Calibration Device and Method for Ultraviolet Wavelength Meter

Abstract

The present invention provides a calibration device and method for an ultraviolet wavelength meter, relating to the technical field of atomic filtering. The calibration device includes: a tunable continuous laser for generating narrow-linewidth continuous laser; a first non-polarizing beam splitter prism for splitting the narrow-linewidth continuous laser into a first laser and a second laser; a wavelength meter for obtaining the measured wavelength value of the first laser; a second non-polarizing beam splitter prism for equally splitting the second laser into a third laser and a fourth laser; a first photodetector for obtaining the first signal intensity of the third laser; an atomic filter for using metastable alkali metal barium vapor to absorb the energy at the central wavelength of the fourth laser and outputting a fifth laser; a second photodetector for obtaining the second signal intensity of the fifth laser; a control system for scanning a preset wavelength band, recording a plurality of preset wavelength values and the ratios between the corresponding plurality of second signal intensities and a plurality of first signal intensities, obtaining a transmittance curve, and calibrating the wavelength meter according to the absorption peak position of the transmittance curve.

Description

Technical Field

[0001] At least one embodiment of the present invention relates to the field of atomic filtering technology, and more particularly to a calibration device and method for an ultraviolet wavelength meter. Background Art

[0002] High-precision laser wavelength detection in the megahertz range is a core component of modern optical technology and plays an irreplaceable role in fields such as scientific research and industrial applications. High-precision laser wavelength detection also provides an important technical approach for fields such as quantum precision measurement. For example, in quantum manipulation and detection technology, precise wavelength control is the key to preparing non-classical states (such as squeezed states) and breaking through the standard quantum limit, and can be used to verify quantum physical theories or detect new physical phenomena (such as extremely weak measurements of the atomic intrinsic electric dipole moment). In frontier fields such as gravitational wave detection and dark matter search, the stability of the laser wavelength directly affects the measurement sensitivity. In addition, in atmospheric detection, high-precision laser frequency stabilization and wavelength monitoring are also of great significance for high-precision measurement of atmospheric parameters.

[0003] Traditional laser wavelength monitoring usually uses a wavelength meter or an interferometer. However, since environmental changes can cause the arm length of the interferometer to change, its measurement accuracy can only reach the order of 10 MHz or even greater. Although a He-Ne laser can be used to calibrate the measurement accuracy of the interferometer in the visible light band in a short time, since the visible light is far from the ultraviolet wavelength, the measurement accuracy in the ultraviolet wavelength range cannot be guaranteed. Atomic filters use the resonance frequency of atoms to selectively filter out signals of specific frequencies, and have characteristics such as narrow linewidth, high transmittance, and high background noise suppression ratio. In addition, atomic filters do not have strict requirements on the working environment such as the incident angle and divergence angle of the incident light. Therefore, atomic filters are often used as key components of high-spectral-resolution lidars and are widely used in the measurement of the optical and microphysical properties of aerosols and clouds. After introducing a buffer gas (such as argon) into the currently widely used alkali metal (such as rubidium, cesium, potassium) atomic filters in the world, the line shape of the transmission spectrum will change from a Doppler-broadened Gaussian distribution to a Voigt line shape (Voigt line shape) dominated by pressure broadening, and the linewidth will increase significantly. This change leads to a decrease in spectral resolution and is difficult to meet the application requirements of high-precision laser frequency stabilization, precision instrument calibration, and high signal-to-noise ratio detection. Summary of the Invention

[0004] In view of the above problems, the present invention provides a calibration device and method for an ultraviolet wavelength meter that improves the measurement accuracy of ultraviolet wavelengths.

[0005] One aspect of the present invention provides a calibration device for an ultraviolet wavelength meter. The calibration device includes: a tunable continuous laser for generating narrow-linewidth continuous laser with multiple preset wavelengths within a preset wavelength band; a first non-polarizing beam splitter prism for splitting the narrow-linewidth continuous laser to output a first laser and a second laser, wherein the energy of the first laser is less than that of the second laser; a wavelength meter for measuring the first laser to obtain a measured wavelength value; a second non-polarizing beam splitter prism for equally splitting the second laser to output a third laser and a fourth laser; a first photodetector for detecting the third laser to obtain a first signal intensity; an atomic filter for using metastable alkali metal barium vapor to absorb the energy at the central wavelength of the fourth laser to perform filtering on the fourth laser and output a fifth laser; a second photodetector for detecting the fifth laser to obtain a second signal intensity; a control system for controlling the tunable continuous laser to scan multiple preset wavelengths within the preset wavelength band, recording multiple preset wavelength values and the ratios between the corresponding multiple second signal intensities and multiple first signal intensities, obtaining the transmittance curve of the atomic filter, and calibrating the measured wavelength value output by the wavelength meter according to the error value between the wavelength value corresponding to the absorption peak position of the transmittance curve and the central wavelength.

