CN212435035U - Laser frequency stabilization system based on differential saturated absorption spectrum - Google Patents
Laser frequency stabilization system based on differential saturated absorption spectrum Download PDFInfo
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- CN212435035U CN212435035U CN202020778135.1U CN202020778135U CN212435035U CN 212435035 U CN212435035 U CN 212435035U CN 202020778135 U CN202020778135 U CN 202020778135U CN 212435035 U CN212435035 U CN 212435035U
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Abstract
The utility model discloses a laser instrument frequency stabilization system based on difference saturated absorption spectrum, including semiconductor laser, first half-wave plate, first polarization beam splitter, second half-wave plate, second polarization beam splitter, rubidium bubble, third polarization beam splitter, photoelectric difference detector and control circuit. The utility model has the advantages that: compared with the existing frequency stabilizing system of a laser, the frequency stabilizing system has the advantages of clear modularization, simpler structure, better performance and lower cost, and because the working waveband of the frequency stabilizing light is positioned at the waveband of near infrared, the frequency stabilizing light can provide a hardware basis for precision measurement and plays a role in promoting the application of the near infrared light.
Description
Technical Field
The utility model relates to a technical field of laser instrument frequency stabilization system particularly, relates to a laser instrument frequency stabilization system based on difference saturation absorption spectrum.
Background
With the rapid development of the narrow-linewidth semiconductor laser diode manufacturing technology, the semiconductor laser becomes the first choice laser light source of the precision measurement technology. However, the frequency stability of the free-running diode laser is poor, and after stable control of temperature and current is adopted, the frequency still has drift, so that the requirement of precise measurement on the laser frequency cannot be met, and further frequency stabilizing measures need to be adopted.
In a conventional frequency stabilization system for a laser, for example, a transmission cavity frequency stabilization system uses a laser with high stability as a reference (for example, an iodine frequency stabilized he-ne laser), laser light of the reference laser and laser light of a laser to be stabilized (a semiconductor laser) are simultaneously incident into a scanning fabry-perot interferometer (a transmission cavity), a photoelectric detector is used to detect a transmission signal of the laser light of the reference laser after passing through the transmission cavity and a transmission signal of the laser light of the laser to be stabilized after passing through the transmission cavity, and a data acquisition card is used to convert the transmission signals into digital signals and input the digital signals into a computer, and the stability of the laser to be stabilized is improved by calculating and locking a transmission peak distance in the transmission signals. The length of the transmission cavity is adjusted by the piezoelectric ceramics, and the expansion and contraction of the piezoelectric ceramics can be adjusted by a sawtooth wave voltage signal output by the piezoelectric ceramics driving source, so that the length of the transmission cavity is changed, and the purpose of changing the resonant frequency of the transmission cavity is achieved. The frequency stabilization system of the laser has a complex structure and poor performance, and cannot well meet the frequency stabilization requirement of the laser
An effective solution to the problems in the related art has not been proposed yet.
SUMMERY OF THE UTILITY MODEL
To the above-mentioned technical problem among the correlation technique, the utility model provides a laser instrument frequency stabilization system based on difference saturation absorption spectrum can solve present semiconductor laser diode's laser frequency spectrum wide, a series of problems such as frequency drift to the simple structure of system, the cost is lower, excellent performance.
In order to achieve the technical purpose, the technical scheme of the utility model is realized as follows:
a laser frequency stabilization system based on a differential saturated absorption spectrum comprises a semiconductor laser, a first half-wave plate, a first polarization beam splitter, a second half-wave plate, a second polarization beam splitter, a beam splitter, rubidium bubbles, a third polarization beam splitter, a photoelectric differential detector and a control circuit;
the laser beam emitted by the semiconductor laser under the control of the control circuit passes through the first half-wave plate and then enters the first polarization beam splitter, and is split by the first polarization beam splitter to obtain a first light beam and a second light beam, the second light beam passes through the second half-wave plate and then enters the second polarization beam splitter, and is split by the second polarization beam splitter to obtain a third light beam and a fourth light beam, the third light beam enters the third polarization beam splitter, and is split by the third polarization beam splitter to obtain a fifth light beam, the fourth light beam enters the beam splitter, and is split by the beam splitter to obtain a sixth light beam and a seventh light beam, the fifth light beam and the sixth light beam have opposite directions and both enter the rubidium bubble, and enter the photoelectric differential detector after being superposed by the rubidium bubble, and the seventh light beam enters the photoelectric differential detector after passing through the rubidium bubble, the photoelectric differential detector outputs signals to the control circuit.
