CN116973076A - Optical vector network analyzer and ultrahigh frequency measurement method - Google Patents
Optical vector network analyzer and ultrahigh frequency measurement method Download PDFInfo
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Abstract
The application provides an optical vector network analyzer and an ultrahigh frequency measurement method, comprising the following steps: an optical transceiver system, an excitation and interference system, and a computer control and signal processing system; the optical receiving and transmitting system receives and transmits the modulated pulse/continuous wave laser signals; the excitation and interference system combines excitation light and detection light to act on the same point of the micro-nano structure to be detected through a dichroic mirror; the computer control and signal processing system regulates and controls the ultrafast pulse laser and the continuous wave laser, and processes signals obtained by the photoelectric detector to obtain the amplitude, phase and frequency characteristics of the scattering parameters. The application is applied to the measurement of the electrodeless ultrahigh frequency micro-nano structure, solves the difficulty that the electrodeless micro-nano device cannot measure, realizes the sweep frequency measurement of the amplitude and the phase of scattering parameters of the electrodeless micro-nano structure in the ultrahigh frequency domain, and simultaneously utilizes tunable ultrashort pulse laser, and has the characteristics of non-contact, small interference and low energy consumption.
Description
Technical Field
The application relates to the technical field of ultrahigh frequency and very small vibration measuring instruments, in particular to an optical vector network analyzer and an ultrahigh frequency measuring method, and especially relates to an all-optical ultrahigh frequency vector network analyzer and a measuring method adopting optical pressure excitation and ultrafast pulse laser stroboscopic interference.
Background
The vector network analyzer is a high-precision intelligent testing instrument which is most important and widely applied in the field of microwave/millimeter wave device testing instruments, enjoys the reputation of 'the king of microwave/millimeter wave testing instruments' in the industry, and is mainly used for measuring characteristic information such as amplitude frequency, phase frequency, group delay and the like of bidirectional S parameters of scattering parameters of a tested network. The basic principle is as follows: the device is provided with a signal generator, can perform frequency scanning on a frequency band, and can judge impedance or reflection condition by applying an excitation signal to a port and measuring amplitude and phase of a reflected signal if the frequency band is measured by the single port.
The existing vector network analyzer is used for measuring in the frequency range of 5Hz-110GHz, and is organically combined with an excitation signal source, an S parameter measuring device (signal separation circuit) and an amplitude-phase receiver. The microwave synthesis sweep frequency signal source generates excitation signals which can reach millimeter wave bands, an incident signal R, a reflected signal A and a transmission signal B of a DUT (tested piece) are separated by a signal separation circuit, and the microwave signals are converted into fixed intermediate frequency signals by adopting a sampling frequency conversion technology to measure the amplitude and phase relation. In the frequency conversion process, a system phase locking technology is adopted to ensure that amplitude information and phase information of a tested network are not lost, a first intermediate frequency signal containing the amplitude information and the phase information of the tested network is changed into a second intermediate frequency signal through an intermediate frequency processing circuit, the second intermediate frequency signal is converted into a digital signal through an A/D converter, the amplitude information and the phase information of the DUT are extracted from the digital signal by an internal computer and a DSP (digital signal processor), and the S parameter of the DUT is obtained through ratio operation.
In short, the existing vector network analyzer adopts an all-electrical method, an excitation signal source is required to output an electric signal driving device, and a amplitude receiver is utilized to read the returned electric signal, so that the vector network analyzer can be applied to frequency response measurement of micro-nano devices with driving electrodes and sensing electrodes. However, this method is not suitable for micro-nano devices of electrodeless structure, such as frequency response of movable nano-film and nano-cantilever, and thus the intrinsic energy dissipation rate of the structure cannot be studied.
Therefore, a new solution is needed to improve the above technical problems.
Disclosure of Invention
Aiming at the defects in the prior art, the application aims to provide an optical vector network analyzer and an ultrahigh frequency measurement method.
According to the present application, there is provided an optical vector network analyzer comprising: an optical transceiver system, an excitation and interference system, and a computer control and signal processing system;
the optical transceiver system receives and transmits the modulated pulse/continuous wave laser signals; the excitation and interference system combines excitation light with detection light through a dichroic mirror and acts on the same point of the micro-nano structure to be detected to excite and detect out-of-plane vibration signals; the computer control and signal processing system regulates and controls the ultrafast pulse laser and the continuous wave laser, and processes signals obtained by the photoelectric detector to obtain the amplitude, phase and frequency characteristics of the scattering parameters.
