A method and apparatus for quantum control of laser power

Abstract

The application discloses a kind of quantum control method and device of laser power, receive input laser signal, modulate the laser signal, output 0 level and "±1" level diffraction light, other diffraction light frequency components except "+1" level diffraction light of output is shielded, "+1" level diffraction light of output is coupled to rubidium atomic clock gas chamber, adjust "+1" level diffraction light direction and the atomic beam direction of rubidium atomic clock gas chamber parallel, the output frequency of rubidium atomic clock is measured in real time, further output frequency is fed back for modulating laser signal.The method and device realize the stable control of laser power.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, in particular to a method and device for quantum control of laser signal power. BACKGROUND

[0002] With the increasing application of laser and laser technology in scientific research and production, the fluctuation of optical power seriously affects the fields of scientific research, and people have higher and higher requirements for the stability of laser power. For example, in the research of laser ranging, the fluctuation of optical power will affect the accuracy of ranging; in the research of cold atom interference, the fluctuation of power of Raman laser will affect the accuracy and sensitivity of measurement.

[0003] At present, the system for measuring laser power is based on the photoelectric conversion of the detected optical signal power into an electrical signal, and then the feedback and stable control of laser power are performed. There are two methods for stabilizing laser power, namely internal modulation and external modulation. Internal modulation is to directly control the current, temperature, cavity length, etc. of the laser, which has the advantages of simple structure and high efficiency. However, when modulating the internal components of the laser, it is easy to affect the frequency of the laser output, and the stability of the laser output power will also be affected by external factors, so the stability of the laser output power is poor. Therefore, the external laser stabilization method is widely used, and the commonly used external modulation method uses acousto-optic modulators, electro-optic modulators, crystal modulators, etc. to control the power and stabilize the laser power. Using the above laser power measurement and stabilization method to control the power, the limit of power stability that can be achieved is 10 -4 orders of magnitude, which cannot meet the needs of scientific research and production.

[0004] Therefore, it is an important and urgent problem to improve the stability of laser power. SUMMARY

[0005] The present application provides a method and device for quantum control of laser power, which solves the problem of low power stability in external laser power control.

[0006] The method for quantum control of laser power provided by the present application comprises the following steps:

[0007] receiving an input laser signal;

[0008] modulating the laser signal to output 0th order and "±1" order diffracted light;

[0009] shielding the frequency components of the output diffracted light other than the "+1" order diffracted light;

[0010] coupling the "+1" order diffracted light to a rubidium atomic clock gas cell;

[0011] adjusting the direction of the "+1" order diffracted light to be parallel to the atomic beam direction of the rubidium atomic clock gas cell.

[0012] The output frequency of the rubidium atomic clock is measured in real time.

[0013] The application further provides a quantum control device for laser power, which comprises an acousto-optic modulator, an optical diaphragm, a coupler, an optical fiber, a rubidium atomic clock and a frequency counter,

[0014] The acousto-optic modulator modulates the input laser to output 0th order and "±1" order diffraction light.

[0015] The optical diaphragm blocks the frequency components of the diffraction light output by the acousto-optic modulator, except the "+1" order diffraction light.

[0016] The coupler is used for coupling the "+1" order diffraction light output by the optical diaphragm into the optical fiber.

[0017] The optical fiber is used for guiding the "+1" order diffraction light output by the coupler into the gas chamber of the rubidium atomic clock.

[0018] The rubidium atomic clock is provided with an opening on the side of the detector, the optical fiber is used for guiding the "+1" order diffraction light output by the coupler into the opening of the rubidium atomic clock, and the direction of the diffraction light is parallel to the direction of the atomic beam of the gas chamber of the rubidium atomic clock.

[0019] The frequency counter is used for measuring the output frequency of the rubidium atomic clock in real time.

[0020] Further, the application further provides a device for controlling laser power, wherein a laser power feedback control system is arranged between the frequency counter and the acousto-optic modulator, the laser power feedback control system modulates the acousto-optic modulator based on the difference between the output frequency and a standard output frequency, and controls the laser output power of the acousto-optic modulator.

