Frequency comb generation device and method

Abstract

The invention discloses a frequency comb generation device and method, and relates to the technical field of laser, the device comprises a first wave plate group, a first electromagnetic wave modulator, a first lens, an adjustable small hole, a second lens, a second electromagnetic wave modulator, a second wave plate group and a spectrograph which are arranged in sequence; the first wave plate group is used for acquiring incident electromagnetic waves and performing polarization; the first electromagnetic wave modulator is used for receiving electromagnetic waves and determining a corresponding first modulation phase diagram, and rotating the first preset phase diagram at a preset angular velocity to load rotating Doppler frequency shift for the electromagnetic waves after primary modulation; the adjustable small hole is used for changing a signal interference state between the two electromagnetic wave modulators; the second electromagnetic wave modulator is used for loading a second preset phase diagram on the basis of the second modulation phase diagram and completing secondary phase modulation, and then sending the second modulation phase diagram to the spectrograph through the second wave plate group; the spectrometer is used for receiving the electromagnetic waves after secondary phase modulation and generating a frequency comb. The method is suitable for frequency comb generation of various waves.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a frequency comb generation device and method. Background Art

[0002] In the frequency domain, the power spectral density forms a frequency comb with evenly spaced discrete lines. Especially in the electromagnetic band, electromagnetic wave frequency comb plays a vital role in various precision measurement technologies and has become one of the representative breakthroughs in modern physics. However, there is currently no universal method for generating frequency combs in different bands. Summary of the invention

[0003] The purpose of the present application is to provide a frequency comb generation device and method, which can be applied to frequency comb generation of various waves.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a frequency comb generating device, comprising a first wave plate group, a first electromagnetic wave modulator, a first lens, an adjustable pinhole, a second lens, a second electromagnetic wave modulator, a second wave plate group and a spectrometer arranged in sequence; wherein the first lens and the second lens make the first electromagnetic wave modulator face the second electromagnetic wave modulator; the second wave plate group makes the second electromagnetic wave modulator face the spectrometer;

[0006] The first wave plate group is used to: obtain the incident electromagnetic wave and polarize it, and then send it to the first electromagnetic wave modulator;

[0007] The first electromagnetic wave modulator is used to: receive an electromagnetic wave and determine a corresponding first modulation phase diagram; load a first preset phase diagram based on the first modulation phase diagram, and rotate the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift for the electromagnetic wave after a single modulation;

[0008] The adjustable aperture is used to: change the signal interference state between the first electromagnetic wave modulator and the second electromagnetic wave modulator;

[0009] The second electromagnetic wave modulator is used to: determine a second modulation phase diagram, load a second preset phase diagram on the basis of the second modulation phase diagram and complete secondary phase modulation, and then send the electromagnetic wave after secondary phase modulation to the spectrometer via the second wave plate group;

[0010] The spectrometer is used to receive electromagnetic waves after secondary phase modulation and generate a frequency comb.

[0011] In a second aspect, the present application provides a frequency comb generation method, comprising:

[0012] Install the frequency comb generation device;

[0013] Opening the adjustable aperture in the frequency comb generating device, and then performing a frequency comb generating process to obtain a first electromagnetic wave frequency comb;

[0014] closing the adjustable aperture in the frequency comb generating device, and then performing a frequency comb generating process to obtain a second electromagnetic wave frequency comb;

[0015] The first electromagnetic wave frequency comb is subtracted from the second electromagnetic wave frequency comb to obtain a final frequency comb.

[0016] According to the specific embodiments provided by the present application, the present application has the following technical effects: the present application provides a frequency comb generation device and method, which obtains the incident electromagnetic wave through the first wave plate group and polarizes it, and then sends it to the first electromagnetic wave modulator. The electromagnetic wave is received by the first electromagnetic wave modulator and the corresponding first modulation phase diagram is determined, so as to provide the superposition state of angular momentum for subsequent processing; then the first preset phase diagram is loaded on the basis of the first modulation phase diagram, and the first preset phase diagram is rotated at a preset angular velocity to load the rotational Doppler frequency shift for the electromagnetic wave after the first modulation, and then the second preset phase diagram is loaded on the basis of the second modulation phase diagram by the second electromagnetic wave modulator and the secondary phase modulation is completed, and then the electromagnetic wave is sent to the spectrometer, so that the orbital angular momentum is manipulated by the pure phase modulation method. Finally, the frequency comb is obtained by the spectrometer. In order to further remove interference, the final frequency comb is calculated by opening and closing the adjustable small hole and combining the two beat frequency differences. The present application can be applied to the frequency comb generation of various waves, with less interference and more accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of a frequency comb generating device provided in one embodiment of the present application;

