Calibration device and method of ultraviolet wavemeter

Abstract

The invention provides a calibration device and method for an ultraviolet wavemeter, and relates to the technical field of atomic filtering, and the calibration device comprises the steps: a tunable continuous laser generates narrow-linewidth continuous laser; the first non-polarization beam splitting prism performs beam splitting on the narrow-linewidth continuous laser to obtain first laser and second laser; the wavelength meter obtains a measurement wavelength value of the first laser; the second non-polarization beam splitting prism performs equal-proportion beam splitting on the second laser to obtain third laser and fourth laser; the first photoelectric detector obtains the first signal intensity of the third laser; the atomic light filter absorbs energy at the central wavelength of the fourth laser by using alkali metal barium steam in a metastable state and outputs fifth laser; the second photoelectric detector obtains the second signal intensity of the fifth laser; and the control system scans a preset wave band, records a plurality of preset wavelength values and ratios between the plurality of corresponding second signal intensities and the plurality of first signal intensities to obtain a transmittance curve, and calibrates the wavemeter 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 specifically to a calibration device and method for an ultraviolet wavelength meter. Background Art

[0002] High-precision laser wavelength detection at the megahertz level is a core component of modern optical technology and plays an irreplaceable role in scientific research, industrial applications and other fields. 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 compressed states) and breaking through the standard quantum limit. It can be used to verify quantum physics theories or detect new physical phenomena (such as extremely weak measurements of the intrinsic electric dipole moment of atoms). In cutting-edge fields such as gravitational wave detection and dark matter searches, the stability of the laser wavelength directly affects the sensitivity of the measurement. In addition, in atmospheric detection, high-precision laser frequency stabilization and wavelength monitoring are also of great significance for high-precision measurements of atmospheric parameters.

[0003] Traditional laser wavelength monitoring usually uses a wavelength meter or interferometer. However, due to environmental changes, the arm length of the interferometer will change, so that its measurement accuracy can only reach the order of 10MHz or even larger. Although the He-Ne laser can be used to calibrate the measurement accuracy of the interferometer in the visible light band in a short time, the measurement accuracy in the ultraviolet wavelength range cannot be guaranteed because the visible light and ultraviolet wavelengths are far apart. The atomic filter uses the resonant frequency of atoms to selectively filter out signals of specific frequencies, and has the characteristics of narrow linewidth, high transmittance, and high background noise suppression ratio. In addition, the atomic filter has no strict requirements on the working environment such as the incident angle and divergence angle of the incident light. Therefore, the atomic filter is often used as a key component of high spectral resolution lidar and is widely used in the measurement of optical and microphysical properties of aerosols and clouds. After the introduction of buffer gas (such as argon), the transmission spectrum line shape of the alkali metal (such as rubidium, cesium, potassium) atomic filter widely used in the world will change from the Gaussian distribution of Doppler broadening to the Voigt line shape dominated by pressure broadening, and the line width will increase significantly. This change leads to a decrease in spectral resolution, making it 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 for improving the measurement accuracy of ultraviolet wavelength.

[0005] One aspect of the present invention provides a calibration device for an ultraviolet wavelength meter, the calibration device comprising: a tunable continuous laser for generating a narrow line width continuous laser with a plurality of preset wavelengths in a preset wavelength band; a first non-polarizing beam splitter prism for splitting the narrow line width continuous laser 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; a wavelength meter for measuring the first laser to obtain a measured wavelength value; a second non-polarizing beam splitter prism for splitting the second laser in equal proportion 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, Used to use alkali metal barium vapor in a metastable state to absorb the energy at the central wavelength of the above-mentioned fourth laser, so as to filter the above-mentioned fourth laser and output a fifth laser; a second photodetector is used to detect the above-mentioned fifth laser and obtain a second signal intensity; a control system is used to control the above-mentioned tunable continuous laser to scan multiple preset wavelengths in the above-mentioned 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 above-mentioned atomic filter, and calibrate the above-mentioned measured wavelength value output by the above-mentioned wavelength meter according to the error value between the wavelength value corresponding to the absorption peak position of the above-mentioned transmittance curve and the above-mentioned central wavelength.