[0006] According to an embodiment of the present invention, the atomic filter includes: an alkali metal cell including alkali metal barium; a vacuum pump for pumping out the air inside the alkali metal cell to keep the alkali metal cell in a vacuum state; a temperature controller for regulating the temperature of the alkali metal cell; a pump light source for generating pump laser.

[0007] According to an embodiment of the present invention, the temperature controller is used to regulate the temperature of the alkali metal cell to a first preset temperature so that the surface coverings of the alkali metal barium volatilize to generate covering vapor, and the vacuum pump is further used to pump out the covering vapor to keep the alkali metal cell in a vacuum state.

[0008] According to an embodiment of the present invention, the temperature controller is further used to regulate the temperature of the alkali metal cell to increase from the first preset temperature to a second preset temperature so that the surface of the alkali metal barium volatilizes to generate alkali metal barium vapor. Wherein, under the action of the pump laser, the alkali metal barium vapor is pumped from the ground state to the excited state, and under the action of the mutual collision and spontaneous radiation between atoms in the alkali metal barium vapor, the alkali metal barium vapor is stabilized in the metastable state from the excited state.

[0009] According to an embodiment of the present invention, the above atomic filter further includes: a beam expander for expanding the above pump laser and compressing the divergence angle; a beam stopper for collecting the remaining pump laser after being absorbed by the above alkali metal atomic cell.

[0010] According to an embodiment of the present invention, the above atomic filter further includes: a first dichroic mirror disposed between the above second non-polarizing beam splitter prism and the above alkali metal atomic cell, for transmitting the above fourth laser to the above alkali metal atomic cell and reflecting the above remaining pump laser to the above beam stopper; a second dichroic mirror disposed between the above alkali metal atomic cell and the above second photodetector, for transmitting the above fifth laser to the above second photodetector and reflecting the expanded pump laser to the above alkali metal atomic cell.

[0011] According to an embodiment of the present invention, the above alkali metal atomic cell further includes: a stainless steel cavity, a first optical window, a second optical window, a third optical window, and a fourth optical window; the above alkali metal barium is disposed at the bottom of the above stainless steel cavity; the above first optical window and the above second optical window are disposed at a first end of the above stainless steel cavity close to the above first dichroic mirror, so that the above fourth laser enters the above alkali metal atomic cell sequentially through the above first optical window and the above second optical window, there is a gap between the above first optical window and the above second optical window, and the above first optical window is used to isolate the above second optical window from the outside of the above alkali metal atomic cell; the above third optical window and the above fourth optical window are disposed at a second end of the above stainless steel cavity close to the above second dichroic mirror, so that the above fifth laser outputs from the above stainless steel cavity sequentially through the above third optical window and the above fourth optical window, there is a gap between the above third optical window and the above fourth optical window, and the above fourth optical window is used to isolate the above third optical window from the outside of the above alkali metal atomic cell.

[0012] Another aspect of the present invention provides a calibration method for a calibration device of the above-mentioned ultraviolet wavelength meter. The above calibration method includes: using a tunable continuous laser to generate narrow-linewidth continuous laser with multiple preset wavelengths within a preset band; using a first non-polarizing beam splitter prism to split the narrow-linewidth continuous laser, and output a first laser and a second laser; wherein, the energy of the first laser is less than the energy of the second laser; using a wavelength meter to measure the first laser to obtain a measured wavelength value; using a second non-polarizing beam splitter prism to equally split the second laser, and output a third laser and a fourth laser; using a first photodetector to detect the third laser to obtain a first signal intensity; using an atomic filter to use metastable alkali metal barium vapor to absorb the energy at the central wavelength of the fourth laser to filter the fourth laser and output a fifth laser; using a second photodetector to detect the fifth laser to obtain a second signal intensity; using a control system to control the tunable continuous laser to scan multiple preset wavelengths within the preset band, record multiple preset wavelength values and the ratios between the corresponding multiple second signal intensities and multiple first signal intensities, and obtain the transmittance curve of the atomic filter; using the control system to calibrate the measured wavelength value output by the wavelength meter according to the error value between the wavelength value corresponding to the absorption peak position of the transmittance curve and the central wavelength.

