CN113540950A - Electro-optic modulation depth real-time measurement and control system and method based on VIPA etalon - Google Patents
Electro-optic modulation depth real-time measurement and control system and method based on VIPA etalon Download PDFInfo
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- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
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Abstract
本发明提供了一种基于VIPA标准具的电光调制深度实时测控系统及方法，该系统包括单频激光器、电光调制器、VIPA色散分光模块、光束分隔器件、探测器阵列和反馈控制模块；所述单频激光器产生的单频线偏振光输入至电光调制器，经电光调制后输出多频率复合光；多频率复合光输入色散分光模块，不同频率的边带光在空间上被分隔成间距为毫米量级的多个光束；间距为毫米量级的多个光束通过光束分隔器件将所需要的几种频率成分的光分离开，同时输入到探测器阵列中；探测器阵列将光强信号转化为电信号，输入至反馈控制模块中，通过反馈控制模块实现对电光调制深度的实时测控；所述色散分光模块包括准直器、柱透镜、虚拟成像相位阵列和聚焦透镜。
The present invention provides a VIPA etalon-based electro-optical modulation depth real-time measurement and control system and method. The system includes a single-frequency laser, an electro-optical modulator, a VIPA dispersion light splitting module, a beam separation device, a detector array and a feedback control module; the The single-frequency linearly polarized light generated by the single-frequency laser is input to the electro-optical modulator, and the multi-frequency composite light is output after electro-optical modulation; the multi-frequency composite light is input to the dispersive light splitting module, and the sideband lights of different frequencies are spatially separated into millimeters. Multiple beams of the order of magnitude; multiple beams with a spacing of the order of millimeters are separated by the beam separation device to separate the required light of several frequency components, and input into the detector array at the same time; the detector array converts the light intensity signal into The electrical signal is input into the feedback control module, and the real-time measurement and control of the electro-optical modulation depth is realized through the feedback control module; the dispersive light splitting module includes a collimator, a cylindrical lens, a virtual imaging phase array and a focusing lens.
Description
Technical Field
The invention relates to the technical field of laser modulation, in particular to a system and a method for measuring and controlling electro-optic modulation depth in real time based on a VIPA etalon.
Background
The electro-optical modulator (EOM) is an optical modulator that operates using the electro-optical effect of a crystal, and changes the characteristics of light waves caused by changes in the refractive index of the crystal, thereby finally realizing control of the phase, amplitude, intensity and polarization state of input light. Typical electro-optic modulators, such as phase modulators and intensity modulators, generate equally spaced sidebands outside the carrier in the optical frequency domain by applying radio frequency modulation to the optical carrier, the frequency spacing between the sidebands being equal to the frequency of the modulated signal, and the power magnitude relationship of the sidebands conforming to a predetermined functional model. Ideally, if the half-wave voltage of the EOM is constant, the voltage amplitude of the applied modulation signal determines the power ratio of each optical frequency component, i.e. the modulation depth, and this rule is also true for single-sideband modulation. However, half-wave voltages of the single EOM are slightly different, and the half-wave voltages also have a drift problem due to the environment, so that the half-wave voltage value of the device is not constant, the modulation depth cannot be kept constant by the constant electro-optic modulation power, and the proportion of the carrier and the sideband power fluctuates. When the application requirements with strict requirements on the ratio of the carrier to the sideband light intensity are met, for example, the power ratio of the atomic interference Raman light needs to be constant to eliminate the transition frequency jitter error, and the modulation depth must be accurately controlled in a feedback mode.
To perform accurate feedback control on modulation depth, a conventional solution is to use a scanning F-P cavity method, sequentially select each optical frequency component by changing the cavity length of the F-P cavity, and perform time-sharing detection on each frequency component by using the same detector. The other idea is to use a high dispersion optical splitter to spatially detect each optical frequency component separately. However, since the frequency of the radio frequency driving signal of the EOM is generally between 0.5GHz and 20GHz, it is difficult for the conventional dispersion elements such as the grating and the prism to spatially separate the frequency components.
Disclosure of Invention
The invention provides a system and a method for measuring and controlling electro-optic modulation depth in real time based on a VIPA etalon, which are used for overcoming the problems that the side-band power ratio of the existing EOM carrier is difficult to measure accurately and the modulation depth cannot be controlled accurately, and have stronger technical innovation and practical value.
