Method for measuring frequency stability of low-temperature monocrystalline silicon optical cavity

Abstract

The invention provides a method for measuring the frequency stability of a low-temperature monocrystalline silicon optical cavity, and relates to the technical field of lasers, and the method comprises the steps: providing a monocrystalline silicon optical cavity to be measured; the monocrystalline silicon optical cavity is cooled through a refrigerator, and the temperature of the monocrystalline silicon optical cavity is reduced to a first preset temperature; after the temperature of the monocrystalline silicon optical cavity is reduced to a first preset temperature, turning off the refrigerating machine, and when the refrigerating machine is turned off and the vibration amplitude of the refrigerating machine is reduced to a first preset value, acquiring the frequency of the monocrystalline silicon optical cavity; and obtaining the frequency stability of the monocrystalline silicon optical cavity based on the frequency of the monocrystalline silicon optical cavity. Due to the fact that when the refrigerating machine is turned off and the vibration amplitude of the refrigerating machine is reduced to the first preset value, the influence of vibration of the refrigerating machine on the frequency stability of the monocrystalline silicon optical cavity can be eliminated, and the measurement method can effectively restrain the influence of the vibration amplitude of the refrigerating machine on accurate measurement of the frequency stability of the monocrystalline silicon optical cavity.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity. Background Art

[0002] A low-temperature single-crystal silicon optical cavity is made of single-crystal silicon and has a temperature of approximately 3 to 5 Kelvin (approximately -270°C). This cavity requires a refrigerator to cool it down to approximately 3 to 5 Kelvin (approximately -270°C). However, during the cooling process, the refrigerator inevitably vibrates, causing vibration noise during frequency stability measurements of the single-crystal silicon optical cavity. Therefore, suppressing the impact of this refrigerator vibration noise on the precise measurement of the inherent high frequency stability of the single-crystal silicon optical cavity has become a key issue for those skilled in the art. Summary of the Invention

[0003] In view of this, the present application provides a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity, the scheme is as follows:

[0004] A method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity, comprising:

[0005] Providing a single crystal silicon optical cavity to be tested;

[0006] Using a refrigerator to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to a first preset temperature;

[0007] After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, the frequency of the single crystal silicon optical cavity is obtained;

[0008] Based on the frequency of the single crystal silicon optical cavity, the frequency stability of the single crystal silicon optical cavity is obtained.

[0009] Optionally, after the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single crystal silicon optical cavity includes:

[0010] After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, turning off the refrigerator;

[0011] During the period when the refrigerator is turned off, when the refrigerator changes from a first state to a second state and while the second state is maintained, obtaining the frequency of the single crystal silicon optical cavity;

[0012] When the refrigerator is in the second state, the vibration amplitude of the refrigerator is reduced to the first preset value, and the vibration amplitude of the refrigerator in the first state is greater than the vibration amplitude in the second state.

[0013] Optionally, during the process of maintaining the second state, obtaining the frequency of the single crystal silicon optical cavity includes:

[0014] acquiring the frequency of the single crystal silicon optical cavity within a first preset time during the process of maintaining the second state;

[0015] There is a second preset time between the first preset time and the start time of the second state, the value of the second preset time is greater than 0, and the value range of the first preset time is 40s~60s, including the endpoint value.

[0016] Optionally, after the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single crystal silicon optical cavity further includes:

[0017] During the process of maintaining the second state, obtaining the temperature of the single crystal silicon optical cavity;

[0018] If the temperature of the single crystal silicon optical cavity is higher than a second preset temperature, stop acquiring the frequency of the single crystal silicon optical cavity, and start the refrigerator to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to the first preset temperature;

[0019] After the temperature of the single crystal silicon optical cavity is lowered to the first preset temperature again, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to the first preset value, the frequency of the single crystal silicon optical cavity is obtained.

[0020] Optionally, using a refrigerator to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to a first preset temperature includes:

[0021] placing the single crystal silicon optical cavity in the sample cavity of the refrigerator;

[0022] Using a first vacuum pumping device to perform a first vacuum pumping on the sample chamber of the refrigerator to pump the sample chamber of the refrigerator to a first vacuum degree;

[0023] Using a second vacuum pumping device to perform a second vacuum pumping on the sample chamber of the refrigerator to pump the sample chamber of the refrigerator to a second vacuum degree; wherein the vacuum degree represented by the second vacuum degree is greater than the vacuum degree represented by the first vacuum degree;

[0024] After the sample cavity of the refrigerator is evacuated to the second vacuum degree, the refrigerator is used to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to the first preset temperature.

[0025] Optionally, providing a single crystal silicon optical cavity includes:

[0026] Providing the single crystal silicon optical cavity having a cavity length of a first cavity length;

[0027] providing a first reference cavity having a cavity length equal to the second cavity length;

[0028] providing a second reference cavity having a cavity length equal to the third cavity length;

[0029] The temperature difference between the first reference cavity and the second reference cavity is not greater than a second preset value, and the temperature range of the first reference cavity and the second reference cavity is 15° C. to 30° C., including the endpoint values.

