A method and device for constructing a 425nm wavelength reference based on induced fluorescence effect

Abstract

The invention discloses a method and device for constructing a 425nm wavelength reference based on induced fluorescence effect, which relates to the field of transition frequency measurement. The device includes a continuously tunable laser, an atomic furnace, a chromium atomic beam, an optical frequency comb, a frequency doubling optical path, a polarization-maintaining optical fiber beam splitter, a polarization-maintaining optical fiber beam combiner, a beat frequency detection optical path, a photoelectric receiver and a frequency counter; the output end of the continuously tunable laser is connected to the input end of the polarization-maintaining optical fiber beam splitter; the output end of the optical frequency comb is connected to the frequency doubling optical path; the frequency doubling optical path and the first output end of the polarization-maintaining optical fiber beam splitter are respectively connected to the input end of the optical fiber beam combiner; the chromium atomic beam is ejected through the atomic furnace and acts on the second output end of the polarization-maintaining optical fiber beam splitter; the output end of the polarization-maintaining optical fiber beam combiner is connected to the input end of the beat frequency detection optical path; the output end of the beat frequency detection optical path is connected to the input end of the frequency counter through a photoelectric receiver. This method fills the gap in the wavelength reference of the blue-violet light band.

Description

Technical Field

[0001] The invention relates to the field of transition frequency measurement, in particular to a method and a device for constructing a 425nm wavelength reference based on an induced fluorescence effect. Background Art

[0002] In the field of cutting-edge manufacturing, the level of ultra-precision measurement determines the manufacturing stability and accuracy. Traceability is a fundamental issue in ultra-precision measurement. The lack of a traceability chain or the accumulation of errors in the process of length measurement transfer will lead to reduced measurement accuracy, consistency and comparability of nano-measurement instruments, thereby limiting the development of nano-manufacturing. The key to solving the above problems is to ensure the uniformity and accuracy of nano-scale geometric measurement tests, which requires nano-measurements to be linked to the definition of "meter" through a continuous and uninterrupted length traceability chain. As the transmission standard for optical quantities in the International System of Units (SI), the wavelength standard can directly reproduce the definition of "meter" and ensure consistency in wavelength measurement between different countries and institutions. It is the source of geometric measurement traceability, allowing measurement results from different locations to be compared and converted with each other, thereby achieving global standardization.

[0003] The development of nano-metrology standard materials is a key link in achieving wavelength reference value transfer and ensuring the uniformity and accuracy of nano-geometric value testing. 7 S3 → 7 P4) transition frequency, using atom lithography technology and soft X-ray interferometry technology, a variety of self-traceable grating standard materials such as 1D212.8nm, 2D212.8nm, 1D106.4nm, etc., taking one-dimensional chromium atomic lithography grating as an example, the one-dimensional chromium atomic lithography grating with a period of 212.8nm has been verified to have an accuracy and consistency of 0.001nm. In the application field, self-traceable grating calibration research on high-precision measuring instruments such as scanning probe microscopes and scanning electron microscopes has been carried out, shortening the nanometer length measurement traceability chain in various precision instruments and processing technologies, and realizing the flattening of value transmission. At the same time, there is a gap in the existing wavelength standard in the 400-435nm blue-violet light band.

[0004] Based on the above situation, in order to fill the blank of 400-435nm blue-violet light band and improve the chromium atomic transition ( 7 S3 → 7 P4) In order to improve the frequency measurement accuracy, a method for constructing a 425nm wavelength benchmark based on the induced fluorescence effect is proposed. Summary of the invention

[0005] To solve the above problems, the present application provides a method and device for constructing a 425nm wavelength reference based on the induced fluorescence effect, with the goal of filling the wavelength reference gap in the blue-violet light band and realizing online real-time measurement of chromium atoms ( 7S3 → 7 P4) The purpose of transition frequency.

