Optical frequency comb generation method and generation system thereof

Abstract

The invention discloses an optical frequency comb generation method and system, and belongs to the technical field of photoelectrons. A light frequency modulation system based on a super-lubricity high-speed micromechanical system is adopted, a static reflector and a sliding reflector are located on the two sides of a dielectric layer respectively, and the moving sliding reflector and the dielectric layer are in super-lubricity contact; the sliding reflecting mirror is driven by alternating electric field force to do reciprocating motion on the dielectric layer at a set motion speed; laser enters along one end of the dielectric layer at a set angle, and is reflected for multiple times and partially transmitted between the two reflectors; the laser is reflected by the moving reflector every time, so that Doppler frequency shift occurs to the frequency, and a series of optical frequency combs separated in the frequency domain are generated. The problems that noise, drifting and the like are generated due to the fact that an existing optical frequency comb is based on the nonlinear optical effect, and the performance and reliability of equipment are reduced are solved. The optical frequency comb generator is widely applied to the optical frequency comb generator technology.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technology, and further relates to the field of optical frequency comb technology, and specifically, to an optical frequency comb generation method and a generation system thereof. Background Art

[0002] Optical frequency combs, also known as optical frequency combs, are characterized by stable, discrete and equally spaced frequency lines in the frequency domain, and highly coherent physical properties. These unique properties make them have broad application prospects in a wide range of applications such as wavelength division multiplexing optical communications, precision measurement, atomic clocks and molecular spectroscopy.

[0003] Existing optical frequency combs are produced using a mode-locked laser system or by using a laser to continuously pump a high-quality factor (Q factor) optical microcavity. It is based on nonlinear optical effects, and a series of equally spaced frequency teeth are generated by modulating laser pulses, which must rely on the nonlinear optical effects of light. However, the use of nonlinear optical effects requires the introduction of strong fields, which will introduce high-order nonlinear effects and thermal effects, both of which will produce noise, drift and other problems, thereby reducing the performance and reliability of the equipment. How to realize optical frequency combs without using nonlinear optical effects is still the focus of promoting the development and practical deployment of optical frequency combs, and it is a topic that the industry has been studying.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to solve the problem that the existing optical frequency comb generates noise, drift and other problems based on nonlinear optical effects, thereby reducing the performance and reliability of the device.

[0006] The inventive concept of the present invention is: according to the optical Doppler effect, when light is reflected by a high-speed moving object, the frequency of light will change. In order to overcome a series of problems caused by the nonlinear optical effect of the traditional optical frequency comb generation system, the optical Doppler effect is used to generate a spectrum comb. The optical frequency modulation system based on the ultra-smooth high-speed micromechanical system is used to generate the optical frequency comb to solve the problem to be solved by the present invention.

[0007] Micromechanical system refers to an industrial technology that integrates microelectronics technology and mechanical engineering, and its operating range is usually within the micrometer scale. The present invention uses an electrode-driven micro slider lens as a micromechanical system.

[0008] To this end, the present invention provides a method for generating an optical frequency comb. The method is: The optical frequency modulation system based on the ultra-smooth high-speed micromechanical system is adopted. The stationary reflector and the sliding reflector are respectively placed on both sides of the dielectric layer, and the moving sliding reflector and the dielectric layer are in super-lubricated contact. The sliding reflector is driven by the alternating electric field force to reciprocate on the dielectric layer at a set speed. The laser is injected from one end of the dielectric layer at a set angle, and is reflected and partially transmitted between the two reflectors for multiple times. Each time the laser is reflected by the moving reflector, the frequency will undergo a Doppler shift, thereby generating a series of light beams separated in the frequency domain, namely, the optical frequency comb.

[0009] The optical frequency comb generating system of the optical frequency comb generating method is as follows: Figure 1-3 As shown, it includes: a laser 1, a coupling layer 2, an insulating layer 3, a sliding reflector 4, a dielectric layer 5, a transparent electrode 6, a stationary reflector 7, and a power module 8.

[0010] The coupling layer 2 is in the shape of a right triangle and is installed at one end of the upper surface of the dielectric layer 5 with a right angle side at a set angle.

[0011] The laser 1 is installed perpendicularly to the hypotenuse of the coupling layer 2 in the incident direction.

[0012] The sliding reflector 4 is located on the upper surface of the dielectric layer 5 and is in super-lubricating contact with the upper surface of the dielectric layer 5 .