The Virtual Imaging Phase Array (VIPA) is a high dispersion etalon, can separate a spectrum with a certain frequency difference, has the advantages of insensitivity to polarization, simple structure, high spectral resolution and the like, and is mainly applied to the fields of dispersion compensation, optical communication, pulse compression shaping, spectrum detection and the like. The invention makes the VIPA high dispersion light act on the EOM or similar electro-optical modulation device, can directly separate the carrier and the sideband with GHz interval into different light beams in space and carry out real-time light intensity detection.
The technical scheme of the invention is as follows:
an electro-optic modulation depth real-time measurement and control system based on a VIPA etalon comprises a single-frequency laser, an electro-optic modulator, a VIPA dispersion splitting module, a beam separation device, a detector array and a feedback control module;
the single-frequency laser is used for generating single-frequency linearly polarized light, the single-frequency linearly polarized light is input to the electro-optic modulator, and multi-frequency composite light consisting of a carrier and a sideband is output after the electro-optic modulation; inputting the multi-frequency composite light to a dispersion light splitting module, and spatially separating sideband light with different frequencies into a plurality of light beams with millimeter-scale intervals; a plurality of light beams with millimeter-scale spacing separate light of several required frequency components through a light beam separation device and simultaneously input the light into a detector array respectively; the detector array converts the light intensity signal into an electric signal, the electric signal is input into the feedback control module, and real-time measurement and control of the electro-optic modulation depth are realized through the feedback control module;
the VIPA dispersion splitting module comprises a collimator, a cylindrical lens, a virtual imaging phase array and a focusing lens; the multi-frequency composite light output after electro-optical modulation passes through the collimator, the cylindrical lens, the virtual imaging phase array and the focusing lens in sequence, and sideband light with different frequencies is spatially divided into a plurality of light beams with millimeter magnitude.
Furthermore, the virtual imaging phase array is composed of two optical coated flat plates which are parallel to each other; the flat plate close to incident light is a front panel, the bottom of the front panel is provided with a window area, the window area is coated with an antireflection film, and the non-window area is coated with a reflecting film with the reflectivity of 100%; the flat plate far away from the incident light is a rear panel coated with a partially transmissive film with a reflectivity of 95% -98%.
Furthermore, an incident angle is formed between the virtual imaging phase array and incident light, the incident light is incident through a window area of the virtual imaging phase array, is reflected back and forth for multiple times, and generates a plurality of parallel light beams with different output angles on the transmission side of the rear panel; the parallel beams of different output angles are spatially separated into a plurality of beams on the order of millimeters by a focusing lens.
Further, the distance between the focusing lens and the beam separation device is one focal length of the focusing lens.
Further, the beam splitting device comprises a diaphragm and a beam splitting prism; a plurality of light beams with the distance of millimeter order firstly pass through the diaphragm to block the unwanted light beams, and then the light beams with the required frequency components are separated through the light splitting prism.
Further, the beam splitter prism is a blade prism; the blade formed by the intersection of the two reflecting mirror surfaces of the blade prism is arranged on one side close to the incident light and is used for separating the light containing two different frequency components.
Furthermore, the feedback control module comprises a signal processor, a PID control circuit, an attenuator and a microwave signal source;
the signal processor is connected with the detector array, the detector array converts the optical signal into an electric signal and inputs the electric signal into the signal processor to obtain a processed electric signal, and the processed electric signal passes through the PID control circuit and then outputs a control signal to control the size of the attenuator; the input end of the attenuator is connected with a microwave signal source which provides a driving signal for the electro-optic modulator, and the output end of the attenuator is connected to a driving interface of the electro-optic modulator and used for adjusting the power of the driving signal through the attenuator and realizing the adjustment and control of the modulation depth of the electro-optic modulator.
The invention also provides a real-time measuring and controlling method of the electro-optic modulation depth based on the VIPA etalon, which comprises the following steps:
single-frequency linearly polarized light generated by the single-frequency laser is input to the electro-optical modulator as a laser source, and multi-frequency composite light consisting of a carrier and a sideband is output after electro-optical modulation;
the multi-frequency composite light is input to the dispersion light splitting module, sequentially passes through the collimator and the cylindrical lens, then is emitted into a window area of the virtual imaging phase array, is reflected for multiple times to output a plurality of parallel light beams with different output angles, and then is formed into a plurality of light beams which are spatially separated into millimeter-scale light beams at a position which is one-time of the focal length away from the focusing lens through the focusing lens;
a plurality of light beams with millimeter-scale spacing separate light of several required frequency components through a light beam separation device and simultaneously input the light into a detector array respectively; the detector array converts the light intensity signal into an electric signal, the electric signal is input into the feedback control module, and the feedback control module realizes real-time measurement and control of the electro-optic modulation depth.