[0006] In the present application, a 425nm wavelength reference construction device based on induced fluorescence effect is provided, including a continuously tunable laser, an atomic furnace, a chromium atomic beam, an optical frequency comb, a frequency doubling optical path, a polarization-maintaining fiber beam splitter, a polarization-maintaining fiber beam combiner, a beat frequency detection optical path, a photoelectric receiver and a frequency counter;

[0007] A first half-wave plate, a first coupler and a polarization-maintaining optical fiber beam splitter are arranged at one side of the output end of the continuously tunable laser;

[0008] The output end of the continuously tunable laser is connected to the input end of the polarization-maintaining optical fiber beam splitter;

[0009] The output end of the optical frequency comb is connected to the frequency doubling optical path;

[0010] The frequency doubling optical path and the first output end of the polarization-maintaining optical fiber beam splitter are respectively connected to the input end of the optical fiber combiner;

[0011] The chromium atomic beam is ejected from the atomic furnace and interacts with the second output end of the polarization-maintaining optical fiber beam splitter;

[0012] The output end of the polarization-maintaining optical fiber combiner is connected to the input end of the beat frequency detection optical path;

[0013] The output end of the beat frequency detection optical path is connected to the input end of the frequency counter through a photoelectric receiver.

[0014] Preferably, the frequency doubling optical path includes a filter, a second half-wave plate, a first convex lens, a frequency doubling crystal PPLN, a second convex lens and a second coupler;

[0015] The output end of the optical frequency comb is connected to the input end of the filter;

[0016] The output end of the filter is connected to the input end of the second half-wave plate;

[0017] The output end of the second half-wave plate is connected to the input end of the frequency doubling crystal PPLN;

[0018] A first convex lens and a second convex lens are respectively disposed at two ends of the frequency doubling crystal PPLN. The first convex lens and the second convex lens are used to focus the light beam inside the frequency doubling crystal PPLN.

[0019] Preferably, the beat frequency detection optical path includes a second collimator, a second reflector, a third half-wave plate, a polarization beam splitter prism, a third reflector and a diffraction grating;

[0020] Wherein, the second reflector and the third reflector are placed in parallel;

[0021] The optical path output end of the polarization-maintaining fiber combiner is connected to the input end of the photoelectric receiver after passing through the second collimator, the second reflector, the third half-wave plate, the polarization beam splitter prism, the third reflector and the diffraction grating in sequence.

[0022] Preferably, the atomic furnace heats the chromium powder to a sublimation state in a vacuum environment and draws out a chromium atomic beam in a leakage manner;

[0023] The second output end of the polarization-maintaining fiber beam splitter passes through the first collimator and the first reflector to form a group of counter-propagating lasers that interact with the collimated chromium atomic beam to generate two fluorescent spots. The overlap of the two fluorescent spots is used as the laser frequency and the chromium (Cr) atom ( 7 S3 → 7 P4) The basis for judging whether the transition frequencies are equal.

[0024] Preferably, the continuously tunable laser output band covers 425.5±1.0nm, and a frequency tuning module is provided at the input end;

[0025] The optical frequency comb reference source is a high-stability time-frequency signal, and the output band covers 851±2nm. After passing through the frequency doubling crystal PPLN, the output band covers 425.5±1.0nm.

[0026] Preferably, the discharge temperature range of the chromium atomic beam ejected from the atomic furnace is 1500-1750 degrees Celsius.

[0027] Preferably, the atomic furnace achieves collimation of the chromium atomic beam through a slit or a transverse laser light field.

[0028] Preferably, the propagation direction of the chromium atomic beam is perpendicular to the propagation direction of a group of laser beams propagating in opposite directions formed by the second output end of the polarization-maintaining fiber beam splitter through the first reflector.

[0029] Preferably, a low-pass filter is provided between the photoelectric receiver and the frequency counter.

[0030] The present application also provides a method for constructing a 425nm wavelength reference based on the induced fluorescence effect, comprising the following steps:

[0031] S1. Build a frequency measurement system of laser and optical frequency comb based on heterodyne beat frequency detection technology;

[0032] S2. Set the temperature of the atomic furnace to the state where the chromium atomic beam is leaking, and initially adjust the laser wavelength to the chromium atomic beam ( 7 S3 → 7P4) Near the theoretical value of the transition frequency, a group of lasers propagating in opposite directions interact with the chromium atomic beam and produce fluorescent spots symmetrically on both sides of the central axis of the chromium atomic beam;

[0033] S3, finely adjust the laser wavelength to make the fluorescent spots induced symmetrically on both sides of the central axis of the chromium atom beam overlap. At this time, the laser frequency is equal to the chromium atom ( 7 S3 → 7 P4) transition frequency, for chromium atoms ( 7 S3 → 7 P4) Transition frequency measurement.

