Device and method for locking dual-wavelength laser frequency through single absorption cell

Abstract

The invention relates to the technical field of neutral atom quantum computing, in particular to a device and method for locking dual-wavelength laser frequency through a single absorption cell. The device comprises an atomic absorption cell, a first reflector and a second reflector, the atomic absorption cell receives a first laser and a second laser, and the first laser and the second laser are respectively emitted into the atomic absorption cell at a first preset angle and a second preset angle relative to a short axis of the atomic absorption cell; the first reflecting mirror and the second reflecting mirror are respectively arranged on two sides of the atomic absorption cell, so that the first laser and the second laser can be reflected back and forth for multiple times between the two reflecting mirrors so as to penetrate through the atomic absorption cell for multiple times; a third reflecting mirror is arranged on a first emergent path of the first laser from the atomic absorption cell, and the first laser is vertically incident to the third reflecting mirror; a fourth reflecting mirror is arranged on a first emergent path of the second laser from the atomic absorption cell, and the second laser is vertically incident to the third reflecting mirror; wherein the light paths of the first laser and the second laser do not coincide.

Description

A device and method for locking the frequency of dual-wavelength lasers using a single absorption cell. Technical Field

[0001] This invention relates to the field of neutral atom quantum computing technology, and in particular to a device and method for locking the frequency of a dual-wavelength laser using a single absorption cell. Background Technology

[0002] Neutral atom quantum computing, due to its excellent scalability, is gradually becoming the mainstream quantum computing system. Neutral atom qubits typically use alkali metal or alkaline earth metal atoms, and the primary manipulation tool is the laser. Lasers are used to cool, confine, and manipulate atoms; arguably, the laser is the most important tool in an atomic quantum computer. Lasers used for quantum computing differ from conventional industrial lasers, requiring extremely narrow linewidths and stable frequencies to ensure high-fidelity manipulation. Since the laser's frequency is affected by factors such as temperature and current, causing jitter and drift, frequency locking is essential for the laser used in atomic quantum computers. For lasers with less stringent linewidth requirements, a common locking method is saturable absorption frequency locking based on atomic absorption cells. This method locks the laser frequency to specific atomic transition lines, thus achieving long-term frequency stability.

[0003] Traditional saturable absorption frequency locking methods can only lock a laser at one frequency. Locking two laser frequencies requires two saturable absorption frequency locking systems, which greatly increases the cost of frequency locking. In addition, the laser is incident from the long axis of the atomic absorption cell and passes through the atomic absorption cell twice, which limits the effective propagation path of the laser and the contrast of the absorbed frequency locking signal.

[0004] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0005] The technical problem to be solved by this invention is that traditional saturated absorption frequency locking methods can only lock a laser at one frequency, resulting in wasted frequency locking resources. Furthermore, the effective propagation path of the laser and the contrast of the absorbed frequency locking signal are limited, leading to poor frequency locking performance.

[0006] The present invention adopts the following technical solution: In a first aspect, the present invention provides a device for locking the frequency of dual-wavelength lasers in a single absorption cell, comprising an atomic absorption cell 1, a first reflector 10, and a second reflector 11; the atomic absorption cell 1 receives a first laser 2 and a second laser 3, the first laser 2 being incident on the atomic absorption cell 1 at a first preset angle relative to the minor axis of the atomic absorption cell 1, and the second laser 3 being incident on the atomic absorption cell 1 at a second preset angle relative to the minor axis of the atomic absorption cell 1; the first reflector 10 and the second reflector 11 are respectively disposed on both sides of the atomic absorption cell 1. Both are parallel to the long axis of the atomic absorption cell 1, allowing the first laser 2 and the second laser 3 to reflect back and forth multiple times between the two rectangular mirrors, thus passing through the atomic absorption cell 1 multiple times. A third mirror 20 is provided on the path of the first laser 2 when it first exits the atomic absorption cell 1, and the first laser 2 is incident perpendicularly to the third mirror 20. A fourth mirror 30 is provided on the path of the second laser 3 when it first exits the atomic absorption cell 1, and the second laser 3 is incident perpendicularly to the third mirror 20. The optical paths of the first laser 2 and the second laser 3 do not overlap.

[0007] Furthermore, it also includes a first beam splitter 21, a first photodetector 22, and a fifth reflector 23; the first beam splitter 21 is used to transmit the first laser 2 to the fifth reflector 23, and the fifth reflector 23 is used to first incident the first laser 2 into the atomic absorption cell 1 at a first preset angle; the fifth reflector 23 is also used to reflect the reflected first laser 2 back to the first beam splitter 21; the first beam splitter 21 is used to reflect the first laser 2 to the first photodetector 22 to complete a saturated absorption spectrum frequency-locked optical path.

[0008] Furthermore, it also includes a first coupler 24 and a first electro-optic modulator 25. The first coupler 24 is used to connect to the first laser to output the first laser 2; the first electro-optic modulator 25 is used to modulate the phase of the first laser 2 to obtain the power of the optical signal corresponding to the first laser 2 at different phases.

[0009] Furthermore, it also includes a first waveplate 26, which is arranged along the optical path propagation direction to calibrate the polarization direction of the modulated first laser 2 and emit it to the first beam splitter 21.

[0010] Furthermore, one side of the first beam splitter 21 is coated with a transmission film to transmit the first laser 2 to the fifth reflecting mirror 23; the other side is coated with a reflection film to reflect the reflected first laser 2 to the first photodetector 22; or, the first beam splitter 21 is a polarizing beam splitter, and a second waveplate 27 is also provided between the third reflecting mirror 20 and the atomic absorption cell 1. The second waveplate 27 is used to change the polarization direction of the first laser 2, so that when the reflected first laser 2 passes through the first beam splitter 21 again, it is reflected to the first photodetector 22.

[0011] Furthermore, the third reflector 20 and the fourth reflector 30 are arranged diagonally relative to the major axis of the atomic absorption cell 1, or the third reflector 20 and the fourth reflector 30 are arranged opposite to each other relative to the major axis of the atomic absorption cell 1.

