Wavelength measuring device and use method

Abstract

The invention discloses a wavelength measurement device and a use method, and relates to the technical field of laser wavelength measurement. Comprising an optical lens cone, an optical fiber input flange, a Cassegrain beam expanding lens group, a Fizeau interference etalon, a cylindrical lens and a linear array CCD sensor, the optical fiber input flange is installed at the incident end of the optical lens cone, the Cassegrain beam expanding lens group is fixed in the lens cone and is coaxial with the optical axis of the system, laser is subjected to beam expanding and collimation in a total reflection mode, and the Fizeau interference etalon is arranged on the cylindrical lens. The Fizeau interference etalon is fixed in the lens cone and is coaxial with the optical axis of the system, so that the expanded and collimated laser forms multi-beam interference and generates interference fringes at specific intervals, and the cylindrical lens is fixed in the lens cone and is coaxial with the optical axis of the system, so that the interference fringes are compressed in a one-dimensional manner, and fringe energy is concentrated in a linear detection area. The linear array CCD sensor is fixed at the emergent end of the lens cone, collects compressed interference fringe light signals, converts the interference fringe light signals into electric signals and outputs the electric signals, the structure is simple, use is convenient, and wide-spectrum applicability and high precision can be both considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser wavelength measurement, in particular to a wavelength measurement device and a use method. BACKGROUND

[0002] In the fields of atomic, molecular and optical physics experiments and quantum computing based on neutral atoms or trapped ions, the accuracy and stability of laser wavelength (frequency) directly determine the success or failure of experiments and system performance. For example, in quantum computing, laser phase jitter and frequency long drift will directly affect the logic gate fidelity. Only with a highly deterministic wavelength reference, can the quantum computer be ensured to run stably for a long time. Therefore, obtaining and maintaining a "absolutely accurate" and "long-term stable" laser wavelength is a prerequisite for building a high-precision quantum system.

[0003] The existing wavelength control means has significant shortcomings, and it is difficult to balance the wide spectrum versatility, absolute accuracy and engineering portability: The frequency stabilization method based on alkali metal atom natural energy level can provide an absolute frequency reference without long-term drift, but it is limited to specific atomic energy level distribution and cannot provide frequency stabilization reference at any wavelength, which is not suitable for experiments with non-standard wavelength or wide-range detuning adjustment; The method of using high-precision Fabry-Perot (F-P) cavity frequency stabilization has good short-time stability but strong wavelength selectivity, and needs to be designed separately for different wavelengths. The film and processing cannot realize wide spectrum measurement, and the system is bulky and inconvenient to carry. The cavity length changes with time and aging, and does not have absolute wavelength accuracy; Although the commercial interferometric wavelength meter (such as HighFinesse WS series) has a wide measurement range, the absolute accuracy (about 30MHz) is difficult to meet the application scenarios such as first ion trapping which is extremely sensitive to cooling light frequency. In addition, the passive thermal insulation design is adopted, and the environmental temperature fluctuation will cause the deformation of the internal interference light path, resulting in significant measurement drift and loss of reliability of the "frequency scale".

[0004] In summary, the current field urgently needs a new technical solution that improves measurement accuracy and reduces environmental sensitivity on the basis of wide spectrum versatility, to overcome the contradiction between precision, cost and environmental robustness of traditional methods. SUMMARY

[0005] The purpose of the present application is to provide a wavelength measurement device and a use method to solve the problems existing in the prior art, which is simple in structure, convenient to use, can balance wide spectrum applicability and high precision, and effectively improves environmental robustness.