[0013] The surface layer of the sliding reflector 4 is an ITO layer 11, the middle layer is a magnesium fluoride layer 9, and the bottom layer is a boron nitride layer 10. The boron nitride has excellent super-slip properties, and the magnesium fluoride has a lower refractive index, which is more likely to cause total reflection, reduce the penetration depth of the evanescent wave, and thus reduce the thickness of the reflector. The function and actuation mechanism of the ITO layer 11: an alternating non-uniform electric field is generated between the two transparent electrodes, and the ITO layer 11 generates induced charges under the action of the electric field. The induced charges move back and forth in the alternating non-uniform electric field under the action of the electric field force.

[0014] The insulating layer 3 is located on the lower surface of the dielectric layer 5 .

[0015] The stationary reflector 7 is fixed to the middle area of ​​the lower surface of the insulating layer 3 .

[0016] The surface layer of the stationary reflector 7 is a silicon dioxide dielectric film 12, and the bottom layer is a molybdenum disulfide prism layer 13. The silicon dioxide dielectric film 12 and the molybdenum disulfide prism layer 13 constitute the stationary reflector 7 (transmission reflector). Under the condition of total reflection, an evanescent wave will appear on the interface, and the evanescent wave will penetrate a certain depth of the low refractive index medium. The triangular molybdenum disulfide prism will guide this part of the evanescent wave to emit, and finally form the output light.

[0017] There are two transparent electrodes 6, which are located at both ends of the stationary reflector 7 and both ends of the lower surface of the insulating layer 3. The function of the transparent electrode is to generate an alternating non-uniform electric field between the two transparent electrodes while maintaining high light transmittance. The material of the transparent electrode is ITO.

[0018] The power module has a first voltage output terminal connected to the laser 1 to provide working power for the laser 1 and drive the laser to emit light; the second and third voltage output terminals are respectively connected to two transparent electrodes 6 to generate an alternating electric field to drive the sliding reflector 4 to reciprocate left and right along the upper surface of the dielectric layer 5 under the action of the alternating electric field force. After the laser 1 emits laser light, it is incident on the dielectric layer 5 through the coupling layer 2 and is reflected and propagated multiple times between the sliding reflector 4 and the stationary reflector 7.

[0019] The operating mechanism of the present invention is: due to the ultra-slippery characteristics between the slidable reflector and the dielectric layer, the friction resistance is extremely small. Under the driving force of the alternating electric field force, the slidable reflector is driven to reciprocate at high speed, so that when reflecting the laser, the laser undergoes a frequency shift due to the optical Doppler effect. The light is reflected multiple times between the two reflectors, and a frequency shift is superimposed each time it is reflected on the slidable reflector, thereby presenting a series of narrow peaks in the frequency domain. The spacing between the narrow peaks, that is, the frequency tooth spacing, is proportional to the frequency shift of the slidable reflector each time it reflects the laser, that is, the movement speed of the slidable reflector, thereby forming a fully adjustable optical frequency comb.

[0020] The beneficial effect of the present invention is that since the present invention only utilizes the optical Doppler effect and does not need to utilize nonlinear effects, even if an extremely weak laser is used as a light source, it can be converted into an optical frequency comb light wave output without introducing high-order nonlinear effects and thermal effects.

[0021] The power module synchronously drives the slidable reflector and the laser, so that the laser is incident when the reflector moves at the fastest speed, thereby increasing the total bandwidth of the optical frequency comb.

[0022] The invention can be widely applied to the optical frequency comb generator technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the optical frequency comb generation system of the present invention.

[0024] Figure 2 Schematic diagram of the structure of the slidable reflector of the optical frequency comb generating system of the present invention.

[0025] Figure 3 Schematic diagram of the structure of the stationary reflector of the optical frequency comb generating system of the present invention.

[0026] Figure 4 It is a schematic diagram of the optical frequency comb simulation effect of the optical frequency comb generating system of the present invention.

[0027] In the figure: 1 is a laser, 2 is a coupling layer, 3 is an insulating layer, 4 is a sliding reflector, 5 is a dielectric layer, 6 is a transparent electrode, 7 is a stationary reflector, 8 is a power module, 9 is a magnesium fluoride layer, 10 is a boron nitride layer, 11 is an ITO layer, 12 is a silicon dioxide dielectric film, and 13 is a molybdenum disulfide prism layer. DETAILED DESCRIPTION

[0028] like Figure 1-4 As shown, the optical frequency comb generation method and generation system thereof are specifically implemented as follows: The dielectric layer is molybdenum disulfide. The surface of molybdenum disulfide has excellent super-slip properties, and the refractive index of molybdenum disulfide is high, which can greatly improve the optical Doppler shift at the same reflector movement speed; and the high refractive index and smaller critical angle make it easier to achieve total reflection propagation in the dielectric layer.