[0006] According to an embodiment of the present invention, the above-mentioned atomic filter includes: an alkali metal atomic pool, including alkali metal barium; a vacuum pump, used to extract the air inside the above-mentioned alkali metal atomic pool to keep the above-mentioned alkali metal atomic pool in a vacuum state; a temperature controller, used to adjust the temperature of the above-mentioned alkali metal atomic pool; and a pump light source, used to generate a pump laser.

[0007] According to an embodiment of the present invention, the 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 evaporates to generate covering steam; the vacuum pump is also used to extract the covering steam to keep the alkali metal atom pool in a vacuum state.

[0008] According to an embodiment of the present invention, the temperature controller is also used to control the temperature of the alkali metal atom pool to increase from the first preset temperature to the second preset temperature, so that the surface of the alkali metal barium evaporates to produce 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 mutual collision and spontaneous radiation between atoms in the alkali metal barium vapor, the alkali metal barium vapor stabilizes from the excited state to the metastable state.

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

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

[0011] According to an embodiment of the present invention, the alkali metal atom pool further comprises: 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 via the first optical window and the second optical window in sequence, a gap is provided 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 exits the stainless steel cavity via the third optical window and the fourth optical window in sequence, a gap is provided 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.

[0012] Another aspect of the present invention provides a calibration method for the calibration device of the ultraviolet wavelength meter, the calibration method comprising: using a tunable continuous laser to generate a narrow line width continuous laser with multiple preset wavelengths in a preset band; using a first non-polarizing beam splitter prism to split the narrow line width continuous laser 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 to measure the first laser to obtain a measured wavelength value; using a second non-polarizing beam splitter prism to split the second laser in equal proportion to 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 force microscope to measure the first ... The 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; uses a second photodetector to detect the fifth laser to obtain a second signal intensity; uses a control system to control the tunable continuous laser to scan multiple preset wavelengths within the preset band, records multiple preset wavelength values ​​and the ratios between the corresponding multiple second signal intensities and the multiple first signal intensities, and obtains the transmittance curve of the atomic filter; uses 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 using the atomic filter to absorb the energy at the central wavelength of the fourth laser using alkali metal barium vapor in a metastable state to filter the fourth laser and output the fifth laser, the method further includes: obtaining alkali metal barium vapor in a metastable state.

[0014] According to an embodiment of the present invention, the atomic filter comprises an alkali metal atom pool, and the alkali metal atom pool comprises alkali metal barium; the step of obtaining the alkali metal barium vapor in a metastable state comprises: regulating the temperature of the alkali metal atom pool to a first preset temperature so that a surface covering of the alkali metal barium evaporates to generate covering vapor; extracting the covering vapor to keep the alkali metal atom pool in a vacuum state; regulating the temperature of the alkali metal atom pool from the first preset temperature to a second preset temperature so that a surface of the alkali metal barium evaporates to generate alkali metal barium vapor; introducing a pump laser into the alkali metal atom pool to pump the alkali metal barium vapor from a ground state to an excited state under the action of the pump laser, so that under the action of mutual collision and spontaneous radiation between atoms in the alkali metal barium vapor, the alkali metal barium vapor stabilizes from the excited state to the metastable state.

[0015] According to an embodiment of the present invention, ultraviolet wavelengths are precisely filtered using alkali metal barium vapor in a metastable state through an atomic filter, and the wavelength value of the precisely filtered ultraviolet wavelength is determined by monitoring and scanning the signal intensity of the laser before and after filtering, thereby achieving calibration of the wavelength meter. The calibration device of the ultraviolet wavelength meter of the embodiment of the present invention calibrates the wavelength meter based on the use of alkali metal barium vapor in a metastable state by an atomic filter, and utilizes the high spectral resolution characteristics of the atomic filter to avoid the pressure broadening effect introduced by the buffer gas, thereby achieving a narrower line width and a higher spectral resolution, which can effectively improve the measurement accuracy of the wavelength meter in the ultraviolet band, and meet the application requirements of high-precision laser frequency stabilization, precision instrument calibration, and high signal-to-noise ratio detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above contents and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