Preferably, the optical transceiver system includes: the device comprises a first photoelectric detector, a second photoelectric detector, an ultrafast pulse laser, a continuous wave laser, a polaroid, a first half wave plate and an electro-optic modulator;
the first photoelectric detector is a low-speed photoelectric detector, the detection bandwidth of the first photoelectric detector is DC-250MHz, and the first photoelectric detector receives interference laser signals from a Michelson interferometer and converts the optical signals into electric signals to be input into the signal processing system;
the second photoelectric detector is a high-speed photoelectric detector, the detection bandwidth of the second photoelectric detector is DC-22GHz, an ultrafast pulse laser signal is received, and the optical signal is converted into an electric signal and is input into the signal processing system;
the ultra-fast pulse laser is a femtosecond fiber laser, the working wavelength is 785nm, the pulse width is 100fm, the repetition frequency is adjustable from 49MHz to 51MHz, the output power is 100mW, and the output mode is free space output;
the continuous wave laser is a tunable digital reference transmitter, the working wavelength is 1550nm, and the output power is 8mW;
the polarizing plate changes the polarization directions of the reference light and the signal light emitted from the second polarizing spectroscope, so that the polarization directions of the reference light and the signal light are consistent and interfere, and interference light passing through the polarizing plate is input into the first photoelectric detector;
the first half-wave plate adjusts the light splitting proportion of the detection light after passing through the first polarization spectroscope, and adjusts the light intensity of the detection light;
the electro-optic modulator is a LiNbO3 electro-optic modulator, intensity modulates continuous wave excitation light with the modulation bandwidth of 14GHz, and the modulation frequency is controlled to be f by a signal generator p ，f p The frequency difference is continuously adjustable in the range from DC to 14GHz, and the frequency is excited to f by the light pressure p The acoustic field at that frequency is expressed as: s (t) =acos (-2pi f) p t+phi), wherein A and phi are the vibration frequencies f, respectively p Amplitude and phase below.
Preferably, the excitation and interference system comprises: the excitation light path and the detection light path are based on the Michelson interferometer principle, and the detection light path comprises a first reflecting mirror, a first polarization spectroscope, a second half-wave plate, a second reflecting mirror, a second polarization spectroscope, a first quarter-wave plate, a dichroic mirror, a focusing objective lens, a second quarter-wave plate and a third reflecting mirror;
the second half-wave plate adjusts the polarization direction of the detection light, so that the light intensity ratio of the two light beams passing through the second polarization spectroscope is continuously adjustable, and the surfaces of devices with different reflectivities are measured;
the dichroic mirror is a short-wave through dichroic mirror, has high laser reflectivity above 950nm and high laser transmissivity below 950nm, couples excitation light with detection light, acts on the same point on the surface of the electrodeless micro-nano structure, and the electrodeless micro-nano structure is arranged on the triaxial displacement table.
Preferably, the computer control and signal processing system comprises: a signal processing circuit, a data storage device and control software;
the signal processing circuit uses a frequency mixing, filtering and phase-locked amplifying circuit structure to perform frequency domain conversion and extraction of signals, demodulates amplitude and phase information and stores the amplitude and phase information in a data storage device; the control software regulates and controls the repetition frequency of the ultrafast pulse laser and the modulation frequency of the electro-optic modulator.
Preferably, the signal processing circuit comprises a mixer, a filter, an amplifier and a phase-locked amplifier;
the mixer mixes the optical excitation signal with the ultrafast pulse laser repetition frequency signal received by the second photoelectric detector, and the optical excitation signal is used as a reference signal to be input into the lock-in amplifier after passing through the filter and the amplifier, and interference light received by the first photoelectric detector is used as a measurement signal to be input into the lock-in amplifier;
the phase-locked amplifier demodulates amplitude and phase data in the interference light signal, and analyzes amplitude and phase frequency characteristics of scattering parameters of the electrodeless micro-nano structure.
The application also provides an ultrahigh frequency measurement method, which is applied to the optical vector network analyzer and comprises the following steps:
step S1: using continuous wave excitation light modulated by intensity to perform nondestructive excitation vibration on the electrodeless micro-nano structure;
step S2: interferometric measuring the surface of the vibration device by using ultra-fast pulse detection light;
step S3: scattering parameters such as amplitude and phase frequency characteristics are obtained by demodulating the photodetector signal, and performing electrical mixing, filtering and amplifying operations.
Preferably, the step of acquiring the scattering parameter in step S3 includes the steps of:
step S3.1: modulating 1550nm laser emitted by a continuous wave laser by adopting an electro-optical modulator;
step S3.2: 785nm laser emitted by the ultrafast pulse laser is converted into linearly polarized light with adjustable polarization direction through a polarizing plate;
step S3.3: the computer control and signal processing system adopts a phase-locked amplifier to demodulate the response signal of the first photoelectric detector;
step S3.4: the frequency response characteristic of the electrodeless micro-nano structure under different excitation frequencies can be obtained by adjusting the modulation frequency of the electro-optic modulator, namely the sweep frequency function of the all-optical network analyzer is realized.
Preferably, the step S3.1 is reflected by a dichroic mirror and focused on the surface of the electrodeless micro-nano structure through a focusing objective lens, and the excitation device is excited to vibrate through light pressure, so that the excitation frequency range DC-14GHz is continuously adjustable.