[0012] Secondly, the present invention provides a method for locking the frequency of a dual-wavelength laser using a single absorption cell. The device for locking the frequency of a dual-wavelength laser using a single absorption cell includes: a first laser 2 entering one end of an atomic absorption cell 1 at a first preset angle, and being reflected multiple times back and forth within the atomic absorption cell 1 to the other end of the atomic absorption cell 1; the first laser 2 being reflected a second time by a third reflecting mirror 20 and being reflected multiple times back and forth within the atomic absorption cell 1 along the same optical path, returning to the end where it was first entered; a second laser 3 entering one end of the atomic absorption cell 1 at a second preset angle, and being reflected multiple times back and forth within the atomic absorption cell 1 to the other end of the atomic absorption cell 1; and the second laser 3 being reflected a second time by a fourth reflecting mirror 30 and being reflected multiple times back and forth within the atomic absorption cell 1 along the same optical path, returning to the end where it was first entered.

[0013] Furthermore, the method further includes: rotating the polarization direction of the first laser 2 emitted for the first time by a preset angle using the second wave plate 27, so that the first laser 2 emitted for the second time is reflected by the first beam splitter 21 to the first photodetector 22, thereby completing a frequency-locked optical path for the saturated absorption spectrum of the first laser 2; rotating the polarization direction of the second laser 3 emitted for the first time by a preset angle using the fourth wave plate 37, so that the second laser 3 emitted for the second time is reflected by the second beam splitter 31 to the second photodetector 32, thereby completing a frequency-locked optical path for the saturated absorption spectrum of the second laser 3.

[0014] Furthermore, the method further includes: mixing and demodulating the optical power signal received by the first photodetector 22 with the modulation signal of the first electro-optic modulator 25 using a mixer to obtain a first error signal corresponding to the saturated absorption spectrum signal, so as to perform frequency locking based on the first error signal; mixing and demodulating the optical power signal received by the second photodetector 32 with the modulation signal of the second electro-optic modulator 35 using a mixer to obtain a second error signal corresponding to the saturated absorption spectrum signal, so as to perform frequency locking based on the second error signal.

[0015] Furthermore, the method further includes: continuously adjusting the frequency of the first laser based on the first error signal until the first error signal is zero, the frequency corresponding to the first error signal being equal to zero being the first locked frequency; and continuously adjusting the frequency of the second laser based on the second error signal until the second error signal is zero, the frequency corresponding to the second error signal being equal to zero being the second locked frequency.

[0016] The beneficial effects of this invention are as follows: the first laser and the second laser can reflect back and forth multiple times between the first and second reflectors to pass through the atomic absorption cell multiple times, which improves the effective propagation path and the contrast of the saturated absorption frequency-locking signal compared with the traditional scheme, thus optimizing the frequency-locking effect; the first laser and the second laser can be frequency-locked by a single atomic absorption cell, which reduces the cost of the locking system in the quantum computer and saves device space. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 is an optical path propagation path of a first laser and a second laser in an atomic absorption cell according to an embodiment of the present invention; Figure 2 is an optical path propagation path of a first laser and a second laser in an atomic absorption cell according to an embodiment of the present invention; Figure 3 is a schematic diagram of a first coupler and a first electro-optic modulator according to an embodiment of the present invention; Figure 4 is a schematic diagram of a first coupler, a first electro-optic modulator, and a first waveplate according to an embodiment of the present invention; Figure 5 is an optical path propagation path of the first laser during its initial incident and second exit according to an embodiment of the present invention; Figure 6 is an optical path propagation path of the first laser according to an embodiment of the present invention; Figure 7 is a second coupler and... Figure 8 is a schematic diagram of the structure of the second electro-optic modulator; Figure 9 is a schematic diagram of the structure of the second coupler, the second electro-optic modulator, and the third waveplate provided in an embodiment of the present invention; Figure 10 is a schematic diagram of the optical path propagation of the second laser during its first incident and second exit provided in an embodiment of the present invention; Figure 11 is a schematic diagram of the optical path propagation of the first laser and the second laser provided in an embodiment of the present invention; Figure 12 is a schematic flowchart of the optical path propagation of the first laser and the second laser in an atomic absorption cell provided in an embodiment of the present invention; Figure 13 is a schematic flowchart of the optical path propagation of the first laser and the second laser provided in an embodiment of the present invention.

[0019] The reference numerals in the accompanying drawings are as follows: atomic absorption cell 1, first reflector 10, second reflector 11, first laser 2, third reflector 20, first beam splitter 21, first photodetector 22, fifth reflector 23, first coupler 24, first electro-optic modulator 25, first waveplate 26, second waveplate 27, second laser 3, fourth reflector 30, second beam splitter 31, second photodetector 32, sixth reflector 33, second coupler 34, second electro-optic modulator 35, third waveplate 36, and fourth waveplate 37. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0022] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0023] In describing some embodiments, the terms "coupled," "coupled," and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the terms "connected" or "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other, such as "optical coupling," "wireless connection," etc. The embodiments disclosed herein are not necessarily limited to the scope of this invention.

[0024] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Example 1: Traditional saturated absorption frequency locking methods can only lock onto one frequency of laser light. When the laser passes through an atomic absorption cell, if the laser frequency resonates with a specific energy level of an atom, the atom will absorb the laser energy in response to achieve an energy level transition. After the atom has saturated absorbed the energy, when the laser passes through the atomic absorption cell again, the saturated atoms will no longer absorb the laser energy, and the intensity of the transmitted laser light will suddenly increase, forming a spike. The frequency corresponding to the extreme point of the spike is the locked frequency. Furthermore, the longer the effective propagation path of the laser in the atomic absorption cell, the more laser energy is absorbed by the atoms in the atomic absorption cell, and the more obvious the contrast of the spike formed by the increase in laser light intensity, i.e., the saturated absorption frequency locking signal, is, the better the frequency locking effect.