[0030] Optionally, after the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single crystal silicon optical cavity includes:

[0031] After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and when the vibration amplitude of the refrigerator drops to the first preset value while the refrigerator is turned off, the frequency of the single crystal silicon optical cavity is obtained;

[0032] And while obtaining the frequency of the single crystal silicon optical cavity, the frequencies of the first reference cavity and the second reference cavity are obtained.

[0033] Optionally, obtaining the frequency stability of the single crystal silicon optical cavity based on the frequency of the single crystal silicon optical cavity includes:

[0034] Obtaining frequency stability of the single crystal silicon optical cavity based on frequency differences between any two of the single crystal silicon optical cavity, the first reference cavity, and the second reference cavity;

[0035] Wherein, obtaining the frequency stability of the single crystal silicon optical cavity based on the frequency difference between any two of the single crystal silicon optical cavity, the first reference cavity, and the second reference cavity includes:

[0036] Obtaining frequency stability of the single crystal silicon optical cavity based on the first frequency difference, the second frequency difference, and the third frequency difference;

[0037] The first frequency difference is the frequency difference between the frequency of the single crystal silicon optical cavity and the frequency of the first reference cavity, the second frequency difference is the frequency difference between the frequency of the single crystal silicon optical cavity and the frequency of the second reference cavity, and the third frequency difference is the frequency difference between the frequency of the first reference cavity and the frequency of the second reference cavity.

[0038] Optionally, the material of the first reference cavity is ULE glass, and the material of the second reference cavity is ULE glass.

[0039] Optionally, the first cavity length, the second cavity length and the third cavity length are equal; or

[0040] The first cavity length, the second cavity length and the third cavity length are not equal; or

[0041] The first cavity length and the second cavity length are not equal, and the second cavity length and the third cavity length are equal.

[0042] Compared with the related art, the technical solution of this application has the following beneficial effects:

[0043] The measurement method includes: providing a single-crystal silicon optical cavity to be measured; using a refrigerator to cool the single-crystal silicon optical cavity to a first preset temperature; after the temperature of the single-crystal silicon optical cavity is reduced to the first preset temperature, shutting down the refrigerator, and obtaining the frequency of the single-crystal silicon optical cavity while the refrigerator is shut down and when the vibration amplitude of the refrigerator drops to a first preset value; and obtaining the frequency stability of the single-crystal silicon optical cavity based on the frequency of the single-crystal silicon optical cavity. Since the refrigerator will not vibrate after it is shut down, the experimental platform on which the single-crystal silicon optical cavity is located will not be shaken, and the vibration of the refrigerator will not affect the cavity length of the single-crystal silicon optical cavity, thereby preventing the vibration of the refrigerator from affecting the measurement of the intrinsic frequency stability of the single-crystal silicon optical cavity. Therefore, when the refrigerator is turned off and the vibration amplitude of the refrigerator drops to the first preset value, the frequency stability of the obtained single-crystal silicon optical cavity will not be affected by the vibration of the refrigerator. That is, the influence of the vibration amplitude of the refrigerator on the measurement of the frequency stability of the single-crystal silicon optical cavity can be effectively avoided, thereby obtaining the frequency stability of the single-crystal silicon optical cavity when it is in a low-temperature state.

[0044] In addition, this measurement method acquires the frequency of the single-crystal silicon optical cavity when the refrigerator is in the off state, thereby measuring the frequency stability of the single-crystal silicon optical cavity, thereby avoiding the influence of the vibration of the refrigerator during the refrigeration process on the frequency of the single-crystal silicon optical cavity. Therefore, regardless of whether the volume of the refrigerator is large or small, that is, whether the vibration degree of the refrigerator is large or small, the frequency stability of the single-crystal silicon optical cavity can be measured. Therefore, this measurement method has no restrictions on the cavity length of the single-crystal silicon optical cavity, can be applied to more application scenarios, and is highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following is a brief introduction to the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0046] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size, without affecting the efficacy and objectives that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0047] Figure 1 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0048] Figure 2 A comparison chart of the frequency stability curves of low-temperature single-crystal silicon optical cavities obtained using the measurement method described in this application;

[0049] Figure 3 A flow chart of another method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0050] Figure 4 A flow chart of another method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0051] Figure 5 A flow chart of another method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0052] Figure 6 A flow chart of another method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0053] Figure 7 A flow chart of another method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0054] Figure 8 A flow chart of another method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application;

[0055] Figure 9 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application. DETAILED DESCRIPTION

[0056] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0057] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0058] As described in the background technology section, the vibration of the refrigerator causes vibration noise during the frequency stability measurement of the single-crystal silicon optical cavity. Specifically, as the refrigerator cools the single-crystal silicon optical cavity, it inevitably shakes the entire experimental setup, causing the cavity length of the optical cavity to become unstable. This in turn generates vibration noise induced by the refrigerator's vibration, which is reflected in the measured frequency stability. Furthermore, because the vibration noise of the refrigerator is larger than the frequency noise corresponding to the optical performance of the single-crystal silicon optical cavity, it greatly affects the measurement of the frequency stability of the low-temperature single-crystal silicon optical cavity, making it impossible to accurately measure the E-17 level frequency stability inherent in the low-temperature single-crystal silicon optical cavity. Therefore, how to suppress the impact of the refrigerator's vibration noise on the frequency stability of the single-crystal silicon optical cavity has become a key issue for those skilled in the art.