Preferably, after passing through the first polarization beam splitter, one beam of laser is obtained by the second photodetector, and the other beam of laser passes through the rotatable second half-wave plate, is converted into linearly polarized light with adjustable polarization direction and adjustable intensity, passes through the second polarization beam splitter, is split into a beam of transmitted light polarized along the horizontal direction and a beam of reflected light polarized along the vertical direction, and the reference light sequentially passes through the second quarter-wave plate, the third reflecting mirror and the second quarter-wave plate, and the polarization direction is reflected along the vertical direction after passing through the second polarization beam splitter and is led to the second reflecting mirror; the signal light sequentially passes through the first quarter wave plate, the dichroic mirror and the focusing objective lens, returns in an original path after being reflected by the surface of the non-electrode micro-nano structure, passes through the first quarter wave plate again, passes through the second polarizing spectroscope again, is transmitted to the second reflecting mirror, passes through the polarizing plate deflected by 45 degrees along the horizontal direction, has consistent polarizing directions, and generates interference, the interference light is acquired by the first photoelectric detector, and the optical signal is converted into an electric signal.
Preferably, the reference signal in step S3.3 is formed by mixing the laser repetition frequency signal obtained by the second photodetector with the modulated signal for controlling the electro-optical crystal, filtering, amplifying, and inputting the amplitude and phase information demodulated by the lock-in amplifier into a computer for storage and display.
Compared with the prior art, the application has the following beneficial effects:
1. the application adopts a vector network analyzer of an all-optical method to excite and measure the electrodeless ultrahigh frequency micro-nano structure, and obtains scattering parameters such as amplitude, phase frequency characteristics.
2. Compared with the traditional electrical network analyzer, the application solves the difficulty that the electrodeless micro-nano device cannot measure, realizes the sweep frequency measurement of the amplitude and the phase of the scattering parameter of the electrodeless micro-nano structure in the ultra-high frequency domain, and simultaneously utilizes the tunable ultra-short pulse laser to realize the characteristics of non-contact, small interference and low energy consumption.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a schematic structural diagram and an optical path diagram of an all-optical ultrahigh frequency vector network analyzer in the application;
FIG. 2 is a schematic diagram of coupling excitation light and detection light to an electrodeless micro-nano device in an embodiment of the present application.
Wherein:
second half-wave plate 11 of computer control and signal processing system 1
First photodetector 2 second mirror 12
Second photodetector 3 second polarizing beamsplitter 13
The first quarter wave plate 14 of the ultrafast pulse laser 4
Dichroic mirror 15 of continuous wave laser 5
Polarizing plate 6 focusing objective lens 16
First half wave plate 7 non-electrode micro-nano structure 17
Triaxial displacement table 18 of electro-optic modulator 8
The first mirror 9 and the second quarter wave plate 19
First polarizing beamsplitter 10 third mirror 20
Detailed Description
The present application will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present application, but are not intended to limit the application in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present application.
Example 1:
according to the present application, there is provided an optical vector network analyzer comprising: an optical transceiver system, an excitation and interference system, and a computer control and signal processing system 1; the optical transceiver system receives and transmits the modulated pulse/continuous wave laser signals; the excitation and interference system combines excitation light and detection light to act on the same point of the micro-nano structure to be detected through a dichroic mirror 15, and excites and detects out-of-plane vibration signals; the computer control and signal processing system 1 regulates and controls the ultrafast pulse laser 4 and the continuous wave laser 5, and processes signals obtained by the photoelectric detector to obtain the amplitude and phase frequency characteristics of the scattering parameters.
The optical transceiver system includes: a first photodetector 2, a second photodetector 3, an ultrafast pulse laser 4, a continuous wave laser 5, a polarizing plate 6, a first half-wave plate 7 and an electro-optic modulator 8; the first photoelectric detector 2 is a low-speed photoelectric detector, the detection bandwidth is DC-250MHz, and the first photoelectric detector receives interference laser signals from a Michelson interferometer and converts the optical signals into electric signals to be input into a signal processing system; the second photoelectric detector 3 is a high-speed photoelectric detector, the detection bandwidth is DC-22GHz, an ultrafast pulse laser signal is received, and the optical signal is converted into an electric signal and is input into the signal processing system; the ultrafast pulse laser 4 is a femtosecond fiber laser, the working wavelength is 785nm, the pulse width is 100fm, the repetition frequency is adjustable from 49MHz to 51MHz, the output power is 100mW, and the output mode is free space output; the continuous wave laser 5 is a tunable digital reference transmitter, the working wavelength is 1550nm, and the output power is 8mW; the polarizing plate 6 changes the polarization directions of the reference light and the signal light emitted from the second polarizing beam splitter 13, so that the polarization directions of the reference light and the signal light are consistent and interfere, and the interference light of the polarizing plate 6 is input into the first photoelectric detector 2; the first half wave plate 7 adjusts the light splitting proportion of the detection light after passing through the first polarization spectroscope 10, and adjusts the light intensity of the detection light; the electro-optic modulator 8 is a LiNbO3 electro-optic modulator 8, intensity-modulates continuous wave excitation light with a modulation bandwidth of 14GHz, and controls the modulation frequency of the continuous wave excitation light to be f by using a signal generator p ，f p The frequency difference is continuously adjustable in the range from DC to 14GHz, and the frequency is excited to f by the light pressure p The acoustic field at that frequency is expressed as: s (t) =acos (-2pi f) p t+phi), wherein A and phi are the vibration frequencies f, respectively p Amplitude and phase below.