[0019] Figure 2 A schematic diagram of a frequency comb provided in accordance with an embodiment of the present application. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] This application uses the means of pure phase control of electromagnetic waves and utilizes the rotational Doppler effect to modulate the frequency spectrum of the electromagnetic wave by modulating its angular momentum spectrum. This achievement can be used in acoustic vortices, microwave vortices, water wave vortices, etc.

[0022] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0023] In an exemplary embodiment, Figure 1 As shown, a frequency comb generating device is provided, comprising a first wave plate group, a first electromagnetic wave modulator SLM1, a first lens Lens1, an adjustable pinhole ID, a second lens Lens2, a second electromagnetic wave modulator SLM2, a second wave plate group and a spectrometer PM which are arranged in sequence.

[0024] Among them, the first lens Lens1 and the second lens Lens2 make the first electromagnetic wave modulator SLM1 face the second electromagnetic wave modulator SLM2; the second wave plate group makes the second electromagnetic wave modulator SLM2 face the spectrometer PM; specifically, the second wave plate group includes a reflector group, a third lens Lens3, a preset pinhole and a fourth lens Lens4 arranged in sequence; the third lens Lens3 and the fourth lens Lens4 make the second electromagnetic wave modulator SLM2 face the spectrometer PM.

[0025] In the first wave plate group, the first polarization beam splitter, the first wave plate WP1, the first reflector M1, and the second reflector M2 are arranged in sequence; the structure of the reflector group is the same as that of the first wave plate group, but the arrangement order of each component is reversed, that is, in the reflector group, the third reflector M3, the fourth reflector M4, the second wave plate WP2, and the second polarization beam splitter PBS are arranged in sequence. Among them, the wave plate is used to modulate the polarization of electromagnetic waves, the reflector is used to reflect laser light, and the wave plate and the polarization beam splitter are used for polarization analysis.

[0026] The first wave plate group is used to: obtain the incident electromagnetic wave and polarize it, and then send it to the first electromagnetic wave modulator; that is, to convert the incident electromagnetic wave into a special polarization so that the subsequent electromagnetic wave phase modulator can respond to it.

[0027] The first electromagnetic wave modulator is used to: receive an electromagnetic wave and determine a corresponding first modulation phase diagram; load a first preset phase diagram based on the first modulation phase diagram, and rotate the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift on the electromagnetic wave after a modulation. Specifically, the first electromagnetic wave modulator is a pure phase electromagnetic wave modulator, and the first preset phase diagram loaded thereon contains a special phase, which separates the reference electromagnetic wave and the modulated electromagnetic wave in space.

[0028] The adjustable small hole is used to change the signal interference state between the first electromagnetic wave modulator and the second electromagnetic wave modulator, thereby changing the presence or absence of the reference electromagnetic wave.

[0029] The second electromagnetic wave modulator is used to determine the second modulation phase diagram, load the second preset phase diagram on the basis of the second modulation phase diagram and complete the secondary phase modulation, and then send the electromagnetic wave after the secondary phase modulation to the spectrometer via the second wave plate group. The first preset phase diagram is completely opposite to the second preset phase diagram, so that the spatially separated reference electromagnetic wave and the modulated electromagnetic wave can return to the same route again. In practical applications, the second wave plate and the second polarization beam splitter are used to analyze the polarization to ensure that the reference electromagnetic wave and the modulated electromagnetic wave can interfere.

[0030] The spectrometer is used to receive electromagnetic waves after secondary phase modulation and generate a frequency comb.

[0031] Based on the same inventive concept, the embodiment of the present application further provides a frequency comb generation method, including:

[0032] Step 100, follow Figure 1 Install a frequency comb generation device as described above.