Further, a collimator is arranged on a light path between the semiconductor laser and the first half-wave plate.
Further, an optical isolator is arranged on a light path between the collimator and the first half-wave plate.
Further, the third light beam sequentially passes through the first mirror and the third mirror and then enters the third polarization beam splitter.
Further, the seventh light beam enters the rubidium bubble after passing through the second mirror.
The utility model also provides a laser instrument frequency stabilization method based on difference saturation absorption spectrum, including following step:
s1, the laser beam emitted by the semiconductor laser under the control of the control circuit is transmitted into the first polarization beam splitter after passing through the first half-wave plate, so as to be split into a first beam and a second beam;
s2, the first light beam is used for interacting with atoms, and the second light beam passes through a second half-wave plate and then enters a second polarization beam splitter to be split into a third light beam and a fourth light beam;
s3 projecting the third light beam into a third polarization beam splitter to split into a fifth light beam and projecting the fourth light beam into a beam splitter to split into a sixth light beam and a seventh light beam;
s4, emitting the fifth light beam and the sixth light beam into the rubidium bubble in a direction opposite to each other for superposition to obtain a first detection light beam, and emitting the seventh light beam into the rubidium bubble to obtain a second detection light beam;
s5, the first detection light beam and the second detection light beam are emitted into a photoelectric differential detector for differential processing, so that a noiseless atom saturated absorption spectral line is obtained;
s6 the control circuit controls the semiconductor laser according to the atomic saturation absorption line to lock the frequency of the laser beam emitted by the semiconductor laser at the peak of the atomic saturation absorption line.
Further, in S1, the light emitted from the semiconductor laser is processed by a collimator and an optical isolator in sequence, and then transmitted to the first half-waveplate.
Further, in S3, the third light beam is reflected by the first mirror and the third mirror in sequence and then incident on the third polarization beam splitter.
Further, in S4, the seventh light beam is reflected by the second mirror and then enters the rubidium bubble.
The utility model has the advantages that: compared with the existing frequency stabilizing system of a laser, the frequency stabilizing system has the advantages of clear modularization, simpler structure, better performance and lower cost, and because the working waveband of the frequency stabilizing light is positioned at the waveband of near infrared, the frequency stabilizing light can provide a hardware basis for precision measurement and plays a role in promoting the application of the near infrared light.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of a laser frequency stabilization system based on differential saturation absorption spectrum according to an embodiment of the present invention.
In the figure:
1. a semiconductor laser; 2. a collimator; 3. an optical isolator; 4. a first half wave plate; 5. a first polarizing beam splitter; 6. a second half-wave plate; 7. a second polarizing beam splitter; 8. a first reflector; 9. a beam splitter; 10. a second reflector; 11. rubidium bubbles; 12. a third reflector; 13. a third polarization beam splitter; 14. a photoelectric differential detector.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art all belong to the protection scope of the present invention.
As shown in fig. 1, according to the embodiment of the present invention, a laser frequency stabilization system based on differential saturated absorption spectrum includes a semiconductor laser 1, a first half-wave plate 4, a first polarization beam splitter 5, a second half-wave plate 6, a second polarization beam splitter 7, a beam splitter 9, a rubidium bubble 11, a third polarization beam splitter 13, a photoelectric differential detector 14, and a control circuit;
the laser beam emitted by the semiconductor laser 1 under the control of the control circuit passes through the first half-wave plate 4 and then enters the first polarization beam splitter 5, and is split by the first polarization beam splitter 5 to obtain a first light beam and a second light beam, the second light beam passes through the second half-wave plate 6 and then enters the second polarization beam splitter 7, and is split by the second polarization beam splitter 7 to obtain a third light beam and a fourth light beam, the third light beam enters the third polarization beam splitter 13, and is split by the third polarization beam splitter 13 to obtain a fifth light beam, the fourth light beam enters the beam splitter 9, and is split by the beam splitter 9 to obtain a sixth light beam and a seventh light beam, the fifth light beam and the sixth light beam are opposite in direction and both enter the rubidium bubble 11, and are overlapped by the rubidium bubble 11 and then enter the photoelectric differential detector 14, the seventh light beam enters the photoelectric differential detector 14 after passing through the rubidium bubble 11, and the photoelectric differential detector 14 outputs a signal to the control circuit.
