Method, apparatus, system and computer-readable storage medium for measuring transmittance

Abstract

The present disclosure relates to the field of optical technologies, and in particular, to a method, apparatus, system, and computer-readable storage medium for measuring transmittance. The method includes: obtaining a first curve of the reflectance of an optical cavity varying with the frequency of light in a first state, and a second curve of the reflectance of the optical cavity varying with the frequency of light in a second state; determining a first value of the optical power attenuation parameter of the optical cavity in the first state according to the full width at half maximum of the first curve; determining a second value of the optical power attenuation parameter of the optical cavity in the second state according to the full width at half maximum of the second curve; obtaining a correlation formula between the reflectance of the optical cavity, the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror; and fitting to obtain the value of the transmittance of the first mirror according to the correlation formula, the first curve, the first value, the second curve, and the second value. The present disclosure can more accurately measure the transmittance of the mirror in the optical cavity.

Description

Technical Field

[0001] The present disclosure relates to the field of optical technologies, and in particular, to a method, apparatus, system, and computer-readable storage medium for measuring transmittance. Background Art

[0002] An optical cavity is an important component in modern optical engineering and modern basic scientific research. The optical cavity is arranged by multiple mirrors according to optical design to achieve photon confinement, enhanced interaction between photons and qubits, etc. The reflectivity and transmittance of the mirrors constituting the optical cavity are very important parameters of the optical cavity.

[0003] In the related art, the transmittance of a single mirror is measured before building the optical cavity. Summary of the Invention

[0004] It is noted that measuring the transmittance of a single mirror before building the optical cavity in the related art may cause several problems.

[0005] First, the transmittance of the mirror will inevitably change during the building process of the optical cavity. For example, due to dust, chemical reactions on the mirror surface, or other reasons, there is a deviation between the transmittance measured after the cavity is formed and the transmittance measured before the cavity is formed, and the accuracy of the measurement is affected. In particular, when the mirror has a very high reflectivity close to 1, the transmittance of the mirror is extremely low. At this time, even a slight change in the transmittance value of the mirror during the building process of the optical cavity can have a greater impact on the accuracy of the measurement.

[0006] Second, accurately measuring the transmittance of a single mirror before building the optical cavity also has relatively high requirements for the mirror itself. For example, for special small mirrors or spherical mirrors with a small radius of curvature, it is technically difficult to measure the transmittance. It is necessary to accurately measure the transmittance while well shielding stray light and completely receiving the transmitted light.

[0007] In view of this, the present disclosure proposes the following technical solutions, which are helpful for more accurately measuring the transmittance of the mirror in the optical cavity.

[0008] According to a first aspect of the embodiments of the present disclosure, a method for measuring transmittance is provided. The method for measuring transmittance includes: obtaining a first curve of the reflectance of an optical cavity varying with the frequency of light in a first state, and a second curve of the reflectance of the optical cavity varying with the frequency of light in a second state, wherein light enters the optical cavity from a first mirror of the optical cavity; determining a first value of the optical power attenuation parameter of the optical cavity in the first state according to the full width at half maximum of the first curve; determining a second value of the optical power attenuation parameter of the optical cavity in the second state according to the full width at half maximum of the second curve, the second value being different from the first value; obtaining a correlation formula between the reflectance of the optical cavity, the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror; and fitting to obtain the value of the transmittance of the first mirror according to the correlation formula, the first curve, the first value, the second curve, and the second value.

[0009] According to some embodiments of the present disclosure, in the first state, there is a first light-shielding object in the optical cavity; in the second state, there is no light-shielding object or there is a second light-shielding object in the optical cavity, and the spatial information of the second light-shielding object is different from the spatial information of the first light-shielding object, and the spatial information includes at least one of shape and position.

[0010] According to some embodiments of the present disclosure, obtaining the correlation formula includes: obtaining a first correlation formula between a first reflectance R1 corresponding to the part that is not coupled to the optical cavity after light is incident on the first mirror and the coupling efficiency C k between them; obtaining a second correlation formula between a second reflectance R2 corresponding to the part that is coupled to the optical cavity after light is incident on the first mirror, the frequency f of light, the optical power attenuation parameter R ’ round , the coupling efficiency C k , and the transmittance t of the first mirror k ; and determining the correlation formula according to the first correlation formula and the second correlation formula.

[0011] According to some embodiments of the present disclosure, the correlation formula is: R k (f)=R1+R2; where R k (f) is the reflectance of the optical cavity.

[0012] According to some embodiments of the present disclosure, the first correlation formula is: R1 = 1 - C k .

[0013] According to some embodiments of the present disclosure, the second correlation formula is: ; where, φ round is the phase change accumulated by light during one cycle of propagation in the optical cavity, φ round = 4πfl / c, where l is the effective length of the optical cavity, c is the speed of light, R ’ round = R round (1 - L), where L is the value of the light loss magnification of the optical cavity in the first state or the second state, and L < 1, , is the product of the reflectivities of all the mirrors that sequentially reflect light during one cycle of propagation of light in the optical cavity, r j is the reflectivity of the mirror that reflects light for the j-th time during one cycle of propagation of light in the optical cavity, and N is the number of times all the mirrors in the optical cavity reflect light during one cycle of propagation of light.

[0014] According to some embodiments of the present disclosure, the first value and the second value are obtained according to the following formula: ; where, R ’ round is the optical power attenuation parameter, f HWHM is the full width at half maximum, l is the effective length of the optical cavity, and c is the speed of light.

[0015] According to some embodiments of the present disclosure, obtaining the transmittance value of the first mirror by fitting according to the correlation formula, the first curve, the first value, the second curve, and the second value includes: obtaining a third value related to the transmittance of the first mirror and the coupling efficiency by fitting according to the correlation formula, the first curve, and the first value; obtaining a fourth value related to the transmittance of the first mirror and the coupling efficiency by fitting according to the correlation formula, the second curve, and the second value; and determining the transmittance value of the first mirror according to the third value and the fourth value.

[0016] According to a second aspect of the embodiments of the present disclosure, a transmittance measurement device is provided. The transmittance measurement device includes: a first acquisition module configured to acquire a first curve of the reflectance of an optical cavity varying with the frequency of light in a first state, and a second curve of the reflectance of the optical cavity varying with the frequency of light in a second state, where light enters the optical cavity from a first mirror of the optical cavity; a first determination module configured to determine a first value of the optical power attenuation parameter of the optical cavity in the first state according to the full width at half maximum of the first curve; a second determination module configured to determine a second value of the optical power attenuation parameter of the optical cavity in the second state according to the full width at half maximum of the second curve, the second value being different from the first value; a second acquisition module configured to acquire a correlation formula between the reflectance of the optical cavity and the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror; and a fitting module configured to fit to obtain the value of the transmittance of the first mirror according to the correlation formula, the first curve, the first value, the second curve, and the second value.