The excitation and interference system includes: the excitation light path and the detection light path are based on the Michelson interferometer principle, and the detection light path comprises a first reflecting mirror 9, a first polarization spectroscope 10, a second half-wave plate 11, a second reflecting mirror 12, a second polarization spectroscope 13, a first quarter-wave plate 14, a dichroic mirror 15, a focusing objective lens 16, a second quarter-wave plate 19 and a third reflecting mirror 20; the second half wave plate 11 adjusts the polarization direction of the detection light, so that the light intensity ratio of the two beams of light passing through the second polarization spectroscope 13 is continuously adjustable, and the surfaces of devices with different reflectivities are measured; the dichroic mirror 15 is a short-wave dichroic mirror 15, has a high laser light transmittance at 950nm or more and a high laser light transmittance at 950nm or less, and is configured to couple excitation light with detection light and act on the same point on the surface of the electrodeless micro-nano structure 17, and the electrodeless micro-nano structure 17 is placed on the triaxial displacement stage 18.
The computer control and signal processing system 1 comprises: a signal processing circuit, a data storage device and control software; the signal processing circuit uses a frequency mixing, filtering and phase-locked amplifying circuit structure to perform frequency domain conversion and extraction of signals, demodulates amplitude and phase information and stores the amplitude and phase information in a data storage device; the control software regulates the repetition frequency of the ultrafast pulse laser 4 and the modulation frequency of the electro-optical modulator 8.
The signal processing circuit comprises a mixer, a filter, an amplifier and a phase-locked amplifier; the mixer mixes the optical excitation signal with the ultrafast pulse laser 4 repetition frequency signal received by the second photoelectric detector 3, and the mixed signal is used as a reference signal to be input into the lock-in amplifier after passing through the filter and the amplifier, and the interference light received by the first photoelectric detector 2 is used as a measurement signal to be input into the lock-in amplifier; the phase-locked amplifier demodulates the amplitude and phase data in the interference light signal, and analyzes the amplitude and phase frequency characteristics of the scattering parameters of the non-electrode micro-nano structure 17.
The application also provides an ultrahigh frequency measurement method, which is applied to the optical vector network analyzer and comprises the following steps:
step S1: non-destructive excitation vibration of the electrodeless micro-nano structure 17 using intensity modulated continuous wave excitation light;
step S2: interferometric measuring the surface of the vibration device by using ultra-fast pulse detection light;
step S3: scattering parameters such as amplitude and phase frequency characteristics are obtained by demodulating the photodetector signal, and performing electrical mixing, filtering and amplifying operations.
The step S3 of acquiring the scattering parameter includes the following steps:
step S3.1: modulating 1550nm laser emitted by the continuous wave laser 5 by adopting an electro-optical modulator 8;
step S3.2: 785nm laser emitted by the ultrafast pulse laser 4 is converted into linearly polarized light with adjustable polarization direction through the polarizing plate 6;
step S3.3: the computer control and signal processing system 1 adopts a lock-in amplifier to demodulate the response signal of the first photoelectric detector 2;
step S3.4: by adjusting the modulation frequency of the electro-optical modulator 8, the frequency response characteristic of the electrodeless micro-nano structure 17 under different excitation frequencies can be obtained, namely the frequency sweeping function of the all-optical network analyzer is realized.
The step S3.1 is reflected by the dichroic mirror 15 and focused on the surface of the electrodeless micro-nano structure 17 by the focusing objective lens 16, and the excitation device is excited to vibrate by light pressure, so that the excitation frequency range DC-14GHz is continuously adjustable.
After passing through the first polarization beam splitter 10, one laser beam is obtained by the second photodetector 3, the other laser beam passes through the rotatable second half-wave plate 11, is converted into linearly polarized light with adjustable polarization direction and adjustable intensity, passes through the second polarization beam splitter 13, is split into a beam of transmitted light polarized along the horizontal direction and a beam of reflected light polarized along the vertical direction, passes through the second quarter-wave plate 19, the third reflecting mirror 20 and the second quarter-wave plate 19 in sequence, and the polarization direction is reflected along the vertical direction after passing through the second polarization beam splitter 13, and is led to the second reflecting mirror 12; the signal light sequentially passes through the first quarter wave plate 14, the dichroic mirror 15 and the focusing objective lens 16, returns from the original path after being reflected by the surface of the non-electrode micro-nano structure 17, passes through the first quarter wave plate 14 again, passes through the second polarization spectroscope 13 again and is transmitted to the second reflecting mirror 12, the reference light and the signal light pass through the polarizing plate 6 deflected at 45 degrees along the horizontal direction, the polarization directions are consistent, interference occurs, the interference light is acquired by the first photoelectric detector 2, and the optical signal is converted into an electric signal.
The reference signal in the step S3.3 is composed of an electric signal obtained by mixing, filtering and amplifying the laser repetition frequency signal obtained by the second photoelectric detector 3 and a modulation signal for controlling the electro-optical crystal, and the amplitude and phase information demodulated by the phase-locked amplifier is input into a computer for storage and display.