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

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

[0019] Figure 3 A schematic diagram showing a transmittance curve of an atomic filter according to an embodiment of the present invention;

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

[0021] Figure 5 An operation flow chart of a calibration method for a calibration device applied to an ultraviolet wavelength meter according to an embodiment of the present invention is shown;

[0022] Figure 6 A flowchart of the operation of obtaining alkali metal barium vapor in a metastable state according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

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

[0025] All terms (including technical and scientific terms) used herein 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] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression 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 A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0027] During long-term use, the measurement accuracy of the wavelength meter will gradually decrease, resulting in an increase in the error of the measurement results, especially in high-precision detection. This phenomenon is more obvious. Therefore, it needs to be calibrated regularly with high precision. In particular, the wavelength of 354.8696nm is located at the third harmonic of the Nd:YAG laser (neodymium-doped yttrium aluminum garnet laser), belongs to the ultraviolet band, and has a wide range of applications. However, the calibration technology in the related art has limitations at the wavelength of 354.8696nm: the use of alkali metal (such as rubidium, cesium, potassium) atomic filters for calibration requires the introduction of inert gas, which will increase the line width and reduce the spectral resolution, and the working wavelength is far away from the ultraviolet band, and the wavelength meter cannot be effectively calibrated. In addition, although interferometers can be used for calibration, interferometers are easily affected by environmental factors, making it difficult to achieve high-precision calibration.

[0028] The invention provides an ultraviolet wavelength meter calibration device and method using a narrow line width atomic filter filled with no inert gas, which is suitable for high-precision calibration of wavelength meters in the ultraviolet band.

[0029] Figure 1 A schematic structural diagram of a calibration device for an ultraviolet wavelength meter according to an embodiment of the present invention is shown.

[0030] like Figure 1 As shown, the calibration device of the ultraviolet wavelength meter includes: a tunable continuous laser 1, a first non-polarizing beam splitter prism 2, a wavelength meter 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 in a preset band. The first non-polarizing beam splitter prism 2 is used 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. The wavelength meter 3 is used to measure the first laser and obtain a measured wavelength value. The second non-polarizing beam splitter prism 4 is used to split the second laser in equal proportion and output a third laser and a fourth laser. The first photodetector 5 is used to detect the third laser and obtain a first signal intensity. The atomic filter 6 is used to use 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. The second photodetector 7 is used to detect the fifth laser and obtain a second signal intensity. The control system 8 is used to control the tunable continuous laser 1 to scan multiple preset wavelengths within a 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 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 center wavelength.

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

[0033] In one example, the tunable continuous laser 1 can output a narrow-linewidth continuous laser with a central wavelength of 354.8696 nm, where the central wavelength is located at the triple frequency 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 2 splits the narrow line width continuous laser into two paths, 1% of the narrow line width continuous laser forms the first laser, which is reflected to the wavelength meter 3, and 99% of the narrow line width continuous laser forms the second laser, which is transmitted to the second non-polarizing beam splitter 4. The energy splitting ratio of the first laser and the second laser can also be 10:90.

[0035] like Figure 2 As 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 to be incident on the wavelength meter 3.

[0036] In one example, the second non-polarization beam splitter prism 4 splits the second laser into two equal 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 to the atomic filter 6 .

[0037] like 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 to be incident on the first photodetector 5.

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

[0039] like Figure 2 As 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 to be incident on the second photodetector 7.