[0026] To reduce the cost of frequency locking systems and optimize frequency locking performance, Embodiment 1 of this invention provides a device for locking the frequency of dual-wavelength lasers using a single absorption cell, comprising an atomic absorption cell 1, a first reflector 10, and a second reflector 11. The atomic absorption cell 1 receives a first laser 2 and a second laser 3. The first laser 2 is incident on the atomic absorption cell 1 at a first preset angle relative to its minor axis, and the second laser 3 is incident on the atomic absorption cell 1 at a second preset angle relative to its minor axis. The first reflector 10 and the second reflector 11 are respectively disposed within the atomic absorption cell. On both sides of the atomic absorption cell 1, and both are parallel to the long axis of the atomic absorption cell 1, the first laser 2 and the second laser 3 can be reflected back and forth between the two rectangular mirrors multiple times, so as to pass through the atomic absorption cell 1 multiple times; a third mirror 20 is provided on the path of the first laser 2 when it first exits the atomic absorption cell 1, and the first laser 2 is perpendicularly incident on the third mirror 20; a fourth mirror 30 is provided on the path of the second laser 3 when it first exits the atomic absorption cell 1, and the second laser 3 is perpendicularly incident on the third mirror 20; wherein, the optical paths of the first laser 2 and the second laser 3 do not overlap.

[0027] The first laser 2 and the second laser 3 can reflect back and forth multiple times between the first reflector 10 and the second reflector 11 to pass through the atomic absorption cell 1 multiple times. Compared with the traditional scheme, this improves the effective propagation path and the contrast of the saturated absorption frequency-locking signal, thus optimizing the frequency-locking effect. The first laser 2 and the second laser 3 can achieve frequency locking by a single atomic absorption cell 1, which reduces the cost of the locking system in the quantum computer and saves device space.

[0028] In practical applications, the first reflector 10 and the second reflector 11 can be set as rectangles, triangles or trapezoids, etc. In order to save device space, in a preferred embodiment, the first reflector 10 and the second reflector 11 are set as rectangles to optimize the space utilization of the frequency locking system.

[0029] In order to improve the effective propagation path of the first laser 2 and the second laser 3 in the atomic absorption cell 1, the first reflector 10 and the second reflector 11 are respectively disposed on both sides of the atomic absorption cell 1 and parallel to the long axis of the atomic absorption cell 1, so that the first laser 2 and the second laser 3 can be reflected back and forth multiple times between the first reflector 10 and the second reflector 11 after entering the atomic absorption cell 1, thereby improving the contrast of the saturated absorption frequency-locked signal.

[0030] Furthermore, the first preset angle refers to the angle between the propagation path of the first laser 2 when it first enters the atomic absorption cell 1 and the minor axis of the atomic absorption cell 1, and the second preset angle refers to the angle between the propagation path of the second laser 3 when it first enters the atomic absorption cell 1 and the minor axis of the atomic absorption cell 1. In a preferred embodiment, both the first preset angle and the second preset angle are small angles. The smaller the preset angle, the more times the light is reflected between the first reflector 10 and the second reflector 11, and the longer the effective propagation path. In actual use, the first preset angle and the second preset angle can be set to 15 degrees to 30 degrees.

[0031] To ensure that the optical paths of the first laser 2 and the second laser 3 do not overlap and do not interfere, the first laser 2 and the second laser 3 are initially incident from opposite sides of the atomic absorption cell 1. In one embodiment, the first laser 2 is incident from one end of the atomic absorption cell 1 onto the second reflecting mirror 11, and after multiple reflections, reaches the other end of the atomic absorption cell 1 and exits through the second reflecting mirror 11 onto the third reflecting mirror 20. Since the third reflecting mirror 20 is perpendicular to the direction of light propagation, the third reflecting mirror 20 reflects the first laser 2 back to the second reflecting mirror 11. Based on the reversibility of the optical path, the first laser 2 returns to the first incident end through the same optical path and exits from the second reflecting mirror 11.

[0032] In one embodiment, the second laser 3 is incident from one end of the atomic absorption cell 1 onto the first reflecting mirror 10. After multiple reflections, it reaches the other end of the atomic absorption cell 1 and exits through the first reflecting mirror 10 onto the fourth reflecting mirror 30. Since the fourth reflecting mirror 30 is perpendicular to the direction of light propagation, it reflects the second laser 3 back to the first reflecting mirror 10. Based on the reversibility of the light path, the second laser 3 returns to the first incident end through the same light path and exits from the first reflecting mirror 10.

[0033] In one embodiment, the first laser 2 can also be incident on the first reflector 10 from one end of the atomic absorption cell 1, and the second laser 3 can also be incident on the second reflector 11 from one end of the atomic absorption cell 1. The optical path propagation principle is the same as in the above embodiment, and will not be repeated here.

[0034] Further referring to Figure 1, the third reflector 20 and the fourth reflector 30 are arranged diagonally relative to the major axis of the atomic absorption cell 1, or the third reflector 20 and the fourth reflector 30 are arranged opposite to each other relative to the major axis of the atomic absorption cell 1.

[0035] In one embodiment, if the first incident ends of the first laser 2 and the second laser 3 are diagonally arranged relative to the long axis of the atomic absorption cell 1, and the first exit ends of the first laser 2 and the second laser 3 after back and forth reflection in the atomic absorption cell 1 are also diagonally arranged relative to the long axis of the atomic absorption cell 1, the third reflector 20 and the fourth reflector 30 are also diagonally arranged relative to the long axis of the atomic absorption cell 1, so as to ensure that the optical paths between the first laser 2 and the second laser 3 are not crowded and do not interfere.

[0036] In one embodiment, referring to FIG2, if the first incident ends of the first laser 2 and the second laser 3 are arranged opposite each other with respect to the long axis of the atomic absorption cell 1, the first exit ends of the first laser 2 and the second laser 3 after back and forth reflection in the atomic absorption cell 1 are also arranged opposite each other with respect to the long axis of the atomic absorption cell 1, so that the third reflector 20 and the fourth reflector 30 are also arranged opposite each other with respect to the long axis of the atomic absorption cell 1, so as to ensure that the optical paths between the first laser 2 and the second laser 3 are not crowded and do not interfere.