In a specific embodiment of the present invention, a collimator 2 is disposed on the light path between the semiconductor laser 1 and the first half-wave plate 4.
In a specific embodiment of the present invention, an optical isolator 3 is disposed on the optical path between the collimator 2 and the first half-wave plate 4.
In a specific embodiment of the present invention, the third light beam enters the third polarization beam splitter 13 after passing through the first mirror 8 and the third mirror 12 in sequence.
In an embodiment of the present invention, the seventh light beam enters the rubidium bubble 11 after passing through the second reflecting mirror 10.
The utility model also provides a laser instrument frequency stabilization method based on difference saturation absorption spectrum, including following step:
s1 the laser beam emitted by the semiconductor laser 1 under the control of the control circuit passes through the first half-wave plate 4 and then enters the first polarization beam splitter 5 to split the laser beam into a first beam and a second beam;
s2 using the first light beam to interact with atoms, passing the second light beam through a second half-wave plate 6 and entering a second polarization beam splitter 7 to split into a third light beam and a fourth light beam;
s3 emitting the third light beam into the third polarization beam splitter 13 to be split into a fifth light beam, and emitting the fourth light beam into the beam splitter 9 to be split into a sixth light beam and a seventh light beam;
s4 projecting the fifth light beam and the sixth light beam into the rubidium bubble 11 in opposite directions for superposition to obtain a first probe light beam, and projecting the seventh light beam into the rubidium bubble 11 to obtain a second probe light beam;
s5, emitting the first detection beam and the second detection beam into the photoelectric differential detector 14 for differential processing to obtain a noise-free atomic saturation absorption line;
s6 the control circuit controls the semiconductor laser 1 according to the atomic saturation absorption line so that the frequency of the laser beam emitted therefrom is locked at the peak of the atomic saturation absorption line.
In a specific embodiment of the present invention, in S1, the light emitted by the semiconductor laser 1 is processed by the collimator 2 and the optical isolator 3 in sequence and then transmitted to the first half-wave plate 4.
In a specific embodiment of the present invention, in S3, the third light beam is reflected by the first mirror 8 and the third mirror 12 in sequence and then enters the third polarization beam splitter 13.
In an embodiment of the present invention, in S4, the seventh light beam is reflected by the second reflecting mirror 10 and then enters the rubidium bubble 11.
For the convenience of understanding the above technical solutions of the present invention, the above technical solutions of the present invention are explained in detail through specific use modes below.
The utility model relates to a compact laser instrument frequency stabilization system based on difference saturated absorption spectrum, including semiconductor laser 1, collimator 2, optoisolator 3, half-wave plate, Polarization Beam Splitter (PBS), speculum, Beam Splitter (BS) 9, rubidium bubble 11, photoelectric differential detector (PD) 14 and control circuit.
The semiconductor laser 1 is for emitting a laser beam and is of the type Photodigm PH795DBR080T 8.
The collimator 2 is of the type Thorlabs C230 TMD-8. The model number of the optoisolator 3 is Thorlabs IOT-5-780-VLP. The photodetector is available in Thorlabs PDB 210A/M.
The half-wave plates include a first half-wave plate 4 and a second half-wave plate 6. The polarization beam splitter includes a first polarization beam splitter 5, a second polarization beam splitter 7, and a third polarization beam splitter 13. The mirrors include a first mirror 8, a second mirror 10 and a third mirror 12.