Furthermore, the feedback control module comprises a signal processor, a PID control circuit, an attenuator and a microwave signal source;
the signal processor is connected with the detector array, the detector array converts the optical signal into an electric signal and inputs the electric signal into the signal processor to obtain a processed electric signal, and the processed electric signal passes through the PID control circuit and then outputs a control signal to control the size of the attenuator; the input end of the attenuator is connected with a microwave signal source which provides a driving signal for the electro-optic modulator, and the output end of the attenuator is connected to a driving interface of the electro-optic modulator and used for adjusting the power of the driving signal through the attenuator and realizing the adjustment and control of the modulation depth of the electro-optic modulator.
The invention also provides application of the electro-optic modulation depth real-time measurement and control system based on the VIPA etalon, and the system is used for real-time high-precision measurement and feedback control of Raman optical power ratio and control of power components of cooling light and pumping light.
The invention has the following beneficial effects:
the electro-optic modulation depth real-time measurement and control system based on the VIPA etalon is used for carrying out light splitting and detection on EOM modulation output light in space by using the VIPA etalon and carrying out acquisition processing on detection results, so that accurate control on modulation depth can be realized through feedback control on the basis of optical power acquisition processing. The laser control technology can directly control the EOM modulation depth with high precision and long-term stability, and has important engineering practical value in the fields of atomic interference, frequency synthesis of coherent light, atomic molecular physics, quantum information technology and the like.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of an electro-optic modulation depth real-time measurement and control system based on a VIPA etalon.
FIG. 2 is a graph of EOM modulation sideband power versus modulation depth; the method comprises the following steps of (a) generating a coherent multi-frequency composite light after single-frequency light is subjected to EOM modulation, and (b) representing the change (percentage) of relative power values corresponding to a carrier and each sideband component when modulation phase shift (corresponding to modulation depth) is increased.
Fig. 3 is a schematic diagram of a VIPA dispersion splitting module according to the present invention.
Fig. 4 is a block diagram of EOM modulation depth feedback control in the preferred embodiment 1 of the present invention.
Fig. 5 is a block diagram of EOM modulation depth feedback control in the preferred embodiment 2 of the present invention.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
As shown in fig. 1, the invention provides a VIPA etalon-based real-time measurement and control system for electro-optic modulation depth, which comprises a single-frequency laser, an electro-optic modulator, a VIPA dispersion and splitting module, a beam splitter, a detector array and a feedback control module;
the single-frequency laser is used for generating single-frequency linearly polarized light, the single-frequency linearly polarized light is input to the electro-optic modulator, and multi-frequency composite light consisting of a carrier and a sideband is output after the electro-optic modulation; inputting the multi-frequency composite light to a dispersion light splitting module, and spatially separating sideband light with different frequencies into a plurality of light beams with millimeter-scale intervals; a plurality of light beams with millimeter-scale spacing separate light of several required frequency components through a light beam separation device and simultaneously input the light into a detector array respectively; the detector array converts the light intensity signal into an electric signal, the electric signal is input into the feedback control module, and real-time measurement and control of the electro-optic modulation depth are realized through the feedback control module;
the VIPA dispersion splitting module comprises a collimator, a cylindrical lens, a virtual imaging phase array and a focusing lens; the multi-frequency composite light output after electro-optical modulation passes through the collimator, the cylindrical lens, the virtual imaging phase array and the focusing lens in sequence, and sideband light with different frequencies is spatially divided into a plurality of light beams with millimeter magnitude.
According to the system for measuring and controlling the electro-optic modulation depth in real time based on the VIPA etalon, the invention also provides a method for measuring and controlling the electro-optic modulation depth in real time based on the VIPA etalon. Firstly, after single-frequency linearly polarized light generated by a single-frequency laser is input to an electro-optical modulator EOM as a laser source, a certain sideband is generated according to the frequency and amplitude of an EOM driving signal (the signal frequency is in the GHz level); then the light beam passes through a dispersion splitting module taking a VIPA device as a core, sideband lights with different frequencies can be spatially separated by millimeter magnitude (the parameter is related to the selection type of the dispersion splitting module device); then, the required component lights are respectively input into the optical detector array through the beam splitter; the detector PD converts the light intensity signal into an electric signal, inputs the electric signal into the feedback control module, and realizes real-time measurement and control of the electro-optic modulation depth through the feedback control module.