[0017] According to a third aspect of the embodiments of the present disclosure, a transmittance measurement device is provided. The transmittance measurement device includes: a memory; and a processor coupled to the memory and configured to execute the transmittance measurement method of any one of the above embodiments based on instructions stored in the memory.

[0018] According to a fourth aspect of the embodiments of the present disclosure, a transmittance measurement system is provided. The transmittance measurement system includes: the transmittance measurement device of any one of the above embodiments; a signal generator configured to generate a swept-frequency signal; a transmitter configured to emit light with a varying frequency to the first mirror according to the swept-frequency signal; and a detection device configured to detect the reflected light signal of the optical cavity and determine the correlation information between the power of the reflected light signal and the frequency of light according to the reflected light signal and the swept-frequency signal; where the transmittance measurement device is configured to acquire the first curve and the second curve according to the correlation information.

[0019] According to a fifth aspect of the embodiments of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium includes computer program instructions, and when the computer program instructions are executed by a processor, the transmittance measurement method of any one of the above embodiments is implemented.

[0020] According to a sixth aspect of the embodiments of the present disclosure, a computer program product is provided. The computer program product includes a computer program, and when the computer program is executed by a processor, the transmittance measurement method of any one of the above embodiments is implemented.

[0021] In the embodiments of the present disclosure, on the one hand, since the entire measurement process is based on the optical cavity that has been built, the influence of the process of building the optical cavity on the value of the transmittance of the first mirror is excluded, and the measured value of the transmittance of the first mirror is more accurate.

[0022] On the other hand, after the optical cavity is built, the measurement result of the above method is basically determined only by the structure of the optical cavity itself. The influence of factors outside the optical cavity (such as the construction and debugging of the optical path) on the measurement result becomes smaller, and the operation error of the measurement is also smaller. Therefore, the measured value of the transmittance of the first mirror is also more accurate.

[0023] On the other hand, since the transmittance of the mirror is related to the incident angle of light, when the incident angle of light changes, the measured transmittance will also change accordingly. According to the above method for measuring the transmittance, only by determining the appropriate structure of the optical cavity so that the light can be incident on the first mirror at a desired incident angle and coupled with the optical cavity, the transmittance of the first mirror at the desired incident angle can be measured. That is, the method for measuring the transmittance in the embodiments of the present disclosure can accurately measure the transmittance of the mirror at any incident angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 is a schematic flowchart of a method for measuring the transmittance according to some embodiments of the present disclosure.

[0026] Figure 2 shows a first curve, a second curve, and a third curve according to some embodiments of the present disclosure.

[0027] Figure 3 is a schematic flowchart of the process of fitting to obtain the value of the transmittance of the first mirror in the method for measuring the transmittance according to some embodiments of the present disclosure.

[0028] Figure 4 is a schematic flowchart of the process of obtaining the correlation formula in the method for measuring the transmittance according to some embodiments of the present disclosure.

[0029] Figure 5 is a schematic diagram of light entering the optical cavity in the method for measuring the transmittance according to some embodiments of the present disclosure.

[0030] Figure 6Schematic diagram of light entering an optical cavity in a method for measuring transmittance according to still other embodiments of the present disclosure.

[0031] Figure 7 Schematic structural diagram of a transmittance measurement device according to some embodiments of the present disclosure.

[0032] Figure 8 Schematic structural diagram of a transmittance measurement device according to still other embodiments of the present disclosure.

[0033] Figure 9 Schematic structural diagram of a transmittance measurement system according to some embodiments of the present disclosure.

[0034] Figure 10 Schematic structural diagram of a transmittance measurement system according to still other embodiments of the present disclosure. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.

[0036] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values described in these embodiments do not limit the scope of the present disclosure.

[0037] Meanwhile, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships.

[0038] For technologies, methods, and devices known to those of ordinary skill in the relevant art, detailed discussions may not be made, but where appropriate, the technologies, methods, and devices should be regarded as part of the description.

[0039] In all the examples shown and discussed here, any specific value should be construed as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0040] It should be noted that: like reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0041] Figure 1 Flow schematic diagram of a method for measuring transmittance according to some embodiments of the present disclosure. As Figure 1 shown, the method for measuring transmittance includes steps S10 - step S50.

[0042] In step S10, a first curve of the reflectivity of the optical cavity varying with the frequency of light in the first state and a second curve of the reflectivity of the optical cavity varying with the frequency of light in the second state are obtained.

[0043] Here, the optical cavity has, for example, M mirrors, where M≥2, and light (such as laser light) enters the optical cavity from the k-th mirror of the optical cavity (hereinafter referred to as the first mirror), where 1≤k≤M. The mirror has, for example, an extremely high reflectivity close to 1.

[0044] It can be understood that the two curves of the optical cavity in the two states are different, and both the first curve and the second curve include multiple sets of data. Each set of data in the first curve includes the reflectivity of the optical cavity in the first state and the corresponding frequency of light, and each set of data in the second curve includes the reflectivity of the optical cavity in the second state and the corresponding frequency of light.

[0045] For example, the reflectivity of the optical cavity is the power reflectivity.

[0046] In some embodiments, before step S10, an optical cavity is built and the optical path of the light incident on the optical cavity is adjusted so that the light enters from the first mirror and the coupling efficiency C of the light with the optical cavity k is relatively high.

[0047] Figure 2 shows a third curve S3 of the reflectivity R k of the optical cavity varying with the frequency f of light in the case where the coupling efficiency C of the light with the optical cavity is relatively low (e.g., close to 0). At this time, due to reasons such as the optical cavity not being built completely or the optical path not being adjusted well, the light is basically not coupled with the optical cavity, so the light incident on the first mirror is basically all reflected back, and the reflectivity R k of the optical cavity is close to 1 and does not vary with the frequency f of light. k (f)

[0048] In step S20, a first value of the optical power attenuation parameter of the optical cavity in the first state is determined according to the full width at half maximum of the first curve.

[0049] It should be understood that the optical power attenuation parameter can reflect the attenuation of the optical power during the propagation of light in the optical cavity. In some embodiments, the optical power attenuation parameter is related to the reflectivity of the mirror that reflects the light during the propagation of light in the optical cavity. In other embodiments, the optical power attenuation parameter is also related to the optical loss caused by the light shielding object in the optical cavity to the propagation of light.

[0050] In step S30, the second value of the optical power attenuation parameter of the optical cavity in the second state is determined according to the full width at half maximum of the second curve. Here, the second value is different from the first value, that is, different values reflecting the different attenuation situations of the optical power during the propagation of light in the optical cavity are determined according to the two curves.