[0013] According to an embodiment of the present invention, before the above step of using an atomic filter to use metastable alkali metal barium vapor to absorb the energy at the central wavelength of the fourth laser to filter the fourth laser and output a fifth laser, the method further includes: obtaining metastable alkali metal barium vapor.

[0014] According to an embodiment of the present invention, the atomic filter includes an alkali metal atomic cell, and the alkali metal atomic cell includes alkali metal barium; the obtaining of metastable alkali metal barium vapor includes: adjusting the temperature of the alkali metal atomic cell to a first preset temperature to volatilize the surface covering of the alkali metal barium to generate covering vapor; extracting the covering vapor to keep the alkali metal atomic cell in a vacuum state; adjusting the temperature of the alkali metal atomic cell from the first preset temperature to a second preset temperature to volatilize the surface of the alkali metal barium to generate alkali metal barium vapor; introducing pump laser into the alkali metal atomic cell, and under the action of the pump laser, pumping the alkali metal barium vapor from the ground state to the excited state, so that under the action of inter-atomic collision and spontaneous emission in the alkali metal barium vapor, the alkali metal barium vapor is stabilized in the metastable state.

[0015] According to an embodiment of the present invention, through an atomic filter, the precise filtering of ultraviolet wavelengths is achieved using metastable alkali metal barium vapor. By monitoring and scanning the signal intensities of the laser before and after filtering, the wavelength value of the precisely filtered ultraviolet wavelength is determined, thereby realizing the calibration of the wavelength meter. The calibration device for the ultraviolet wavelength meter according to the embodiment of the present invention calibrates the wavelength meter using metastable alkali metal barium vapor based on the atomic filter. Utilizing the high spectral resolution characteristics of the atomic filter, the pressure broadening effect introduced by the buffer gas is avoided, enabling a narrower linewidth and higher spectral resolution. It can effectively improve the measurement accuracy of the wavelength meter in the ultraviolet band, meeting the application requirements such as high-precision laser frequency stabilization, precision instrument calibration, and high signal-to-noise ratio detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Through the following description of the embodiments of the present invention with reference to the accompanying drawings, the above content and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0017] Figure 1 The structural schematic diagram of the calibration device for the ultraviolet wavelength meter according to the embodiment of the present invention is shown;

[0018] Figure 2 The structural schematic diagram of the calibration device for the ultraviolet wavelength meter according to another embodiment of the present invention is shown;

[0019] Figure 3 The schematic diagram of the transmittance curve of the atomic filter according to the embodiment of the present invention is shown;

[0020] Figure 4 The structural schematic diagram of the atomic filter according to the embodiment of the present invention is shown;

[0021] Figure 5 The operation flowchart of the calibration method for the calibration device applied to the ultraviolet wavelength meter according to the embodiment of the present invention is shown;

[0022] Figure 6 The operation flowchart of obtaining metastable alkali metal barium vapor according to the embodiment of the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the purpose of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0024] The terms used herein are for describing specific embodiments only and are not intended to limit the present invention. The terms "comprising", "including" and the like used herein indicate the presence of the described features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0025] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0026] In the case of using expressions such as "at least one of A, B, and C", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0027] During the long-term use of a wavemeter, the measurement accuracy gradually decreases, resulting in an increase in the error of the measurement result. Especially during high-precision detection, this phenomenon is more obvious. Therefore, it is necessary to calibrate it regularly with high precision. In particular, a wavelength of 354.8696 nm, which is at the third harmonic of a Nd:YAG laser (neodymium-doped yttrium aluminum garnet laser) and belongs to the ultraviolet band, has a wide range of applications. However, the calibration techniques in the related art have limitations at a wavelength of 354.8696 nm: using an alkali metal (such as rubidium, cesium, potassium) atomic filter for calibration requires introducing an inert gas, which will increase the line width, reduce the spectral resolution, and the operating wavelength is far from the ultraviolet band, making it impossible to effectively calibrate the wavemeter. In addition, although an interferometer can be used for calibration, the interferometer is extremely vulnerable to environmental factors and it is difficult to achieve high-precision calibration.