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

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

[0042] like Figure 3 As shown, the horizontal axis is marked as "Relative frequency (GHz)", which indicates the frequency shift relative to the transition frequency of the barium atom from the metastable state to the excited state, and the unit is gigahertz (GHz). The vertical axis is marked as "transmittance", which indicates the energy transmittance of the fourth laser after the atomic filter uses the alkali metal barium vapor in the metastable state to filter. The atomic transition frequency corresponding to the absorption peak position of the transmittance curve of the atomic filter is locked. When the atomic filter is in this state, the output frequency of the tunable continuous laser corresponds to the transition frequency of the barium atom from the metastable state to the excited state, so that the wavelength meter can be accurately calibrated at this frequency.

[0043] The calibration device of the ultraviolet wavelength meter of the embodiment of the present invention uses the alkali metal barium vapor in a metastable state to accurately filter the ultraviolet wavelength through an atomic filter, and determines the wavelength value of the accurately filtered ultraviolet wavelength by monitoring and scanning the signal intensity of the laser before and after filtering, thereby realizing the calibration of the wavelength meter. The calibration device of the ultraviolet wavelength meter of the embodiment of the present invention uses the alkali metal barium vapor in a metastable state to calibrate the wavelength meter based on the atomic filter, and utilizes the high spectral resolution characteristics of the atomic filter to avoid the pressure broadening effect introduced by the buffer gas, thereby realizing a narrower line width and a higher spectral resolution, which can effectively improve the measurement accuracy of the wavelength meter in the ultraviolet band, and meet the application requirements of high-precision laser frequency stabilization, precision instrument calibration, and high signal-to-noise ratio detection.

[0044] Figure 4 A schematic structural diagram of an atomic filter according to an embodiment of the present invention is shown.

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

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

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

[0048] like Figure 4 As shown, the temperature controller 67 is also used to control the temperature of the alkali metal atom pool 62 to increase from the first preset temperature to the second preset temperature, so that the surface of the alkali metal barium 621 is volatilized 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 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.

[0049] In one example, the pump light source 66 can generate a narrow line width continuous laser with tunable 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 temperature controller 67 can be a heating control system, including a heating function part and a temperature measurement function part. The heating function part can be used to heat the alkali metal atom pool 62 to a first preset temperature and a second preset temperature. The temperature measurement function part can be used to measure the middle surface temperature of the heated alkali metal atom pool 62.

[0051] In one example, the vacuum pump 68 can be used to continuously extract the air in the alkali metal atom pool 62 and the covering vapor volatilized by the covering on the surface of the alkali metal barium 621, such as kerosene or silicone oil vapor. After the covering vapor generated by the volatilization of the covering on the surface of the alkali metal barium 621 is extracted and the vacuum is reached, the vacuum pump 68 needs to be turned off.

[0052] like Figure 4 As 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 cutoff 64 is used to collect the remaining pump laser after being absorbed by the alkali metal atom pool 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] like Figure 4 As 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-polarized beam splitting prism 4 and the alkali metal atom pool 62, and is used to transmit the fourth laser to the alkali metal atom pool 62, and reflect the remaining pump laser to the beam cutoff 64. The second dichroic mirror 63 is disposed between the alkali metal atom pool 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 atom pool 62.

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

[0058] like Figure 4 As shown, the alkali metal atom pool 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 arranged at the first end of the stainless steel cavity 626 close to the first dichroic mirror 61. The fourth laser enters the alkali metal atom pool 62 through the first optical window 622 and the second optical window 623 in sequence. 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 atom pool 62.

[0061] The third optical window 624 and the fourth optical window 625 are arranged in the stainless steel cavity 626 near the second end of the second dichroic mirror 63, and the fifth laser is output from the stainless steel cavity 626 through the third optical window 624 and the fourth optical window 625 in sequence. There is a gap between the third optical window 624 and the fourth optical window 625, and the fourth optical window 625 is used to isolate the third optical window 624 from the outside of the alkali metal atom pool 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 that are temperature resistant above 600° C. and have 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 may be formed with sapphire, respectively.

[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 may 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 the fourth optical window and the third optical window and enters the alkali metal atom pool, so that the barium atoms in the alkali metal barium vapor are excited from the ground state to the metastable state, and the remaining pump laser transmits the second optical window and the first optical window and is output from the alkali metal atom pool. The second optical window and the third optical window are isolated from the outside air, so that the alkali metal atom pool can maintain a vacuum and high temperature state.