[0037] Taking the components required for frequency locking of the first laser 2 as an example, the frequency corresponding to the extreme point of the light intensity peak formed by the first laser 2 re-intruding into the atomic absorption cell 1 is the first locking frequency. Since the area near the extreme point of the light intensity peak is very smooth, in order to accurately identify the extreme point, referring to Figure 3, the device also includes a first coupler 24 and a first electro-optic modulator 25. The first coupler 24 is used to connect to the first laser (not shown in the figure) to output the first laser 2; the first electro-optic modulator 25 is used to modulate the phase of the first laser 2 to obtain the power of the optical signal corresponding to the first laser 2 with different phases.

[0038] In one embodiment, by modulating the phase of the first laser 2, the frequency of the first laser 2 can be periodically fine-tuned around the locked frequency. By measuring the power of the optical signal corresponding to the first laser 2 at different phases, it is possible to determine whether the frequency of the first laser is close to the locked frequency.

[0039] After the first laser 2 is modulated, its polarization state may change, which is different from the laser polarization state required for the operation of subsequent components, affecting the normal operation of subsequent components. In order to make the polarization state of the modulated first laser 2 match that of the subsequent components, referring to FIG4, the device further includes a first waveplate 26. The first waveplate 26 is arranged along the optical path propagation direction and is used to calibrate the polarization direction of the modulated first laser 2 and emit it to the first beam splitter 21.

[0040] The first waveplate 26 is disposed along the optical path propagation direction of the first electro-optic modulator 25. The first waveplate 26 is used to perform phase or polarization state calibration on the modulated first laser 2. Specifically, the first waveplate 26 calibrates the polarization direction of the modulated first laser 2 to adapt to subsequent components.

[0041] To obtain the contrast of the saturated absorption frequency-locked signal, referring to Figure 5, the device further includes a first beam splitter 21, a first photodetector 22, and a fifth reflector 23; the first beam splitter 21 is used to transmit the first laser 2 to the fifth reflector 23, and the fifth reflector 23 is used to initially incident the first laser 2 into the atomic absorption cell 1 at a first preset angle; the fifth reflector 23 is also used to reflect the reflected first laser 2 back to the first beam splitter 21; the first beam splitter 21 is used to reflect the first laser 2 to the first photodetector 22 to complete one saturated absorption spectrum frequency-locked optical path.

[0042] The fifth reflector 23 is disposed on the transmission path of the first beam splitter 21. The first laser 2, after polarization direction calibration, is transmitted through the first beam splitter 21 to the fifth reflector 23. The fifth reflector 23 first incident the first laser 2 into the atomic absorption cell 1 at a first preset angle. When the first laser 2 returns to the first incident end along the original optical path and exits the fifth reflector 23 for the second time, the fifth reflector 23 reflects the first laser 2 back to the first beam splitter 21. The first photodetector 22 is disposed on the reflection path of the first beam splitter 21. The first photodetector 22 receives the first laser 2 and identifies the spike formed by the increase in laser intensity. Combined with the first modulation signal of the first electro-optic modulator 25, it obtains the first error signal required for frequency locking to perform frequency locking.

[0043] To achieve the transmission and reflection functions of the first beam splitter 21, one side of the first beam splitter 21 is coated with a transmission film to transmit the first laser 2 to the fifth reflecting mirror 23; the other side is coated with a reflection film to reflect the reflected first laser 2 to the first photodetector 22. In one embodiment, when the first beam splitter 21 receives the first laser 2 calibrated by the first waveplate 26, it is necessary to emit the first laser 2 to the fifth reflecting mirror 23 so that the first laser 2 can enter the atomic absorption cell 1 for the first time. Since the fifth reflecting mirror 23 is set in the transmission direction of the first beam splitter 21, the end of the first beam splitter 21 near the first waveplate 26 is provided with a transmission film to transmit the first laser 2 to the fifth reflecting mirror 23.

[0044] In one embodiment, when the first laser 2 is emitted from the atomic absorption cell 1 for the second time to the fifth reflecting mirror 23, the fifth reflecting mirror 23 reflects the first laser 2 to the first beam splitter 21. At this time, the first photodetector 22 needs to receive the first laser 2 to convert the optical signal into an electrical signal and then detect the optical power. The side of the first beam splitter 21 closest to the fifth reflecting mirror 23 is provided with a reflective film, and the first photodetector 22 is provided on the reflection path of the first beam splitter 21, so that the first beam splitter 21 can reflect the first laser 2 to the first photodetector 22.

[0045] In another embodiment, referring to FIG6, the first beam splitter 21 is a polarizing beam splitter prism, and a second waveplate 27 is further disposed between the third reflecting mirror 20 and the atomic absorption cell 1. The second waveplate 27 is used to change the polarization direction of the first laser 2, so that when the reflected first laser 2 passes through the first beam splitter 21 again, it is reflected to the first photodetector 22. In one embodiment, the polarizing beam splitter prism can transmit lasers with a polarization direction parallel to the upper surface of the polarizing beam splitter prism and reflect lasers with a polarization direction perpendicular to the upper surface of the polarizing beam splitter prism. After the first laser 2 is calibrated by the first waveplate 26, the polarization direction of the first laser 2 is parallel to the upper surface of the polarizing beam splitter prism, so that the first beam splitter 21 can transmit the first laser 2 to the fifth reflecting mirror 23.

[0046] In one embodiment, the second waveplate 27 is disposed on the optical path of the first laser 2 when it is first emitted. The first laser 2 passes through the second waveplate 27 and is emitted onto the third reflector 20. Since the third reflector 20 is disposed perpendicular to the optical path, the third reflector 20 reflects the first laser 2 back to the second waveplate 27 along the original optical path. The first laser 2 passes through the second waveplate 27 again and returns to the atomic absorption cell 1 along the original optical path. Further, the second waveplate 27 is a quarter-wave plate. The first laser 2 passes through the second waveplate 27 twice, causing the polarization direction of the first laser 2 to rotate by 90 degrees. When the first laser 2 is reflected by the fifth reflector 23 to the first beam splitter 21, since the deflection direction of the first laser 2 is converted to the vertical direction, and a first photodetector 22 is disposed on the reflection path of the first beam splitter 21, the first beam splitter 21 can reflect the first laser 2 to the first photodetector 22.