[0028] The present invention provides an ultraviolet wavemeter calibration device and method using a narrow-linewidth atomic filter without inert gas filling, which is suitable for high-precision calibration of wavemeters in the ultraviolet band.

[0029] Figure 1 The structural schematic diagram of the calibration device of the ultraviolet wavemeter according to an embodiment of the present invention is shown.

[0030] As Figure 1 shown, the calibration device of the ultraviolet wavemeter includes: a tunable continuous laser 1, a first non-polarizing beam splitter prism 2, a wavemeter 3, a second non-polarizing beam splitter prism 4, a first photodetector 5, an atomic filter 6, a second photodetector 7, and a control system 8.

[0031] The tunable continuous laser 1 is used to generate a narrow-linewidth continuous laser with multiple preset wavelengths within a preset wavelength band. The first non-polarizing beam splitter prism 2 is used to split the narrow-linewidth continuous laser, and output the first laser and the second laser; wherein, the energy of the first laser is less than that of the second laser. The wavelength meter 3 is used to measure the first laser to obtain a measured wavelength value. The second non-polarizing beam splitter prism 4 is used to equally split the second laser, and output the third laser and the fourth laser. The first photodetector 5 is used to detect the third laser to obtain a first signal intensity. The atomic filter 6 is used to use the metastable alkali metal barium vapor to absorb the energy at the central wavelength of the fourth laser, so as to filter the fourth laser and output the fifth laser. The second photodetector 7 is used to detect the fifth laser to obtain a second signal intensity. The control system 8 is used to control the tunable continuous laser 1 to scan multiple preset wavelengths within the preset wavelength band, record multiple preset wavelength values and the ratios between the corresponding multiple second signal intensities and multiple first signal intensities, obtain the transmittance curve of the atomic filter 6, and calibrate the measured wavelength value output by the wavelength meter 3 according to the error value between the wavelength value corresponding to the absorption peak position of the transmittance curve and the central wavelength.

[0032] Figure 2 Fig. shows a schematic structural diagram of a calibration device for an ultraviolet wavelength meter according to another embodiment of the present invention.

[0033] In one example, the tunable continuous laser 1 can output a narrow-linewidth continuous laser with a central wavelength of 354.8696 nm, and this central wavelength is located at the third harmonic position of the Nd:YAG laser. The frequency and power of the narrow-linewidth continuous laser can be continuously tuned.

[0034] In one example, the first non-polarizing beam splitter prism 2 splits the narrow-linewidth continuous laser into two paths. 1% of the narrow-linewidth continuous laser forms the first laser and is reflected to the wavelength meter 3, and 99% of the narrow-linewidth continuous laser forms the second laser and is transmitted to the second non-polarizing beam splitter prism 4. The energy splitting ratio of the first laser and the second laser can also be 10:90.

[0035] As Figure 2 shown, in one example, the wavelength meter 3 can receive the first laser through the first coupling lens 31. The first coupling lens 31 is used to couple the first laser in the spatial optical path into the optical fiber link, and focus the coupled first laser onto the wavelength meter 3.

[0036] In one example, the second non-polarizing beam splitter prism 4 equally divides the second laser into two paths. One path forms the third laser and is reflected to the first photodetector 5, and the other path forms the fourth laser and is transmitted and incident on the atomic filter 6.

[0037] As Figure 2As shown, in one example, the first photodetector 5 can receive the third laser through the second coupling lens 51. The second coupling lens 51 is used to couple the third laser in the spatial optical path into the optical fiber link and focus the coupled third laser onto the first photodetector 5.

[0038] In one example, the atomic filter 6 utilizes metastable alkali metal barium vapor and can absorb the laser energy with a central wavelength of 354.8696 nm.

[0039] As Figure 2 shown, in one example, the second photodetector 7 can receive the fifth laser through the third coupling lens 71. The third coupling lens 71 is used to couple the fifth laser in the spatial optical path into the optical fiber link and focus the coupled fifth laser onto the second photodetector 7.

[0040] In one example, the control system 8 can include a controller, a signal collector, and a signal processor. The control system 8 can output an analog signal, send an instruction to finely tune the emission laser wavelength, and change the output frequency of the tunable continuous laser 1 within a preset wavelength band through the controller. The signal collector collects multiple first signal intensities detected by the first photodetector 5 correspondingly, and the signal collector collects multiple second signal intensities detected by the second photodetector 7 correspondingly. Through the signal processor, calculate the ratio of the corresponding multiple second signal intensities to the multiple first signal intensities, and based on the wavelength value measured by the wavelength meter 3, obtain the transmittance curve of the atomic filter.