Example 2:
the application relates to the field of measuring instruments for extremely high frequency and extremely small vibration, in particular to an all-optical ultra-high frequency vector network analyzer for measuring vibration by utilizing ultra-high frequency modulated light excitation and ultra-fast pulse laser stroboscopic interference.
The optical vector network analyzer of the all-optical design solves the problem that the electrodeless micro-nano structure is difficult to characterize and measure, and the measuring frequency reaches an ultrahigh frequency band through design.
Aiming at the electrodeless ultrahigh frequency micro-nano structure, the application provides an all-optical ultrahigh frequency vector network analyzer based on an ultrafast pulse laser stroboscopic interferometer and an optical excitation system, which cannot measure the electrodeless micro-nano structure, and realizes the real-time and rapid detection of the electrodeless ultrahigh frequency micro-nano structure by utilizing ultrahigh frequency modulated light and measuring femtosecond ultrafast pulse laser.
The application relates to an all-optical ultrahigh frequency vector network analyzer based on an ultrafast pulse laser stroboscopic interferometer and an optical excitation system, which comprises: an optical transceiver system, an excitation and interference system, and a computer control and signal processing system, wherein: the optical transceiver system is used for receiving and transmitting the modulated pulse/continuous wave laser signals, the excitation and interference system is used for combining excitation light and detection light through the dichroic mirror and acting on the same point of the micro-nano structure to be detected, the excitation and detection light is used for exciting and detecting out-of-plane vibration signals, and the computer control and signal processing system is responsible for regulating and controlling the ultrafast pulse laser and the continuous wave laser and processing signals obtained by the photoelectric detector to obtain the amplitude, phase and frequency characteristics of scattering parameters.
The optical transceiver system includes: the device comprises a first photoelectric detector, a second photoelectric detector, an ultrafast pulse laser, a continuous wave laser, a polaroid, a first half wave plate and an electro-optic modulator.
The excitation and interference system includes: the excitation light path and the detection light path are based on the Michelson interferometer principle, and the detection light path comprises a first reflecting mirror, a first polarization spectroscope, a second half-wave plate, a second reflecting mirror, a second polarization spectroscope, a first quarter-wave plate, a dichroic mirror, a focusing objective lens, a second quarter-wave plate and a third reflecting mirror.
The computer control and signal processing system comprises: signal processing circuitry, data storage means and control software. The signal processing circuit uses circuit structures such as mixing, filtering, phase-locked amplifying and the like to realize frequency domain conversion and extraction of signals, demodulates information such as amplitude, phase and the like, stores the information in the data storage device, and the control software is used for regulating and controlling the repetition frequency of the ultrafast pulse laser and the modulation frequency of the electro-optic modulator.
The ultra-fast pulse laser is a femtosecond fiber laser, the working wavelength is 785nm, the pulse width is 100fm, the repetition frequency is adjustable from 49MHz to 51MHz, the output power is 100mW, and the output mode is free space output.
The continuous wave laser is a tunable digital reference transmitter, the typical working wavelength is 1550nm, the output power is 8mW, the digital reference transmitter has a frequency offset function, and offset from-30 GHz to +30GHz can be realized in 1MHz increment, so that the working wavelength is adjusted to be 1527.6 to 1565.5nm continuously.
The first photoelectric detector is a low-speed photoelectric detector, the detection bandwidth of which is DC-250MHz, and the first photoelectric detector is used for receiving interference laser signals from a Michelson interferometer and converting the optical signals into electric signals to be input into a signal processing system.
The second photoelectric detector is a high-speed photoelectric detector, the detection bandwidth of which is DC-22GHz and is used for receiving the ultrafast pulse laser signals and converting the optical signals into electric signals to be input into the signal processing system.
The polarizing plate is used for changing the polarization directions of the reference light and the signal light emitted from the second polarizing spectroscope, so that the polarization directions of the reference light and the signal light are consistent and interfere, and interference light passing through the polarizing plate is input into the first photoelectric detector.
The first half-wave plate is used for adjusting the light splitting proportion of the detection light passing through the first polarization spectroscope and can be used for adjusting the light intensity of the detection light, and the second half-wave plate is used for adjusting the polarization direction of the detection light, so that the light intensity proportion of two light beams passing through the second polarization spectroscope is continuously adjustable, and the device is suitable for measuring the surfaces of devices with different reflectivities.
The electro-optic modulator is a LiNbO3 electro-optic modulator for intensity modulating continuous wave excitation light with the modulation bandwidth of 14GHz, and the modulation frequency of the electro-optic modulator is controlled to be f by a signal generator p ，f p The frequency difference is continuously adjustable in the range from DC to 14GHz, and the frequency is excited to f by the light pressure p The acoustic field at that frequency is expressed as: s (t) =acos (-2pi f) p t+phi), wherein A and phi are the vibration frequencies f, respectively p Amplitude and phase below.
The dichroic mirror is a short-wave through dichroic mirror, has high laser reflectivity of more than 950nm and high laser transmissivity of less than 950nm, is used for coupling excitation light with detection light and acts on the same point on the surface of the electrodeless micro-nano structure, and the electrodeless micro-nano structure is placed on the triaxial displacement table.