[0034] In summary, the method and device for constructing a 425nm wavelength reference based on the induced fluorescence effect of the present invention, compared with the traditional transition frequency measurement technology, the method and device adopt the principle of Doppler cooling as a corresponding suppression method of thermal effect to measure the chromium atom ( 7 S3 → 7 The P4) transition frequency can be accurately measured, and the stability of the laser used can be effectively evaluated while preparing the atomic lithography grating.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The optical frequency comb of the 425nm wavelength reference construction device based on the induced fluorescence effect of the present invention precisely measures the chromium atom ( 7 S3 → 7 P4) Schematic diagram of the transition frequency method;

[0037] Figure 2 This is a diagram showing the transition frequency measurement results of an optical frequency comb according to a 425nm wavelength reference construction method based on the induced fluorescence effect of the present invention.

[0038] Reference numerals:

[0039] 1. Continuously tunable laser; 2. First half-wave plate; 3. First coupler; 4. Polarization-maintaining fiber beam splitter; 5. First collimator; 6. Atomic furnace; 7. Chromium atomic beam; 8. First reflector; 9. Fluorescent spot; 10. Optical frequency comb; 11. Filter; 12. Second half-wave plate; 13. First convex lens; 14. Frequency doubling crystal PPLN; 15. Second convex lens; 16. Second coupler; 17. Polarization-maintaining fiber beam combiner; 18. Second collimator; 19. Second reflector; 20. Third half-wave plate; 21. Polarization beam splitter prism; 22. Third reflector; 23. Diffraction grating; 24. Photoelectric receiver; 25. Frequency counter. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below by means of the accompanying drawings and embodiments. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​described in these embodiments do not limit the scope of the present application.

[0041] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

[0042] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0043] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0044] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0045] like Figure 1 As shown, a 425nm wavelength reference construction device based on induced fluorescence effect includes a continuously tunable laser 1, an atomic furnace 6, a chromium atomic beam 7, an optical frequency comb 10, a frequency doubling optical path, a polarization-maintaining fiber beam splitter, a polarization-maintaining fiber beam combiner 17, a beat frequency detection optical path, a photoelectric receiver 24 and a frequency counter 25;

[0046] A first half-wave plate 2, a first coupler 3 and a polarization-maintaining fiber beam splitter 4 are arranged at one side of the output end of the continuously tunable laser 1;

[0047] The output end of the continuously tunable laser 1 is connected to the input end of the polarization-maintaining optical fiber beam splitter 4;

[0048] The output end of the optical frequency comb 10 is connected to the frequency doubling optical path;

[0049] The frequency doubling optical path and the first output end of the polarization-maintaining optical fiber beam splitter 4 are respectively connected to the input end of the optical fiber combiner;

[0050] The chromium atomic beam 7 is ejected by the atomic furnace 6 and interacts with the second output end of the polarization-maintaining optical fiber beam splitter 4;

[0051] The output end of the polarization-maintaining optical fiber combiner 17 is connected to the input end of the beat frequency detection optical path;

[0052] The output end of the beat frequency detection optical path is connected to the input end of the frequency counter 25 through the photoelectric receiver 24 .

[0053] Further, the frequency doubling optical path includes a filter 11, a second half-wave plate 12, a first convex lens 13, a frequency doubling crystal PPLN 14, a second convex lens 15 and a second coupler 16;

[0054] The output end of the optical frequency comb 10 is connected to the input end of the filter 11;

[0055] The output end of the filter plate 11 is connected to the input end of the second half-wave plate 12;

[0056] The output end of the second half-wave plate 12 is connected to the input end of the frequency doubling crystal PPLN14;

[0057] A first convex lens 13 and a second convex lens 15 are respectively disposed at two ends of the frequency doubling crystal PPLN14. The first convex lens 13 and the second convex lens 15 are used to focus the light beam inside the frequency doubling crystal PPLN14.

[0058] Further, the beat frequency detection optical path includes a second collimator 18, a second reflector 19, a third half-wave plate 20, a polarization beam splitter prism 21, a third reflector 22 and a diffraction grating 23;

[0059] Wherein, the second reflector 19 and the third reflector 22 are placed in parallel;

[0060] The optical path output end of the polarization-maintaining fiber combiner 17 passes through the second collimator 18 , the second reflector 19 , the third half-wave plate 20 , the polarization beam splitter prism 21 , the third reflector 22 and the diffraction grating 23 in sequence and is connected to the input end of the photoelectric receiver 24 .