[0051] The execution order of step S20 and step S30 is not limited. For example, step S20 can be executed before step S30, after step S30, or synchronously with step S30.

[0052] In some embodiments, the first value and the second value of the optical power attenuation parameter can be determined according to the following formula:

[0053]

[0054] where R ’ round is the optical power attenuation parameter, f HWHM is the full width at half maximum, l is the effective length of the optical cavity, and c is the speed of light.

[0055] According to formula (1), when the value of the optical power attenuation parameter of the optical cavity changes, the full width at half maximum of the curve of the measured reflectivity of the optical cavity varying with the frequency of light will change accordingly. Conversely, according to the first curve and the second curve with different full widths at half maximum, the first value of the optical power attenuation parameter of the optical cavity in the first state and the second value in the second state can be determined. The detailed derivation of formula (1) will be given below.

[0056] In some embodiments, the optical power attenuation parameter can be defined as the ratio of the power after light propagates in the optical cavity for one period (i.e., light is incident from a certain initial position along a certain initial propagation direction to a certain mirror, and after being reflected by each mirror in the M - surface mirrors at least once and then returning to the initial position in the initial propagation direction again) to the current power. By changing the propagation state of light in the optical cavity, the value of the optical power attenuation parameter of the optical cavity can be changed.

[0057] For example, the optical power attenuation parameter R ’ round can be:

[0058]

[0059] where L is the value of the optical loss magnification of the optical cavity in a certain state (such as the first state or the second state), L < 1, , is the product of the reflectivities of all the mirrors that sequentially reflect light during the process of light propagating in the optical cavity for one period, and r j$R_j$ is the reflectivity of the $j$-th mirror that reflects light during one cycle of light propagation in the optical cavity, and $N$ is the number of times all the mirrors in the optical cavity reflect light during one cycle of light propagation. Since each of the $M$ mirrors in the optical cavity reflects light at least once, $N\geq M$.

[0060] According to Equation (2), during one cycle of light propagation in the optical cavity, the attenuation of power includes the attenuation caused by the reflection of each mirror ($R$ round ), and the attenuation caused by other factors (such as partial occlusion of the light beam, etc.) ($1 - L$).

[0061] In some embodiments, the value of the light loss magnification ($L$) of the optical cavity can be changed by placing a light-blocking object in the optical cavity or changing the spatial information of the light-blocking object when there is already a light-blocking object in the optical cavity, thereby changing the value of the optical power attenuation parameter. Here, the spatial information includes at least one of shape and position.

[0062] For example, in the first state, there is a first light-blocking object in the optical cavity; in the second state, there is no light-blocking object in the optical cavity.

[0063] Again, for example, in the first state, there is a first light-blocking object in the optical cavity; in the second state, there is a second light-blocking object in the optical cavity, and the spatial information of the second light-blocking object is different from that of the first light-blocking object.

[0064] In this way, the value of the light loss magnification of the optical cavity can be made different in the first state and the second state, and further, the first value of the optical power attenuation parameter in the first state of the optical cavity can be made different from the second value of the optical power attenuation parameter in the second state of the optical cavity.

[0065] In some embodiments, when there is no light-blocking object in the optical cavity in the second state, $L = 0$, and at this time . In this case, according to Equation (1), the product of the reflectivities of all the mirrors that sequentially reflect light during one cycle of light propagation in the optical cavity can be determined from the full width at half maximum of the second curve.

[0066] It can be seen from Equation (1) and Equation (2) that when the spatial information of the light-blocking object in the optical cavity is changed (such as making the light-blocking object closer to the optical axis) to increase $L$, the full width at half maximum of the curve of the reflectivity $R$ k $(f)$ of the optical cavity varying with the frequency $f$ of the light increases; when the spatial information of the light-blocking object in the optical cavity is changed (such as making the light-blocking object farther from the optical axis) to decrease $L$, the full width at half maximum of the curve of the reflectivity $R$ k $(f)$ of the optical cavity varying with the frequency $f$ of the light decreases.

[0067] Figure 2Shows a first curve and a second curve according to some embodiments of the present disclosure. The value of the optical loss magnification of the optical cavity corresponding to the second curve S2 on the right is greater than the value of the optical loss magnification of the optical cavity corresponding to the first curve S1 on the left. It can be seen that as it increases, the full width at half maximum of the curve increases accordingly.

[0068] In addition, from Figure 2 It can also be seen that as L increases, the lowest point of the curve moves upward, and the depth of the valley of the curve decreases.

[0069] In some embodiments, based on the electromagnetic field equation, according to the spatial information of the light shielding object (such as shape and position) and the structure of the optical cavity (such as shape), an approximate value of L can be calculated. In this way, it is beneficial to the implementation of the transmittance measurement method.

[0070] In step S40, obtain the correlation formula between the reflectivity of the optical cavity, the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror.

[0071] The coupling efficiency of light and the optical cavity is the ratio of the power of the part of the light incident on the first mirror that is coupled to the optical cavity to the power of the light incident on the first mirror.

[0072] In some embodiments, the reflected light of the optical cavity is divided into two parts. The first part of the light is the light directly reflected by the first mirror from the part of the light incident on the first mirror that is not coupled to the optical cavity, and the second part of the light is the light reflected by the optical cavity from the part of the light incident on the first mirror that is coupled to the optical cavity (including being directly reflected by the first mirror and transmitted out of the first mirror after entering the optical cavity). According to the first part of the light and the second part of the light, the reflectivity of the optical cavity can be determined, and thus the correlation formula between the reflectivity of the optical cavity, the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror can be obtained.

[0073] In some embodiments, the reflectivity R k (f) of the optical cavity, the frequency f of light, the optical power attenuation parameter R ’ round , the coupling efficiency C k of light and the optical cavity, and the transmittance t k of the first mirror are related by the formula:

[0074]

[0075] where φ round is the phase change accumulated by light during one cycle of propagation in the optical cavity, φ round = 4πfl / c, l is the effective length of the optical cavity, c is the speed of light, R ’round =R round (1 - L), R round The meanings of R and L are the same as above. The detailed derivation of formula (3) will be given below.

[0076] It should be noted that formula (3) is only an exemplary way of the correlation formula. In other ways, depending on different factors considered (such as whether to consider two parts of light, whether to perform approximation processing, etc.), the correlation formula can also be other forms of formulas.

[0077] In step S50, based on the correlation formula, the first curve, the first value of the optical power attenuation parameter, the second curve, and the second value of the optical power attenuation parameter, the value of the transmittance of the first mirror is obtained by fitting.