The control circuit comprises an MCU module, a passive filter and a drive circuit; the MCU module is used for outputting PWM signals and controlling output voltage values by adjusting the duty ratio of the PWM signals, the passive filter is used for converting the PWM signals into direct-current voltage, the output end of the passive filter is connected with the driving circuit, the driving circuit is used for driving the semiconductor laser 1 to emit light, the photoelectric differential detector 14 converts collected light signals into electric signals, and the MCU module adjusts the duty ratio of the PWM signals according to the electric signals.
The saturated absorption spectroscopy is to use monochromatic light for optical pumping, tune the laser frequency at the atomic transition frequency, and make the atoms in the ground state transition absorbed photons to the excited state. When the laser intensity is increased, the number of atoms in the excited state increases. However, when the laser intensity is further increased to saturation, the number of atoms in the upper and lower energy levels reaches equilibrium, and atoms in the ground state are no longer reduced by the transition of absorbed electrons to the excited state. Thereby saturating one transition of the atoms to cause a non-linear change in the energy level topology, making the absorption no longer proportional to the intensity of the incident light, and thus achieving high resolution spectroscopy.
When the laser device is used specifically, a laser beam emitted by the semiconductor laser device 1 is input into the optical isolator 3 after being calibrated by the collimator 2, so that the laser beam is prevented from returning to the semiconductor laser device 1, and the damage to the semiconductor laser device 1 is effectively avoided. The laser beam output from the optical isolator 3 enters the first polarization beam splitter 5 after passing through the first half wave plate 4. The laser beam passes through the first polarization beam splitter 5 and is split into a first beam (i.e., the beam horizontally to the left in fig. 1) for interacting with atoms and a second beam (i.e., the beam vertically downward in fig. 1) for frequency stabilization. The second light beam enters the second polarization beam splitter 7 after passing through the second half-wave plate 6, the second light beam is split into a third light beam and a fourth light beam after passing through the second polarization beam splitter 7 and then emitted, and the third light beam enters the third polarization beam splitter 13 after being reflected by the reflecting mirror 1 and the reflecting mirror 3. The third light beam passes through the third polarization beam splitter 13 to form a fifth light beam, and the fifth light beam enters the rubidium bubble 11. This fifth beam is called pump light and is of higher intensity. The fourth light beam is split into a sixth light beam and a seventh light beam through the beam splitter 9, and the sixth light beam and the seventh light beam are both called probe light and have weak intensity. The sixth light beam enters the rubidium bulb 11, and the seventh light beam enters the rubidium bulb 11 along another light path after being reflected by the reflector 2. The rubidium bubble 11 is disposed between the beam splitter 9 and the third polarization beam splitter 13, so that the sixth light beam and the fifth light beam are incident into the rubidium bubble 11 in two opposite directions, and thus atoms in the rubidium bubble 11 in the ground state transition to the excited state after absorbing photons. When the laser intensity of the fifth beam is increased, the number of atoms of the excited state increases, but when the laser intensity is further increased to saturation, the number of atoms of the upper and lower energy levels reaches an equilibrium, and atoms of the ground state no longer transition to the excited state by absorption of photons. The sixth beam will no longer be absorbed and a saturated absorption line will appear reflecting the position of the atomic fine structure energy level.
Atomic lines are originally doppler broadened lines due to the collection of a large number of very narrow lines of absorption or emission by atoms of various velocities. When an optical field interacts with an atomic system, the optical wave interacts with only that portion of the atom with which it resonates. If the light field is now composed of two laser beams propagating in opposite directions, the components of the laser beams propagating in both directions will interact with the atoms with zero axial velocity at the same time, so that a doppler-free saturated absorption spectrum can be obtained.
In this embodiment, the fifth beam and the sixth beam are two laser beams propagating in opposite directions, so that the components of the fifth beam and the sixth beam propagating in the respective directions will interact with atoms with zero axial velocity at the same time, thereby obtaining a doppler-free saturated absorption spectrum.
