CN109193333B

CN109193333B - Atomic dichroism laser frequency stabilization integration method

Info

Publication number: CN109193333B
Application number: CN201811302407.4A
Authority: CN
Inventors: 王鹏程; 李洁; 赵博涛; 张天宇; 李嘉华; 魏小刚
Original assignee: Beijing Aerospace Wanda Hi Tech Ltd
Current assignee: Beijing Aerospace Wanda Hi Tech Ltd
Priority date: 2018-11-02
Filing date: 2018-11-02
Publication date: 2020-03-24
Anticipated expiration: 2038-11-02
Also published as: CN109193333A

Abstract

The invention discloses an atomic dichroism laser frequency stabilization integrated method, in the method, a fixed magnetic field required by the atomic dichroism laser frequency stabilization technology is provided by an external magnetic field of an optical isolator, devices such as a permanent magnet or an electrified solenoid coil, a power supply and control circuit and the like which provide a required magnetic field environment in an original system are omitted, the effective utilization of the external magnetic field of the optical isolator is realized, and a DAVLL-based laser frequency stabilization device is simplified. According to the method, an atomic gas chamber is arranged on one side of an optical isolator, and the optical isolator provides a magnetic field required by DAVLL to enable the atomic energy level in the atomic gas chamber to generate splitting and frequency shift due to the Zeeman effect, so that laser frequency stabilization based on DAVLL is achieved. The invention reduces the number of DAVLL-based laser frequency stabilization device components, reduces the volume of the device and improves the integration level of the device.

Description

Atomic dichroism laser frequency stabilization integration method

Technical Field

The invention belongs to the technical field of laser frequency stabilization, and particularly relates to an atomic dichroism laser frequency stabilization integration method.

Background

In recent years, with the rapid development of semiconductor laser frequency stabilization technology, semiconductor lasers with narrow line width and high stability are increasingly widely applied in the field of optoelectronics such as atomic spectroscopy, quantum metrology, optical fiber communication, atomic magnetometer, laser atomic cooling, and the like. The frequency stabilization method based on DAVLL (dichromatic Atomic Vapor Laser Lock) has the advantages of simple structure, no need of additional modulation signals (internal modulation), wide frequency stabilization range, low requirement on a magnetic field, influence of the intensity of the magnetic field on the slope of the frequency discrimination curve at a zero point, independence of the frequency at the zero point and the like, and is one of the commonly used methods for obtaining the Laser source with stable frequency.

In the process of miniaturization of the DAVLL frequency stabilized laser light source, the external magnetic field of the optical isolator can generate extra influence on nearby atomic gas, so that the optical isolator is far away from the atomic gas chamber, and the miniaturization is not facilitated. Therefore, how to reduce the distance between the optical isolator and the atomic gas chamber and compress the volume; whether the external magnetic field of the isolator can be reasonably utilized to replace the magnetic field generated by an atomic air chamber and a permanent magnet or an electrified solenoid coil, the system structure is simplified, the system volume is reduced, and the problem needs to be considered and solved in the miniaturization and integration processes of the DAVLL laser frequency stabilizing device.

Disclosure of Invention

The technical problem of the invention is solved: the method is characterized in that an atomic gas chamber is arranged in the range of an external magnetic field of an optical isolator to provide the magnetic field intensity required by the DAVLL technology, and the atomic energy level of the external magnetic field of the optical isolator is split and shifted due to the Zeeman effect by adjusting the relative position of the atomic gas chamber and the optical isolator, so that the laser frequency stabilization is realized.

In order to solve the technical problem, the invention discloses an atomic dichroism laser frequency stabilization integration method, which comprises the following steps:

controlling the laser module (1) to emit light and providing laser with frequency scanning;

adjusting the position of the optical isolator (2) to enable laser to pass through the optical isolator (2);

rotating the half wave plate (3) to adjust the light intensity of the first and second light beams (12, 11) passing through the first polarizing beam splitter (4); wherein the laser light is split by a first polarizing beam splitter (4) to form a first beam (12) and a second beam (11);

adjusting the position of the reflector (5) to make the first light beam (12) incident to the atomic gas cell unit (100); wherein the atomic gas cell unit (100) comprises: the device comprises a reflector (5), an atom gas chamber (6), a quarter wave plate (7), a second polarization beam splitter (8), a first photoelectric detector (9) and a second photoelectric detector (10);

connecting a first photoelectric detector (9) and a second photoelectric detector (10) with an oscilloscope;

carrying out differential processing on two paths of detection signals output by the first photoelectric detector (9) and the second photoelectric detector (10) through an oscilloscope to obtain a frequency discrimination curve;

adjusting the distance between the reflector (5) and the first polarization beam splitter (4), the angle of the reflector (5) and the distance between the reflector and the atomic gas cell (6) so as to change the relative position of the atomic gas cell (6) and the optical isolator (2); observing and recording a frequency discrimination curve on the oscilloscope in the process of changing the position;

and judging and determining the optimal relative position of the atomic gas chamber (6) and the optical isolator (2) according to the recorded frequency discrimination curve.