[0078] According to the correlation formula, the reflectivity of the optical cavity is related to the optical power attenuation parameter, and is also related to the frequency of light, the transmittance of the first mirror, and the coupling efficiency. In addition, both the first curve and the second curve include multiple sets of acquired data, and each set of data includes the reflectivity of the optical cavity and the frequency of light. Therefore, based on the multiple sets of data in the known first curve, the multiple sets of data in the second curve, the first value, and the second value, the value of the unknown transmittance of the first mirror in the correlation formula can be obtained by fitting.

[0079] In some embodiments, step S50 can also obtain the value of the coupling efficiency between light and the optical cavity that is unknown in the correlation formula. That is, while measuring the transmittance of the first mirror, the coupling efficiency between light and the optical cavity can also be measured.

[0080] Through steps S10 - S50, the measurement of the transmittance of the mirror to be measured, that is, the first mirror, is achieved.

[0081] On the one hand, since the entire measurement process is based on the fact that the optical cavity has been built, the influence of the process of building the optical cavity on the value of the transmittance of the first mirror is excluded, and the measured value of the transmittance of the first mirror is more accurate.

[0082] On the other hand, after the optical cavity is built, the measurement results of the above method are basically only determined by the structure of the optical cavity itself. The influence of factors outside the optical cavity (such as the building and debugging of the optical path) on the measurement results becomes smaller, and the operation error of the measurement is also smaller. Therefore, the measured value of the transmittance of the first mirror is also more accurate.

[0083] On the other hand, since the transmittance of the mirror is related to the incident angle of light, when the incident angle of light changes, the measured transmittance will also change accordingly. According to the above method for measuring the transmittance, it is only necessary to determine the structure of a suitable optical cavity so that light can be incident on the first mirror at a desired incident angle and coupled with the optical cavity, and then the transmittance of the first mirror at the desired incident angle can be measured. That is, the above method for measuring the transmittance can accurately measure the transmittance of the mirror at any incident angle.

[0084] Figure 3 It is a schematic flow chart of fitting to obtain the value of the transmittance of the first mirror in the method for measuring the transmittance according to some embodiments of the present disclosure.

[0085] In some embodiments, as Figure 3 shown, step S50 includes steps S501 - S503.

[0086] In step S501, according to the correlation formula, the first curve, and the first value, a third value related to the transmittance of the first mirror and the coupling efficiency is fitted.

[0087] For example, after substituting the first value into the correlation formula, a first equation of the correlation formula between the reflectance of the optical cavity, the frequency of light, the coupling efficiency, and the transmittance of the first mirror can be obtained. Further, according to the first equation of the correlation formula and the first curve, a third value related to the transmittance of the first mirror and the coupling efficiency can be fitted.

[0088] In the first equation of the correlation formula, the unknowns include the transmittance of the first mirror and the coupling efficiency. Using the multiple sets of data in the first curve, each set of which includes the reflectance of the optical cavity and the frequency of light, and the first equation of the correlation formula, a third value related to the transmittance of the first mirror and the coupling efficiency can be fitted. When fitting, some sets or all sets of data in the first curve can be used.

[0089] In step S502, according to the correlation formula, the second curve, and the second value, a fourth value related to the transmittance of the first mirror and the coupling efficiency is fitted.

[0090] Similarly, after substituting the second value into the correlation formula, a second equation of the correlation formula between the reflectance of the optical cavity, the frequency of light, the coupling efficiency, and the transmittance of the first mirror can be obtained. Further, according to the second equation of the correlation formula and the second curve, a fourth value related to the transmittance of the first mirror and the coupling efficiency can be fitted.

[0091] In the second equation of the correlation formula, the unknowns also include the transmittance and coupling efficiency of the first mirror. Using the multiple sets of data including the reflectivity of the optical cavity and the frequency of light in each set of data in the second curve, and the second equation of the correlation formula, a fourth value related to the transmittance and coupling efficiency of the first mirror can be obtained by fitting. Similarly, when fitting, part or all of the data in the second curve can be used.

[0092] In step S503, the value of the transmittance of the first mirror is determined according to the third value and the fourth value.

[0093] In some embodiments, the value of the coupling efficiency can also be determined according to the third value and the fourth value.

[0094] In the above steps S501 - S503, since the second curve is different from the first curve, and the second value is different from the first value, the fourth value obtained by fitting is also different from the third value. Thus, two different relationships satisfied by the transmittance and coupling efficiency of the first mirror are obtained, and then the value of the transmittance of the first mirror can be determined according to these two different relationships.

[0095] Figure 4 It is a schematic flow chart of obtaining the correlation formula in the transmittance measurement method according to some embodiments of the present disclosure.

[0096] In some embodiments, as Figure 4 shown, step S40 of obtaining the correlation formula includes steps S401 - S403.

[0097] In step S401, the first correlation formula between the first reflectivity R1 corresponding to the part of the light that is not coupled to the optical cavity after entering the first mirror and the coupling efficiency C k is obtained. Here, the first reflectivity R1 is the contribution of the part of the light that is not coupled to the optical cavity after entering the first mirror to the reflectivity of the optical cavity.

[0098] In step S402, the second correlation formula between the second reflectivity R2 corresponding to the part of the light that is coupled to the optical cavity after entering the first mirror, the frequency f of the light, the optical power attenuation parameter R ’ round of the optical cavity, the coupling efficiency C k and the transmittance t k of the first mirror is obtained. Here, the second reflectivity R2 is the contribution of the part of the light that is coupled to the optical cavity after entering the first mirror to the reflectivity of the optical cavity.

[0099] In step S403, the correlation formula is determined according to the first correlation formula and the second correlation formula.

[0100] As some implementation manners, the correlation formula is:

[0101]

[0102] Among them, R k (f) is the reflectivity of the optical cavity.

[0103] In the above steps S401 - S403, the reflected light from the optical cavity is divided into two parts: the reflected light directly reflected by the first mirror of the part of the light not coupled to the optical cavity, and the reflected light reflected by the entire optical cavity of the part of the light coupled to the optical cavity. At this time, the light intensity of the reflected light of the optical cavity is equal to the sum of the light intensities of these two parts of the reflected light. Therefore, the reflectivity of the optical cavity is equal to the sum of the ratios of the light intensities or powers of these two parts of the reflected light to the light intensity or power of the light incident on the first mirror.

[0104] Figure 5 is a schematic diagram of light entering the optical cavity in the transmittance measurement method according to some embodiments of the present disclosure.

[0105] As Figure 5 shown, the optical cavity is, for example, a Fabry - Perot (F - P) resonator composed of two plane mirrors parallel to each other. The reflectivity and transmittance of the first mirror M1 are r1 and t1 respectively, and the reflectivity and transmittance of the other mirror (referred to as the second mirror) M2 are r2 and t2 respectively. The amplitude of the light incident on the first mirror is A0, the phase is 0, the frequency is f, and the effective length of the optical cavity (the distance between the first mirror M1 and the second mirror M2) is l.