[0061] Furthermore, the atomic furnace 6 heats the chromium powder to a sublimation state in a vacuum environment and draws out a chromium atomic beam 7 in a leakage manner;

[0062] The second output end of the polarization-maintaining fiber beam splitter 4 passes through the first collimator 5 and the first reflector 8 to form a group of counter-propagating lasers that interact with the collimated chromium atomic beam 7 to generate two fluorescent spots 9. The overlap of the two fluorescent spots 9 is used as the laser frequency and the chromium (Cr) atom ( 7 S3 → 7 P4) The basis for judging whether the transition frequencies are equal.

[0063] Furthermore, the output band of the continuously tunable laser 1 covers 425.5±1.0nm, and a frequency tuning module is provided at the input end;

[0064] The optical frequency comb 10 reference source is a high-stability time-frequency signal with an output band covering 851±2nm. After passing through the frequency doubling crystal PPLN14, the output band covers 425.5±1.0nm.

[0065] Furthermore, the discharge temperature range of the chromium atomic beam 7 emitted by the atomic furnace 6 is 1500-1750 degrees Celsius.

[0066] Furthermore, the atomic furnace 6 achieves collimation of the chromium atomic beam 7 through a slit or a transverse laser light field.

[0067] Furthermore, the propagation direction of the chromium atomic beam 7 is perpendicular to the propagation direction of a group of laser beams propagating in opposite directions formed by the second output end of the polarization-maintaining fiber beam splitter 4 through the first reflector 8 .

[0068] Furthermore, a low-pass filter is provided between the photoelectric receiver 24 and the frequency counter 25 .

[0069] The present application also provides a method for constructing a 425nm wavelength reference based on the induced fluorescence effect, comprising the following steps:

[0070] S1. Build a frequency measurement system of laser and optical frequency comb based on heterodyne beat frequency detection technology;

[0071] S2, the temperature of the atomic furnace 6 is set to the state where the chromium atomic beam 7 is leaking, and the laser wavelength is initially adjusted to the chromium atomic beam ( 7 S3 → 7 P4) Near the theoretical value of the transition frequency, a group of lasers propagating in opposite directions interact with the chromium atomic beam 7 and form fluorescent spots 9 symmetrically on both sides of the central axis of the chromium atomic beam 7;

[0072] S3, finely adjust the laser wavelength so that the fluorescent spots 9 induced symmetrically on both sides of the central axis of the chromium atom beam 7 overlap. At this time, the laser frequency is equal to the chromium atom ( 7 S3 → 7 P4) transition frequency, for chromium atoms ( 7 S3 → 7 P4) Transition frequency measurement.

[0073] In the specific implementation process, the output wavelength of the continuously tunable laser 1 is adjusted to the chromium atom ( 7 S3 → 7 P4) near the theoretical value of the transition frequency, the atomic furnace 6 is set to a temperature of 1600 degrees Celsius, the chromium powder is heated to a sublimation state in a vacuum environment and a chromium atomic beam 7 is led out in a leakage manner, one of the paths of the continuously tunable laser 1 forms a group of lasers that propagate in opposite directions and react with the collimated chromium atomic beam 7 to produce two fluorescent spots 9; a frequency measurement system is built, the other path of the continuously tunable laser 1 and the frequency-doubled optical frequency comb 10 generate a beat frequency signal with a signal-to-noise ratio greater than 30dB through a fiber combiner, and the beat frequency signal is connected to a counter to realize the wavelength measurement of the 425.5nm continuously tunable laser 1; the laser wavelength is finely adjusted to make the fluorescent spots 9 induced symmetrically on both sides of the central axis of the chromium atomic beam 7 overlap, at which time the laser frequency is equal to the chromium atom ( 7 S3 →7 P4) transition frequency, for chromium atoms ( 7 S3 → 7 P4) Measurement of transition frequency.