When the EOM modulation depth is measured and controlled in real time, feedback control is carried out based on a PID module, the proportion of sideband components required by EOM output is set, the sideband components and a detection value of a detector are calculated, the deviation is converted into a feedback control signal, the feedback control signal is input to a driving signal end of the EOM, a closed loop is formed, and stable real-time control of the EOM output sideband light intensity is achieved. Specifically, the feedback control module comprises a signal processor, a PID control circuit and an attenuator VCA; the signal processor is connected with the detector array, the detector array converts the optical signal into an electric signal and inputs the electric signal into the signal processor to obtain a processed electric signal, and the processed electric signal passes through the PID control circuit and then outputs a control signal to control the size of the attenuator; the input end of the attenuator is connected with a microwave signal source which provides a driving signal for the electro-optic modulator, and the output end of the attenuator is connected to a driving interface of the electro-optic modulator and used for adjusting the power of the driving signal through the attenuator and realizing the adjustment and control of the modulation depth of the electro-optic modulator.
Fig. 2 shows a schematic diagram of a principle of generating sideband light by using an EOM phase modulator, where (a) in fig. 2 is a schematic diagram of generating coherent multifrequency composite light after a single-frequency light is subjected to EOM modulation, and a carrier light frequency is f0The corresponding relative power under a certain modulation depth is P0(ii) a Frequency of sideband light fiThe corresponding relative power under a certain modulation depth is PiI is + -1, + -2 and + -3. Fig. 2 (b) shows the change in relative power values (expressed in percentage) for the carrier and each sideband component as the modulation phase shift (corresponding to the modulation depth) increases. The relative intensity of each component sideband and the modulation depth (corresponding phase shift) follow a Bessel function, and different modulation depths result in different intensities of each component sideband light. Let the optical frequency corresponding to the 0-level light be v0Microwave drive frequency f of phase modulatormThe interval of the side band light is, the optical frequency corresponding to the k-level light is v±kAnd has a size of v±k＝ν0±k·fm。
Because the frequency of the radio frequency driving signal of the EOM is generally between 0.5GHz and 20GHz, the traditional dispersion elements such as a grating and a prism are difficult to separate all frequency components at equal intervals in space, and how to separate and measure the carrier and the sideband is a great difficulty. The VIPA device just makes up for the defect, provides the capability of spatially separating composite lights with different frequencies, and can realize the separation and measurement of the light power of each frequency component by using a dispersion light splitting component based on the VIPA.
The VIPA virtual imaging phase array is used as a novel spectral dispersion device and consists of two high-quality optical flat plates which are coated with films in parallel, and the high-quality optical flat plates can be called as a front panel and a rear panel. The flat plate close to the incident light is a front panel, and the flat plate far away from the incident light is a rear panel. The inner side or the reflecting surface of the back panel is coated with a partial projection film (the reflectivity is more than 95%, preferably 95% -98%), so that a small part of light incident to the back panel can be output in parallel through the VIPA; the inner side or light reflective side of the front panel is coated with a reflective film having a reflectivity of almost 100%. Meanwhile, an incident window (also called a window area) is designed at the bottom of the front panel, the surface of the window (coated with an antireflection film) is almost flush with the front panel, a narrow slit is specially designed on the surface, incident light can pass through the slit smoothly only after being pressed to be narrow, and the incident light irradiates the inner side of the rear panel to enter the VIPA and then enters a state mode of circular reflection between two optical flat plates. The VIPA-based dispersion splitting module comprises: collimator, cylindrical lens, VIPA, and focusing lens, as shown in fig. 3. Firstly, a light beam is collimated and transmitted by a collimator in a small spot diameter, and then the size of the light beam is further compressed in the direction of a VIPA etalon window by using a cylindrical lens, so that the light beam is easier to enter a narrow window of the VIPA; the laser beam can undergo multiple back-and-forth reflections, each reflection can generate a weaker output light beam from the rear non-total reflection optical flat plate, thus multiple reflections can output multiple parallel light beams from the transmission side of the rear panel, and simultaneously because the frequencies of sideband components are different, the angles of the parallel light beams output by the light with different frequencies are different, so that parallel light beams with different output angles can be formed; and finally, a focusing lens is arranged at the rear end of the VIPA output beam, light of different frequency components can be seen from different positions in the space near the position of one time of the focal length of the lens, and the space distance of the GHz frequency interval composite light after final beam splitting can reach mm magnitude.