[0106] Figure 5 also shows the amplitude of the light incident on the first mirror M1, as well as the partial reflected light and transmitted light.

[0107] The following is based on Figure 5 to introduce the derivation process of the associated formula (3).

[0108] For the light that is mode - matched to the optical cavity and can thus be coupled to the optical cavity (it can be considered that the coupling efficiency C k of the light to the optical cavity is equal to 1), the reflected light directly reflected by the first mirror M1 and the transmitted light that enters the optical cavity from the first mirror M1 and then is transmitted out from the first mirror M1 (including the transmitted light that is reflected once by the second mirror M2 in the cavity and then transmitted out from the first mirror M1 after being reflected 0, 1, 2, 3... infinitely many times by the first mirror M1 and the second mirror M2) can undergo coherent superposition.

[0109] In some embodiments, the complex representations of the amplitudes of the respective parts of the light included in the reflected light of the optical cavity are:

[0110] …。

[0111] Among them, the first term represents the reflected light directly reflected by the first mirror M1, and the subsequent terms successively represent the light that enters the optical cavity from the first mirror M1, is reflected once by the second mirror M2, and then is reflected 0, 1, 2, 3... infinitely many times by the first mirror M1 and the second mirror M2 respectively, and then the transmitted light that is transmitted out from the first mirror M1, φ r is the phase change accumulated by the light when propagating one cycle in the optical cavity, φ r = 4πfl / c, where c is the speed of light.

[0112] Since the reflection of light occurs at the interface between the film and the mirror body (such as glass) of the mirror, the different refractive indices of the film and the mirror body will cause the vibration direction of the light to suddenly change to the opposite of the vibration direction before reflection when the light travels from the one with the lower refractive index in the film and the mirror body to the one with the higher refractive index, that is, while the amplitude size changes, the phase also undergoes a mutation of π, which is called "half-wave loss". In the above embodiments, the case where the refractive index of the film of the mirror is lower than that of the mirror body is considered. Therefore, only the light directly reflected by the first mirror M1 satisfies the condition of half-wave loss, and only the first term in the complex representation of the amplitude of each part of the light has e iπ .

[0113] Therefore, the complex representation A of the amplitude of the reflected light of the optical cavity r is:

[0114]

[0115] In some other embodiments, the complex representations of the amplitudes of the respective parts of the light included in the reflected light of the optical cavity are respectively: …

[0116] In the above embodiments, the refractive index of the film of the mirror is higher than that of the mirror body. In this case, except for the light directly reflected by the first mirror M1, each reflection of the light in the optical cavity satisfies the condition of half-wave loss, and only the first term in the complex representation of the amplitude of each part of the light does not have e iπ . Therefore, the complex representation A of the amplitude of the reflected light of the optical cavity r is the A in formula (5) r multiplied by -1.

[0117] For any one of the above two cases, the reflectivity R c (f) of the optical cavity is all:

[0118]

[0119] Similarly, the transmitted light transmitted through the second mirror M2 of the optical cavity includes the transmitted light that exits from the second mirror M2 after the light enters the optical cavity from the first mirror M1 and is reflected 0, 1, 2, 3... infinitely many times by the second mirror M2 and the first mirror M1 respectively, and these transmitted lights can be coherently superposed.

[0120] In some embodiments, the complex representations of the amplitudes of the respective partial lights included in the transmitted light of the optical cavity are respectively: …。

[0121] Among them, each term successively represents the transmitted light that exits from the second mirror M2 after the light enters the optical cavity from the first mirror M1 and is reflected 0, 1, 2, 3... infinitely many times by the second mirror M2 and the first mirror M1 respectively.

[0122] In the above embodiments, the refractive index of the film of the mirror is lower than that of the mirror body. Therefore, before the light exits from the second mirror M2, no half-wave loss occurs when the light is reflected by the second mirror M2 and the first mirror M1 in the optical cavity.

[0123] In some other embodiments, the complex representations of the amplitudes of the respective partial lights included in the transmitted light of the optical cavity are respectively: …。

[0124] In the above embodiments, the refractive index of the film of the mirror is higher than that of the mirror body. Therefore, before the light exits from the second mirror M2, every time the light is reflected one more time by the second mirror M2 and the first mirror M1 respectively in the optical cavity, two additional half-wave losses occur.

[0125] For any one of the above two cases, the complex representation A of the amplitude of the transmitted light of the optical cavity t is:

[0126]

[0127] The transmittance T c of the optical cavity (f) is:

[0128]

[0129] Generally, a part of the light does not match the mode of the optical cavity and thus cannot be coupled to the optical cavity. At this time, the coupling efficiency C k of the light and the optical cavity is less than 1. The first reflectance R1 corresponding to the part of the light that is not coupled to the optical cavity after entering the first mirror is:

[0130]

[0131] This formula indicates that the proportion of the light incident on the first mirror M1 is (1 - C kThe part that is not coupled to the optical cavity is directly reflected by the first mirror M1.

[0132] When the coupling efficiency C of light with the optical cavity k is less than 1, according to Equation (6), the second reflectivity R2 corresponding to the part of the light that is coupled to the optical cavity after entering the first mirror is:

[0133]

[0134] This equation shows that the proportion of the light incident on the first mirror M1 that is C k is coupled to the optical cavity. A part of this part of the light is directly reflected by the first mirror M1, and the other part enters the optical cavity and then is transmitted through the first mirror M1. The part of the light directly reflected by the first mirror M1 and the part of the light transmitted through the first mirror M1 after entering the optical cavity can be coherently superposed.

[0135] Combining Equation (9), Equation (10) and Equation (4), the reflectivity R k of the optical cavity (f) can be:

[0136]

[0137] After extending the optical cavity from the case of a Fabry - Perot resonator to the general case of an optical cavity composed of M - plane mirrors, Equation (11) can be rewritten as:

[0138]

[0139] where the reflectivity of the first mirror is rewritten from r1 to r k , and the transmittance is rewritten from t1 to t k , and the phase change accumulated by the light during one - cycle propagation in the optical cavity is rewritten from φ r to φ round . φ round = 4πfl / c, where l is the effective length of the optical cavity and c is the speed of light. r1r2 in the denominator on the right side of the "+" is rewritten as , indicating the attenuation of the amplitude of the light after each additional cycle of propagation in the optical cavity. r2 in the numerator on the right side of the "+" is rewritten as , indicating the attenuation of the amplitude of the light during the process of entering the optical cavity from the first mirror and being transmitted through the first mirror without a complete cycle of propagation in the optical cavity.