The optical path system is integrally built based on a cage system with compact structure and good stability, and all optical components have the same size specification, so that the optical path system becomes more compact, meanwhile, the stability and portability are improved, different optical components are connected through 4 rigid straight rods, coaxial installation and debugging are realized, and the accuracy and stability of a space optical path are improved.
The signal processing circuit comprises a mixer, a filter, an amplifier and a phase-locked amplifier, wherein the mixer is used for mixing the optical excitation signal with the ultrafast pulse laser repetition frequency signal received by the second photoelectric detector, the optical excitation signal is used as a reference signal to be input into the phase-locked amplifier after passing through the filter and the amplifier, interference light received by the first photoelectric detector is used as a measuring signal to be input into the phase-locked amplifier, and the phase-locked amplifier is used for demodulating amplitude and phase data in the interference light signal and is used for analyzing amplitude and phase frequency characteristics of scattering parameters of the non-electrode micro-nano structure.
As shown in fig. 1, an all-optical ultrahigh frequency vector network analyzer based on an ultrafast pulse laser stroboscopic interferometer and an optical excitation system according to an embodiment includes: the system comprises an optical transceiver system, an excitation and interference system, a computer control and signal processing system and an electrodeless sample to be measured.
As shown in fig. 2, a schematic diagram of coupling excitation light and detection light to an electrodeless device according to an embodiment includes: the device comprises continuous wave excitation light 1, ultra-fast pulse detection light 2, a dichroic mirror 3, a focusing objective lens 4, a silicon micro-cantilever 5 and a silicon substrate 6.
The application adopts the measuring method of light pressure excitation and ultrafast pulse laser stroboscopic interference, uses continuous wave excitation light modulated by intensity to perform nondestructive excitation vibration on the electrodeless micro-nano structure, uses ultrafast pulse detection light to perform interferometry on the surface of a vibration device, and obtains scattering parameters such as amplitude and phase frequency characteristics by demodulating a photoelectric detector signal and performing electric mixing, filtering and amplifying operation, thereby realizing the function of an optical network analyzer.
The optical transceiver system includes: a first photodetector 2, a second photodetector 3, an ultrafast pulse laser 4, a continuous wave laser 5, a polarizing plate 6, a first half-wave plate 7, and an electro-optic modulator 8 are arranged in this order.
The excitation and interference system includes: a first reflecting mirror 9, a first polarizing beam splitter 10, a second half-wave plate 11, a second reflecting mirror 12, a second polarizing beam splitter 13, a first quarter-wave plate 14, a dichroic mirror 15, a focusing objective lens 16, a second quarter-wave plate 19, and a third reflecting mirror 20 are arranged in this order.
The electrodeless sample to be measured is a silicon nano cantilever structure, can also be a nano thin film structure or a nano thin plate structure, and is manufactured by photoetching, thermal oxidation, wet etching, electron beam lithography, ion etching and other complex processes on a silicon wafer on an insulator. The continuous wave laser after intensity modulation is reflected by the dichroic mirror, and is focused on the surface of the cantilever by the focusing objective lens to perform optical pressure excitation, and the ultrafast pulse laser is transmitted by the dichroic mirror and is focused on the same point on the surface of the cantilever by the focusing objective lens to perform detection.
The specific steps for acquiring the scattering parameters are as follows:
(1) The 1550nm laser emitted by the continuous wave laser is modulated by adopting an electro-optical modulator, reflected by a dichroic mirror and converged on the surface of the electrodeless micro-nano structure by a focusing objective lens, and the excitation device is excited to vibrate by light pressure, so that the excitation frequency range DC-14GHz is continuously adjustable.
(2) 785nm laser emitted by the ultrafast pulse laser is converted into linearly polarized light with an adjustable polarization direction through a polarizing plate, one beam of laser is acquired by a second photoelectric detector after passing through a first polarizing spectroscope, the other beam of laser is converted into linearly polarized light with an adjustable polarization direction and adjustable intensity through a rotatable second half-wave plate, the linearly polarized light is split into a beam of transmitted light (reference light) polarized along a horizontal direction and a beam of reflected light (signal light) polarized along a vertical direction through a second polarizing spectroscope, the reference light sequentially passes through a second quarter-wave plate (rotated 45 degrees with the horizontal direction), a third reflecting mirror and a second quarter-wave plate, and the polarization direction is reflected along a vertical direction after passing through the second polarizing spectroscope and is led to the second reflecting mirror; the signal light sequentially passes through the first quarter wave plate, the dichroic mirror and the focusing objective lens, returns in an original path after being reflected by the surface of the non-electrode micro-nano structure, passes through the first quarter wave plate again, passes through the second polarizing spectroscope again, is transmitted to the second reflecting mirror, passes through the polarizing plate deflected by 45 degrees along the horizontal direction, has consistent polarizing directions, and generates interference, the interference light is acquired by the first photoelectric detector, and the optical signal is converted into an electric signal.
(3) The computer control and signal processing system demodulates the response signal of the first photoelectric detector by using a phase-locked amplifier, the reference signal consists of the laser repetition frequency signal obtained by the second photoelectric detector and the electric signal obtained by controlling the frequency mixing, filtering and amplifying of the modulating signal of the electro-optic crystal, and the amplitude and phase information demodulated by the phase-locked amplifier is input into the computer for storage and display.