[0033] Step 200, opening the adjustable aperture in the frequency comb generating device, and then executing a frequency comb generating process to obtain a first electromagnetic wave frequency comb.

[0034] In an application example, step 200 includes:

[0035] (21) The incident electromagnetic wave is acquired and polarized through the first wave plate group, and then sent to the first electromagnetic wave modulator.

[0036] (22) Receive electromagnetic waves through the first electromagnetic wave modulator and determine the corresponding first modulation phase diagram, load a first preset phase diagram based on the first modulation phase diagram, and rotate the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift for the electromagnetic wave after a modulation.

[0037] Specifically, the method of pure phase control of electromagnetic waves is used to obtain a specific vortex electromagnetic spectrum containing OAM (Orbital Angular Momentum), which can be expressed by the following formula:

[0038]

[0039] Wherein, E0 is the amplitude of the electromagnetic wave after the primary modulation emitted from the first electromagnetic wave modulator SLM1, l is the angular momentum carried by the vortex, ω0 is the frequency of the incident electromagnetic wave, and a l is the relative complex amplitude coefficient of the corresponding vortex component, and A is the azimuth angle, and A is the amplitude intensity.

[0040] The above-mentioned method of using pure phase control of electromagnetic waves specifically refers to: the spatial light modulator is a liquid crystal display screen, and the size of the liquid crystal display screen used in the experiment is 1064*1152px. The modulation of the electromagnetic wave can be achieved by projecting the modulated phase diagram generated by the program onto the spatial light modulator, that is, the superposition state of angular momentum is prepared. Then the first preset phase diagram (a special phase, a phase diagram containing 10 vortex values ​​from -15 to +15) loaded by the first electromagnetic wave modulator SLM1 is rotated at a preset angular velocity Ω, and after the light rotates, the light beam has a frequency shift, and the emitted vortex electromagnetic wave with different rotational Doppler frequency shifts is obtained, and its amplitude E l for:

[0041]

[0042] The electromagnetic wave after pure phase modulation by the first electromagnetic wave modulator SLM1 will contain ten topological charge values ​​at the same time, among which the frequency of the primary modulated electromagnetic wave after loading the rotational Doppler frequency shift is: l =ω0+lΩ.

[0043] (23) The once modulated electromagnetic wave loaded with the rotational Doppler frequency shift and the unmodulated electromagnetic wave are sequentially transmitted through the first lens, the adjustable aperture and the second lens to the second electromagnetic wave modulator; the unmodulated electromagnetic wave is the electromagnetic wave that has not been phase modulated in the first electromagnetic wave modulator.

[0044] (24) Determine a second modulation phase diagram through the second electromagnetic wave modulator, load a second preset phase diagram based on the second modulation phase diagram and complete secondary phase modulation, and then send the electromagnetic wave after secondary phase modulation to the spectrometer via the second wave plate group.

[0045] Compared with the first electromagnetic wave modulator, the second preset phase diagram loaded in the second electromagnetic wave modulator is a static phase. Loading a suitable static phase on the second electromagnetic wave modulator can restore only one value of the topological charge phase each time, and then restore different topological charges (referring to the order of the vortex electromagnetic wave) to the fundamental mode electromagnetic wave, and collect the restored fundamental mode electromagnetic wave to the spectrometer. The electromagnetic wave amplitude E2 obtained by the spectrometer is:

[0046]

[0047] Among them, b l Depending on the second preset phase pattern loaded by the second electromagnetic wave modulator, the frequency interval between different frequencies of the electromagnetic wave is controllable because the frequency shift is proportional to the topological charge comb.

[0048] (25) Receiving the secondarily phase modulated electromagnetic wave through the spectrometer and generating a first electromagnetic wave frequency comb. Specifically, determining the light intensity distribution of the secondarily phase modulated electromagnetic wave through the spectrometer, and performing Fourier transform to obtain the first electromagnetic wave frequency comb.