The sixth light beam and the fifth light beam are superposed in the rubidium bubble 11 to obtain a first detection light beam, the first detection light beam is emitted into the photoelectric differential detector 14, the seventh light beam passes through the rubidium bubble 11 to obtain a second detection light beam, and the second detection light beam is also emitted into the photoelectric differential detector 14. Since the first detection beam and the second detection beam entering the photo-differential detector 14 both have noise components, the photo-differential detector 14 can eliminate the noise components in the first detection beam and the second detection beam after differentiating the first detection beam and the second detection beam, thereby obtaining a noiseless atomic saturation absorption line.
After passing through the photoelectric differential detector 14, atomic saturation absorption lines can be displayed. When the laser frequency deviates from the center frequency of an atom, two absorption spectra symmetrical to the center of a spectral line respectively appear in the velocity distribution of the atom. When the frequency of the laser is tuned to the center frequency of the atom, the two absorption spectra will overlap. The signal output by the photo-differential detector 14 is fed back to a control circuit (not shown) of the semiconductor laser 1, which locks the frequency of the semiconductor laser 1 on the peak of the atomic saturation absorption line, i.e. adjusts the frequency of the laser light to the center frequency of the atom.
To sum up, with the help of the utility model discloses an above-mentioned technical scheme, system scientific and reasonable, it is simple and convenient, compare current laser instrument steady frequency system, this system modularization is clear, the structure is simpler, the performance is better, the cost is lower, because steady frequency light work wave band is located near-infrared place wave band, consequently, can provide the hardware basis for precision measurement, the promotion effect has been played for the application of near-infrared light, this system is with semiconductor laser, the collimater, optical isolator, half wave plate, polarization beam splitter, the speculum, the beam splitter, rubidium bubble, device integration such as photoelectric differential detector in a device, high durability and convenient use, the device is compact, small.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A laser frequency stabilization system based on a differential saturated absorption spectrum is characterized by comprising a semiconductor laser (1), a first half-wave plate (4), a first polarization beam splitter (5), a second half-wave plate (6), a second polarization beam splitter (7), a beam splitter (9), a rubidium bubble (11), a third polarization beam splitter (13), a photoelectric differential detector (14) and a control circuit;
the laser beam emitted by the semiconductor laser (1) under the control of the control circuit enters the first polarization beam splitter (5) after passing through the first half-wave plate (4), the laser beam is split by the first polarization beam splitter (5) to obtain a first light beam and a second light beam, the second light beam enters the second polarization beam splitter (7) after passing through the second half-wave plate (6), the second light beam is split by the second polarization beam splitter (7) to obtain a third light beam and a fourth light beam, the third light beam enters the third polarization beam splitter (13), the third light beam is split by the third polarization beam splitter (13) to obtain a fifth light beam, the fourth light beam enters the beam splitter (9), the sixth light beam and the seventh light beam are obtained after being split by the beam splitter (9), the directions of the fifth light beam and the sixth light beam are opposite, and both of the fifth light beam and the sixth light beam enter the rubidium bubble (11), the beams are overlapped by the rubidium bubbles (11) and then enter the photoelectric differential detector (14), the seventh beam enters the photoelectric differential detector (14) after passing through the rubidium bubbles (11), and the photoelectric differential detector (14) outputs a signal to the control circuit.
2. The laser frequency stabilization system based on differential saturated absorption spectrum according to claim 1, characterized in that a collimator (2) is arranged on the optical path between the semiconductor laser (1) and the first half-wave plate (4).
3. The differential saturable absorption spectrum-based laser frequency stabilization system according to claim 2, wherein an optical isolator (3) is disposed on the optical path between the collimator (2) and the first half-wave plate (4).
4. The laser frequency stabilization system based on the differential saturated absorption spectrum of claim 1, wherein the third light beam enters the third polarization beam splitter (13) after passing through the first mirror (8) and the third mirror (12) in sequence.
5. The laser frequency stabilization system based on differential saturated absorption spectrum according to claim 1, wherein the seventh light beam enters the rubidium bubble (11) after passing through the second mirror (10).
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| CN202020778135.1U CN212435035U (en) | 2020-05-12 | 2020-05-12 | Laser frequency stabilization system based on differential saturated absorption spectrum |
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| CN202020778135.1U CN212435035U (en) | 2020-05-12 | 2020-05-12 | Laser frequency stabilization system based on differential saturated absorption spectrum |
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