[0059] For example, how can one measure the E-17 frequency stability inherent in a low-temperature single-crystal silicon optical cavity when subjected to E-16 refrigerator vibration noise? Currently, while frequency stability levels of 1E-16 or even 6.5E-17 can be achieved in low-temperature single-crystal silicon optical cavity systems with a cavity length of no more than 6 cm, longer single-crystal silicon cavities require a more powerful refrigerator, which in turn increases the size of the refrigerator. This in turn leads to stronger vibrations, which in turn significantly impact the frequency stability of the cavity. Therefore, single-crystal silicon cavities must be kept short, no longer than 6 cm, which is highly restrictive and unfavorable for practical applications.

[0060] Based on the above, the present application provides a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity, such as Figure 1 As shown, Figure 1 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application. The measurement method includes:

[0061] S1: Provide a single crystal silicon optical cavity to be tested. For example, based on high-purity single crystal silicon raw materials, the cavity shape (also known as the optical cavity) and the cavity mirror shape are processed, and a high-precision reflective film is coated on the surface of the cavity mirror. The optical cavity and the cavity mirror are then assembled into a complete optical cavity to obtain a single crystal silicon optical cavity. After assembling the above-mentioned single crystal silicon optical cavity, the traditional and very mature PDH (Pound-Drever-Hall, PDH for short) frequency locking technology can be used to lock the frequency of a laser to the cavity length of the single crystal silicon optical cavity. That is, how the cavity length of the single crystal silicon optical cavity changes, the frequency of the laser changes, that is, the frequency change of the laser is determined by the change in the cavity length of the single crystal silicon optical cavity. It should be noted that, in order to simplify the description, the frequency of the single crystal silicon optical cavity is used to represent the frequency of the laser corresponding to the single crystal silicon optical cavity, and the frequency stability of the single crystal silicon optical cavity is used to represent the change of the frequency of the laser corresponding to the single crystal silicon optical cavity over time.

[0062] S2: Use a refrigerator to cool the single crystal silicon optical cavity, and reduce the temperature of the single crystal silicon optical cavity to a first preset temperature. The refrigerator can be a GM-type constant temperature vibration isolation vacuum refrigerator, that is, the GM-type constant temperature vibration isolation vacuum refrigerator can be used to cool the single crystal silicon optical cavity, and reduce the temperature of the single crystal silicon optical cavity from room temperature 20°C to a first preset temperature. It should be noted that the first preset temperature can be about -270°C, that is, the refrigerator can cool the single crystal silicon optical cavity to about -270°C, but the present application does not limit the value of the first preset temperature, and it can also be a value other than -270°C, depending on the specific situation.

[0063] S3: After the temperature of the single crystal silicon optical cavity is lowered to the first preset temperature, the refrigerator is turned off, and while the refrigerator is off and the vibration amplitude of the refrigerator drops to the first preset value, the frequency of the single crystal silicon optical cavity is obtained. It should be noted that after the refrigerator is turned off, although the refrigerator is no longer performing cooling work, the low-temperature state of the single crystal silicon optical cavity will not change in a short period of time, that is, the temperature of the single crystal silicon optical cavity will not rise rapidly in a short period of time. Therefore, while the refrigerator is off and the vibration amplitude of the refrigerator drops to the first preset value, the frequency obtained is still the frequency of the single crystal silicon optical cavity when it is in a low-temperature state, that is, the frequency of the low-temperature single crystal silicon optical cavity. It should also be noted that the present application does not limit the specific value of the above-mentioned first preset value. For example, the value of the first preset value can be zero, but it can also be other values, depending on the specific circumstances.

[0064] S4: Obtaining the frequency stability of the single-crystal silicon optical cavity based on the frequency of the single-crystal silicon optical cavity. That is, obtaining the frequency stability of the single-crystal silicon optical cavity based on the frequency of the single-crystal silicon optical cavity obtained in step S3 above. It should be noted that the frequency stability of the single-crystal silicon optical cavity can indicate the operating performance of the single-crystal silicon optical cavity, and thus obtaining the frequency stability of the low-temperature single-crystal silicon optical cavity can indicate the quality of its operating performance.