[0049] Based on this, the first electromagnetic wave frequency comb can be obtained, but at this time the first electromagnetic wave frequency comb has many interference signals (beat frequencies of different frequencies of the electromagnetic wave frequency comb). In order to remove the interference signals, the present application adopts an interference method to obtain the beat frequency signal and then remove it.

[0050] Step 300, closing the adjustable aperture in the frequency comb generating device, and then performing a frequency comb generating process to obtain a second electromagnetic wave frequency comb;

[0051] In an application example, step 300 includes:

[0052] (31) The incident electromagnetic wave is acquired and polarized through the first wave plate group, and then sent to the first electromagnetic wave modulator.

[0053] (32) Receive electromagnetic waves through the first electromagnetic wave modulator and determine the corresponding first modulation phase diagram, load a first preset phase diagram based on the first modulation phase diagram, and rotate the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift for the electromagnetic wave after a modulation.

[0054] (33) The first modulated electromagnetic wave loaded with the rotational Doppler frequency shift passes through the first lens and the second lens in sequence to the second electromagnetic wave modulator.

[0055] (34) Determine a second modulation phase diagram through the second electromagnetic wave modulator, load a second preset phase diagram based on the second modulation phase diagram and complete secondary phase modulation, and then send the electromagnetic wave after secondary phase modulation to the spectrometer via the second wave plate group.

[0056] (35) The spectrometer receives the electromagnetic wave after secondary phase modulation and generates a second electromagnetic wave frequency comb.

[0057] The difference between step 300 and step 200 lies in the opening and closing of the adjustable aperture, and its different opening and closing states make the signal interference state between the first electromagnetic wave modulator and the second electromagnetic wave modulator different. Specifically, in step 200, the adjustable aperture is opened, and the first interference is emitted, which is the interference of the unmodulated electromagnetic wave with the electromagnetic wave after the first modulation and restoration, that is, the zero-order electromagnetic wave and the first-order electromagnetic wave pass through the adjustable aperture at the same time, which can also be understood as allowing the unmodulated electromagnetic wave and the first-order modulated electromagnetic wave loaded with the rotational Doppler frequency shift to pass through the aperture. In step 300, the adjustable aperture is closed, and the second interference occurs, which only filters out the electromagnetic wave reflected by the first phase, that is, the modulated electromagnetic wave, so that the unmodulated electromagnetic wave cannot pass through the adjustable aperture.

[0058] In a specific application example, the first preset phase diagram is completely opposite to the second preset phase diagram.

[0059] Step 400, subtract the first electromagnetic wave frequency comb from the second electromagnetic wave frequency comb to remove the interference phase and obtain the final frequency comb, such as Figure 2 shown.

[0060] In summary, this application uses rotating Doppler and Fourier transform data processing methods to modulate the frequency shift of electromagnetic waves; it also uses pure phase modulation to manipulate the longitudinal angular momentum of the orbit, and finally uses the two beat frequency differences to remove other signal interference. The frequency comb with up to 10 teeth is experimentally obtained and verified, and the frequency shift of the electromagnetic wave can be measured. Since this application gives different frequency shifts to electromagnetic waves during pure phase modulation, the method of this application can be used in subsequent calculations to apply to frequency combs with frequency shifts in different bands.

[0061] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A frequency comb generating device, characterized in that: The frequency comb generating device comprises a first wave plate group, a first electromagnetic wave modulator, a first lens, an adjustable pinhole, a second lens, a second electromagnetic wave modulator, a second wave plate group and a spectrometer which are arranged in sequence; wherein the first lens and the second lens make the first electromagnetic wave modulator face the second electromagnetic wave modulator; and the second wave plate group makes the second electromagnetic wave modulator face the spectrometer; The first wave plate group is used to: obtain the incident electromagnetic wave and polarize it, and then send it to the first electromagnetic wave modulator; The first electromagnetic wave modulator is used to: receive an electromagnetic wave and determine a corresponding first modulation phase diagram; load a first preset phase diagram based on the first modulation phase diagram, and rotate the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift for the electromagnetic wave after a single modulation; The adjustable aperture is used to: change the signal interference state between the first electromagnetic wave modulator and the second electromagnetic wave modulator; The second electromagnetic wave modulator is used to: determine a second modulation phase diagram, load a second preset phase diagram on the basis of the second modulation phase diagram and complete secondary phase modulation, and then send the electromagnetic wave after secondary phase modulation to the spectrometer via the second wave plate group; The spectrometer is used to receive electromagnetic waves after secondary phase modulation and generate a frequency comb.