In the atomic dichroism laser frequency stabilization integration method, a first light beam (12) is laser deflected by 90 degrees after passing through a first polarization beam splitter (4) and is used for DAVLL frequency stabilization; the second beam (11) is a working laser.

In the above atomic dichroic laser frequency stabilization integration method, the method further includes:

an optical isolator (2) is placed adjacent to the atom gas cell (6) to provide the required magnetic field for the atoms in the atom gas cell (6) instead of a permanent magnet or an energized solenoid.

In the atomic dichroism laser frequency stabilization integration method,

the atomic gas chamber (6) and the optical isolator (2) are arranged in parallel; or the atomic gas chamber (6) and the optical isolator (2) are arranged at a set inclination angle.

The invention has the following advantages:

(1) the method of the invention adopts the external magnetic field of the optical isolator in the light path to replace the magnetic field generated by an external permanent magnet or an electrified solenoid coil, thereby providing the magnetic field required by the DAVLL technology. The method effectively utilizes the external magnetic field of the optical isolator, saves a permanent magnet or an electrified solenoid coil which is additionally arranged for providing the magnetic field required by the atomic gas chamber, and simplifies a DAVLL frequency stabilizing device; because the atomic gas chamber and the optical isolator can be placed very close to each other, the size of the laser frequency stabilizing device can be reduced, and the integration level of the device is improved.

(2) The invention provides the magnetic field intensity required by DAVLL technology by placing the atomic gas chamber in the range of the external magnetic field of the optical isolator, and leads the atomic energy level of the external magnetic field in the optical isolator to generate splitting and frequency shifting due to Zeeman effect by adjusting the relative position of the atomic gas chamber and the optical isolator, thereby realizing laser frequency stabilization.

(3) The experimental test of the invention has the advantages that the atomic gas chamber and the optical isolator are arranged in parallel, the interval can be less than 15mm, and the effect is better. The method effectively utilizes the external magnetic field of the optical isolator, saves a permanent magnet or an electrified solenoid coil which is additionally arranged for providing the magnetic field required by the DAVLL technology, and simplifies a DAVLL frequency stabilizing device; because the distance between the atomic gas chamber and the optical isolator is shortened, the size of the laser frequency stabilizer can be reduced, and the integration level of the device is improved.

Drawings

FIG. 1 is a light path diagram of an atomic dichroic laser frequency stabilization integration method in an embodiment of the present invention;

FIG. 2 is a flowchart illustrating steps of an integrated method for frequency stabilization of atomic dichroic lasers according to an embodiment of the present invention;

FIG. 3 is Rb as one embodiment of the present invention⁸⁷Atom D2 line F is 2-F' discriminator curve.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The invention relates to an atomic dichroism laser frequency stabilization integrated method, which is used for realizing the frequency stabilization of atomic dichroism laser based on a magnetic field of an optical isolator and has the following principle: the applied magnetic field splits and shifts the energy levels of the atoms in the gas cell by the zeeman effect by an amount of a frequency shift of guB. After linearly polarized light passes through the atomic air chamber and interacts with atoms in a magnetic field, outgoing laser is divided into left-handed polarized light and right-handed polarized light, due to the fact that absorption losses of two circular polarized components are different, splitting and frequency shift of a light intensity and frequency curve are generated due to the Zeeman effect, a frequency discrimination curve is obtained after difference is made between two paths of signals, and laser frequency stabilization is achieved through the zero position of the frequency discrimination curve. One characteristic of the frequency stabilization technology based on atomic dichroism laser is that the frequency at the zero point of a frequency discrimination curve is irrelevant to the magnetic field intensity, and the intensity influences the slope at the zero point of the frequency discrimination curve. The method has low requirements on the strength uniformity of the magnetic field and the direction consistency of the magnetic field, so that the magnetic field can be provided by using an external magnetic field of the optical isolator to realize laser frequency stabilization.

Referring to fig. 1, a light path diagram of an atomic dichroic laser frequency stabilization integration method in an embodiment of the present invention is shown: the atom gas chamber is placed in the optical isolator to provide a magnetic field environment, the magnetic field intensity of the atoms is changed by changing the relative position of the optical isolator and the atom gas chamber, and the relative position relation of the optical isolator and the atom gas chamber is determined by observing a frequency discrimination curve.