[0041] Figure 3 Shows a schematic diagram of the transmittance curve of the atomic filter according to an embodiment of the present invention.

[0042] As Figure 3 shown, the abscissa is marked as "relative frequency (GHz)", indicating the frequency shift amount relative to the transition frequency of barium atoms from the metastable state to the excited state, and the unit is gigahertz (GHz). The ordinate is marked as "transmittance", indicating the energy transmittance after the atomic filter uses metastable alkali metal barium vapor to filter the fourth laser. Lock the atomic transition frequency corresponding to the absorption peak position of the transmittance curve of the atomic filter. When the atomic filter is in this state, the output frequency of the tunable continuous laser corresponds to the transition frequency of barium atoms from the metastable state to the excited state, so as to achieve precise calibration of the wavelength meter at this frequency.

[0043] The calibration device of the ultraviolet wavelength meter according to the embodiments of the present invention accurately filters ultraviolet wavelengths through an atomic filter using metastable alkali metal barium vapor, and determines the wavelength value of the accurately filtered ultraviolet wavelength by monitoring and scanning the signal intensities of the laser before and after filtering, thereby realizing the calibration of the wavelength meter. The calibration device of the ultraviolet wavelength meter according to the embodiments of the present invention calibrates the wavelength meter based on an atomic filter using metastable alkali metal barium vapor, utilizes the high spectral resolution characteristics of the atomic filter, avoids the pressure broadening effect introduced by the buffer gas, realizes a narrower line width and higher spectral resolution, can effectively improve the measurement accuracy of the wavelength meter in the ultraviolet band, and meets the application requirements such as high-precision laser frequency stabilization, precision instrument calibration, and high signal-to-noise ratio detection.

[0044] Figure 4 Fig. shows a schematic structural diagram of an atomic filter according to an embodiment of the present invention.

[0045] As Figure 4 shown, the atomic filter 6 further includes an alkali metal atomic cell 62, a vacuum pump 68, a temperature controller 67, and a pump light source 66. The alkali metal atomic cell 62 includes alkali metal barium 621.

[0046] The vacuum pump 68 is used to extract the air inside the alkali metal atomic cell 62 to keep the alkali metal atomic cell 62 in a vacuum state. The temperature controller 67 is used to control the temperature of the alkali metal atomic cell 62. The pump light source 66 is used to generate pump laser.

[0047] As Figure 4 shown, the temperature controller 67 is used to control the temperature of the alkali metal atomic cell 62 to a first preset temperature, so that the surface covering of the alkali metal barium 621 volatilizes to generate covering vapor. The vacuum pump 68 is also used to extract the covering vapor to keep the alkali metal atomic cell 62 in a vacuum state.

[0048] As Figure 4 shown, the temperature controller 67 is further used to increase the temperature of the alkali metal atomic cell 62 from the first preset temperature to a second preset temperature, so that the surface of the alkali metal barium 621 volatilizes to generate alkali metal barium vapor. Under the action of the pump laser, the alkali metal barium vapor is pumped from the ground state to the excited state, and under the action of interatomic collisions and spontaneous radiation in the alkali metal barium vapor, the alkali metal barium vapor is stabilized in the metastable state from the excited state.

[0049] In one example, the pump light source 66 can generate a narrow linewidth continuous laser with adjustable power and a central wavelength of 791.3505 nm. During the pumping process of the pump laser acting on the alkali metal barium vapor, the pump light source 66 continuously outputs the pump laser.

[0050] In one example, the thermostat 67 can be a heating control system, including a heating function part and a temperature measuring function part. The heating function part can be used to heat the alkali metal atomic cell 62 to a first preset temperature and a second preset temperature. The temperature measuring function part can be used to measure the intermediate surface temperature of the heated alkali metal atomic cell 62.

[0051] In one example, the vacuum pump 68 can be used to continuously extract the air in the alkali metal atomic cell 62 and the covering vapor volatilized from the surface of the alkali metal barium 621, such as kerosene or silicone oil vapor. After achieving a vacuum after extracting the covering vapor generated by the volatilization of the surface covering of the alkali metal barium 621, the vacuum pump 68 needs to be turned off.