After passing through the VIPA and converging through the focusing lens, the output light field at the focal plane can be represented as:
wherein, IoutTo output light intensity, EoutElectric field of laserIntensity, Δ represents the variation of the optical path difference, t is the VIPA thickness (i.e., the distance between the front and back panels), W is the radius of the collimated beam before the cylindrical lens, R and R are the reflectivities of the front and back panels of the VIPA, respectively, F and F are the focal lengths of the cylindrical and focusing lenses, respectively, θ is the angle of incidence of the light into the VIPA, x is the angle of incidence of the light into the VIPA, andFand lambda is the laser wavelength, which is the coordinate perpendicular to the optical path direction at one focal length of the focusing lens.
When light with a certain frequency passes through the EOM to generate sidebands, taking a secondary sideband as an example, when the light intensities of three wavelength components are equal, through simulation, the intensity distribution of an output light field is shown as one-time focal length of the rightmost lens in fig. 3, and after passing through the VIPA system, the central light and each stage of sidebands can be separated by a certain distance in space. Through simulation experiment analysis, the separation interval of the three components of light at the strongest part of the light field can be optimized by adjusting system parameters. The adjustable parameters of the system are a VIPA incident angle, a focusing lens focal length, a cylindrical lens focal length, a beam diameter and a VIPA thickness, wherein the two parameters of the VIPA incident angle and the focusing lens focal length have obvious influence on the sideband separation distance, and the smaller the incident angle is (the minimum angle limit is adopted, the smaller the angle is, the light is weakened), the longer the focusing lens focal length is, and the larger the separation distance is.
Specifically, the beam splitting device includes a diaphragm and a beam splitting prism. In the last step, after the VIPA dispersion splitting module is used for separating sideband light at a certain distance, unnecessary light beams are shielded by using the diaphragm, and the needed light splitting beams with different frequencies are separated by a larger distance by using the splitting prism, so that the next step of accurately and efficiently detecting each component by the photoelectric detector is facilitated.
Preferably, the beam splitter prism is a blade prism; the blade formed by the intersection of the two reflecting mirror surfaces of the blade prism is arranged on one side close to the incident light and is used for separating the light containing two different frequency components. A very fine intersecting surface (less than millimeter) is arranged between two mutually vertical reflecting surfaces of the blade prism and looks like a blade, incident light faces the blade and irradiates the blade prism, and light is split by the blade and is incident on the left side reflecting surface and the right side reflecting surface.
The invention provides a real-time measuring and controlling method of electro-optic modulation depth based on a VIPA etalon, which specifically comprises the following steps:
single-frequency linearly polarized light generated by the single-frequency laser is input to the electro-optical modulator as a laser source, and multi-frequency composite light consisting of a carrier and a sideband is output after electro-optical modulation;
the multi-frequency composite light is input to a VIPA dispersion light splitting module, sequentially passes through a collimator and a cylindrical lens, then is emitted into a window area of a virtual imaging phase array, is reflected for multiple times to output a plurality of parallel light beams with different output angles, and then is formed into a plurality of light beams which are spatially separated into millimeter-scale light beams at a position which is one-time of the focal length away from a focusing lens through the focusing lens;
a plurality of light beams with millimeter-scale spacing separate light of several required frequency components through a light beam separation device and simultaneously input the light into a detector array respectively; the detector array converts the light intensity signal into an electric signal, the electric signal is input into the feedback control module, and the feedback control module realizes real-time measurement and control of the electro-optic modulation depth.