[0074] like Figure 2 As shown in the figure, the result of the optical frequency comb measurement of the transition frequency shows that the frequency measurement method of the present invention can measure the chromium atom ( 7 S3 → 7 P4) The transition frequency is accurately measured.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A 425nm wavelength reference construction device based on induced fluorescence effect, characterized in that: Including, continuously tunable laser, atomic furnace, chromium atomic beam, optical frequency comb, frequency doubling optical path, polarization-maintaining fiber beam splitter, polarization-maintaining fiber beam combiner, beat frequency detection optical path, photoelectric receiver and frequency counter; A first half-wave plate, a first coupler and a polarization-maintaining optical fiber beam splitter are arranged at one side of the output end of the continuously tunable laser; The output end of the continuously tunable laser is connected to the input end of the polarization-maintaining optical fiber beam splitter; The output end of the optical frequency comb is connected to the frequency doubling optical path; The frequency doubling optical path and the first output end of the polarization-maintaining optical fiber beam splitter are respectively connected to the input end of the optical fiber combiner; The chromium atomic beam is ejected from the atomic furnace and interacts with the second output end of the polarization-maintaining optical fiber beam splitter; The output end of the polarization-maintaining optical fiber combiner is connected to the input end of the beat frequency detection optical path; The output end of the beat frequency detection optical path is connected to the input end of the frequency counter through a photoelectric receiver; The beat frequency detection optical path includes a second collimator, a second reflector, a third half-wave plate, a polarization beam splitter prism, a third reflector and a diffraction grating; Wherein, the second reflector and the third reflector are placed in parallel; The optical path output end of the polarization-maintaining fiber combiner is connected to the input end of the photoelectric receiver after passing through the second collimator, the second reflector, the third half-wave plate, the polarization beam splitter prism, the third reflector and the diffraction grating in sequence; The 425nm wavelength reference construction device based on induced fluorescence effect is constructed by a 425nm wavelength reference construction method based on induced fluorescence effect, comprising the following steps: S1. Build a frequency measurement system of laser and optical frequency comb based on heterodyne beat frequency detection technology; S2. Set the temperature of the atomic furnace to the state where the chromium atomic beam is leaking, and initially adjust the laser wavelength to the chromium atomic beam ( 7 S3 → 7 P4) Near the theoretical value of the transition frequency, a group of lasers propagating in opposite directions interact with the chromium atomic beam and produce fluorescent spots symmetrically on both sides of the central axis of the chromium atomic beam; S3, finely adjust the laser wavelength to make the fluorescent spots induced symmetrically on both sides of the central axis of the chromium atom beam overlap. At this time, the laser frequency is equal to the chromium atom ( 7 S3 → 7 P4) transition frequency, for chromium atoms ( 7 S3 → 7 P4) Transition frequency measurement.

2. A 425nm wavelength reference construction device based on induced fluorescence effect according to claim 1, characterized in that: The frequency doubling optical path includes a filter, a second half-wave plate, a first convex lens, a frequency doubling crystal PPLN, a second convex lens and a second coupler; The output end of the optical frequency comb is connected to the input end of the filter; The output end of the filter is connected to the input end of the second half-wave plate; The output end of the second half-wave plate is connected to the input end of the frequency doubling crystal PPLN; A first convex lens and a second convex lens are respectively disposed at two ends of the frequency doubling crystal PPLN. The first convex lens and the second convex lens are used to focus the light beam inside the frequency doubling crystal PPLN.

3. The 425nm wavelength reference construction device based on induced fluorescence effect according to claim 1, characterized in that: The atomic furnace heats the chromium powder to a sublimation state in a vacuum environment and draws out a chromium atomic beam in a leakage flow manner; The second output end of the polarization-maintaining fiber beam splitter passes through the first collimator and the first reflector to form a group of counter-propagating lasers that interact with the collimated chromium atomic beam to generate two fluorescent spots. The overlap of the two fluorescent spots is used as the laser frequency and the chromium (Cr) atom ( 7 S3 → 7 P4) The basis for judging whether the transition frequencies are equal.

4. The 425nm wavelength reference construction device based on induced fluorescence effect according to claim 2, characterized in that: The continuously tunable laser output band covers 425.5±1.0nm, and a frequency tuning module is provided at the input end; The optical frequency comb reference source is a high-stability time-frequency signal, and the output band covers 851±2nm. After passing through the frequency doubling crystal PPLN, the output band covers 425.5±1.0nm.

5. The 425nm wavelength reference construction device based on induced fluorescence effect according to claim 1, characterized in that: The discharge temperature range of the chromium atomic beam ejected from the atomic reactor is 1500-1750 degrees Celsius.

6. The 425nm wavelength reference construction device based on induced fluorescence effect according to claim 1, characterized in that: The atomic furnace achieves the collimation of the chromium atomic beam through a slit or a transverse laser light field.

7. The 425nm wavelength reference construction device based on induced fluorescence effect according to claim 3, characterized in that: The propagation direction of the chromium atomic beam is perpendicular to the propagation direction of a group of laser beams propagating in opposite directions formed by the second output end of the polarization-maintaining optical fiber beam splitter through the first reflector.

8. The 425nm wavelength reference construction device based on induced fluorescence effect according to claim 1, characterized in that: A low-pass filter is arranged between the photoelectric receiver and the frequency counter.

Images