration and miniaturization. Utilizing the thermo-optical effect of silicon oxide, its refractive index changes with temperature, leading to variations in the resonant frequency. Due to the extremely small mode volume of the microcavity, it is highly sensitive to temperature changes. Replacing existing thermistors with microcavities can further improve the precision of temperature control, thereby making the temperature of the ULE (unidirectional lightweight package) optical path in the calcium atom furnace more stable and further reducing the impact of temperature fluctuations on the Ramsey-Borde interference fringe frequency.

[0007] To achieve the above objectives, this invention proposes a calcium atom furnace temperature monitoring system, and the method for monitoring the temperature of the calcium atom furnace using the monitoring system is as follows:

[0008] Hollow silica capillary tubes are heated over a hydrogen flame, and both ends are stretched during heating to thin the capillary wall.

[0009] Seal one end of the capillary tube and apply pressure from the other end.

[0010] Irradiating capillaries with a carbon dioxide laser causes them to swell and form microbubble cavities;

[0011] The optical fiber is heated over a hydrogen flame, and its ends are stretched while it is being heated, making the fiber thinner and forming a tapered fiber that is thinner in the middle and thicker at both ends.

[0012] The fiber taper is coupled to the microbubble cavity, and then sealed and fixed to the ULE optical path base plate of the calcium atom furnace.

[0013] The laser inputs laser light from one end of the fiber taper, which interacts with the microbubble cavity and outputs it from the other end of the fiber taper.

[0014] The laser wavelength output from the scanning fiber taper is detected at the detector receiving end to obtain a Lorentz-shaped transmission spectrum.

[0015] The position of the peak of the Lorentz linear transmission spectrum is measured to obtain the change in system temperature.

[0016] Preferably, the capillary has an inner diameter of 100 μm and an outer diameter of 140 μm. After stretching, the inner diameter of the capillary becomes 9 μm and the outer diameter becomes 10 μm.

[0017] Preferably, the inside of the capillary is pressurized to a pressure of three atmospheres.

[0018] Preferably, the microbubble cavity has a diameter of 30 μm and a sidewall thickness of 500 nm.

[0019] Preferably, the thinnest part of the fiber taper has a diameter of less than 1 μm.

[0020] Preferably, the linewidth of the laser used is less than 10 kHz, and the measured Lorentz transmission spectrum linewidth is less than 100 kHz.

[0021] The temperature monitoring system for a calcium atomic furnace proposed in this invention can bring the following beneficial effects:

[0022] 1. This invention utilizes whispering-gallery mode microbubble cavities to replace commonly used thermistors for temperature monitoring in the ULE optical path within a calcium atom furnace. The microbubble cavities used in this invention have the advantages of high quality factor and sensitivity to external temperature, which can improve the temperature measurement accuracy of current thermistors.

[0023] 2. The whispering-gallery mode optical microcavity used in this invention is technologically advanced and highly specialized. The proposed measurement system is a technological innovation with disruptive significance. It is expected to have important implications for the development of calcium atom optical clocks, further addressing the influence of external temperature fluctuations on the interference fringe frequency of calcium atom optical clocks. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 This is a flowchart illustrating the preparation process of the microbubble cavity of the present invention.

[0026] Figure 2 This is a schematic diagram of the monitoring system of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the measurement method involved in this invention clearer, the following description and explanation will be based on the method of this invention and in conjunction with specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] A temperature monitoring system for a calcium atomizing furnace, and a method for monitoring the temperature of the calcium atomizing furnace using the monitoring system, are as follows:

[0029] A hollow silica capillary with an inner diameter of 100 μm and an outer diameter of 140 μm was heated over a hydrogen flame until the inner diameter became 9 μm and the outer diameter became 10 μm. During heating, the hydrogen flow rate was 120 ml / s. The two ends of the capillary were fixed with a clamp, which was then placed on a stepper motor. The stepper motor was driven to stretch the capillary, thinning its wall thickness. The stepper motor's displacement speed was 10 μm / s. Figure 1 As shown in the first and second steps.

[0030] Seal one end of the capillary tube, and pressurize the other end with a syringe until the pressure inside the capillary tube reaches three atmospheres, or 3.03 × 10⁵ Pa. Figure 1 As shown in the third step.