[0047] Example 2: Based on the device for locking dual-wavelength laser frequencies using a single absorption cell described in Example 1, the example is illustrated by setting the first incident ends of the first laser 2 and the second laser 3 diagonally relative to the major axis of the atomic absorption cell 1.

[0048] The frequency corresponding to the extreme point of the light intensity peak formed by the second laser 3 re-intruding into the atomic absorption cell 1 is the second locked frequency. Since the area near the extreme point of the light intensity peak is very smooth, in order to accurately identify the extreme point, referring to Figure 7, the device also includes a second coupler 34 and a second electro-optic modulator 35. The second coupler 34 is used to connect with the second laser (not shown in the figure) to output the second laser 3; the second electro-optic modulator 35 is used to modulate the phase of the second laser 3 to obtain the power of the optical signal corresponding to the second laser 3 with different phases.

[0049] In one embodiment, by modulating the phase of the second laser 3, the frequency of the second laser 3 can be periodically fine-tuned near the locked frequency. By measuring the power of the optical signal corresponding to the second laser 3 at different phases, it is possible to determine whether the frequency of the second laser is close to the locked frequency.

[0050] After modulation, the polarization state of the second laser 3 may change, differing from the polarization state required for the operation of subsequent components, thus affecting their normal operation. To ensure that the polarization state of the modulated second laser 3 matches that of the subsequent components, referring to Figure 8, the device further includes a third waveplate 36. The third waveplate 36 is positioned along the optical path propagation direction of the second laser 3 and is used to calibrate the polarization direction of the modulated second laser 3 before it is emitted to the second beam splitter 31. The third waveplate 36 is positioned along the optical path propagation direction of the second electro-optic modulator 35. The third waveplate 36 is used to perform phase or polarization state calibration on the modulated second laser 3. Specifically, the third waveplate 36 calibrates the polarization direction of the modulated second laser 3 to adapt it to the subsequent components.

[0051] To obtain the contrast of the saturated absorption frequency-locked signal, referring to Figure 9, the device further includes a second beam splitter 31, a second photodetector 32, and a sixth reflector 33; the second beam splitter 31 is used to transmit the second laser 3 to the sixth reflector 33, and the sixth reflector 33 is used to initially incident the second laser 3 into the atomic absorption cell 1 at a second preset angle; the sixth reflector 33 is also used to reflect the reflected second laser 3 back to the second beam splitter 31; the second beam splitter 31 is used to reflect the second laser 3 to the second photodetector 32 to complete one saturated absorption spectrum frequency-locked optical path.

[0052] The sixth reflecting mirror 33 is disposed on the transmission path of the second beam splitter 31. The second laser 3, after polarization direction calibration, is transmitted through the second beam splitter 31 to the sixth reflecting mirror 33. The sixth reflecting mirror 33 first incidents the second laser 3 into the atomic absorption cell 1 at a second preset angle. When the second laser 3 returns to the first incident end along the original optical path and exits the sixth reflecting mirror 33 for the second time, the sixth reflecting mirror 33 reflects the second laser 3 back to the second beam splitter 31. The second photodetector 32 is disposed on the reflection path of the second beam splitter 31. The second photodetector 32 receives the second laser 3 and identifies the spike formed by the increase in laser intensity. Combined with the second modulation signal of the second electro-optic modulator 35, it obtains the second error signal required for frequency locking to perform frequency locking.

[0053] To achieve the transmission and reflection functions of the second beam splitter 31, one side of the second beam splitter 31 is coated with a transmission film to transmit the second laser 3 to the sixth reflecting mirror 33; the other side is coated with a reflection film to reflect the reflected second laser 3 to the second photodetector 32. In one embodiment, when the second beam splitter 31 receives the second laser 3 calibrated by the third waveplate 36, it is necessary to emit the second laser 3 to the sixth reflecting mirror 33 so that the second laser 3 can be incident on the atomic absorption cell 1 for the first time. Since the sixth reflecting mirror 33 is set in the transmission direction of the second beam splitter 31, the end of the second beam splitter 31 near the third waveplate 36 is provided with a transmission film to transmit the second laser 3 to the sixth reflecting mirror 33.

[0054] In one embodiment, when the second laser 3 is emitted from the atomic absorption cell 1 for the second time to the sixth reflecting mirror 33, the sixth reflecting mirror 33 reflects the second laser 3 to the second beam splitter 31. At this time, the second photodetector 32 needs to receive the second laser 3 to convert the optical signal into an electrical signal and then detect the optical power. The side of the second beam splitter 31 closest to the sixth reflecting mirror 33 is provided with a reflective film, and the second photodetector 32 is provided on the reflection path of the second beam splitter 31, so that the second beam splitter 31 can reflect the second laser 3 to the second photodetector 32.

[0055] In another embodiment, referring to FIG10, the second beam splitter 31 is a polarizing beam splitter prism. A fourth waveplate 37 is also disposed between the fourth reflecting mirror 30 and the atomic absorption cell 1. The fourth waveplate 37 is used to change the polarization direction of the second laser 3, so that when the reflected second laser 3 passes through the second beam splitter 31 again, it is reflected to the second photodetector 32. In one embodiment, the polarizing beam splitter prism can transmit laser with a polarization direction parallel to the upper surface of the polarizing beam splitter prism and reflect laser with a polarization direction perpendicular to the upper surface of the polarizing beam splitter prism. After the second laser 3 is calibrated by the third waveplate 36, the polarization direction of the second laser 3 is parallel to the upper surface of the polarizing beam splitter prism, so that the second beam splitter 31 can transmit the second laser 3 to the sixth reflecting mirror 33.