[0140] For example, as Figure 6As shown, the optical cavity is a triangular optical cavity with M = 3. The optical cavity includes a first mirror M1 (reflectivity r1) for light incidence, a second mirror M2 (reflectivity r2), and a third mirror M3 (reflectivity r3). Light is incident on the first mirror M1 along the first direction P1 and transmitted from the first mirror M1 along the second direction P2. The effective length l of the optical cavity is the sum of the first distance l1 and the second distance l2. The first distance l1 is the distance between the first mirror M1 and the second mirror M2, and the second distance l2 is the distance between the first mirror M1 and the third mirror M3.

[0141] In this case, for light to propagate one cycle in the optical cavity, it needs to be reflected once at the first mirror M1, the second mirror M2, the first mirror M1, and the third mirror M3 in sequence. Therefore, it can be specifically written as r1·r2·r1·r3.

[0142] In addition, for light to be transmitted from the first mirror M1 after entering the optical cavity without propagating a complete cycle in the optical cavity, it needs to be reflected once at the second mirror M2, the first mirror M1, and the third mirror M3 in sequence. Therefore, it can be specifically written as r2·r1·r3.

[0143] Denote the denominator of the right side of the “+” in Equation (12) as and record it as , R round which represents the power attenuation after light propagates one more cycle in the optical cavity. At the same time, when all the mirrors in the optical cavity are mirrors with extremely high reflectivity (approaching 1), or the relative measurement accuracy requirement for t k is much less than , replace all the reflectivities except the denominator of the right side of the “+” in Equation (12) with 1. Equation (12) can be further rewritten as:

[0144]

[0145] In the above derivation process, only the attenuation caused by the reflection of each mirror is considered in the attenuation of the amplitude of light after propagating one cycle in the optical cavity ( ), so the power attenuation only includes the attenuation caused by the reflection of each mirror.

[0146] After further considering the power attenuation caused by other factors (such as partial occlusion of the light beam by an opaque object, etc.), introduce the optical loss magnification L, and rewrite R round in the denominator of the right side of Equation (12) as R ’ round (1 - L), and record it as R ’ round, which represents the power attenuation of light after each additional propagation cycle in the optical cavity considering other factors. At this time, Equation (13) can be further rewritten as:

[0147]

[0148] Thus, the correlation formula (3) is obtained.

[0149] Based on the above derivation, the first reflectivity R1 corresponding to the part of the light that is not coupled to the optical cavity after incident on the first mirror and the coupling efficiency C k The first correlation formula between them can be correspondingly written as:

[0150]

[0151] The second reflectivity R2 corresponding to the part of the light that is coupled to the optical cavity after incident on the first mirror, the frequency f of the light, the optical power attenuation parameter R of the optical cavity ’ round , the coupling efficiency C k , and the transmittance t of the first mirror k The second correlation formula between them can be correspondingly written as:

[0152]

[0153] Next, the derivation of Equation (1) for determining the first value (or second value) of the optical power attenuation parameter of the optical cavity in the first state (or second state) according to the full width at half maximum of the first curve (or second curve) is introduced.

[0154] First, according to the above derivation, considering that the coupling efficiency C k of the light and the optical cavity is less than 1, the transmittance T k (f) of the optical cavity (such as a Fabry-Perot resonator) is:

[0155]

[0156] This equation shows that the proportion C k of the light incident on the first mirror M1 is coupled to the optical cavity, and the light coupled to the optical cavity and transmitted out of the optical cavity is the transmitted light of the optical cavity.

[0157] Secondly, according to the law of conservation of energy, the sum of the reflectivity R k (f) and the transmittance T k (f) of the optical cavity is 1, so:

[0158]

[0159] It can be seen from Equation (17) that regardless of the coupling efficiency C kRegardless of the value of the reflectivity R of the optical cavity k (f)and the transmittance T of the optical cavity c (f)have the same full width at half maximum. Therefore, according to Equation (8), the full width at half maximum f HWHM The relationship with r1r2 also applies to the associated formula (3) (in this case, r1r2 is extended to R ’ round )

[0160] According to Equation (8), when φ r is φ0 = 2nπ, where n is an integer, the value of Equation (8) is minimized. For Equation (8), when φ r is used as the independent variable of T c (f), the full width at half maximum Δφ r of φ r satisfies:

[0161]

[0162] Since Δφ r approaches 0, after approximation, we get:

[0163]

[0164] The relationship between the full width at half maximum f HWHM derived from Equation (8) and r1r2 is:

[0165]

[0166] Therefore, for the associated formula (3), the full width at half maximum f HWHM The relationship with R ’ round is:

[0167]

[0168] So far, Equation (1) has been obtained based on which the first value (or the second value) of the optical power attenuation parameter of the optical cavity in the first state (or the second state) is determined according to the full width at half maximum of the first curve (or the second curve).

[0169] At the same time, it can be seen from Equation (17) that the reflectivity R k (f)of the optical cavity and the full width at half maximum of the curve (such as the first curve or the second curve) that changes with the frequency of light satisfy:

[0170]

[0171] where f res is the value of the frequency of light (i.e., the resonance frequency) when the reflectivity R k (f)of the optical cavity takes the minimum value.

[0172] In summary, before determining the first value of the optical power attenuation parameter of the optical cavity in the first state or the second value of the optical power attenuation parameter of the optical cavity in the second state according to Equation (1), the full width at half maximum of the first curve or the second curve can be obtained based on Equation (21) and the data included in the first curve or the second curve.

[0173] The present disclosure also provides a transmittance measurement device configured to implement the method of any of the foregoing embodiments.

[0174] Figure 7 It is a schematic structural diagram of a transmittance measurement device according to some embodiments of the present disclosure.

[0175] As Figure 7 shown, the transmittance measurement device includes a first acquisition module 701, a first determination module 702, a second determination module 703, a second acquisition module 704, and a fitting module 705.

[0176] The first acquisition module 701 is configured to acquire a first curve of the reflectance of the optical cavity varying with the frequency of light in the first state and a second curve of the reflectance of the optical cavity varying with the frequency of light in the second state. Here, light enters the optical cavity from the first mirror of the optical cavity.

[0177] The first determination module 702 is configured to determine the first value of the optical power attenuation parameter of the optical cavity in the first state according to the full width at half maximum of the first curve.

[0178] The second determination module 703 is configured to determine the second value of the optical power attenuation parameter of the optical cavity in the second state according to the full width at half maximum of the second curve. Here, the second value is different from the first value.

[0179] The second acquisition module 704 is configured to acquire the correlation formula between the reflectance of the optical cavity, the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror.

[0180] The fitting module 705 is configured to fit and obtain the value of the transmittance of the first mirror according to the correlation formula, the first curve, the first value, the second curve, and the second value.

[0181] Figure 8 It is a schematic structural diagram of a transmittance measurement device according to some other embodiments of the present disclosure.