[0065] After the refrigerator is turned off, that is, it stops operating, the refrigerator will not vibrate due to the refrigeration operation, thereby not shaking the experimental platform where the single-crystalline silicon optical cavity is located. Furthermore, the vibration of the refrigerator will not affect the cavity length of the single-crystalline silicon optical cavity, and further, the vibration of the refrigerator will not affect the measurement of the frequency stability of the single-crystalline silicon optical cavity. Therefore, when the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, the frequency stability of the single-crystalline silicon optical cavity is measured. The obtained frequency stability of the single-crystalline silicon optical cavity is not affected by the vibration of the refrigerator, that is, the influence of the vibration amplitude of the refrigerator on the measurement of the frequency stability of the single-crystalline silicon optical cavity can be effectively avoided, thereby obtaining the frequency stability of the single-crystalline silicon optical cavity when it is in a low-temperature state, that is, obtaining the frequency stability of the low-temperature single-crystalline silicon optical cavity. It should be noted that the vibration amplitude of the refrigerator is an important determinant of the vibration noise of the refrigerator. Therefore, the measurement method of the present application measures the frequency stability of the single-crystal silicon optical cavity when the vibration amplitude of the refrigerator is reduced to a first preset value. That is, the measurement method can measure the frequency stability of the single-crystal silicon optical cavity when the vibration noise of the refrigerator is relatively small, which can effectively reduce the impact of the vibration noise of the refrigerator on the measurement.

[0066] For example Figure 2 As shown, Figure 2 The horizontal axis is time, the vertical axis is the frequency stability of the single crystal silicon optical cavity, and Figure 2 Curve 1 in the middle shows the frequency stability curve of the single-crystal silicon optical cavity measured when the refrigerator is continuously running and the refrigerator has an E-16 vibration amplitude. Curve 2 shows the intrinsic frequency stability curve of the single-crystal silicon optical cavity measured by this method when the refrigerator has an E-16 vibration amplitude. Based on curves 1 and 2, it can be seen that the measurement method provided by this application can successfully measure the E-17 frequency stability inherent in the single-crystal silicon optical cavity when the refrigerator has an E-16 vibration amplitude. Therefore, it can be seen that this measurement method can successfully measure a frequency stability of 6E-17 or even better for a single-crystal silicon optical cavity in the liquid helium temperature range when the refrigerator has an E-16 vibration amplitude, providing an experimental means to support the excellent optical performance of single-crystal silicon optical cavities in the liquid helium temperature range.

[0067] In addition, it can be seen from the above that this measurement method is to obtain the frequency of the single-crystal silicon optical cavity when the refrigerator is in the off state, and realize the measurement of the frequency stability of the single-crystal silicon optical cavity, thereby avoiding the influence of the vibration of the refrigerator during the refrigeration process on the frequency of the single-crystal silicon optical cavity. Therefore, regardless of whether the volume of the refrigerator is large or small, that is, whether the vibration level of the refrigerator is large or small, the frequency stability of the single-crystal silicon optical cavity can be measured, that is, this measurement method can realize the measurement of the frequency stability of the single-crystal silicon optical cavity with a small cavity length, and can also realize the measurement of the frequency stability of the single-crystal silicon optical cavity with a large cavity length. It can be seen that this measurement method is not limited to the cavity length of the single-crystal silicon optical cavity, can be applied to more application scenarios, and is highly practical.

[0068] It should be noted that after the temperature of the above-mentioned single-crystal silicon optical cavity is lowered to the first preset temperature, the refrigerator is turned off, and while the refrigerator is off, the frequency of the single-crystal silicon optical cavity is obtained when the vibration amplitude of the refrigerator drops to the first preset value. This is because although the refrigerator has stopped working and no longer generates active vibration due to refrigeration, the process from turning off the refrigerator to the end of the refrigerator vibration takes some time. That is, after the refrigerator stops working, there will still be a period of vibration relaxation. Therefore, after the refrigerator is turned off, and while the refrigerator is off, the frequency of the single-crystal silicon optical cavity is not obtained until the vibration amplitude of the refrigerator drops to the first preset value, so as to minimize the influence of the refrigerator vibration on the measured frequency stability of the single-crystal silicon optical cavity and thus obtain the frequency stability of the low-temperature single-crystal silicon optical cavity. It should also be noted that the frequency of the single-crystal silicon optical cavity is only acquired when the vibration amplitude of the known refrigerator drops to a first preset value. This is intended to minimize the impact of refrigerator vibration on the frequency stability of the single-crystal silicon optical cavity. Therefore, the specific value of the aforementioned first preset value may depend on the tolerance for the refrigerator vibration amplitude when measuring the frequency stability of the single-crystal silicon optical cavity. A greater tolerance may result in a larger first preset value, while a smaller tolerance may result in a smaller first preset value. In other words, when measuring the frequency stability of the single-crystal silicon optical cavity, if the accuracy requirement is low, the first preset value may be large; if the accuracy requirement is high, the first preset value may be small, for example, the first preset value may be zero.

[0069] In one embodiment of the present application, Figure 3 As shown, Figure 3 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in the present application. After the temperature of the single-crystal silicon optical cavity drops to a first preset temperature, the refrigerator is turned off. While the refrigerator is off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single-crystal silicon optical cavity includes:

[0070] S31: After the temperature of the single crystal silicon optical cavity drops to a first preset temperature, the refrigerator is turned off.