[0021] The quantum control method and device for laser power provided by the application solve the defect of low power stability in the cavity laser power control, realize the control of laser power outside the cavity, reduce the control difficulty, and improve the quantum control stability of the laser power. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and serve to explain the application without imposing undue limitation thereon. In the drawings:

[0023] Figure 1 A flowchart of the quantum control method for laser power provided by the application is shown in the figure;

[0024] Figure 2 A first structural schematic diagram of the device for controlling laser power provided by the application is shown in the figure;

[0025] Figure 3 A second structural schematic diagram of a laser power control device provided by the present application;

[0026] Figure 4 A third structural schematic diagram of a laser power control device provided by the present application. DETAILED DESCRIPTION

[0027] For the purpose, technical solutions and advantages of the present application to be clearer, the technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative work fall within the scope of protection of the present application.

[0028] A rubidium atomic clock is composed of a rubidium quantum part and a voltage-controlled crystal oscillator. The frequency of the voltage-controlled crystal oscillator is multiplied and frequency-synthesized, and then sent to the quantum system to compare with the rubidium atomic transition frequency. The error signal is sent back to the voltage-controlled crystal oscillator to adjust the frequency, so that it is locked on the frequency corresponding to the energy level transition specific to the rubidium atom.

[0029] The technical solutions provided by the embodiments of the present application will be described in detail below in combination with the drawings.

[0030] Embodiment 1

[0031] The method of laser power control of the present application will be described below in combination with Figure 1

[0032] Step 110: receiving an input laser signal.

[0033] The input laser signal is received, which can be generated by a semiconductor laser. As an embodiment, the laser wavelength is 795 nm.

[0034] Step 120: modulating the laser signal to output 0th order and "±1" order diffracted light.

[0035] After the laser signal is modulated by grating diffraction, 0th order and "±1" order diffracted light is output. As an embodiment, after the laser signal is modulated by acousto-optic modulation effect, multi-order diffracted light is output.

[0036] Further, the "+1" order diffracted light is used to control the laser power. The angle of the laser incident to the acousto-optic modulator is changed so that the diffraction efficiency of the "+1" order diffracted light reaches the maximum.

[0037] Step 130: shielding the frequency components of the output diffracted light other than the "+1" order diffracted light.

[0038] ​Step 140: coupling the output "+1" order diffracted light to the rubidium atomic clock cell.

[0039] Preferably, the "+1" order diffracted light is coupled into the optical fiber through the coupler and then input to the rubidium atomic clock cell.

[0040] Step 150: adjusting the direction of the "+1" order diffracted light to be parallel to the atomic beam direction of the rubidium atomic clock cell.

[0041] Adjusting the direction of the "+1" order diffracted light to be parallel to the atomic beam direction of the rubidium atomic clock cell allows the detector of the rubidium atomic clock to detect the atomic beam.

[0042] Step 160: measuring the output frequency of the rubidium atomic clock in real time.

[0043] Measuring the output frequency of the rubidium atomic clock in real time, the change of the output frequency reflects the change of the laser power.

[0044] Further, the difference between the output frequency and the calibrated output frequency is used as feedback to modulate the laser signal in step 120 to output 0 order and "+1" order diffracted light. The calibrated output frequency refers to the output frequency measured by the frequency counter after introducing a laser with a certain frequency and power into the rubidium atomic clock cell. As an example, the difference between the output frequency and the calibrated output frequency is fed back to the acousto-optic modulator through a feedback loop, and the acousto-optic modulator modulates the laser to control the output of 0 order and "+1" order diffracted light. Finally, the purpose of controlling and stabilizing the size of "+1" order diffracted light is achieved, realizing closed-loop control of laser power and improving the stability of power control.

[0045] Example 2

[0046] Figure 2 A schematic diagram of a quantum control device for laser power is shown, which includes an acousto-optic modulator 210, an optical diaphragm 220, a coupler 230, an optical fiber 240, a rubidium atomic clock 250, and a frequency counter 260, as follows:

[0047] The acousto-optic modulator 210 modulates the input laser to output 0 order and "+1" order diffracted light.