[0056] In one embodiment, the fourth waveplate 37 is disposed on the optical path of the first emission of the second laser 3. The second laser 3 passes through the fourth waveplate 37 and is emitted onto the fourth reflecting mirror 30. Since the fourth reflecting mirror 30 is disposed perpendicular to the optical path, the fourth reflecting mirror 30 reflects the second laser 3 back to the fourth waveplate 37 along the original optical path. The second laser 3 passes through the fourth waveplate 37 again and returns to the atomic absorption cell 1 along the original optical path. Further, the fourth waveplate 37 is a quarter-wave plate. The second laser 3 passes through the fourth waveplate 37 twice, causing the polarization direction of the second laser 3 to rotate by 90 degrees. When the second laser 3 is reflected by the sixth reflecting mirror 33 to the second beam splitter 31, since the deflection direction of the second laser 3 changes to the vertical direction, and a second photodetector 32 is disposed on the reflection path of the second beam splitter 31, the second beam splitter 31 can reflect the second laser 3 to the second photodetector 32.

[0057] Example 3: Referring to Figures 11 and 12, the present invention provides a method for locking the frequency of a dual-wavelength laser using a single absorption cell, employing the apparatus for locking the frequency of a dual-wavelength laser using a single absorption cell as described in Examples 1 and 2, comprising: in step 101, a first laser 2 is incident at one end of an atomic absorption cell 1 at a first preset angle, and is reflected back and forth multiple times in the atomic absorption cell 1 to the other end of the atomic absorption cell 1; the first laser 2 is reflected a second time into the atomic absorption cell 1 by a third reflecting mirror 20, and is reflected back and forth multiple times in the atomic absorption cell 1 along the same optical path, returning to the end where it was first incident.

[0058] The first coupler 24 is connected to the first laser to output the first laser 2 to the first electro-optic modulator 25. The first electro-optic modulator 25 modulates the phase of the first laser 2, so that the frequency of the first laser 2 is finely adjusted within the phase modulation range. In one embodiment, if the original phase of the first laser 2 is set to f1, the modulation phase is f 10 Then the frequency of the first laser 2 is at a phase of f1±f 10 Within the range, the first laser 2 with different phases corresponds to the first laser 2 with different frequencies, and the first laser 2 with different frequencies corresponds to different optical powers. The optical power detected by the first photodetector 22 can determine whether the frequency of the first laser is close to the locked frequency.

[0059] Taking the first beam splitter 21 as a polarizing beam splitter as an example, the deflection direction of the modulated first laser 2 is calibrated to be parallel to the upper surface of the first beam splitter 21 by the first wave plate 26. The first laser 2 is transmitted to the fifth reflecting mirror 23 and reflected by the fifth reflecting mirror 23, and is incident on the atomic absorption cell 1 at a first preset angle. The first laser 2 is reflected back and forth between the first reflecting mirror 10 and the second reflecting mirror 11 multiple times to the other end of the atomic absorption cell 1.

[0060] Since the third reflector 20 is perpendicular to the light path of the first laser 2 when it is first emitted, the first laser 2 is again incident on the atomic absorption cell 1 along the same light path, and is reflected back and forth between the first reflector 10 and the second reflector 11 multiple times along the same light path to the end where it was first incident. After the first laser 2 is emitted from the atomic absorption cell 1 for the second time, it is reflected by the fifth reflector 23 to the first beam splitter 21.

[0061] Referring again to Figures 11 and 12, in step 102, the second laser 3 is injected into one end of the atomic absorption cell 1 at a second preset angle, and is reflected back and forth multiple times in the atomic absorption cell 1 to the other end of the atomic absorption cell 1; the second laser 3 is reflected by the fourth reflector 30 and is injected into the atomic absorption cell 1 for the second time, and is reflected back and forth multiple times in the atomic absorption cell 1 along the same optical path, returning to the end where it was first injected.

[0062] The second coupler 34 is connected to the second laser to output the second laser 3 to the second electro-optic modulator 35. The second electro-optic modulator 35 modulates the phase of the second laser 3, so that the frequency of the second laser 3 is finely adjusted within the phase modulation range. In one embodiment, if the original phase of the second laser 3 is set to f2, the modulation phase is f... 20 Then the frequency of the second laser 3 is at a phase of f2±f 20 The second laser 3 is periodically fine-tuned within the range. Different phases of the second laser 3 correspond to different frequencies of the second laser 3, and different frequencies of the second laser 3 correspond to different optical powers. The optical power detected by the second photodetector 32 can determine whether the frequency of the second laser is close to the locked frequency.

[0063] Taking the second beam splitter 31 as a polarizing beam splitter as an example, the deflection direction of the modulated second laser 3 is calibrated to be parallel to the upper surface of the second beam splitter 31 by the third waveplate 36. The second laser 3 is transmitted to the sixth reflecting mirror 33 and reflected by the sixth reflecting mirror 33, and then incident on the atomic absorption cell 1 at the second preset angle. The second laser 3 is reflected back and forth between the first reflecting mirror 10 and the second reflecting mirror 11 multiple times to the other end of the atomic absorption cell 1.

[0064] Since the fourth reflector 30 is perpendicular to the light path of the second laser 3 when it is first emitted, the second laser 3 is again incident on the atomic absorption cell 1 along the same light path, and is reflected back and forth between the first reflector 10 and the second reflector 11 multiple times along the same light path to the end where it was first incident. After the second laser 3 is emitted from the atomic absorption cell 1 for the second time, it is reflected by the sixth reflector 33 to the second beam splitter 31.

[0065] Referring to Figures 11 and 13, after step 102, there is also step 103. In step 103, the polarization direction of the first laser 2 emitted for the first time is rotated by a preset angle by the second wave plate 27, so that the first laser 2 emitted for the second time is reflected by the first beam splitter 21 to the first photodetector 22, so as to complete the saturated absorption spectrum frequency locking optical path of the first laser 2.