[0071] S32: When the refrigerator is turned off, when the refrigerator changes from the first state to the second state and is maintained in the second state, obtaining the frequency of the single crystal silicon optical cavity.

[0072] Among them, when the refrigerator is in the second state, the vibration amplitude of the refrigerator is reduced to a first preset value, that is, when the refrigerator is in the second state, the vibration amplitude of the refrigerator is smaller, so the vibration amplitude of the refrigerator in the first state is greater than the vibration amplitude in the second state.

[0073] After the refrigerator lowers the temperature of the single-crystal silicon optical cavity to a first preset temperature, the refrigerator is turned off. The refrigerator undergoes a period of relaxation, approximately 150 seconds, which is the aforementioned first state. After the aforementioned vibration relaxation ends, the refrigerator enters a quiet state, in which the refrigerator's vibration amplitude is the first preset value. At this time, the refrigerator's vibration amplitude can be zero, i.e., the refrigerator changes from the first state to the second state, and the second state lasts for approximately 100 seconds. Therefore, after the refrigerator is turned off and changes from the first state to the second state, the refrigerator enters a quiet state, in which the vibration amplitude is the first preset value, thereby avoiding the impact of the refrigerator's vibration amplitude on the frequency stability of the single-crystal silicon optical cavity. Furthermore, since the low-temperature state of the single-crystal silicon optical cavity does not change within a short period of time after the refrigerator is turned off, the impact of the refrigerator's vibration amplitude on the frequency stability of the single-crystal silicon optical cavity can be avoided, while the frequency stability of the single-crystal silicon optical cavity can be obtained, thereby achieving the frequency stability of the low-temperature single-crystal silicon optical cavity.

[0074] In one embodiment of the present application, Figure 4 As shown, Figure 4 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application. During the second state maintenance process, obtaining the frequency of the single-crystal silicon optical cavity includes:

[0075] S33: Acquire the frequency of the single crystal silicon optical cavity within a first preset time during the second state maintenance process.

[0076] There is a second preset time between the first preset time and the start time of the second state, and the value of the second preset time is greater than 0. The value of the first preset time can be 40s~60s, including endpoint values.

[0077] After the refrigerator is shut down, its vibration amplitude should gradually decrease, or in other words, go from active to non-active. Therefore, after the refrigerator changes from the first state to the second state, the refrigerator's vibration amplitude remains at the first preset value throughout the second state. Based on this, the frequency of the single-crystal silicon optical cavity is acquired during the first preset time while the second state is maintained. Specifically, the frequency of the single-crystal silicon optical cavity is acquired during the time period when the refrigerator's vibration amplitude remains at the first preset value. This mitigates the impact of the refrigerator's vibration amplitude on the frequency stability of the single-crystal silicon optical cavity.

[0078] It should be noted that the value range of the first preset time can be 40s to 60s, including the endpoint values. Preferably, the value of the first preset time can be 50s. However, this application does not limit the value range and specific value of the first preset time, which will be determined according to specific circumstances.

[0079] In one embodiment of the present application, Figure 5 As shown, Figure 5 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in the present application. After the temperature of the single-crystal silicon optical cavity drops to a first preset temperature, the refrigerator is turned off. While the refrigerator is off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single-crystal silicon optical cavity also includes:

[0080] S34: During the second state maintenance process, the temperature of the single crystal silicon optical cavity is obtained.

[0081] S35: If the temperature of the single crystal silicon optical cavity is higher than the second preset temperature, stop acquiring the frequency of the single crystal silicon optical cavity, and start the refrigerator to cool the single crystal silicon optical cavity, reducing the temperature of the single crystal silicon optical cavity to the first preset temperature. For example, after the temperature of the single crystal silicon optical cavity has significantly increased, that is, the temperature of the single crystal silicon optical cavity is higher than the second preset temperature, the refrigerator is restarted and the refrigerator is allowed to operate for 2-3 hours until the temperature of the single crystal silicon optical cavity is reduced to the first preset temperature (approximately -270°C).

[0082] S36: After the temperature of the single crystal silicon optical cavity is lowered to the first preset temperature again, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to the first preset value, the frequency of the single crystal silicon optical cavity is obtained.

[0083] Since the refrigerator is no longer cooling the single-crystal silicon optical cavity after it is turned off, the temperature of the single-crystal silicon optical cavity will gradually increase. Therefore, during the second state maintenance process, or more precisely, during the frequency acquisition process of the single-crystal silicon optical cavity, the temperature of the single-crystal silicon optical cavity needs to be frequently or periodically acquired. If the temperature of the single-crystal silicon optical cavity rises significantly and no longer meets the temperature requirement for a low-temperature single-crystal silicon optical cavity, acquiring the frequency of the single-crystal silicon optical cavity is stopped, and the refrigerator is restarted to cool the single-crystal silicon optical cavity again until the temperature of the single-crystal silicon optical cavity returns to the first preset temperature, at which point the frequency of the single-crystal silicon optical cavity is acquired again. In other words, this measurement method can repeatedly acquire the frequency of the single-crystal silicon optical cavity by temporarily removing the vibration amplitude of the refrigerator. Each time the frequency of the single-crystal silicon optical cavity is acquired, the frequency stability of the acquired single-crystal silicon optical cavity is calculated, and the average frequency stability of the single-crystal silicon optical cavity is obtained after averaging the multiple acquisitions. In other words, this measurement method can acquire the frequency stability of the single-crystal silicon optical cavity based on a large amount of data, thereby ensuring that the acquired frequency stability of the single-crystal silicon optical cavity has a high degree of accuracy.