[0182] As Figure 8 shown, the transmittance measurement device includes a memory 801 and a processor 802 coupled to the memory 801. The processor 802 is configured to execute the method of any of the foregoing embodiments based on instructions stored in the memory 801.

[0183] The memory 801 may include, for example, a system memory, a fixed non-volatile storage medium, etc. The system memory may store, for example, an operating system, application programs, a boot loader, and other programs.

[0184] In some embodiments, the transmittance measurement device may further include an input / output interface 803, a network interface 804, a storage interface 805, etc. These interfaces 803, 804, 805, and between the memory 801 and the processor 802 may be connected through a bus 806, for example. The input / output interface 803 provides a connection interface for input / output devices such as a display, a mouse, a keyboard, a touch screen, etc. The network interface 804 provides a connection interface for various networking devices. The storage interface 805 provides a connection interface for external storage devices such as an SD card, a USB flash drive, etc.

[0185] The present disclosure also proposes a transmittance measurement system.

[0186] Figure 9 It is a schematic structural diagram of a transmittance measurement system according to some embodiments of the present disclosure.

[0187] As Figure 9 shown, the transmittance measurement system includes the transmittance measurement device 900, a signal generator 901, a transmitter 902, and a detection device 903 of any one of the above embodiments.

[0188] The transmittance measurement device 900 may be, for example, Figure 7 the transmittance measurement device shown, or Figure 8 the transmittance measurement device shown.

[0189] The signal generator 901 is configured to generate a swept-frequency signal.

[0190] The transmitter 902 is configured to emit light with a changing frequency to the first mirror according to the swept-frequency signal.

[0191] The detection device 903 is configured to detect the reflected light signal of the optical cavity, and determine the correlation information between the power of the reflected light signal and the frequency of the light according to the reflected light signal and the swept-frequency signal generated by the signal generator 901.

[0192] In some embodiments, as Figure 9 shown, the detection device 903 includes a detector 904 and an oscilloscope 905. The detector 904 is configured to detect the reflected light signal of the optical cavity. The oscilloscope 905 is configured to determine the correlation information between the power of the reflected light signal and the frequency of the light according to the reflected light signal detected by the detector 904 and the swept-frequency signal generated by the signal generator 901. The detector 904 may be, for example, a photodetector (PD).

[0193] The transmittance measurement device 900 is configured to obtain a first curve and a second curve of the reflectance of the optical cavity varying with the frequency of light according to the correlation information determined by the detection device 903. For example, the measurement device can calculate the reflectance of the optical cavity according to the power of the reflected light signal in the correlation information, and then obtain the first curve and the second curve of the reflectance of the optical cavity varying with the frequency of light.

[0194] Figure 10 It is a schematic structural diagram of a transmittance measurement system according to some other embodiments of the present disclosure.

[0195] As Figure 10 shown, the transmittance measurement system can measure the transmittance of the first mirror M1 of the Fabry - Perot resonator. In this case, since it is difficult to detect that the transmitted light transmitted from the first mirror M1 and the light vertically incident on the first mirror M1 are on the same straight line, a lens assembly can be provided between the emitter 902 and the first mirror M1, so as to deflect the propagation direction of the reflected light by 90° while not changing the propagation direction of the light vertically incident on the first mirror M1, so that the detection device 903 can detect it. For example, the lens assembly includes a polarization beam splitter (PBS) 906 and a quarter - wave plate 907, and the quarter - wave plate 907 is arranged between the polarization beam splitter 906 and the first mirror M1.

[0196] In some embodiments, as Figure 10 shown, the transmittance measurement system may further include another detector 904'. The detector 904' is configured to receive the transmitted light signal of the light transmitted from the optical cavity (i.e., transmitted from the second mirror M2), so that the detection device 903 can also determine the correlation information between the power of the transmitted light signal of the optical cavity and the frequency of light according to this transmitted light signal.

[0197] In some other embodiments, the transmittance measurement system is used to measure the transmittance of different components of light by the mirror at different incident angles. For example, the transmittance measurement system can also measure the transmittance of the first mirror M1 of other optical cavities (such as a butterfly - type optical cavity with M = 4, a ring - shaped optical cavity, or Figure 6 the triangular optical cavity shown, etc.). In this case, since the light is not vertically incident on the first mirror M1, the transmittances of the component of the light with the polarization direction perpendicular to the incident plane (S - component) and the component with the polarization direction parallel to the incident plane (P - component) by the first mirror M1 are different. Before the light is incident on the first mirror M1, a polarizer (such as a polarizing film) can be passed through first to retain only the S - component or P - component of the light, so as to measure the transmittance of the S - component or P - component of the light incident on the first mirror M1 at the current incident angle.

[0198] The following briefly introduces the measurement scheme for measuring the transmittance using the transmittance measurement system of the present disclosure.

[0199] First, set up the optical cavity and adjust the optical path so that light enters from the k-th mirror, i.e., the first mirror, and the coupling efficiency is as high as possible. When the light is not coupled to the optical cavity, for example, as shown by the third curve S3 in Figure 2 , no change in reflectance is observed when scanning the frequency of the light. At this time, continue to adjust the optical path and the structure of the optical cavity.

[0200] Subsequently, when the light is well coupled to the optical cavity, scan the frequency of the light, observe the reflected light power signal, find the resonance frequency, and the change in reflectance with frequency can be observed near the resonance frequency.

[0201] Subsequently, place the light-shielding object into the optical cavity, adjust the spatial information of the light-shielding object, observe the curve of the change in reflectance with frequency and record it. It can be seen that as the light-shielding object blocks part of the light, the depth of the valley of the reflectance curve seen during frequency scanning decreases, and at the same time the width increases.

[0202] Subsequently, change the position of the light-shielding object and repeat the previous step. It can be seen that as the effective light-shielding area increases, i.e., the laser loss increases, the depth of the valley of the reflectance will further decrease, and at the same time the width will further increase.

[0203] Subsequently, according to the recorded reflectance curve, obtain the minimum value of the reflectance when the light-shielding object has different spatial information, and then obtain the R of the optical cavity ’ round .

[0204] Finally, according to the recorded reflectance curve, different R values of the optical cavity ’ round and Equation (3), fit to obtain t k 2 .

[0205] The embodiments of the present disclosure also provide a computer-readable storage medium, including computer program instructions, which when executed by a processor implement the method of any one of the above embodiments.

[0206] The embodiments of the present disclosure also provide a computer program product, including a computer program, which when executed by a processor implement the method of any one of the above embodiments.

[0207] So far, the embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details well known in the art have not been described. Those skilled in the art can clearly understand how to implement the technical solutions disclosed herein based on the above description.