[0029] The reflectivity of the reflectors (sliding reflector 4 and stationary reflector 7) is higher than 99%. By improving the reflectivity of the reflectors, the laser can be less attenuated when it is reflected multiple times between the two reflectors, and the amplitude difference of each comb tooth frequency of the optical frequency comb is small.

[0030] The propagation angle of the laser in the medium is greater than the critical angle of total reflection in the medium. When propagating through total reflection, the laser has a small loss during reflection, and the amplitude difference of the frequencies of the comb teeth of the optical frequency comb is small.

[0031] The boron nitride layer 10 is a hexagonal boron nitride layer 10. Hexagonal boron nitride has excellent super-slip properties, while magnesium fluoride has a lower refractive index and is more likely to have total reflection, which reduces the penetration depth of the evanescent wave, thereby reducing the thickness of the reflector.

[0032] The line width of the laser is less than 1 MHz. A smaller laser line width can improve the coherence of the optical frequency comb.

[0033] The specific cases are as follows: like Figure 1 As shown, the laser 1 emits a laser with a wavelength of 1064 nanometers, which is coupled to the inside of the MoS2 dielectric layer 5 through the coupling layer 2 and propagates inside the intrinsic MoS2 dielectric layer 5, with a propagation angle of 35 degrees. Since the refractive index of the MoS2 dielectric layer 5 is about 4.2, the propagation angle is higher than the critical angle, and total reflection occurs, and the laser does not overflow outside the dielectric layer 5.

[0034] The sliding reflector 4 is located on the upper part of the molybdenum disulfide dielectric layer 5 .

[0035] The thickness of the MoS2 dielectric layer 5 is (500±50) nm, that is, the optical path is twice the wavelength of the light. Since the MoS2 dielectric layer 5 has a certain conductivity, a (20±5) nm thick SiO2 insulating layer 3 is disposed under the MoS2 dielectric layer 5 .

[0036] The transparent electrode 6 and the stationary reflector 7 are located below the molybdenum disulfide dielectric layer 5 .

[0037] The first voltage output terminal of the power module 8 is connected to the laser 1, outputs the laser working voltage, provides working power for the laser 1, and drives the laser to emit light; the second and third voltage output terminals are respectively connected to the two transparent electrodes 6, output alternating driving voltages, and generate electric field force through the alternating voltage difference between the two transparent electrodes to drive the sliding reflector 4 to move back and forth at high speed, and control the light emission time of the laser 1. The driving voltage is a sinusoidal alternating voltage with a peak voltage of 5V to 20V and a frequency of 10kHz to 100Mhz. The most suitable frequency and interface friction coefficient are determined according to relevant factors such as the mirror area, thickness, and dielectric layer thickness of the sliding reflector 4. Typical values ​​of the driving voltage are 10V and 100KHz.

[0038] After being emitted by the laser 1 , the laser is incident on the dielectric layer 5 through the coupling layer 2 , and is reflected and propagated multiple times between the sliding reflector 4 and the stationary reflector 7 .

[0039] The reflectors (4, 7) are multi-layer dielectric film reflectors, such as distributed Bragg reflectors, total reflectors composed of dielectric films, etc.

[0040] The sliding reflector 4 is a total reflector formed by a dielectric film. Figure 2 As shown. It is composed of a 200-nanometer magnesium fluoride layer 9, a 10-nanometer hexagonal boron nitride 10, and a 20-nanometer ITO layer 11. The length and width of the sliding reflector are 20 microns respectively. Hexagonal boron nitride and molybdenum disulfide are easy to form super-lubricating contact; magnesium fluoride 9 has a lower refractive index and is more likely to form total reflection and reflect the laser back to the dielectric layer; the ITO layer generates induced charges under the action of the electric field force generated by the two transparent electrodes, and drives the sliding reflector 4 to move under the drive of the electric field force.

[0041] The stationary reflector 7 is a partially transmitted reflector composed of a silicon dioxide dielectric film 12 and a triangular molybdenum disulfide prism. Under the condition of total reflection, an evanescent wave will appear at the interface, and the evanescent wave will penetrate a certain depth of the low refractive index medium. The triangular molybdenum disulfide prism will guide this part of the evanescent wave to emit, and finally form the output light. The thickness of the silicon dioxide medium is (720±50) nanometers. At this time, the reflectivity of the lens is (99.99±0.01)%, and the transmittance is (0.01±0.005)%.

[0042] The frequency domain distribution diagram of the output light finally formed is as follows: Figure 4 shown.

[0043] Finally, it should be noted that the above embodiments are merely examples for the purpose of clear explanation. The present invention includes but is not limited to the above embodiments. It is not necessary and impossible to list all implementation methods exhaustively. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description, such as adjustment, modification, replacement or modification. All implementation methods that meet the requirements of the present invention belong to the protection scope of the present invention.