[0006] To achieve the above purpose, the present application provides the following solutions: The application provides a wavelength measuring device, comprising an optical barrel, a fiber input flange, a Cassegrain beam expander, a Fizeau interference standard gauge, a cylindrical lens and a linear array CCD sensor, the optical barrel is an integrated structure, and the optical barrel has a system optical axis; the fiber input flange is arranged at an incident end of the optical barrel and used for accessing a laser to be measured along the system optical axis of the optical barrel; the Cassegrain beam expander is fixed in the optical barrel and arranged coaxially with the system optical axis and located on an outgoing light path of the laser to be measured, so that the incident laser is subjected to total reflection type beam expansion and collimation; the Fizeau interference standard gauge is fixed in the optical barrel and arranged coaxially with the system optical axis and located on an outgoing light path of the Cassegrain beam expander, so that the laser subjected to beam expansion and collimation forms a multi-beam interference to generate interference fringes with a specific pitch; the cylindrical lens is fixed in the optical barrel and arranged coaxially with the system optical axis and located on an outgoing light path of the Fizeau interference standard gauge, so that the interference fringes are one-dimensionally compressed in space to concentrate the fringe energy on a linear detection area; and the linear array CCD sensor is fixed at an outgoing end of the optical barrel and located on an imaging light path of the cylindrical lens, so as to collect the interference fringe light signal compressed by the cylindrical lens and convert the interference fringe light signal into an electrical signal output.

[0007] Preferably, the Cassegrain beam expander comprises a hyperboloid sub-mirror and a parabolic main mirror, the parabolic main mirror is provided with a light transmission hole in the middle part, the hyperboloid sub-mirror has a first reflection curved surface, the parabolic main mirror has a second reflection curved surface, the laser to be measured is incident to the first reflection curved surface of the hyperboloid sub-mirror after passing through the light transmission hole, is reflected to the second reflection curved surface of the parabolic main mirror through the first reflection curved surface, and is then reflected by the second reflection curved surface to form a parallel light beam, and the optical axis of the parallel light beam is consistent with the system optical axis.

[0008] Preferably, the optical barrel is a rigid structure with a cylindrical inner cavity made of brass or invar, and the fiber input flange, the Fizeau interference standard gauge, the cylindrical lens and the linear array CCD sensor are coaxially installed in the cylindrical inner cavity.

[0009] Preferably, the application further comprises a temperature control system arranged on the outer wall of the optical barrel to stably maintain the temperature in the optical barrel.

[0010] Preferably, the temperature control precision of the temperature control system is not less than ±0.01℃.

[0011] Preferably, the temperature control system is a heating sheet temperature control, and the heating sheet is bent and attached to the outer wall of the optical barrel.

[0012] Preferably, the temperature control system is a TEC temperature control device, the outer wall of the optical lens barrel is a polyhedral structure, and the TEC temperature control device is closely fitted to each plane of the polyhedron.

[0013] Preferably, the optical power direction of the cylindrical lens is perpendicular to the linear array direction of the linear CCD sensor.

[0014] Preferably, the Fizeau interference etalon is made of ULE or microcrystalline glass.

[0015] The present invention also provides a method of using the wavelength measuring device as described in any of the preceding claims, characterized by comprising the following steps: The laser to be tested is connected through the optical fiber input flange; The laser under test is expanded and collimated by total internal reflection using the Cassegrain beam expander group. The collimated laser is incident on the Fizeau interferometer to produce interference fringes with a specific spacing; The interference fringes are compressed by the cylindrical lens and then imaged onto the linear CCD sensor. The interference fringe information collected by the linear CCD sensor is obtained, and the absolute order of the interference fringes is determined by combining the independent coarse wavelength values, thereby calculating the absolute wavelength value.

[0016] The present invention achieves the following technical effects compared to the prior art: This invention provides a wavelength measurement device and its usage method. By using a one-piece molded optical tube to provide stable and rigid support for all core components, it ensures that all components are strictly coaxial, reducing the impact of mechanical disturbances on the optical path. This characteristic allows the device to function as a portable "frequency standard." For example, after calibration in a laboratory with a high-precision optical clock, the device can be transported to another laboratory and quickly and accurately reproduce the target wavelength. This will greatly reduce the difficulty and time cost of searching for cooling light frequencies in experiments such as "first-time ion trapping." Furthermore, the compact, one-piece molded optical tube provides uniform heat distribution, facilitating high-precision active temperature control. Moreover, the total internal reflection Cassegrain beam expander eliminates chromatic aberration, and when combined with a Fizeau interferometer, it enables broadband measurement capabilities. Attached Figure Description