[0084] It should be noted that this measurement method can be based on the frequency of the single-crystal silicon optical cavity obtained repeatedly. When the frequency stability of the single-crystal silicon optical cavity is obtained, the frequency stability of the single-crystal silicon optical cavity is calculated once each time the frequency of the single-crystal silicon optical cavity is obtained, and then the final average frequency stability is obtained based on the frequency stabilities of the single-crystal silicon optical cavity obtained multiple times.

[0085] It should also be noted that after the temperature of the single-crystal silicon optical cavity is lowered back to the first preset temperature, the refrigerator should not be immediately shut down to proceed with frequency acquisition of the single-crystal silicon optical cavity. Instead, the refrigerator should be run for a period of time after the temperature of the single-crystal silicon optical cavity is lowered back to the first preset temperature to stabilize the low-temperature state of the single-crystal silicon optical cavity. That is, after the temperature of the single-crystal silicon optical cavity is lowered back to the first preset temperature and the single-crystal silicon optical cavity has stabilized at the low temperature, the refrigerator should be shut down to proceed with subsequent steps.

[0086] In one embodiment of the present application, Figure 6 As shown, Figure 6 This application provides a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity. Using a refrigerator to cool the single-crystal silicon optical cavity to a first preset temperature includes:

[0087] S21: Place the single crystal silicon optical cavity in the sample cavity of the refrigerator.

[0088] S22: evacuating the sample chamber of the refrigerator for the first time by using a first vacuuming device to evacuate the sample chamber of the refrigerator to a first vacuum degree.

[0089] S23: Using a second vacuum pumping device to perform a second vacuum pumping on the sample chamber of the refrigerator to a second vacuum level, wherein the vacuum level represented by the second vacuum level is higher than the vacuum level represented by the first vacuum level.

[0090] S24: After the sample cavity of the refrigerator is evacuated to the second vacuum degree, the refrigerator is used to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to a first preset temperature.

[0091] The first vacuum pumping device can be a cascade molecular pump, and the second vacuum pumping device can be an ion pump. The first vacuum level can be 1E-6 Torr, and the second vacuum level can be 3E-7 Torr. Specifically, the single-crystal silicon optical cavity is placed behind the sample chamber of a refrigerator. Before the refrigerator begins cooling, at room temperature, the cascade molecular pump assembly is first used to evacuate the refrigerator sample chamber to a vacuum level of 1E-6 Torr. Then, an ion pump with a pumping speed of 45 L / s is used to evacuate the refrigerator to a vacuum level of 3E-7 Torr. The refrigerator cold head is then turned on to initiate cooling. After five days of continuous operation, the temperature of the single-crystal silicon optical cavity can be reduced from a room temperature of 20 degrees Celsius to a first preset value (approximately -270 degrees Celsius), completing the cooling of the single-crystal silicon optical cavity.

[0092] In one embodiment of the present application, Figure 7 As shown, Figure 7 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in this application. A single-crystal silicon optical cavity is provided, comprising:

[0093] S11: providing a single crystal silicon optical cavity having a cavity length equal to a first cavity length.

[0094] S12: Provide a first reference cavity having a cavity length equal to the second cavity length.

[0095] S13: Provide a second reference cavity with a cavity length of the third cavity length. The temperature difference between the first reference cavity and the second reference cavity is not greater than the second preset value, that is, the temperature difference between the first reference cavity and the second reference cavity can be small, so that the temperatures of the first reference cavity and the second reference cavity can be similar, or even approximately the same. In addition, the temperature range of the first reference cavity and the second reference cavity is 15°C~30°C, including the endpoint values. It should be noted that the temperature of the first reference cavity and the second reference cavity can be room temperature 20°C, but this application does not limit this, and it depends on the specific circumstances. It should also be noted that the temperatures of the above-mentioned first reference cavity and the second reference cavity can also be significantly different, but in order to reduce the variable factors in the process of obtaining the frequency stability of the single crystal silicon optical cavity, the first reference cavity and the second reference cavity preferably have the same or similar material properties and the same or similar operating temperatures.

[0096] As can be seen from the above, this measurement method utilizes a triangular hat precision frequency measurement method to obtain the frequency stability of a single-crystal silicon optical cavity. Specifically, this method requires the construction of a triangular hat measurement system. This involves providing two reference cavities, based on the aforementioned single-crystal silicon optical cavity. The frequencies of the lasers corresponding to these two reference cavities are locked to the cavity lengths of their respective optical cavities, namely, the first and second reference cavities. This system, required for the triangular hat precision frequency measurement method, provides a measurement basis for obtaining the frequency stability of a single-crystal silicon optical cavity.