[0066] Taking the first beam splitter 21 as a polarizing beam splitter as an example, a second waveplate 27 is arranged along the propagation path of the first laser 2 when it is first emitted. The first laser 2 passes through the second waveplate 27 and is emitted onto the third reflecting mirror 20. Since the third reflecting mirror 20 is arranged perpendicular to the propagation path, it reflects the first laser 2 back to the second waveplate 27 along the original path. The first laser 2 passes through the second waveplate 27 again and returns to the atomic absorption cell 1 along the original path. Further, the second waveplate 27 is a quarter-wave plate. The first laser 2 passes through the second waveplate 27 twice, causing the polarization direction of the first laser 2 to rotate by 90 degrees. When the first laser 2 is reflected by the fifth reflecting mirror 23 to the first beam splitter 21, since the deflection direction of the first laser 2 changes to the vertical direction, and a first photodetector 22 is arranged on the reflection path of the first beam splitter 21, the first beam splitter 21 can reflect the first laser 2 to the first photodetector 22 to complete one saturation absorption spectrum frequency locking optical path of the first laser 2.

[0067] Referring again to Figures 11 and 13, in step 104, the polarization direction of the second laser 3 emitted for the first time is rotated by a preset angle by the fourth wave plate 37, so that the second laser 3 emitted for the second time is reflected by the second beam splitter 31 to the second photodetector 32, thereby completing the saturated absorption spectrum frequency locking optical path of the second laser 3.

[0068] Taking the second beam splitter 31 as a polarizing beam splitter as an example, a fourth waveplate 37 is arranged along the propagation path of the light initially emitted by the second laser 3. The second laser 3 passes through the fourth waveplate 37 and is emitted onto the fourth reflecting mirror 30. Since the fourth reflecting mirror 30 is arranged perpendicular to the light propagation path, it reflects the second laser 3 back to the fourth waveplate 37 along the original light path. The second laser 3 then passes through the fourth waveplate 37 again and returns to the atomic absorption cell 1 along the original light path. Furthermore, the fourth waveplate 37... The second laser 3 is set as a quarter-wave plate. The second laser 3 passes through the fourth wave plate 37 twice, causing the polarization direction of the second laser 3 to rotate by 90 degrees. When the second laser 3 is reflected by the sixth reflecting mirror 33 to the second beam splitter 31, the deflection direction of the second laser 3 changes to the vertical direction. Since the second beam splitter 31 is provided with a second photodetector 32 on the reflection path, the second beam splitter 31 can reflect the second laser 3 to the second photodetector 32 to complete one saturated absorption spectrum frequency-locked optical path of the second laser 3.

[0069] Referring again to Figures 11 and 13, in step 105, the optical power signal received by the first photodetector 22 is mixed and demodulated with the modulation signal of the first electro-optic modulator 25 by a mixer to obtain a first error signal corresponding to the saturated absorption spectrum signal, so as to perform frequency locking based on the first error signal.

[0070] The frequency corresponding to the extreme point of the intensity spike formed by the first laser 2 re-intruding into the atomic absorption cell 1 is the first locking frequency. Since the area near the extreme point of the intensity spike is very smooth, in order to accurately identify the extreme point, in one embodiment, the intensity spike can be placed in a two-dimensional coordinate system. The horizontal axis of the two-dimensional coordinate system represents frequency, and the vertical axis represents intensity. By mixing and demodulating the optical power signal received by the first photodetector 22 with the modulation signal of the first electro-optic modulator 25 using a mixer, the corresponding intensity within a preset frequency range near the extreme point can be obtained, i.e., a corresponding curve. The preset frequency range corresponds to the phase modulation range. Differentiating this curve yields a linear function with a corresponding zero-crossing point. The frequency value corresponding to this zero point is the first locking frequency, and the vertical axis of this linear function can be considered as the first error signal.

[0071] Referring again to Figures 11 and 13, in step 106, the optical power signal received by the second photodetector 32 is mixed and demodulated with the modulation signal of the second electro-optic modulator 35 by a mixer to obtain a second error signal corresponding to the saturated absorption spectrum signal, so as to perform frequency locking based on the second error signal.

[0072] The frequency corresponding to the extreme point of the intensity spike formed by the second laser 3 re-entering the atomic absorption cell 1 is the second locking frequency. Since the area near the extreme point of the intensity spike is very smooth, in order to accurately identify the extreme point, in one embodiment, the intensity spike can be placed in a two-dimensional coordinate system. The horizontal axis of the two-dimensional coordinate system represents frequency, and the vertical axis represents intensity. By mixing and demodulating the optical power signal received by the second photodetector 32 with the modulation signal of the second electro-optic modulator 35 through a mixer, the corresponding intensity within a preset frequency range near the extreme point can be obtained, i.e., a corresponding curve. The preset frequency range corresponds to the phase modulation range. Differentiating this curve yields a linear function with a corresponding zero-crossing point. The frequency value corresponding to this zero point is the second locking frequency, and the vertical axis of this linear function can be regarded as the second error signal.

[0073] Referring again to Figures 11 and 13, in step 107, the frequency of the first laser is continuously adjusted based on the first error signal until the first error signal is zero. The frequency corresponding to the first error signal being equal to zero is the first locked frequency.

[0074] The sign of the first error signal represents the direction in which the frequency of the first laser needs to be adjusted, and the absolute value of the first error signal represents the magnitude of the frequency adjustment required for the first laser. In one embodiment, when the first error signal is negative, it indicates that the frequency of the first laser needs to be reduced to approach zero; when the first error signal is positive, it indicates that the frequency of the first laser needs to be increased to approach zero.

[0075] Referring again to Figures 11 and 13, in step 108, the frequency of the second laser is continuously adjusted based on the second error signal until the second error signal is zero. The frequency corresponding to the second error signal being equal to zero is the second locked frequency.