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

[0018] Figure 1 This is a schematic diagram of the wavelength measurement device provided by the present invention; In the diagram: 1. Fiber optic input flange; 2. Hyperboloid secondary mirror; 3. Parabolic primary mirror; 4. Fizeau interferometer; 5. Cylindrical lens; 6. Linear CCD sensor; 7. Optical tube. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to provide a wavelength measurement device and its usage method to solve the problems existing in the prior art. It has a simple structure, is easy to use, can take into account both wide spectrum applicability and high precision, and effectively improves environmental robustness.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1 This embodiment provides a wavelength measurement device, as shown in Figure 1, including: an optical barrel 7, an optical fiber input flange 1, a Cassegrain beam expander assembly, a Fizeau interferometer 4, a cylindrical lens 5, and a linear CCD sensor 6. The optical barrel 7 is an integrally formed structure and has a system optical axis. The optical fiber input flange 1 is disposed at the incident end of the optical barrel 7 for receiving the laser to be measured along the system optical axis of the optical barrel 7. The Cassegrain beam expander assembly is fixed inside the optical barrel 7 and coaxially arranged with the system optical axis, and is located on the outgoing optical path of the laser to be measured, so as to perform total internal reflection beam expansion and collimation on the incident laser. The Fizeau interferometer 4 is fixed inside the optical barrel 7 and coaxially arranged with the system optical axis, and is located on the outgoing optical path of the Cassegrain beam expander assembly, so that the expanded and collimated laser forms multi-beam interference, producing interference fringes with a specific spacing. The cylindrical lens 5 is fixed inside the optical barrel 7 and coaxially arranged with the system optical axis, and is located on the Fizeau interferometer 6. In the output optical path of the interferometer etalon 4, the interference fringes are compressed one-dimensionally in space, concentrating the fringe energy in the linear detection region. The linear CCD sensor 6 is fixed at the output end of the optical barrel 7 and located in the imaging optical path of the cylindrical lens 5 to collect the interference fringe light signal compressed by the cylindrical lens 5 and convert it into an electrical signal output. The integrally molded optical barrel 7 provides stable rigid support for all core components, ensuring that all components are strictly coaxial and reducing the impact of mechanical disturbances on the optical path. The total internal reflection Cassegrain beam expander eliminates chromatic aberration and, together with the Fizeau interferometer etalon 4, achieves broadband measurement capability. The one-dimensional compression of the cylindrical lens 5 concentrates the fringe energy, which, together with the linear CCD sensor 6, improves the accuracy and efficiency of signal acquisition. The overall structure has a high degree of integration, laying the foundation for high-stability measurement.

[0023] In a preferred embodiment, the Cassegrain beam expander group includes a hyperboloid secondary mirror 2 and a parabolic primary mirror 3. The parabolic primary mirror 3 has a light-transmitting aperture in its center. The hyperboloid secondary mirror 2 has a first reflecting surface, and the parabolic primary mirror 3 has a second reflecting surface. The laser beam to be measured passes through the light-transmitting aperture and is incident on the first reflecting surface of the hyperboloid secondary mirror 2. It is then reflected by the first reflecting surface to the second reflecting surface of the parabolic primary mirror 3, and further reflected by the second reflecting surface to form a parallel beam that exits. The optical axis of the parallel beam is aligned with the system's optical axis. This combination of the hyperboloid secondary mirror 2 and the parabolic primary mirror 3 achieves total internal reflection beam expansion through the optical path of "light-transmitting aperture - hyperboloid reflection - parabolic reflection," completely avoiding the chromatic aberration problem of traditional lens groups. The parallel beam is strictly aligned with the system's optical axis, ensuring the stability of subsequent interference fringes and improving the accuracy of wavelength measurement. Simultaneously, the compact optical path design is compatible with the integrated layout of the optical tube 7.