[0097] In one embodiment of the present application, Figure 8 As shown, Figure 8 This is a flow chart of a method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity provided in the present application. After the temperature of the single-crystal silicon optical cavity drops to a first preset temperature, the refrigerator is turned off. While the refrigerator is off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single-crystal silicon optical cavity includes:

[0098] S37: When the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, the frequency of the single crystal silicon optical cavity is obtained.

[0099] S38: While obtaining the frequency of the single crystal silicon optical cavity, the frequencies of the first reference cavity and the second reference cavity are obtained.

[0100] In one embodiment of the present application, Figure 7 As shown, based on the frequency of the single crystal silicon optical cavity, obtaining the frequency stability of the single crystal silicon optical cavity includes:

[0101] S41: Obtaining frequency stability of the single crystal silicon optical cavity based on frequency differences between any two of the single crystal silicon optical cavity, the first reference cavity, and the second reference cavity.

[0102] Wherein, obtaining the frequency stability of the single crystal silicon optical cavity based on the frequency difference between any two of the single crystal silicon optical cavity, the first reference cavity, and the second reference cavity includes:

[0103] The frequency stability of the single crystal silicon optical cavity is obtained based on the first frequency difference, the second frequency difference, and the third frequency difference, wherein the first frequency difference is the frequency difference between the frequency of the single crystal silicon optical cavity and the frequency of the first reference cavity, the second frequency difference is the frequency difference between the frequency of the single crystal silicon optical cavity and the frequency of the second reference cavity, and the third frequency difference is the frequency difference between the frequency of the first reference cavity and the frequency of the second reference cavity.

[0104] As can be seen above, after establishing the measurement system required for the cocked hat measurement, this measurement method obtains the frequency difference between the single-crystal silicon optical cavity and the frequency of the first reference cavity, the frequency difference between the single-crystal silicon optical cavity and the frequency of the second reference cavity, and the frequency difference between the first reference cavity and the frequency of the second reference cavity. Based on these frequency difference settings, the cocked hat precision frequency measurement method is then used to analyze these frequency difference data to determine the frequency stability of the single-crystal silicon optical cavity.

[0105] In one embodiment of the present application, the first reference cavity is made of ULE glass, and the second reference cavity is made of ULE glass. Because ULE glass (Ultra-Low Expansion Glass, abbreviated as ULE glass) has an extremely low thermal expansion coefficient, or even zero thermal expansion coefficient, the length of the first and second reference cavities does not change due to thermal expansion. This ensures that the lengths of the first and second reference cavities are stable, and does not affect the accuracy of measuring the frequency stability of the single-crystal silicon optical cavity. Therefore, the frequency stability of the single-crystal silicon optical cavity can be accurately obtained.

[0106] In one embodiment of the present application, the first cavity length, the second cavity length, and the third cavity length can be equal, or the first cavity length, the second cavity length, and the third cavity length can be unequal, or the first cavity length and the second cavity length can be unequal, while the second cavity length and the third cavity length can be equal. In other words, when using this measurement method to measure the frequency stability of a single-crystal silicon optical cavity, the relative cavity lengths between the single-crystal silicon optical cavity, the first reference cavity, and the second reference cavity are not restricted and can be flexibly set. This measurement method is therefore applicable to a wider range of application scenarios and is highly practical.

[0107] Optionally, the length of the second cavity may be 30 cm, and the length of the third cavity may also be 30 cm, but this application does not limit this, and it depends on the specific circumstances.

[0108] In order to more clearly understand the method for measuring the frequency stability of a single crystal silicon optical cavity provided in the present application, the measurement method described in the present application is described in detail below through a flow chart.

[0109] like Figure 9As shown, a refrigerator is started to cool the single-crystal silicon optical cavity to a first preset temperature. The refrigerator is then shut down, and the refrigerator sequentially enters a relaxation state (first state) and a quiet state (second state). While the refrigerator is in the quiet state, the frequency stability is measured using the triangular hat precision frequency measurement method. Simultaneously, the temperature of the single-crystal silicon optical cavity is measured. When the temperature of the single-crystal silicon optical cavity significantly rises, the measurement is stopped, and the refrigerator is restarted to cool the single-crystal silicon optical cavity. After the temperature of the single-crystal silicon optical cavity is lowered to the first preset temperature, the refrigerator is shut down. Once the refrigerator is in the quiet state, the triangular hat precision frequency measurement method is used for measurement and analysis to achieve frequency stability measurement. These steps are repeated until the acquired frequency and frequency stability data of the single-crystal silicon optical cavity meet the requirements of subsequent calculations.

[0110] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on the differences from other embodiments, and reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For relevant parts, refer to the description of the methods.

[0111] It should be noted that in the description of this application, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting this application. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a centrally located component.