In this embodiment, as shown in fig. 1, the optical path of the integrated frequency stabilization method for atomic dichroic lasers at least includes a laser module 1, an optical isolator 2, a half-wave plate 3, a first polarization beam splitter 4, an atomic gas cell unit 100, a second light beam 11 and a first light beam 12, wherein the atomic gas cell unit 100 includes a reflector 5, an atomic gas cell 6, a quarter-wave plate 7, a second polarization beam splitter 8, a first photodetector 9 and a second photodetector 10, specifically, the laser module 1, the optical isolator 2, the half-wave plate 3 and the first polarization beam splitter 4 are sequentially placed in parallel, so as to ensure that the light exit of the laser module 1, the light aperture of the optical isolator 2, the central axis of the half-wave plate 3, and the central axis of the front and rear surfaces of the first polarization beam splitter 4 are in a straight line, the included angle between the reflector 5 and the central axis of the atomic gas cell 6 is 45 degrees, the atomic gas cell 6, the quarter-wave plate 7 and the second polarization beam splitter 8 are sequentially placed in parallel, the central axis of the atomic gas cell 6, the central axis of the atomic gas cell 7, the central axis of the second polarization beam splitter 4, the central axis of the atomic gas cell is placed in a straight line, and the central axis of the side surfaces of the second polarization beam splitter 5, and the central axis of the second polarization beam splitter are respectively placed behind the side surfaces of the second polarization beam splitter 5.

Referring to fig. 2, a flowchart of steps of an atomic dichroic laser frequency stabilization integration method in an embodiment of the present invention is shown. In this embodiment, the atomic dichroic laser frequency stabilization and integration method includes:

step 101, controlling the laser module 1 to emit light and providing laser with frequency scanning.

Step 102, adjusting the position of the optical isolator 2 to make the laser pass through the optical isolator 2.

Step 103, the half wave plate 3 is rotated to adjust the light intensity of the first light beam 12 and the second light beam 11 passing through the first polarization beam splitter 4.

In this embodiment, the laser light is split by the first polarization beam splitter 4 to form a first beam 12 and a second beam 11. The first light beam 12 is a 90 ° laser beam deflected by the first polarization beam splitter 4, and is used for DAVLL frequency stabilization; the second beam 11 is the working laser.

Step 104, adjusting the position of the reflector 5 to make the first light beam 12 incident on the atomic gas cell unit 100.

In this embodiment, the atomic gas cell unit 100 may specifically include: the device comprises a reflector 5, an atom gas chamber 6, a quarter wave plate 7, a second polarization beam splitter 8, a first photoelectric detector 9 and a second photoelectric detector 10.

Preferably, an optical isolator 2 may be placed adjacent to the atom gas cell 6 to provide the required magnetic field for the atoms in the atom gas cell 6, instead of a permanent magnet or an energized solenoid.

Preferably, the atomic gas cell 6 and the optical isolator 2 can be placed in parallel; or the atomic gas chamber 6 and the optical isolator 2 are arranged at a set inclination angle.

Wherein the optical isolator 2 is placed adjacent to the atomic gas cell 6, including but not limited to: the atom gas cell 6 is placed at any suitable position above, below, to the left, or to the right of the optical isolator 2.

Preferably, when the atomic gas cell 6 is placed in parallel with the optical isolator 2, the distance between the two may be less than 15 mm. The external magnetic field of the optical isolator is effectively utilized, a permanent magnet or an electrified solenoid coil which is additionally arranged for providing the magnetic field required by the DAVLL technology is omitted, and a DAVLL frequency stabilizing device is simplified; because the distance between the atomic gas chamber and the optical isolator is shortened, the size of the laser frequency stabilizer can be reduced, and the integration level of the device is improved.

And 105, connecting the first photoelectric detector 9 and the second photoelectric detector 10 with an oscilloscope.

And 106, performing differential processing on the two paths of detection signals output by the first photoelectric detector 9 and the second photoelectric detector 10 through an oscilloscope to obtain a frequency discrimination curve.

Step 107, adjusting the distance between the mirror 5 and the second polarization beam splitter 8, the angle of the mirror 5, and the distance between the mirror and the atom gas cell 6 to change the relative positions of the atom gas cell 6 and the optical isolator 2; and a frequency discrimination curve on the oscilloscope was observed and recorded during the repositioning process.

And step 108, judging and determining the optimal relative position of the atomic gas chamber 6 and the optical isolator 2 according to the recorded frequency discrimination curve.