[0076] The sign of the second error signal indicates the direction in which the frequency of the second laser needs to be adjusted, and the absolute value of the second error signal indicates the magnitude of the frequency adjustment required for the second laser. In one embodiment, when the second error signal is negative, it indicates that the frequency of the second laser needs to be reduced to approach zero; when the second error signal is positive, it indicates that the frequency of the second laser needs to be increased to approach zero.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for locking the frequency of a dual-wavelength laser using a single absorption cell, characterized in that, The system includes an atomic absorption cell (1), a first reflector (10), and a second reflector (11). The atomic absorption cell (1) receives a first laser (2) and a second laser (3). The first laser (2) is incident into the atomic absorption cell (1) at a first preset angle relative to the minor axis of the atomic absorption cell (1), and the second laser (3) is incident into the atomic absorption cell (1) at a second preset angle relative to the minor axis of the atomic absorption cell (1). The first reflector (10) and the second reflector (11) are respectively disposed on both sides of the atomic absorption cell (1), and both are parallel to the length of the atomic absorption cell (1). The optical paths of the first laser (2) and the second laser (3) are arranged such that the first laser (2) and the second laser (3) can be reflected back and forth between the two mirrors multiple times to pass through the atomic absorption cell (1) multiple times; a third mirror (20) is provided on the path of the first laser (2) when it first exits from the atomic absorption cell (1), and the first laser (2) is incident perpendicularly to the third mirror (20); a fourth mirror (30) is provided on the path of the second laser (3) when it first exits from the atomic absorption cell (1), and the second laser (3) is incident perpendicularly to the third mirror (20); wherein the optical paths of the first laser (2) and the second laser (3) do not overlap.

2. The device for locking dual-wavelength laser frequencies using a single absorption cell according to claim 1, characterized in that, It also includes a first beam splitter (21), a first photodetector (22), and a fifth reflector (23); the first beam splitter (21) is used to transmit the first laser (2) to the fifth reflector (23), and the fifth reflector (23) is used to first incident the first laser (2) into the atomic absorption cell (1) at a first preset angle; the fifth reflector (23) is also used to reflect the reflected first laser (2) back to the first beam splitter (21); the first beam splitter (21) is used to reflect the first laser (2) to the first photodetector (22) to complete a saturated absorption spectrum frequency-locked optical path.

3. The device for locking dual-wavelength laser frequencies using a single absorption cell according to claim 2, characterized in that, It also includes a first coupler (24) and a first electro-optic modulator (25). The first coupler (24) is used to connect to the first laser to output the first laser (2). The first electro-optic modulator (25) is used to modulate the phase of the first laser (2) to obtain the power of the optical signal corresponding to the first laser (2) with different phases.

4. The device for locking dual-wavelength laser frequencies using a single absorption cell according to claim 3, characterized in that, It also includes a first waveplate (26), which is set along the optical path propagation direction to calibrate the polarization direction of the modulated first laser (2) and emit it to the first beam splitter (21).

5. The device for locking dual-wavelength laser frequencies using a single absorption cell according to claim 2, characterized in that, One side of the first beam splitter (21) is coated with a transmission film to transmit the first laser (2) to the fifth reflecting mirror (23); the other side is coated with a reflection film to reflect the reflected first laser (2) to the first photodetector (22); or, the first beam splitter (21) is a polarizing beam splitter, and a second waveplate (27) is also provided between the third reflecting mirror (20) and the atomic absorption cell (1). The second waveplate (27) is used to change the polarization direction of the first laser (2) so that when the reflected first laser (2) passes through the first beam splitter (21) again, it is reflected to the first photodetector (22).

6. The device for locking dual-wavelength laser frequencies using a single absorption cell according to claim 1, characterized in that, The third mirror (20) and the fourth mirror (30) are arranged diagonally relative to the long axis of the atomic absorption cell (1), or the third mirror (20) and the fourth mirror (30) are arranged opposite to each other relative to the long axis of the atomic absorption cell (1).

7. A method for locking the frequency of a dual-wavelength laser using a single absorption cell, characterized in that, The apparatus for locking the frequency of a dual-wavelength laser using a single absorption cell according to any one of claims 1 to 6 comprises: a first laser (2) being injected into one end of an atomic absorption cell (1) at a first preset angle and reflected back and forth multiple times in the atomic absorption cell (1) to the other end of the atomic absorption cell (1); the first laser (2) being reflected a second time into the atomic absorption cell (1) by a third reflector (20), and being reflected back and forth multiple times in the atomic absorption cell (1) along the same optical path, returning to the end into which it was first injected; a second laser (3) being injected into one end of an atomic absorption cell (1) at a second preset angle and reflected back and forth multiple times in the atomic absorption cell (1) to the other end of the atomic absorption cell (1); the second laser (3) being reflected a second time into the atomic absorption cell (1) by a fourth reflector (30), and being reflected back and forth multiple times in the atomic absorption cell (1) along the same optical path, returning to the end into which it was first injected.

8. The method for locking dual-wavelength laser frequencies using a single absorption cell according to claim 7, characterized in that, Also includes: The polarization direction of the first laser (2) emitted for the first time is rotated by a preset angle by the second wave plate (27), so that the first laser (2) emitted for the second time is reflected by the first beam splitter (21) to the first photodetector (22), thereby completing the saturated absorption spectrum frequency-locking optical path of the first laser (2); the polarization direction of the second laser (3) emitted for the first time is rotated by a preset angle by the fourth wave plate (37), so that the second laser (3) emitted for the second time is reflected by the second beam splitter (31) to the second photodetector (32), thereby completing the saturated absorption spectrum frequency-locking optical path of the second laser (3).

9. The method for locking dual-wavelength laser frequencies using a single absorption cell according to claim 8, characterized in that, Also includes: The optical power signal received by the first photodetector (22) and the modulation signal of the first electro-optic modulator (25) are mixed and demodulated by a mixer to obtain a first error signal corresponding to the saturated absorption spectrum signal, so as to perform frequency locking based on the first error signal; the optical power signal received by the second photodetector (32) and the modulation signal of the second electro-optic modulator (35) are mixed and demodulated by a mixer to obtain a second error signal corresponding to the saturated absorption spectrum signal, so as to perform frequency locking based on the second error signal.

10. The method for locking dual-wavelength laser frequencies using a single absorption cell according to claim 9, characterized in that, Also includes: The frequency of the first laser is continuously adjusted based on the first error signal until the first error signal is zero. The frequency corresponding to the first error signal being equal to zero is the first locked frequency. The frequency of the second laser is continuously adjusted based on the second error signal until the second error signal is zero. The frequency corresponding to the second error signal being equal to zero is the second locked frequency.

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