[0112] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such article or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the article or device comprising the aforementioned elements.

[0113] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity, characterized in that: include: Providing a single crystal silicon optical cavity to be tested; Using a refrigerator to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to a first preset temperature; After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, the frequency of the single crystal silicon optical cavity is obtained; Based on the frequency of the single crystal silicon optical cavity, the frequency stability of the single crystal silicon optical cavity is obtained.

2. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 1, characterized in that: After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single crystal silicon optical cavity includes: After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, turning off the refrigerator; During the period when the refrigerator is turned off, when the refrigerator changes from a first state to a second state and while the second state is maintained, obtaining the frequency of the single crystal silicon optical cavity; When the refrigerator is in the second state, the vibration amplitude of the refrigerator is reduced to the first preset value, and the vibration amplitude of the refrigerator in the first state is greater than the vibration amplitude in the second state.

3. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 2, characterized in that: During the process of maintaining the second state, obtaining the frequency of the single crystal silicon optical cavity includes: acquiring the frequency of the single crystal silicon optical cavity within a first preset time during the process of maintaining the second state; There is a second preset time between the first preset time and the start time of the second state, the value of the second preset time is greater than 0, and the value range of the first preset time is 40s~60s, including the endpoint value.

4. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 2, wherein: After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single crystal silicon optical cavity further includes: During the process of maintaining the second state, obtaining the temperature of the single crystal silicon optical cavity; If the temperature of the single crystal silicon optical cavity is higher than a second preset temperature, stop acquiring the frequency of the single crystal silicon optical cavity, and start the refrigerator to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to the first preset temperature; After the temperature of the single crystal silicon optical cavity is lowered to the first preset temperature again, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to the first preset value, the frequency of the single crystal silicon optical cavity is obtained.

5. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 1, wherein: Using a refrigerator to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to a first preset temperature includes: placing the single crystal silicon optical cavity in the sample cavity of the refrigerator; Using a first vacuum pumping device to perform a first vacuum pumping on the sample chamber of the refrigerator to pump the sample chamber of the refrigerator to a first vacuum degree; Using a second vacuum pumping device to perform a second vacuum pumping on the sample chamber of the refrigerator to pump the sample chamber of the refrigerator to a second vacuum degree; wherein the vacuum degree represented by the second vacuum degree is greater than the vacuum degree represented by the first vacuum degree; After the sample cavity of the refrigerator is evacuated to the second vacuum degree, the refrigerator is used to cool the single crystal silicon optical cavity to reduce the temperature of the single crystal silicon optical cavity to the first preset temperature.

6. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 1, wherein: A single crystal silicon optical cavity is provided, comprising: Providing the single crystal silicon optical cavity having a cavity length of a first cavity length; providing a first reference cavity having a cavity length equal to the second cavity length; providing a second reference cavity having a cavity length equal to the third cavity length; The temperature difference between the first reference cavity and the second reference cavity is not greater than a second preset value, and the temperature range of the first reference cavity and the second reference cavity is 15° C. to 30° C., including the endpoint values.

7. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 6, characterized in that: After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and while the refrigerator is turned off and the vibration amplitude of the refrigerator drops to a first preset value, obtaining the frequency of the single crystal silicon optical cavity includes: After the temperature of the single crystal silicon optical cavity drops to the first preset temperature, the refrigerator is turned off, and when the vibration amplitude of the refrigerator drops to the first preset value while the refrigerator is turned off, the frequency of the single crystal silicon optical cavity is obtained; And while obtaining the frequency of the single crystal silicon optical cavity, the frequencies of the first reference cavity and the second reference cavity are obtained.

8. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 6, characterized in that: Obtaining frequency stability of the single crystal silicon optical cavity based on the frequency of the single crystal silicon optical cavity includes: Obtaining frequency stability of the single crystal silicon optical cavity based on frequency differences between any two of the single crystal silicon optical cavity, the first reference cavity, and the second reference cavity; Wherein, obtaining the frequency stability of the single crystal silicon optical cavity based on the frequency difference between any two of the single crystal silicon optical cavity, the first reference cavity, and the second reference cavity includes: Obtaining frequency stability of the single crystal silicon optical cavity based on the first frequency difference, the second frequency difference, and the third frequency difference; The first frequency difference is the frequency difference between the frequency of the single crystal silicon optical cavity and the frequency of the first reference cavity, the second frequency difference is the frequency difference between the frequency of the single crystal silicon optical cavity and the frequency of the second reference cavity, and the third frequency difference is the frequency difference between the frequency of the first reference cavity and the frequency of the second reference cavity.

9. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 6, wherein: The material of the first reference cavity is ULE glass, and the material of the second reference cavity is ULE glass.

10. The method for measuring the frequency stability of a low-temperature single-crystal silicon optical cavity according to claim 6, wherein: The first cavity length, the second cavity length and the third cavity length are equal; or The first cavity length, the second cavity length and the third cavity length are not equal; or The first cavity length and the second cavity length are not equal, and the second cavity length and the third cavity length are equal.

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