In a preferred embodiment of the present invention, as shown in FIG. 1, the mirror is adjusted to make an angle α with the incident laser light (first beam) 45 degrees, so that the laser light passing through the atomic gas cell is parallel to and opposite to the incident laser light passing through the optical isolator, so that the atomic gas cell is placed parallel to the optical isolator.

In a preferred embodiment of the present invention, as shown in fig. 1, the distance L between the mirror and the first polarization beam splitter, the angle α between the mirror, and the distance R between the mirror and the atom cell in the atom cell unit can be changed to change the relative positions of the atom cell and the optical isolator, the test is repeated, each time the parameter is changed, the optimal position phase is obtained, the position parameter and the corresponding frequency discrimination curve are recorded, and finally the recorded curves are compared to determine the optimal position.

In a preferred embodiment of the present invention, the infrared video lens can be disposed at the upper portion of the atom gas chamber 6 to observe and record the fluorescence emission in the atom gas chamber 6, which is convenient for finding and handling abnormal problems in time.

On the basis of the above embodiments, a specific example is described below. Specifically, the atomic dichroism laser frequency stabilization integration method comprises the following implementation steps:

a. opening the laser module with tunable external cavity to enable the laser to be in a frequency scanning state, and horizontally emitting the laser, wherein the emitted light spot is a circular parallel light beam;

b. adjusting an optical isolator to enable the laser transmission efficiency to be higher than 80%;

c. rotating the half wave plate to adjust the light intensity of the two beams of laser passing through the first polarization beam splitter;

d. the first light beam is incident to the air chamber unit, two paths of detection signals are output, and the two paths of output detection signals are subtracted to obtain a corresponding frequency discrimination curve;

e. the angle α between the mirror and the incident laser (first beam) is adjusted to 45 degrees, so that the laser passing through the atom air chamber is parallel to and opposite to the incident laser passing through the optical isolator, and the atom air chamber and the optical isolator are arranged in parallel.

f. The distance L between the reflector and the first polarization beam splitter in the air chamber unit, the angle α of the reflector and the distance R between the reflector and the atom air chamber are respectively changed to change the relative positions of the atom air chamber and the optical isolator, the test is repeated, the optimal position phase exists when the parameters are changed every time, the position parameters and the corresponding frequency discrimination curves are recorded once, and finally the recorded curves are compared to determine the optimal position.

Preferably, the initial position of α can be selected to be 45 degrees, so that the atomic gas chamber and the optical isolator are placed in parallel, the included angle α between the reflector and the incident laser is adjusted to be 45 degrees plus or minus 5 degrees, so that the included angle between the optical isolator and the atomic gas chamber is plus or minus 10 degrees, and the invention has the advantages of simple structure, small volume and high integration through multiple use verification.

For example, laser light is provided by a laser module of an external cavity type tunable semiconductor, the wavelength is 780nm, and the polarization state of the laser light is linear polarization; the optical isolator is 'thorlabs IO-3-780-HP', the laser transmission efficiency is 82%, a half wave plate is adjusted to enable the light intensity of the first light beam to be less than 100 mu w, the angle of a reflector is 45 degrees, an atom gas chamber is aligned with the center of the optical isolator, the atom gas chamber is a quartz glass cavity, rubidium atom steam is packaged in the atom gas chamber, and the pressure is 10%^-5Torr, providing a nonlinear working medium for atomic spectroscopy, the volume of the atomic gas chamber of this example is 50X 20mm³(ii) a The photodetector uses a thorlabs FDS02 silicon photonics chip. FIG. 3 shows Rb as one of the embodiments of the present invention⁸⁷Atom D2 line F is 2-F' discriminator curve. In fig. 3, the position of the zero point in the discrimination curve 2, i.e., the line D2F of the absorption line 1, is 2 — F' absorption peak. Fig. 3 illustrates that the laser frequency is locked at the zero point of the frequency discrimination curve, namely, the laser frequency is locked at the peak of the absorption peak of F-2-F'.

The embodiments in the present description are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Those skilled in the art will appreciate that the invention may be practiced without these specific details.

Claims

1. An atomic dichroism laser frequency stabilization integration method is characterized by comprising the following steps:

the optical isolator (2) is arranged adjacent to the atom gas chamber (6) to provide a required magnetic field for atoms in the atom gas chamber (6) to replace a permanent magnet or an electrified solenoid coil;

2. The atomic dichroic laser frequency stabilization integration method according to claim 1, wherein the first light beam (12) is 90 ° laser deflected by the first polarization beam splitter (4) for DAVLL frequency stabilization; the second beam (11) is a working laser.

3. The atomic dichroic laser frequency stabilization integration method according to claim 1,