After the light splitting, the specific embodiments differ for the two different functions. The method comprises the following specific steps:
example 1:
in embodiment 1, a spatial dispersion spectroscopic detection and feedback control method is used to realize accurate and stable real-time control of the modulation depth of the EOM, and a specific design scheme is shown in fig. 4. After single-frequency laser generated by a single-frequency laser is modulated by an optical fiber EOM, light with different frequencies is subjected to beam splitting and focusing by a VIPA dispersion light splitting module consisting of a collimator, a cylindrical lens, a VIPA and a focusing lens, only 0-level light and 1-level light in a single Free Spectral Range (FSR) pass through a diaphragm, transmitted light beams are separated by a blade prism due to mm-level spatial distance and respectively pass through a photoelectric detector, optical power signals are converted into electric signals, and then the signal processing results are input into a PID control circuit. Calculating the ratio of 0-level light power to 1-level light power, comparing the ratio with a set required ratio, inputting an error-controlled voltage signal serving as a feedback signal to a voltage control end of an attenuator VCA, connecting a microwave input end of the VCA to a micro-signal source for providing a driving signal for an EOM, and connecting the output of the VCA to a microwave driving signal interface of the EOM; therefore, the drive signal of the EOM can be adjusted and controlled by controlling the attenuation of the VCA, so that the modulation depth of the EOM can be regulated and controlled, the feedback control of the modulation depth can be completed by closed-loop feedback control, and finally the output carrier and sideband light of the EOM can be stabilized on the required power ratio.
Example 2:
as shown in fig. 5, the difference between the embodiment 2 and the embodiment 1 is that after passing through the front VIPA dispersion splitting module, the scheme 1 obtains only two spatially separated light beams (0-level light and 1-level light) through the diaphragm and the blade prism, the scheme 2 locally adjusts the beam angle and the position of the light spot near the focal plane through the diaphragm and the beam turning prism, and then the carrier and the multiple target sidebands are simultaneously detected by directly using the array detector reasonably designed for the effective detection position of the light beam, and the size and the interval of the photosensitive surface of each unit of the array detector are equal; the array detector outputs a voltage signal of optical power conversion, then simultaneously collects a plurality of electric signals for signal processing, and utilizes the electric signals to accurately generate an error-controlled voltage signal as a feedback signal to be input to a voltage control end of an attenuator VCA, a microwave input end of the VCA is connected with a micro-signal source for providing a driving signal for the EOM, and an output of the VCA is connected to a microwave driving signal interface of the EOM; therefore, the drive signal of the EOM can be adjusted and controlled by controlling the attenuation of the VCA, so that the modulation depth of the EOM can be regulated and controlled, the feedback control of the modulation depth can be completed by closed-loop feedback control, and finally the EOM output carrier and sideband light can be accurately locked on a required power ratio.
In summary, the electro-optical modulation depth real-time measurement and control system based on the VIPA etalon provided by the invention can realize accurate control of modulation depth through feedback control on the basis of optical power acquisition and processing by performing light splitting and detection on EOM modulated output light in space by using the VIPA etalon and acquiring and processing a detection result. The laser control technology can directly control the EOM modulation depth with high precision and long-term stability, and has important engineering practical value in the fields of atomic interference, frequency synthesis of coherent light, atomic molecular physics, quantum information technology and the like. Specifically, the system can be directly used for real-time high-precision measurement and feedback control of Raman optical power ratio in the atomic interference process and control of power components of cooling light and pumping light; in addition, the method can be used for frequency synthesis and power control of coherent light, real-time monitoring and accurate control of coherent control light in atomic molecular physics and quantum information technologies, and the like.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An electro-optic modulation depth real-time measurement and control system based on a VIPA etalon is characterized by comprising a single-frequency laser, an electro-optic modulator, a VIPA dispersion splitting module, a beam separation device, a detector array and a feedback control module;
the single-frequency laser is used for generating single-frequency linearly polarized light, the single-frequency linearly polarized light is input to the electro-optic modulator, and multi-frequency composite light consisting of a carrier and a sideband is output after the electro-optic modulation; inputting the multi-frequency composite light to a dispersion light splitting module, and spatially separating sideband light with different frequencies into a plurality of light beams with millimeter-scale intervals; a plurality of light beams with millimeter-scale spacing separate light of several required frequency components through a light beam separation device and simultaneously input the light into a detector array respectively; the detector array converts the light intensity signal into an electric signal, the electric signal is input into the feedback control module, and real-time measurement and control of the electro-optic modulation depth are realized through the feedback control module;
the VIPA dispersion splitting module comprises a collimator, a cylindrical lens, a virtual imaging phase array and a focusing lens; the multi-frequency composite light output after electro-optical modulation passes through the collimator, the cylindrical lens, the virtual imaging phase array and the focusing lens in sequence, and sideband light with different frequencies is spatially divided into a plurality of light beams with millimeter magnitude.