[0048] Preferably, as shown in Figure 4 The acousto-optic modulator is followed by a laser 410, which outputs laser light to the acousto-optic modulator. The wavelength of the laser in this embodiment is 795 nm. After the laser, there is an isolator 420, which is used to ensure one-way transmission of the laser output light and prevent reflected light from coupling into the laser, affecting the normal operation of the laser.

[0049] Further, as shown in Figure 4As shown, there is a mirror 430 before the acousto-optic modulator, which is used to adjust the position and angle of the laser incident to the acousto-optic modulator. Similarly, there can also be a mirror combination, a prism or a prism combination before the acousto-optic modulator, which is used to adjust the position and angle of the laser incident to the acousto-optic modulator. By adjusting the incident position and angle, it is ensured that the " + 1" order diffracted light output by the acousto-optic modulator has high efficiency and works in the linear region, at which the acousto-optic modulator is sensitive to the change of the radio frequency modulation voltage, facilitating accurate control of the incident light power.

[0050] The diaphragm 220 blocks the frequency components of the diffracted light other than the "+1" order diffracted light output by the acousto-optic modulator;

[0051] The coupler 230 is used to couple the "+1" order diffracted light output by the diaphragm into the optical fiber;

[0052] Further, as shown, Figure 4 There is an optical beam splitter 440 before the coupler, which is used to divide the laser into multiple beams, one of which is input into the coupler for power control, and the others are output to external devices for other practical applications.

[0053] The optical fiber 240 is used to guide the "+1" order diffracted light output by the coupler into the rubidium atomic clock cell;

[0054] The rubidium atomic clock 250 is provided with an opening on the side of the detector, and the optical fiber is used to guide the "+1" order diffracted light output by the coupler into the opening of the rubidium atomic clock, the direction of the diffracted light is parallel to the direction of the atomic beam of the rubidium atomic clock cell, which increases the interaction intensity between the light and the rubidium atoms in the rubidium atomic clock cell, so that more rubidium atoms participate in the light frequency shift process. The detector of the rubidium atomic clock detects the atomic beam and outputs the clock frequency.

[0055] The frequency counter 260 measures the output frequency of the rubidium atomic clock in real time.

[0056] Further, as shown, Figure 3 There is a laser power feedback control system 300 between the frequency counter 260 and the acousto-optic modulator 210, which modulates the acousto-optic modulator based on the difference between the output frequency and the calibrated output frequency, and controls the laser output power of the acousto-optic modulator.

[0057] Further, the laser power feedback control system 300 comprises a host computer 310 and a servo control part 320, the host computer 310 collects the output frequency of the atomic clock from the frequency counter, takes the output frequency and the calibration output frequency as error signals, processes the error compensation signals after a proportional-integral-derivative feedback control algorithm 311, and sends the error compensation signals to the servo control part 320; the servo control part 320 comprises a radio frequency driver 321, which is used to control the output voltage of the radio frequency driver according to the error compensation signals to drive the acousto-optic modulator to modulate the laser signal.

[0058] The acousto-optic modulator is modulated by the laser power feedback control system, the cavity-out modulation of the laser is realized, and the control is convenient; meanwhile, the feedback control technology improves the power control efficiency and effect of the acousto-optic modulator, so that the diffraction light power after modulation is consistent with the calibration laser.

[0059] Further, the output voltage of the radio frequency driver 321 controls the diffraction efficiency of the acousto-optic modulator, and further controls the power of the "+1" order diffraction light.

[0060] Preferably, in order to provide sufficient power to drive the acousto-optic modulator to work normally, the control signal emitted by the radio frequency driver 321 is first amplified by a power amplifier 322.

[0061] The application realizes the conversion of the laser power control to the measurement of the high-precision atomic clock output frequency, and feeds back the deviation of the frequency measurement result to control the stability of the laser power. For example, in a quantum system constructed by using the laser power control method and device, the laser second-level relative power can be stabilized to the order of 1E-4 and the long-term stability is 1E-6 at 1mW, with a rubidium atomic clock second stability of 3E-12 and a long-term stability of 3E-14.