[0208] Those skilled in the art should understand that the embodiments of the present disclosure can be provided as methods, systems, or computer program products. Therefore, the present disclosure can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present disclosure can take the form of a computer program product implemented on one or more computer-usable non-transitory storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) that contain computer-usable program code.

[0209] The present disclosure is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that the functions specified in one or more processes in the flowchart and / or one or more blocks in the block diagram can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more processes and / or Figure 1 one or more blocks.

[0210] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one or more processes and / or Figure 1 one or more blocks.

[0211] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are performed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more processes and / or Figure 1 one or more blocks.

[0212] Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or some technical features can be equivalently replaced without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A method for measuring transmittance, characterized in that, Including: Obtaining a first curve of the reflectivity of the optical cavity varying with the frequency of light in a first state, and a second curve of the reflectivity of the optical cavity varying with the frequency of light in a second state, wherein light enters the optical cavity from a first mirror of the optical cavity, in the first state, there is a first light-shielding object in the optical cavity, in the second state, there is no light-shielding object or there is a second light-shielding object in the optical cavity, and at least one of the shape and position of the second light-shielding object is different from that of the first light-shielding object; Determining a first value of the optical power attenuation parameter of the optical cavity in the first state according to the full width at half maximum of the first curve; Determining a second value of the optical power attenuation parameter of the optical cavity in the second state according to the full width at half maximum of the second curve, and the second value is different from the first value; Obtaining a correlation formula between the reflectivity of the optical cavity and the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light and the optical cavity, and the transmittance of the first mirror; and Fitting to obtain the value of the transmittance of the first mirror according to the correlation formula, the first curve, the first value, the second curve, and the second value; Obtaining the correlation formula includes: Obtain the first correlation formula between the first reflectivity R1 corresponding to the part that is not coupled to the optical cavity after the light is incident on the first mirror and the coupling efficiency C k ; Obtain the second reflectivity R2 corresponding to the part coupled to the optical cavity after the light is incident on the first mirror, and the relationship between the second reflectivity R2 and the frequency f of the light, the optical power attenuation parameter R of the optical cavity ’ round , the coupling efficiency C k , and the transmittance t of the first mirror k ; and the second correlation formula therebetween; and Determining the correlation formula according to the first correlation formula and the second correlation formula.

2. The method for measuring the transmittance according to claim 1, characterized in that, The correlation formula is: R k (f) = R1 + R2; where R k (f) is the reflectivity of the optical cavity.

3. The method for measuring the transmittance according to claim 2, characterized in that The first correlation formula is: R1 = 1 - C k .

4. The method for measuring the transmittance according to claim 2 or 3, characterized in that, The second correlation formula is: ； where, φ round is the phase change accumulated by light during one period of propagation in the optical cavity, φ round = 4πfl / c, where l is the effective length of the optical cavity, c is the speed of light, R ’ round = R round (1 - L), where L is the value of the optical loss magnification of the optical cavity in the first state or the second state, L < 1, , is the product of the reflectivities of all the mirrors that successively reflect light during one period of propagation of light in the optical cavity, r j is the reflectivity of the mirror that reflects light for the j-th time during one period of propagation of light in the optical cavity, and N is the number of times all the mirrors in the optical cavity reflect light during one period of propagation of light.

5. The method for measuring the transmittance according to any one of claims 1-3, characterized in that, The first value and the second value are obtained according to the following formula: ； wherein, R ’ round is the optical power attenuation parameter, f HWHM is the full width at half maximum, l is the effective length of the optical cavity, and c is the speed of light.

6. The method for measuring the transmittance according to any one of claims 1 to 3, characterized in that, Fitting to obtain the value of the transmittance of the first mirror according to the correlation formula, the first curve, the first value, the second curve, and the second value includes: Fitting to obtain a third value related to the transmittance of the first mirror and the coupling efficiency according to the correlation formula, the first curve and the first value; Fitting to obtain a fourth value related to the transmittance of the first mirror and the coupling efficiency according to the correlation formula, the second curve and the second value; and Determining the value of the transmittance of the first mirror according to the third value and the fourth value.

7. A measuring device for transmittance, characterized in that, Including: A first obtaining module configured to obtain a first curve of the reflectivity of the optical cavity varying with the frequency of light in a first state, and a second curve of the reflectivity of the optical cavity varying with the frequency of light in a second state, wherein light enters the optical cavity from a first mirror of the optical cavity, in the first state, there is a first light-shielding object in the optical cavity, in the second state, there is no light-shielding object or there is a second light-shielding object in the optical cavity, and at least one of the shape and position of the second light-shielding object is different from that of the first light-shielding object; A first determining module configured to determine a first value of the optical power attenuation parameter of the optical cavity in the first state according to the full width at half maximum of the first curve; A second determining module configured to determine a second value of the optical power attenuation parameter of the optical cavity in the second state according to the full width at half maximum of the second curve, and the second value is different from the first value; A second acquisition module, configured to acquire a correlation formula between the reflectivity of the optical cavity, the frequency of light, the optical power attenuation parameter of the optical cavity, the coupling efficiency of light with the optical cavity, and the transmittance of the first mirror, including: acquiring a first correlation formula between a first reflectivity R1 corresponding to a part that is not coupled to the optical cavity after light is incident on the first mirror and the coupling efficiency C k ; acquiring a second correlation formula between a second reflectivity R2 corresponding to a part that is coupled to the optical cavity after light is incident on the first mirror, the frequency f of light, the optical power attenuation parameter R ’ round , the coupling efficiency C k , and the transmittance t of the first mirror k ; and determining the correlation formula according to the first correlation formula and the second correlation formula; and A fitting module, configured to obtain the value of the transmittance of the first mirror by fitting according to the correlation formula, the first curve, the first value, the second curve, and the second value.

8. A measuring device for transmittance, characterized in that Comprising: A memory; And A processor coupled to the memory, configured to execute the transmittance measurement method according to any one of claims 1-6 based on instructions stored in the memory.

9. A measurement system for transmittance, characterized in that, Comprising: The transmittance measurement device according to claim 7 or 8; A signal generator, configured to generate a swept-frequency signal; A transmitter, configured to emit light with a changing frequency to the first mirror according to the swept-frequency signal; And A detection device, configured to detect the reflected light signal of the optical cavity and determine the correlation information between the power of the reflected light signal and the frequency of the light according to the reflected light signal and the swept-frequency signal; Wherein, the transmittance measurement device is configured to obtain the first curve and the second curve according to the correlation information.

10. A computer-readable storage medium, characterized in that, Including computer program instructions, which implement the transmittance measurement method according to any one of claims 1-6 when executed by a processor.

11. A computer program product, characterized in that, Including a computer program, which implements the transmittance measurement method according to any one of claims 1-6 when executed by a processor.

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