[0052] As Figure 4 shown, the atomic filter 6 further includes a beam expander 65 and a beam stopper 64.

[0053] The beam expander 65 is used to expand the pump laser and compress the divergence angle. The beam stopper 64 is used to collect the remaining pump laser after being absorbed by the alkali metal atomic cell 62.

[0054] According to an embodiment of the present invention, the beam expander can compress the emission angle of the laser emitted by the pump light source and expand the spot diameter.

[0055] As Figure 4 shown, the atomic filter 6 further includes a first dichroic mirror 61 and a second dichroic mirror 63.

[0056] The first dichroic mirror 61 is disposed between the second non-polarizing beam splitting prism 4 and the alkali metal atomic cell 62, and is used to transmit the fourth laser to the alkali metal atomic cell 62 and reflect the remaining pump laser to the beam stopper 64. The second dichroic mirror 63 is disposed between the alkali metal atomic cell 62 and the second photodetector 7, and is used to transmit the fifth laser to the second photodetector 7 and reflect the expanded pump laser to the alkali metal atomic cell 62.

[0057] According to an embodiment of the present invention, the first dichroic mirror and the second dichroic mirror can enable the alkali metal atomic cell to receive the fourth laser and output the fifth laser, and can enable the pump laser to pass through the alkali metal atomic cell and be collected in the beam stopper.

[0058] As Figure 4 shown, the alkali metal atomic cell 62 further includes a stainless steel cavity 626, a first optical window 622, a second optical window 623, a third optical window 624, and a fourth optical window 625.

[0059] The alkali metal barium 621 is disposed at the bottom of the stainless steel cavity 626.

[0060] The first optical window 622 and the second optical window 623 are disposed at the first end of the stainless steel cavity 626 close to the first dichroic mirror 61. The fourth laser enters the alkali metal atomic cell 62 sequentially via the first optical window 622 and the second optical window 623. There is a gap between the first optical window 622 and the second optical window 623. The first optical window 622 is used to isolate the second optical window 623 from the outside of the alkali metal atomic cell 62.

[0061] The third optical window 624 and the fourth optical window 625 are disposed at the second end of the stainless steel cavity 626 close to the second dichroic mirror 63. The fifth laser outputs from the stainless steel cavity 626 sequentially via the third optical window 624 and the fourth optical window 625. There is a gap between the third optical window 624 and the fourth optical window 625. The fourth optical window 625 is used to isolate the third optical window 624 from the outside of the alkali metal atomic cell 62.

[0062] In one example, the first optical window 622, the second optical window 623, the third optical window 624, and the fourth optical window 625 can be made of materials resistant to temperatures above 600 °C and having high light transmittance.

[0063] According to an embodiment of the present invention, the first optical window, the second optical window, the third optical window, and the fourth optical window can be respectively formed of sapphire.

[0064] According to an embodiment of the present invention, the materials of the first optical window, the second optical window, the third optical window, and the fourth optical window can also be calcium fluoride respectively.

[0065] According to an embodiment of the present invention, the connection angles of the first optical window, the second optical window, the third optical window, and the fourth optical window with the stainless steel cavity can be designed based on the Brewster angle of the optical window material.

[0066] According to an embodiment of the present invention, the pump laser transmits through the fourth optical window and the third optical window and enters the alkali metal atomic cell, so that the barium atoms in the alkali metal barium vapor are excited from the ground state to the metastable state. The remaining pump laser transmits through the second optical window and the first optical window and outputs from the alkali metal atomic cell. The space between the second optical window and the third optical window is isolated from the outside air, so that the alkali metal atomic cell can maintain a vacuum and high temperature state.

[0067] The present invention also provides a calibration method for a calibration device applied to an ultraviolet wavelength meter.

[0068] Figure 5 The operation flowchart of the calibration method for the calibration device applied to the ultraviolet wavelength meter according to an embodiment of the present invention is shown.

[0069] As Figure 5As shown, the calibration method includes operations S510 - S590.

[0070] In operation S510, a narrow-linewidth continuous laser with multiple preset wavelengths within a preset wavelength band is generated using a tunable continuous laser.

[0071] In operation S520, the narrow-linewidth continuous laser is split using a first non-polarizing beam splitter prism to output a first laser and a second laser; wherein, the energy of the first laser is less than that of the second laser.

[0072] In operation S530, the first laser is measured using a wavelength meter to obtain a measured wavelength value.