[0062] It should be further understood that the terms "comprise", "contain" or any other variant thereof are intended to cover non-exclusive inclusions, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device. Without more limitations, the element defined by the statement "comprises a" does not exclude the presence of another identical element in the process, method, article or device comprising the element.

[0063] The above description is only an embodiment of the application and is not intended to limit the application. Those skilled in the art can make various changes and modifications to the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the scope of the claims of the application.

Claims

1. A method of quantum control of laser power, characterized in that, The application relates to a laser frequency stabilization system for a rubidium atomic clock. The application comprises: receiving an input laser signal; modulating the laser signal to output 0th and "±1"th order diffracted light; shielding other diffracted light frequency components of the output light except the "+1"th order diffracted light; coupling the "+1"th order diffracted light into a rubidium atomic clock cell; adjusting the direction of the "+1"th order diffracted light to be parallel to the atomic beam direction of the rubidium atomic clock cell; measuring the output frequency of the rubidium atomic clock in real time; 2. The method of quantum control of laser power according to claim 1, characterized in that, feeding back the difference between the output frequency and a standard output frequency to the modulator to modulate the laser, so as to stabilize the "+1"th order diffracted light.

3. A quantum control device for laser power for implementing the method of claim 1 or 2, characterized in that, The difference between the output frequency and a standard output frequency is used as feedback to modulate the laser signal to output 0th and "±1"th order diffracted light. The application comprises an acousto-optic modulator, an optical diaphragm, a coupler, an optical fiber, a rubidium atomic clock and a frequency counter, the acousto-optic modulator modulates the input laser to output 0th and "±1"th order diffracted light; the optical diaphragm shields other diffracted light frequency components of the output light of the acousto-optic modulator except the "+1"th order diffracted light; the coupler is used for coupling the "+1"th order diffracted light output by the optical diaphragm into the optical fiber; the optical fiber is used for guiding the "+1"th order diffracted light output by the coupler into the rubidium atomic clock cell; the rubidium atomic clock is provided with an opening on the side of a detector, and the optical fiber is used for guiding the "+1"th order diffracted light output by the coupler into the opening of the rubidium atomic clock, and the direction of the diffracted light is parallel to the atomic beam direction of the rubidium atomic clock cell; 4. The quantum control of laser power device of claim 3, wherein, the frequency counter is used for measuring the output frequency of the rubidium atomic clock in real time.

5. The quantum control of laser power device of claim 4, wherein, The laser power feedback control system between the frequency counter and the acousto-optic modulator modulates the acousto-optic modulator based on the difference between the output frequency and a standard output frequency, so as to control the laser output power of the acousto-optic modulator. The laser power feedback control system comprises a host computer and a servo control part, the host computer collects the output frequency of the rubidium atomic clock from the frequency counter, and takes the output frequency and a standard output frequency as an error signal, processes the error signal through a proportional-integral-derivative feedback control algorithm to output an error compensation signal, and sends the error compensation signal to the servo control part; 6. The quantum control of laser power device of claim 5, wherein, the servo control part comprises a radio frequency driver, which is used for controlling the output voltage of the radio frequency driver according to the error compensation signal, and driving the acousto-optic modulator to modulate the laser signal.

7. The quantum control of laser power device of claim 3, wherein, The output voltage of the radio frequency driver controls the diffraction efficiency of the acousto-optic modulator, and further controls the power of the "+1"th order diffracted light.

8. The quantum control of laser power device of claim 3, wherein, The acousto-optic modulator is further provided with a mirror or a prism, which is used for adjusting the position and angle of the laser incident to the acousto-optic modulator.

9. The quantum control device of laser power according to any of claims 3 to 8, characterized in that, The coupler is further provided with an optical beam splitter, which is used for dividing the laser into multiple beams, and one of the beams is input into the coupler. The acousto-optic modulator is further provided with a laser, which outputs the laser to the acousto-optic modulator.

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