[0024] In a preferred embodiment, the optical barrel is preferably a rigid structure with a cylindrical inner cavity made of brass or Invar. The fiber optic input flange, the Fizeau interferometer, the cylindrical lens, and the linear CCD sensor are all coaxially mounted within the cylindrical inner cavity. Both brass and Invar have extremely low coefficients of thermal expansion, which can significantly suppress barrel dimensional deformation caused by changes in ambient temperature, thereby preventing misalignment of the spacing and relative positions of the optical components in the optical path and ensuring the long-term stability of the system's optical axis. The cylindrical inner cavity design, combined with precision machining, improves the coaxiality accuracy of the fiber optic input flange, Fizeau interferometer, cylindrical lens, and linear CCD sensor. High-precision coaxial mounting ensures that the laser beam always propagates along the system's optical axis, reducing aberrations and interference fringe distortion caused by eccentricity.

[0025] In a preferred embodiment, the wavelength measurement device further includes a temperature control system. This system is located on the outer wall of the optical barrel to stably maintain the temperature inside the barrel. The system monitors the temperature of the optical barrel in real time and dynamically adjusts it according to a set target temperature. This ensures that the core optical components inside the barrel (such as the Fizeau interferometer and cylindrical lenses) are in a constant temperature environment, preventing any impact on the stability of the optical path and the accuracy of the interference fringes. For example, the thickness of the Fizeau interferometer is highly sensitive to temperature; even small temperature fluctuations can cause changes in the spacing of the interference fringes, introducing wavelength measurement errors. Precise control by the temperature control system minimizes these temperature-related error sources, providing a stable "internal environment" for the device, allowing it to maintain high measurement accuracy and long-term stability even when the external ambient temperature changes.

[0026] In a preferred embodiment, the temperature control system has a temperature control accuracy of not less than ±0.01℃. High-precision temperature control can suppress temperature fluctuations inside the optical barrel to a very small range, thereby significantly reducing the minute deformations of optical components (such as the thickness and refractive index of the Fizeau interferometer) and mechanical structures (such as the length of the optical barrel and the relative positions of each component) caused by temperature changes, ensuring the stability of the interference fringes and the reliability of the wavelength measurement results.

[0027] In a preferred embodiment, the temperature control system uses a heating element. The heating element is bent and fitted to the outer wall of the optical lens barrel. The heating element has good flexibility and thermal conductivity, allowing it to fit tightly against the cylindrical outer wall of the optical lens barrel for uniform heating. The power density of the heating element can be designed based on the heat capacity of the optical lens barrel and the range of ambient temperature fluctuations, ensuring that the lens barrel can be quickly heated to the target temperature and maintained stably even in low-temperature environments.

[0028] In a preferred embodiment, the temperature control system is a TEC temperature control device, and the outer wall of the optical lens barrel has a polyhedral structure. The TEC temperature control device is tightly fitted onto each plane of the polyhedron. The TEC temperature control device has bidirectional temperature control capabilities for both heating and cooling, and can flexibly switch operating modes according to the ambient temperature and the actual temperature of the lens barrel. Whether cooling is required in a high-temperature environment or heating is required in a low-temperature environment, it can respond quickly and control precisely, thereby achieving a wider range of temperature regulation and higher temperature control accuracy. Designing the outer wall of the optical lens barrel as a polyhedral structure, such as a regular tetrahedron, regular hexahedron, or regular octahedron, ensures that each plane provides a flat and large contact surface for the TEC temperature control device. The tight fit of the TEC temperature control device onto these planes effectively increases the contact area with the optical lens barrel and improves heat exchange efficiency. Multiple TEC temperature control devices are distributed on different planes, which can achieve uniform temperature control around the optical tube, avoid the generation of local temperature gradients, ensure the uniformity of the temperature field inside the tube, further enhance the device's resistance to changes in ambient temperature, and ensure the long-term stability of wavelength measurement.

[0029] In a preferred embodiment, the optical power direction of the cylindrical lens is perpendicular to the linear array direction of the linear CCD sensor. The perpendicularity of the optical power direction to the linear array direction of the CCD allows for precise compression of interference fringes in non-measurement dimensions without affecting the fringe spacing and phase information in the measurement dimension. The fringe energy is concentrated in the detection area of ​​the linear CCD, improving signal strength and signal-to-noise ratio, enabling the CCD to more accurately acquire the phase information of the interference fringes and providing reliable data support for high-precision wavelength calculations.