[0073] In operation S540, the second laser is equally split using a second non-polarizing beam splitter prism to output a third laser and a fourth laser.

[0074] In operation S550, the third laser is detected using a first photodetector to obtain a first signal intensity.

[0075] In operation S560, an atomic filter uses alkali metal barium vapor in a metastable state to absorb the energy at the central wavelength of the fourth laser to filter the fourth laser and output a fifth laser.

[0076] In operation S570, the fifth laser is detected using a second photodetector to obtain a second signal intensity.

[0077] In operation S580, a control system is used to control the tunable continuous laser to scan multiple preset wavelengths within the preset wavelength band, record multiple preset wavelength values and the ratios between the corresponding multiple second signal intensities and multiple first signal intensities, and obtain the transmittance curve of the atomic filter.

[0078] In operation S590, a control system is used to calibrate the measured wavelength value output by the wavelength meter according to the error value between the wavelength value corresponding to the absorption peak position of the transmittance curve and the central wavelength.

[0079] According to an embodiment of the present invention, before operation S560, the calibration method further includes obtaining alkali metal barium vapor in a metastable state.

[0080] Figure 6 The operation flowchart of obtaining alkali metal barium vapor in a metastable state according to an embodiment of the present invention is shown.

[0081] The atomic filter includes an alkali metal atom cell, and the alkali metal atom cell includes alkali metal barium.

[0082] It should be noted that before performing the operation steps of obtaining alkali metal barium vapor in a metastable state, the atomic filter is first assembled.

[0083] As Figure 6 shown, obtaining metastable alkali metal barium vapor includes operations S610 - S640.

[0084] In operation S610, the temperature of the alkali metal atomic cell is regulated to a first preset temperature so that the surface coverings of alkali metal barium volatilize to generate covering vapor.

[0085] In operation S620, the covering vapor is extracted to keep the alkali metal atomic cell in a vacuum state.

[0086] In operation S630, the temperature of the alkali metal atomic cell is regulated to increase from the first preset temperature to a second preset temperature so that the surface of alkali metal barium volatilizes to generate alkali metal barium vapor.

[0087] In operation S640, pump laser is introduced into the alkali metal atomic cell so that, under the action of the pump laser, the alkali metal barium vapor is pumped from the ground state to the excited state, and in order that, under the action of inter - atomic collision and spontaneous radiation in the alkali metal barium vapor, the alkali metal barium vapor is stabilized at the metastable state.

[0088] The present invention utilizes the resonance absorption characteristics generated by the transition between the electronic states of alkali metal atoms, and proposes an atomic filter with a narrow linewidth, and performs high - precision calibration on the wavelength meter through the atomic transition frequency corresponding to the absorption peak position of the transmittance curve. The atomic filter of the present invention does not need to be filled with any inert gas, and the obtained narrow - linewidth transmission spectrum is of great significance for application fields with high requirements for the system signal - to - noise ratio.

[0089] Those skilled in the art can understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present invention.

[0090] The above describes the embodiments of the present invention. However, these embodiments are only for illustrative purposes and not for limiting the scope of the present invention. Although the embodiments are separately described above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, and all such substitutions and modifications should fall within the scope of the present invention.

Claims

1. A calibration device for an ultraviolet wavelength meter, characterized in that: The calibration device comprises: A tunable continuous laser for generating narrow linewidth continuous laser light having multiple preset wavelengths within a preset wavelength band; A first non-polarizing beam splitter prism is used to split the narrow line width continuous laser beam to output a first laser beam and a second laser beam; wherein the energy of the first laser beam is less than the energy of the second laser beam; A wavelength meter, used to measure the first laser to obtain a measured wavelength value; A second non-polarizing beam splitter prism is used to split the second laser beam in equal proportion to output a third laser beam and a fourth laser beam; A first photoelectric detector, used to detect the third laser to obtain a first signal intensity; an atomic filter, used for using alkali metal barium vapor in a metastable state to absorb energy at the central wavelength of the fourth laser, so as to filter the fourth laser and output a fifth laser; Among them, the atomic filter includes: Alkali metal atom pools, including alkali metal barium; A temperature controller is used to adjust the temperature of the alkali metal atom pool to a first preset temperature so that the surface covering of the alkali metal barium volatilizes to generate covering vapor; and to adjust the temperature of the alkali metal atom pool from the first preset temperature to a second preset temperature so that the surface of the alkali metal barium volatilizes to generate alkali metal barium vapor; a vacuum pump to extract vapor from the covering; Among them, under the action of pump laser, alkali metal barium vapor is pumped from the ground state to the excited state, and under the action of mutual collision and spontaneous radiation between atoms in the alkali metal barium vapor, the alkali metal barium vapor is stabilized from the excited state to the metastable state; A second photoelectric detector is used to detect the fifth laser to obtain a second signal intensity; A control system is used to control the tunable continuous laser to scan multiple preset wavelengths within the preset band, record multiple preset wavelength values ​​and the ratios between the corresponding multiple second signal intensities and the multiple first signal intensities, obtain the transmittance curve of the atomic filter, and calibrate the measured wavelength value output by the wavelength meter according to the error value between the wavelength value corresponding to the absorption peak position of the transmittance curve and the central wavelength, so as to realize the calibration of the ultraviolet wavelength meter.