(4) The frequency response characteristic of the electrodeless micro-nano structure under different excitation frequencies can be obtained by adjusting the modulation frequency of the electro-optic modulator, namely the sweep frequency function of the all-optical network analyzer is realized.
According to the all-optical ultrahigh frequency vector network analyzer based on the ultrafast pulse laser stroboscopic interferometer and the optical excitation system, after optical pressure excitation is applied, scattering parameters of the measured electrodeless micro-nano structure can be directly obtained, and further frequency response, phase parameters and vibration amplitude of a measured device can be analyzed.
And scanning and measuring the electrodeless micro-nano structure under the ultra-high frequency domain by using an ultra-fast pulse laser stroboscopic interferometer and an all-optical ultra-high frequency vector network analyzer of an optical excitation system to determine network parameters, and giving the amplitude and phase frequency characteristics of scattering parameters in a sweep frequency mode. Characterized by comprising the following steps: optical transceiver systems, excitation and interference systems, and computer control and signal processing systems.
The present embodiment will be understood by those skilled in the art as a more specific description of embodiment 1.
Those skilled in the art will appreciate that the application provides a system and its individual devices, modules, units, etc. that can be implemented entirely by logic programming of method steps, in addition to being implemented as pure computer readable program code, in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers, etc. Therefore, the system and various devices, modules and units thereof provided by the application can be regarded as a hardware component, and the devices, modules and units for realizing various functions included in the system can also be regarded as structures in the hardware component; means, modules, and units for implementing the various functions may also be considered as either software modules for implementing the methods or structures within hardware components.
The foregoing describes specific embodiments of the present application. It is to be understood that the application is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the application. The embodiments of the application and the features of the embodiments may be combined with each other arbitrarily without conflict.
Claims (10)
1. An optical vector network analyzer, comprising: an optical transceiver system, an excitation and interference system and a computer control and signal processing system (1);
the optical transceiver system receives and transmits the modulated pulse/continuous wave laser signals; the excitation and interference system is used for combining excitation light and detection light to act on the same point of the micro-nano structure to be detected through a dichroic mirror (15), and exciting and detecting out-of-plane vibration signals; the computer control and signal processing system (1) regulates and controls the ultrafast pulse laser (4) and the continuous wave laser (5) and processes signals obtained by the photoelectric detector to obtain the amplitude and phase frequency characteristics of the scattering parameters.
2. The optical vector network analyzer of claim 1, wherein the optical transceiver system comprises: the device comprises a first photoelectric detector (2), a second photoelectric detector (3), an ultrafast pulse laser (4), a continuous wave laser (5), a polaroid (6), a first half-wave plate (7) and an electro-optic modulator (8);
the first photoelectric detector (2) is a low-speed photoelectric detector, the detection bandwidth of the first photoelectric detector is DC-250MHz, interference laser signals from a Michelson interferometer are received, and the optical signals are converted into electric signals and input into the signal processing system;
the second photoelectric detector (3) is a high-speed photoelectric detector, the detection bandwidth of the second photoelectric detector is DC-22GHz, an ultrafast pulse laser signal is received, and the optical signal is converted into an electric signal and is input into the signal processing system;
the ultra-fast pulse laser (4) is a femtosecond optical fiber laser, the working wavelength is 785nm, the pulse width is 100fm, the repetition frequency is adjustable from 49MHz to 51MHz, the output power is 100mW, and the output mode is free space output;
the continuous wave laser (5) is a tunable digital reference transmitter, the working wavelength is 1550nm, and the output power is 8mW;
the polarizing plate (6) changes the polarization directions of the reference light and the signal light emitted from the second polarizing beam splitter (13) to make the polarization directions of the reference light and the signal light consistent and interfere, and the interference light of the polarizing plate (6) is input into the first photoelectric detector (2);
the first half-wave plate (7) adjusts the light splitting proportion of the detection light after passing through the first polarization spectroscope (10) and adjusts the light intensity of the detection light;
the electro-optic modulator (8) is a LiNbO3 electro-optic modulator (8) for modulating the intensity of continuous wave excitation light with the modulation bandwidth of 14GHz, and the modulation frequency of the continuous wave excitation light is controlled to be f by a signal generator p ，f p The frequency difference is continuously adjustable in the range from DC to 14GHz, and the frequency is excited to f by the light pressure p The acoustic field at that frequency is expressed as: s (t) =acos (-2pi f) p t+phi), wherein A and phi are the vibration frequencies f, respectively p Amplitude and phase below.