[0030] In a preferred embodiment, the Cassegrain beam expander group amplifies the fiber optic beam to the aperture of the Fizeau interferometer. The collimation error of the beam after expansion and collimation by the Cassegrain beam expander group is no greater than 1 mrad. This ensures that the beam uniformly covers the entire aperture of the Fizeau interferometer, avoiding uneven energy distribution or a reduced number of effective fringes due to an excessively small beam size. This guarantees the quality of the interference fringes and the accuracy of subsequent measurements. A collimation error controlled within 1 mrad means that the beam has extremely high parallelism during propagation, resulting in minimal wavefront distortion of the beam incident on the Fizeau interferometer. This leads to the formation of clear, sharp, and stably spaced interference fringes, laying a solid optical path foundation for accurate wavelength measurement.

[0031] In a preferred embodiment of this invention, the Fizeau interference etalon is made of ULE (ultra-low expansion quartz glass) or microcrystalline glass. Both ULE and microcrystalline glass have extremely low coefficients of thermal expansion, which can effectively resist the effects of temperature changes on the thickness and parallelism of the etalon.

[0032] Example 2 This embodiment also provides a method of using the wavelength measurement device as described in any of the above embodiments, including the following steps: Device Calibration Phase (First Use): Place the device in a temperature-controlled, vibration-proof experimental environment, ensuring the optical tube temperature remains stable within the set target value ±0.01℃. Connect a high-precision wavelength standard source (such as a frequency-stabilized laser with a known precise wavelength) to the fiber optic input flange. Following the normal operating procedure, allow the standard laser to pass sequentially through the Cassegrain beam expander group, the Fizeau interferometer, and the cylindrical lens, finally acquiring interference fringe information via a linear CCD sensor. Record the position data of the interference fringes on the linear CCD sensor and, combined with the known precise wavelength value of the standard laser, calibrate the device's system parameters (such as the center wavelength of the Fizeau interferometer, air refractive index correction factor, etc.), establishing a precise mapping relationship between the interference fringe spacing and wavelength. This completes the device calibration, ensuring the accuracy of subsequent measurements is traceable to this high-precision wavelength standard.

[0033] On-site measurement phase: The calibrated device is transported to the test site. If there are significant temperature fluctuations in the environment, the temperature control system must be activated to stabilize the optical tube temperature within ±0.01℃ of the target temperature during calibration, ensuring consistency between the measurement and calibration environments. Subsequently, the laser to be tested is connected to the fiber optic input flange via optical fiber. The laser is incident along the system optical axis of the optical tube, passing sequentially through the Cassegrain beam expander group for total internal reflection expansion and collimation, forming a parallel beam with a parallelism error of no more than 1 mrad. This parallel beam enters the Fizeau interferometer, generating multi-beam interference and forming interference fringes with a specific spacing. The interference fringes are then compressed one-dimensionally by a cylindrical lens (whose optical power direction is perpendicular to the linear array direction of the linear CCD sensor), concentrating the fringe energy. Finally, the linear CCD sensor acquires the compressed interference fringe optical signal and converts it into an electrical signal output. Based on the precise mapping relationship between the interference fringe spacing and wavelength established during the device calibration phase, the collected interference fringe position data is processed and calculated to obtain the wavelength value of the laser to be tested. Throughout the measurement process, the one-piece molded optical tube provides stable and rigid support, the total reflection Cassegrain beam expander eliminates chromatic aberration, and the Fizeau interferometer achieves broadband measurement, ensuring that wavelength measurement tasks can be completed quickly and accurately even in the field environment.

[0034] In actual operation, we use a standard commercial wavelength meter for coarse measurement to determine the integer order (m) of the interference fringes. Simultaneously, this device uses a high-resolution CCD to precisely analyze the phase information of the interference fringes, determining the fractional part of the fringes. Combining these two methods yields extremely high-precision absolute wavelength values.