2. The calibration device according to claim 1, characterized in that: The vacuum pump is also used to extract the air inside the alkali metal atom pool to keep the alkali metal atom pool in a vacuum state; The temperature controller is used to control the temperature of the alkali metal atom pool; The atomic filter further includes a pump light source for generating the pump laser.

3. The calibration device according to claim 2, characterized in that: The atomic filter also includes: A beam expander, used for expanding the pump laser and compressing its divergence angle; A beam cutoff is used to collect the remaining pump laser after being absorbed by the alkali metal atom pool.

4. The calibration device according to claim 3, characterized in that: The atomic filter also includes: a first dichroic mirror, disposed between the second non-polarizing beam splitter prism and the alkali metal atom pool, for transmitting the fourth laser to the alkali metal atom pool and reflecting the remaining pump laser to the beam cutoff; The second dichroic mirror is arranged between the alkali metal atom pool and the second photodetector, and is used for transmitting the fifth laser to the second photodetector and reflecting the expanded pump laser to the alkali metal atom pool.

5. The calibration device according to claim 4, characterized in that: The alkali metal atom pool further includes: a stainless steel cavity, a first optical window, a second optical window, a third optical window and a fourth optical window; The alkali metal barium is arranged at the bottom of the stainless steel cavity; The first optical window and the second optical window are arranged at the first end of the stainless steel cavity close to the first dichroic mirror, so that the fourth laser enters the alkali metal atom pool through the first optical window and the second optical window in sequence, and there is a gap between the first optical window and the second optical window, and the first optical window is used to isolate the second optical window from the outside of the alkali metal atom pool; The third optical window and the fourth optical window are arranged at the second end of the stainless steel cavity close to the second dichroic mirror, so that the fifth laser is output from the stainless steel cavity via the third optical window and the fourth optical window in sequence, and there is a gap between the third optical window and the fourth optical window, and the fourth optical window is used to isolate the third optical window from the outside of the alkali metal atom pool.

6. A calibration method for a calibration device of an ultraviolet wavelength meter as claimed in any one of claims 1 to 5, characterized in that: The calibration method comprises: Using a tunable continuous laser, a narrow line width continuous laser with multiple preset wavelengths in a preset band is generated; Using a first non-polarizing beam splitter prism, the narrow line width continuous laser is split into beams to output a first laser and a second laser; wherein the energy of the first laser is less than the energy of the second laser; Using a wavelength meter, measuring the first laser to obtain a measured wavelength value; Using a second non-polarization beam splitter prism, the second laser beam is split in equal proportion to output a third laser beam and a fourth laser beam; Using a first photodetector to detect the third laser, and obtain a first signal intensity; Using an atomic filter, using alkali metal barium vapor in a metastable state to absorb energy at the central wavelength of the fourth laser, so as to filter the fourth laser and output a fifth laser; Using a second photodetector to detect the fifth laser to obtain a second signal intensity; Using a control system, controlling the tunable continuous laser to scan a plurality of preset wavelengths within the preset wavelength band, recording a plurality of preset wavelength values ​​and a ratio between a plurality of corresponding second signal intensities and a plurality of corresponding first signal intensities, and obtaining a transmittance curve of the atomic filter; The control system is used to calibrate the measured wavelength value output by the wavelength meter according to the error value between the wavelength value corresponding to the absorption peak position of the transmittance curve and the central wavelength, thereby achieving calibration of the ultraviolet wavelength meter.

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