2. The frequency comb generating device according to claim 1, characterized in that: The second wave plate group includes a reflector group, a third lens, a preset pinhole and a fourth lens which are arranged in sequence; The structure of the reflector group is the same as that of the first wave plate group.

3. A frequency comb generation method, characterized in that: The frequency comb generation method comprises: Installing a frequency comb generating device as described in any one of claims 1 to 2; Opening the adjustable aperture in the frequency comb generating device, and then performing a frequency comb generating process to obtain a first electromagnetic wave frequency comb; closing the adjustable aperture in the frequency comb generating device, and then performing a frequency comb generating process to obtain a second electromagnetic wave frequency comb; The first electromagnetic wave frequency comb is subtracted from the second electromagnetic wave frequency comb to obtain a final frequency comb.

4. The frequency comb generation method according to claim 3, characterized in that: Opening the adjustable aperture in the frequency comb generating device and then performing a frequency comb generating process to obtain a first electromagnetic wave frequency comb includes: The incident electromagnetic wave is acquired and polarized by the first wave plate group, and then sent to the first electromagnetic wave modulator; receiving an electromagnetic wave through the first electromagnetic wave modulator and determining a corresponding first modulation phase diagram, loading a first preset phase diagram on the basis of the first modulation phase diagram, and rotating the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift for the electromagnetic wave after a single modulation; The once modulated electromagnetic wave loaded with the rotational Doppler frequency shift and the unmodulated electromagnetic wave are sequentially transmitted through the first lens, the adjustable pinhole and the second lens to the second electromagnetic wave modulator; the unmodulated electromagnetic wave is the electromagnetic wave that has not been phase modulated in the first electromagnetic wave modulator; Determine a second modulation phase diagram by the second electromagnetic wave modulator, load a second preset phase diagram on the basis of the second modulation phase diagram and complete secondary phase modulation, and then send the electromagnetic wave after secondary phase modulation to the spectrometer via the second wave plate group; The spectrometer receives the secondary phase modulated electromagnetic wave and generates a first electromagnetic wave frequency comb.

5. The frequency comb generation method according to claim 3, characterized in that: Closing the adjustable aperture in the frequency comb generating device, and then performing a frequency comb generating process to obtain a second electromagnetic wave frequency comb, comprising: The incident electromagnetic wave is acquired and polarized by the first wave plate group, and then sent to the first electromagnetic wave modulator; receiving an electromagnetic wave through the first electromagnetic wave modulator and determining a corresponding first modulation phase diagram, loading a first preset phase diagram on the basis of the first modulation phase diagram, and rotating the first preset phase diagram at a preset angular velocity to load a rotational Doppler frequency shift for the electromagnetic wave after a single modulation; The primary modulated electromagnetic wave loaded with the rotational Doppler frequency shift passes through the first lens and the second lens in sequence to the second electromagnetic wave modulator; Determine a second modulation phase diagram by the second electromagnetic wave modulator, load a second preset phase diagram on the basis of the second modulation phase diagram and complete secondary phase modulation, and then send the electromagnetic wave after secondary phase modulation to the spectrometer via the second wave plate group; The spectrometer receives the secondary phase modulated electromagnetic wave and generates a second electromagnetic wave frequency comb.

6. The frequency comb generation method according to claim 4 or 5, characterized in that: The first preset phase map is a phase map including 10 swirl values ​​from -15 to +15.

7. The frequency comb generation method according to claim 4 or 5, characterized in that: The first preset phase diagram is completely opposite to the second preset phase diagram.

8. The frequency comb generation method according to claim 4, characterized in that: Receiving the electromagnetic wave after the primary phase modulation through the spectrometer and generating the first electromagnetic wave frequency comb includes: determining the light intensity distribution of the electromagnetic wave after the secondary phase modulation through the spectrometer, and performing Fourier transform to obtain the first electromagnetic wave frequency comb.

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