Claims

1. A method for generating an optical frequency comb, characterized in that: The method is: An optical frequency modulation system based on an ultra-slip high-speed micromechanical system is used, and a stationary reflector and a sliding reflector are respectively placed on both sides of a dielectric layer, and a super-lubricated contact is formed between the moving sliding reflector and the dielectric layer; The sliding reflector is driven to move back and forth on the dielectric layer at a set speed by an alternating electric field force; The laser is injected at a set angle along one end of the dielectric layer, and is reflected multiple times and partially transmitted between the two mirrors; Each time the laser is reflected by a moving mirror, the frequency will undergo a Doppler shift, resulting in a series of optical frequency combs separated in the frequency domain.

2. A system for generating an optical frequency comb according to claim 1, characterized in that: It comprises a laser (1), a coupling layer (2), an insulating layer (3), a sliding reflector (4), a dielectric layer (5), a transparent electrode (6), a stationary reflector (7), and a power module (8); The coupling layer (2) is in the form of a right triangle and is installed at one end of the upper surface of the dielectric layer (5) with a right angle side at a set angle; The laser (1) is mounted vertically on the hypotenuse of the coupling layer (2) in the incident direction; The sliding reflector (4) is located on the upper surface of the dielectric layer (5) and is in super-lubricating contact with the upper surface of the dielectric layer (5); The sliding reflector (4) has a surface layer of an ITO layer (11), an intermediate layer of a magnesium fluoride layer (9), and a bottom layer of a boron nitride layer (10); The insulating layer (3) is located on the lower surface of the dielectric layer (5); The stationary reflector (7) is fixed to the middle area of ​​the lower surface of the insulating layer (3); The surface layer of the stationary reflector (7) is a silicon dioxide dielectric film (12), and the bottom layer is a molybdenum disulfide prism layer (13), and the silicon dioxide dielectric film (12) and the molybdenum disulfide prism layer (13) constitute the stationary reflector (7); There are two transparent electrodes (6), which are located at two ends of the stationary reflector (7) and two ends of the lower surface of the insulating layer (3); The first voltage output terminal of the power module is connected to the laser (1) to provide working power for the laser (1) and drive the laser to emit light; the second and third voltage output terminals are respectively connected to two transparent electrodes (6), and an alternating electric field is generated by utilizing the voltage difference between the second and third electrodes. Under the action of the alternating electric field force, the sliding reflector (4) is driven to reciprocate left and right along the upper surface of the dielectric layer (5). After the laser (1) emits laser light, it is incident on the dielectric layer (5) through the coupling layer (2) and is reflected and propagated multiple times between the sliding reflector (4) and the stationary reflector (7).

3. A generating system for an optical frequency comb generating method as claimed in claim 2, characterized in that: The dielectric layer (5) is a molybdenum disulfide layer with a thickness of (500±50) nanometers.

4. The generation system of the optical frequency comb generation method according to claim 2, characterized in that: The reflectivity of the reflector is higher than 99%; the reflector is a distributed Bragg reflector or a total reflector formed by a dielectric film.

5. The generation system of the optical frequency comb generation method according to claim 2, characterized in that: The wavelength of the laser is 1064 nanometers, the line width is less than 1 MHz, and the propagation angle in the medium is greater than the critical angle of total reflection in the medium.

6. A system for generating an optical frequency comb as claimed in claim 2, characterized in that: The boron nitride layer (10) is a hexagonal boron nitride layer.

7. The generation system of the optical frequency comb generation method according to claim 2, characterized in that: The insulating layer (3) is a silicon dioxide layer with a thickness of (20±5) nm.

8. The generation system of the optical frequency comb generation method according to claim 2, characterized in that: The driving voltage between the two transparent electrodes (6) is a sinusoidal alternating voltage with a peak voltage of 5V to 20V and a frequency of 10kHz to 100Mhz. The most suitable frequency and interface friction coefficient are determined according to the mirror surface area, thickness, and dielectric layer thickness of the sliding reflector 4.

9. The generation system of the optical frequency comb generation method according to claim 2, characterized in that: The ITO layer (11) of the sliding reflector (4) has a thickness of 20 nanometers, the magnesium fluoride layer (9) has a thickness of 200 nanometers, and the hexagonal boron nitride layer (10) has a thickness of 10 nanometers. The length and width of the sliding reflector are 20 micrometers respectively.

10. The generation system of the optical frequency comb generation method according to claim 2, characterized in that: The thickness of the silicon dioxide dielectric film (12) of the stationary reflector (7) is (720±50) nanometers, the reflectivity of the lens is (99.99±0.01)%, and the transmittance is (0.01±0.005)%.

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