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

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

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

[0070] In operation S510, a narrow linewidth continuous laser having a plurality of preset wavelengths in a preset wavelength band is generated using a tunable continuous laser.

[0071] In operation S520, a narrow line width continuous laser is split by using a first non-polarization beam splitter prism to output a first laser and a second laser; wherein energy of the first laser is less than energy 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 light is split in equal proportion by using a second non-polarization beam splitting prism to output a third laser light and a fourth laser light.

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

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

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

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

[0078] In operation S590, 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.

[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 A flowchart of the operation 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 atomic pool including alkali metal barium.

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

[0083] like Figure 6 As shown, obtaining the alkali metal barium vapor in a metastable state includes operations S610 to S640.

[0084] In operation S610 , the temperature of the alkali metal atom pool is adjusted to a first preset temperature so that the surface coating of the alkali metal barium is volatilized to generate coating vapor.

[0085] In operation S620, the cover vapor is extracted to maintain the alkali metal atom pool in a vacuum state.

[0086] In operation S630, the temperature of the alkali metal atom pool is adjusted to increase from a first preset temperature to a second preset temperature so that the surface of the alkali metal barium is volatilized to generate alkali metal barium vapor.

[0087] In operation S640, a pump laser is introduced into the alkali metal atom pool to pump the alkali metal barium vapor from a ground state to an excited state under the action of the pump laser, so that the alkali metal barium vapor is stabilized from the excited state to a metastable state under the action of mutual collision and spontaneous radiation between atoms in the alkali metal barium vapor.

[0088] The present invention utilizes the resonant absorption characteristics generated by the transition between the electronic states of alkali metal atoms to propose a narrow-linewidth atomic filter, and uses the atomic transition frequency corresponding to the absorption peak position of the transmittance curve to calibrate the wavelength meter with high precision. 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 to the application field with high system signal-to-noise ratio requirements.

[0089] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may 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 may be combined and / or combined in various ways. All of these combinations and / or combinations fall within the scope of the present invention.

[0090] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all 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; 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.

2. The calibration device according to claim 1, characterized in that: The atomic filter comprises: Alkali metal atom pools, including alkali metal barium; A vacuum pump, used for extracting air from the alkali metal atom pool to keep the alkali metal atom pool in a vacuum state; A temperature controller, used for regulating the temperature of the alkali metal atom pool; Pump light source, used to generate pump laser.

3. The calibration device according to claim 2, characterized in that: The 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 is volatilized to generate covering steam; The vacuum pump is also used to extract the cover vapor to keep the alkali metal atom pool in a vacuum state.

4. The calibration device according to claim 3, characterized in that: The temperature controller is also used to control the temperature of the alkali metal atom pool to increase from the first preset temperature to the 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 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.

5. 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.

6. The calibration device according to claim 5, 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.

7. The calibration device according to claim 6, 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.

8. A calibration method for a calibration device of an ultraviolet wavelength meter as claimed in any one of claims 1 to 7, 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.

9. The calibration method according to claim 8, characterized in that: Before using the atomic filter to absorb the energy at the central wavelength of the fourth laser using the alkali metal barium vapor in the metastable state to filter the fourth laser and output the fifth laser, the calibration method further includes: obtaining the alkali metal barium vapor in the metastable state.

10. The calibration method according to claim 9, characterized in that: The atomic filter comprises an alkali metal atom pool, and the alkali metal atom pool comprises alkali metal barium; and obtaining the alkali metal barium vapor in a metastable state comprises: Regulating the temperature of the alkali metal atom pool to a first preset temperature so that the surface covering of the alkali metal barium is volatilized to generate covering vapor; extracting the cover vapor to keep the alkali metal atom pool in a vacuum state; Regulating 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 pump laser is introduced into the alkali metal atom pool to pump the alkali metal barium vapor from a ground state to an excited state under the action of the pump laser, so that 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.

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