3. The optical vector network analyzer of claim 1, wherein the excitation and interference system comprises: the excitation light path and the detection light path are based on the Michelson interferometer principle, and the detection light path comprises a first reflecting mirror (9), a first polarization spectroscope (10), a second half-wave plate (11), a second reflecting mirror (12), a second polarization spectroscope (13), a first quarter-wave plate (14), a dichroic mirror (15), a focusing objective lens (16), a second quarter-wave plate (19) and a third reflecting mirror (20);
the second half wave plate (11) adjusts the polarization direction of the detection light, so that the light intensity ratio of the two light beams passing through the second polarization spectroscope (13) is continuously adjustable, and the surfaces of devices with different reflectivities are measured;
the dichroic mirror (15) is a short-wave dichroic mirror (15), has high laser reflectivity of 950nm or more and high laser transmissivity of 950nm or less, couples excitation light with detection light, acts on the same point on the surface of the electrodeless micro-nano structure (17), and the electrodeless micro-nano structure (17) is placed on the triaxial displacement table (18).
4. The optical vector network analyzer according to claim 1, characterized in that said computer control and signal processing system (1) comprises: a signal processing circuit, a data storage device and control software;
the signal processing circuit uses a frequency mixing, filtering and phase-locked amplifying circuit structure to perform frequency domain conversion and extraction of signals, demodulates amplitude and phase information and stores the amplitude and phase information in a data storage device; the control software regulates and controls the repetition frequency of the ultrafast pulse laser (4) and the modulation frequency of the electro-optic modulator (8).
5. The optical vector network analyzer of claim 4, wherein the signal processing circuit comprises a mixer, a filter, an amplifier, and a phase-locked amplifier;
the mixer mixes the optical excitation signal with the ultrafast pulse laser (4) repetition frequency signal received by the second photoelectric detector (3), and the mixed signal is used as a reference signal to be input into the lock-in amplifier after passing through the filter and the amplifier, and interference light received by the first photoelectric detector (2) is used as a measuring signal to be input into the lock-in amplifier;
the phase-locked amplifier demodulates amplitude and phase data in the interference light signal, and analyzes amplitude and phase frequency characteristics of scattering parameters of the non-electrode micro-nano structure (17).
6. An ultrahigh frequency measurement method, characterized in that the method employs the optical vector network analyzer according to any one of claims 1 to 5, the method comprising the steps of:
step S1: non-destructive excitation vibration of the electrodeless micro-nano structure (17) using intensity modulated continuous wave excitation light;
step S2: interferometric measuring the surface of the vibration device by using ultra-fast pulse detection light;
step S3: scattering parameters such as amplitude and phase frequency characteristics are obtained by demodulating the photodetector signal, and performing electrical mixing, filtering and amplifying operations.
7. The uhf measurement method according to claim 6, wherein the step S3 of acquiring scattering parameters comprises the steps of:
step S3.1: modulating 1550nm laser emitted by a continuous wave laser (5) by adopting an electro-optical modulator (8);
step S3.2: 785nm laser emitted by the ultrafast pulse laser (4) is converted into linearly polarized light with adjustable polarization direction through the polarizing plate (6);
step S3.3: the computer control and signal processing system (1) adopts a phase-locked amplifier to demodulate the response signal of the first photoelectric detector (2);
step S3.4: the frequency response characteristic of the electrodeless micro-nano structure (17) under different excitation frequencies can be obtained by adjusting the modulation frequency of the electro-optical modulator (8), namely, the frequency sweeping function of the all-optical network analyzer is realized.
8. The ultra-high frequency measurement method according to claim 7, wherein the step S3.1 is reflected by a dichroic mirror (15) and focused by a focusing objective lens (16) on the surface of the electrodeless micro-nano structure (17), and the excitation device is excited to vibrate by the light pressure, and the excitation frequency range DC-14GHz is continuously adjustable.
9. The ultra-high frequency measurement method according to claim 7, wherein after the linearly polarized light in the step S3.2 passes through the first polarizing beam splitter (10), one laser beam is obtained by the second photodetector (3), the other laser beam passes through the rotatable second half-wave plate (11), is converted into linearly polarized light with adjustable polarization direction and adjustable intensity, passes through the second polarizing beam splitter (13), is split into a beam of transmitted light polarized in the horizontal direction, and a beam of reflected light polarized in the vertical direction, the reference light passes through the second quarter-wave plate (19), the third reflecting mirror (20) and the second quarter-wave plate (19) in sequence, and the polarization direction is reflected in the vertical direction after passing through the second polarizing beam splitter (13) and is led to the second reflecting mirror (12); the signal light sequentially passes through a first quarter wave plate (14), a dichroic mirror (15) and a focusing objective lens (16), returns to the original path after being reflected by the surface of the non-electrode micro-nano structure (17), passes through the first quarter wave plate (14) again, passes through a second polarization spectroscope (13) and is transmitted, and is led to the second reflecting mirror (12), the reference light and the signal light pass through a polarizing plate (6) deflected at an angle of 45 degrees along the horizontal direction, the polarization directions are consistent, interference is generated, the interference light is acquired by a first photoelectric detector (2), and the optical signal is converted into an electric signal.
10. The ultra-high frequency measurement method according to claim 7, wherein the reference signal in step S3.3 is composed of an electric signal obtained by mixing, filtering and amplifying a laser repetition frequency signal obtained by the second photodetector (3) and a modulation signal for controlling the electro-optical crystal, and the amplitude and phase information demodulated by the lock-in amplifier is input into a computer for storage and display.
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