[0031] A pressurized capillary is irradiated with a carbon dioxide laser, causing it to heat up, soften, and swell, forming microbubble-like structures called microbubble cavities. These microbubble cavities have a diameter of 30 μm and a sidewall thickness of 500 nm. For example... Figure 1 As shown in step four. Microbubbles have a ring-shaped outer edge structure, thus they can form whispering-gallery optical modes and can be used as whispering-gallery optical microcavities.

[0032] A 125μm diameter optical fiber is heated over a hydrogen flame while being stretched at both ends until its diameter is less than 1μm, using the same method as that used for capillary stretching. Because the stretched fiber has a tapered geometry, thinner in the middle and thicker at the ends, it can be called an optical fiber taper.

[0033] The fiber taper is coupled to the microbubble cavity, and then encapsulated and fixed to the substrate of the calcium atom furnace ULE (ultra-low expansion coefficient) optical path with UV adhesive. For example... Figure 2 As shown.

[0034] A laser with a linewidth less than 10 kHz is input from one end of an optical fiber taper. After interacting with a microcavity, the transmitted laser signal is received at the other end of the taper for measurement. The resonance condition of the whispering-gallery mode microcavity can be used to obtain...

[0035] Where n is the order of the interference fringes, Δn is the number of interference fringes that have shifted, λ is the center wavelength of the laser, and Δλ is the change in wavelength.

[0036] Substituting the thermo-optical coefficient of silicon dioxide into the above formula, we can obtain Δλ = 6 × 10 -6 λ0ΔT, that is Where λ0 is the initial value of the wavelength, and ΔT is the change in temperature.

[0037] When the laser wavelength is 780 nm and the quality factor of the microbubble cavity is greater than 10⁹ (i.e., the linewidth of the resonant mode is < 7.8 × 10⁻⁷ nm), the measurement accuracy of ΔT can reach 0.16 mK. This is an order of magnitude improvement over the temperature measurement sensitivity of existing thermistors.

[0038] The laser wavelength at the output end of the scanning fiber taper is used to detect the Lorentz line-shaped transmission spectrum at the detector receiving end. The measured Lorentz transmission linewidth is less than 100 kHz.

[0039] The position of the peak of the Lorentz linear transmission spectrum is measured to obtain the change in system temperature.

[0040] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A temperature monitoring system for a calcium atomic furnace, characterized in that, The method for monitoring the temperature of the calcium atom furnace using the aforementioned monitoring system is as follows: Hollow silica capillary tubes are heated over a hydrogen flame, and both ends are stretched while heating to thin the capillary wall. Seal one end of the capillary tube and apply pressure from the other end; Irradiating capillaries with a carbon dioxide laser causes them to swell and form microbubble cavities; The optical fiber is heated over a hydrogen flame, and its ends are stretched while it is being heated, making the fiber thinner and forming a tapered fiber that is thinner in the middle and thicker at both ends. The fiber taper is coupled to the microbubble cavity, and then sealed and fixed to the ULE optical path base plate of the calcium atom furnace; The laser inputs laser light from one end of the fiber taper, which interacts with the microbubble cavity and outputs it from the other end of the fiber taper. The laser wavelength output from the scanning fiber taper is detected at the detector receiving end to obtain the Lorentz-shaped transmission spectrum. The position of the peak of the Lorentz linear transmission spectrum is measured to obtain the change in system temperature.

2. The calcium atom furnace temperature monitoring system according to claim 1, characterized in that, The capillary has an inner diameter of 100 μm and an outer diameter of 140 μm. After stretching, the inner diameter of the capillary becomes 9 μm and the outer diameter becomes 10 μm.

3. The calcium atom furnace temperature monitoring system according to claim 1, characterized in that, The inside of the capillary is pressurized to a pressure of three atmospheres.

4. The calcium atom furnace temperature monitoring system according to claim 1, characterized in that, The microbubble cavity has a diameter of 30 μm and a sidewall thickness of 500 nm.

5. The calcium atom furnace temperature monitoring system according to claim 1, characterized in that, The thinnest part of the fiber taper has a diameter of less than 1 μm.

6. The calcium atom furnace temperature monitoring system according to claim 1, characterized in that, The linewidth of the laser used is less than 10 kHz, and the measured Lorentz transmission spectrum linewidth is less than 100 kHz.

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