2. The system according to claim 1, wherein the virtual imaging phase array is composed of two parallel optical coated flat plates; the flat plate close to incident light is a front panel, the bottom of the front panel is provided with a window area, the window area is coated with an antireflection film, and the non-window area is coated with a reflecting film with the reflectivity of 100%; the flat plate far away from the incident light is a rear panel coated with a partially transmissive film with a reflectivity of 95% -98%.
3. The system according to claim 2, wherein there is an incident angle between the virtual imaging phased array and the incident light, and the incident light is incident through a window area of the virtual imaging phased array, and after multiple back and forth reflections, parallel light beams with different output angles are generated on the transmission side of the rear panel; the parallel beams of different output angles are spatially separated into a plurality of beams on the order of millimeters by a focusing lens.
4. The VIPA etalon-based electro-optic modulation depth real-time measurement and control system of claim 3, wherein the distance between the focusing lens and the beam separation device is one focal length of the focusing lens.
5. The VIPA etalon-based electro-optic modulation depth real-time measurement and control system of claim 1, wherein the beam splitting device comprises a diaphragm and a beam splitting prism; a plurality of light beams with the distance of millimeter order firstly pass through the diaphragm to block the unwanted light beams, and then the light beams with the required frequency components are separated through the light splitting prism.
6. The VIPA etalon-based electro-optic modulation depth real-time measurement and control system of claim 5, wherein the beam splitter prism is a blade prism; the blade formed by the intersection of the two reflecting mirror surfaces of the blade prism is arranged on one side close to the incident light and is used for separating the light containing two different frequency components.
7. The system according to claim 1, wherein the feedback control module comprises a signal processor, a PID control circuit, an attenuator and a microwave signal source;
the signal processor is connected with the detector array, the detector array converts the optical signal into an electric signal and inputs the electric signal into the signal processor to obtain a processed electric signal, and the processed electric signal passes through the PID control circuit and then outputs a control signal to control the size of the attenuator; the input end of the attenuator is connected with a microwave signal source which provides a driving signal for the electro-optic modulator, and the output end of the attenuator is connected to a driving interface of the electro-optic modulator and used for adjusting the power of the driving signal through the attenuator and realizing the adjustment and control of the modulation depth of the electro-optic modulator.
8. The real-time measuring and controlling method of the electro-optic modulation depth based on the VIPA etalon is characterized by comprising the following steps:
single-frequency linearly polarized light generated by the single-frequency laser is input to the electro-optical modulator as a laser source, and multi-frequency composite light consisting of a carrier and a sideband is output after electro-optical modulation;
the multi-frequency composite light is input to a VIPA dispersion light splitting module, sequentially passes through a collimator and a cylindrical lens, then is emitted into a window area of a virtual imaging phase array, is reflected for multiple times to output a plurality of parallel light beams with different output angles, and then is formed into a plurality of light beams which are spatially separated into millimeter-scale light beams at a position which is one-time of the focal length away from a focusing lens through the focusing lens;
a plurality of light beams with millimeter-scale spacing separate light of several required frequency components through a light beam separation device and simultaneously input the light into a detector array respectively; the detector array converts the light intensity signal into an electric signal, the electric signal is input into the feedback control module, and the feedback control module realizes real-time measurement and control of the electro-optic modulation depth.
9. The method for real-time measurement and control of the electro-optic modulation depth based on the VIPA etalon according to claim 8, wherein the feedback control module comprises a signal processor, a PID control circuit, an attenuator and a microwave signal source;
the signal processor is connected with the detector array, the detector array converts the optical signal into an electric signal and inputs the electric signal into the signal processor to obtain a processed electric signal, and the processed electric signal passes through the PID control circuit and then outputs a control signal to control the size of the attenuator; the input end of the attenuator is connected with a microwave signal source which provides a driving signal for the electro-optic modulator, and the output end of the attenuator is connected to a driving interface of the electro-optic modulator and used for adjusting the power of the driving signal through the attenuator and realizing the adjustment and control of the modulation depth of the electro-optic modulator.
10. The application of the VIPA etalon-based electro-optic modulation depth real-time measurement and control system is characterized in that the system is used for real-time high-precision measurement and feedback control of Raman optical power ratio in an atomic interference process and control of power components of cooling light and pumping light.
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