[0035] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A wavelength measuring device, characterized in that: include: Optical lens barrel (7), the optical lens barrel (7) is an integrally formed structure, the optical lens barrel (7) has a system optical axis; Fiber optic input flange (1) is provided at the incident end of the optical tube (7) and is used to input the laser to be tested along the system optical axis of the optical tube (7); Cassegrain beam expander assembly, which is fixed inside the optical tube (7) and coaxially arranged with the optical axis of the system, and located on the outgoing optical path of the laser to be tested, so as to perform total internal reflection beam expansion and collimation on the incident laser; Fizeau interference etalon (4), the Fizeau interference etalon (4) is fixed inside the optical tube (7) and coaxially arranged with the optical axis of the system, and is located in the outgoing optical path of the Cassegrain beam expander group, so that the laser beam after beam expansion and collimation forms multi-beam interference and produces interference fringes with a specific spacing; Cylindrical lens (5), the cylindrical lens (5) is fixed inside the optical tube (7) and coaxial with the optical axis of the system, and is located on the outgoing light path of the Fizeau interferometer (4) so ​​as to compress the interference fringes in space in one dimension and concentrate the fringe energy in the linear detection region; as well as Linear CCD sensor (6) is fixed to the exit end of the optical barrel (7) and located in the imaging optical path of the cylindrical lens (5) to collect the interference fringe light signal compressed by the cylindrical lens (5) and convert it into an electrical signal output.

2. The wavelength measuring device according to claim 1, characterized in that: The Cassegrain beam expander assembly includes a hyperboloid secondary mirror (2) and a parabolic primary mirror (3). The parabolic primary mirror (3) has a light-transmitting hole in the middle. The hyperboloid secondary mirror (2) has a first reflecting surface, and the parabolic primary mirror (3) has a second reflecting surface. The laser beam to be tested passes through the light-transmitting hole and is incident on the first reflecting surface of the hyperboloid secondary mirror (2). It is reflected by the first reflecting surface to the second reflecting surface of the parabolic primary mirror (3), and then reflected by the second reflecting surface to form a parallel beam beam that is emitted, and the optical axis of the parallel beam beam is kept consistent with the optical axis of the system.

3. The wavelength measuring device according to claim 1, characterized in that: The optical lens tube (7) is a rigid structure with a cylindrical inner cavity made of brass or Invar. The fiber optic input flange (1), the Fizeau interference etalon (4), the cylindrical lens (5) and the linear CCD sensor (6) are all coaxially mounted in the cylindrical inner cavity.

4. The wavelength measuring device according to claim 1, characterized in that: It also includes a temperature control system, which is disposed on the outer wall of the optical barrel to maintain the temperature inside the optical barrel (7).

5. The wavelength measuring device according to claim 4, characterized in that: The temperature control system has a temperature control accuracy of no less than ±0.01℃.

6. The wavelength measuring device according to claim 4, characterized in that: The temperature control system uses a heating element to control the temperature, and the heating element is bent and attached to the outer wall of the optical lens barrel.

7. The wavelength measuring device according to claim 4, characterized in that: The temperature control system is a TEC temperature control device, and the outer wall of the optical lens barrel is a polyhedral structure. The TEC temperature control device is closely fitted to each plane of the polyhedron.

8. The wavelength measuring device according to claim 1, characterized in that: The optical power direction of the cylindrical lens (5) is perpendicular to the linear array direction of the linear CCD sensor (6).

9. A wavelength measuring device according to claim 1, characterized in that: The Fizeau interference etalon (4) is made of ULE or microcrystalline glass.

10. A method of using the wavelength measuring device as described in any one of claims 1 to 9, characterized in that: Includes the following steps: The laser to be tested is connected through the fiber optic input flange (1); The laser under test is expanded and collimated by total internal reflection using the Cassegrain beam expander group. The collimated laser is incident on the Fizeau interferometer (4) to produce interference fringes with a specific spacing; The interference fringes are compressed by the cylindrical lens (5) and then imaged onto the linear CCD sensor (6). The interference fringe information collected by the linear CCD sensor (6) is obtained, and the absolute order of the interference fringes is determined by combining the independent coarse wavelength values, thereby calculating the absolute wavelength value.

Images