CN110335522A - Small Quantum Interferometer Using Piezoelectric Ceramics to Simulate Gravitational Waves - Google Patents

Abstract

The invention discloses a small-scale quantum interferometer which uses piezoelectric ceramics to simulate gravitational waves, uses a helium-neon laser as a laser light source, and the interferometer system includes a 50:50 beam splitter, a reflector, and a continuously adjustable attenuation sheet; the gravitational wave simulation The system includes piezoelectric ceramics with mirrors and piezoelectric ceramic drive power, signal generators, and high-voltage amplifiers; the detection system includes focusing lenses, silicon-based photodetectors, oscilloscopes, and spectrum analyzers. The electrical signal generated by the signal generator is amplified by the high-voltage amplifier and then input to the piezoelectric ceramic, which produces a corresponding periodic expansion and contraction change, simulating the impact of small external changes such as gravitational waves on the optical path difference between the two beams of the M-Z interferometer Impact. The components of the present invention are relatively simple and commonly used, and the structure and optical path design are compact and flexible, and can be adjusted according to needs. It has the characteristics of small size, low cost, and simple operation. It has high research value and application prospect.

Description

Small Quantum Interferometer Using Piezoelectric Ceramics to Simulate Gravitational Waves

technical field

The invention belongs to the technical field of quantum measurement and relates to the exploration and verification of the gravitational wave measurement principle, specifically a small quantum interferometer that uses piezoelectric ceramics to simulate gravitational waves.

Background technique

1. Gravitational waves and the Laser Interferometer Gravitational-Wave Observatory (LIGO)

Gravitational waves are ripples in the curvature of space-time that propagate outward from a radiation source in the form of waves that transmit energy in the form of gravitational radiation. In 1916, Einstein predicted the existence of gravitational waves based on general relativity. When a gravitational wave passes through an observer, due to the strain effect, the observer will find that space-time is warped. The distance between objects would increase and decrease rhythmically, with a frequency corresponding to the frequency of gravitational waves. The strength of this effect is inversely proportional to the distance between the sources that generate gravitational waves. The revolving binary neutron star system is predicted to be a very strong gravitational wave source when they merge, usually because the distance from these wave sources is very far, so the effect is very small when observed on the earth, and the deformation effect is less than 10 ^-21 , so The measurement of gravitational waves requires high-precision instruments.

The most successful case in detecting gravitational waves is the Laser Interferometer Gravitational-Wave Observatory (LIGO). LIGO is essentially a super-large Michelson interferometer improved with F-P cavity, but this interferometer is expensive and the operating system is complicated. It is very difficult to set up as an undergraduate experiment in ordinary physics laboratories. In common physics experiments, Michelson interference, as a comprehensive experiment, is well known to students majoring in physics. However, in this kind of optical experiment, it is usually by observing the spatial interference fringes and counting the number of fringes to understand the interference phenomenon of the light field and test the light interference formula. In the measurement of gravitational waves, the focus is no longer on the basic phenomenon of interference and the rough observation of space interference fringes, but the quantum measurement technology is needed to obtain the final displacement by measuring the noise and signal size of the interference light field.

2. Current research status

At present, quantum mechanics experiments are relatively rare in university physics experiment courses, because quantum mechanics experiments involve microscopic phenomena, and have very high requirements for experimental equipment and acquisition and detection devices, which will lead to very expensive experimental equipment required by most quantum experiments. There are millions of devices, and even tens of millions of experimental platforms. Obviously, the operation and debugging of these experimental platforms will be very complicated. However, the requirements and characteristics of university physics experiment teaching are clear physical images, intuitive experimental phenomena, easy operation and maintenance of instruments, and the price can be accepted by most university physics laboratories. To sum up, the contradiction between the two is also the fundamental reason why there is no quantum mechanics experiment in the university physics experiment course so far. So far, very few researchers have simulated the measurement of gravitational waves in a fundamental physics laboratory setting. Therefore, the present invention proposes to use piezoelectric ceramics to simulate the influence of gravitational waves on one optical path of the M-Z interferometer, and build a small, movable quantum interferometer.

Contents of the invention

The purpose of the present invention is to propose a scheme for simulating gravitational wave measurement in a basic physics laboratory environment on the basis of a Mach-Zehnder interferometer (M-Z interferometer). The small quantum interferometer is flexible in design, easy to implement and easy to integrate.

The concrete technical scheme that realizes the object of the invention is:

A small quantum interferometer using piezoelectric ceramics to simulate gravitational waves, the interferometer includes a helium-neon laser, a polarizing beam splitter, a polarizer, a first beam splitter, a first reflector, a second reflector, a third reflector mirror, the second beam splitter mirror, converging lens, photodetector, attenuation sheet, piezoelectric ceramics with mirror, signal generator, voltage amplifier and spectrum analyzer or oscilloscope; the helium-neon laser, polarizing beam splitter, The polarizer, the first beam splitter, the first reflector, the second reflector, the third reflector, the second beam splitter, the converging lens, and the photodetector are sequentially connected in an optical path; the first beam splitter, the attenuation plate The piezoelectric ceramics with reflective mirrors are sequentially connected to the optical path; the signal generator, the voltage amplifier, and the piezoelectric ceramics with reflective mirrors are sequentially connected to the circuit; the piezoelectric ceramics with reflective mirrors are connected to the second beam splitter optical path The photodetector is connected with a spectrum analyzer or an oscilloscope circuit; wherein, the helium-neon laser emits laser light, enters a polarizing beam splitter and a polarizer to modulate light intensity, enters a beam splitter to split beams, and obtains two beams, and one beam passes through The first reflector, the second reflector and the third reflector enter the beam splitter; the other beam enters the attenuation plate to attenuate, enter the piezoelectric ceramics to adjust the optical path of the beam, and reflect into the beam splitter; The two beams of light from the beam splitter are combined again, converged by the converging lens, and then converted into electrical signals by the photodetector, and then enter the spectrum analyzer or oscilloscope for signal analysis; the signal generator sends out a signal, which is converted to Piezoelectric ceramics are used for regulation; it is used to simulate the influence of gravitational waves on a path of light.

The electrical signal generated by the signal generator has any amplitude and any frequency, and is biased when amplified by the voltage amplifier to ensure that the signal input to the piezoelectric ceramic is positive; the piezoelectric ceramic drives the reflector to produce a certain displacement, so that one of the arm produces a phase change.

The input and output energy of the invention is conserved, and the process of interference beam splitting and beam combining is a passive device and a linear laser M-Z interferometer. Use an oscilloscope to observe the interference contrast or use a spectrum analyzer to detect and analyze the output signal and noise of the interferometer.

The small quantum interferometer of the present invention can be used to observe the relative phase shift changes produced by different paths and media after the light beam emitted from a single light source is split into two collimated light beams. Obviously different from the Michelson interferometer, the two split beams of this quantum interferometer will only travel through the two strictly separated paths of the interferometer once. Compared with the Michelson interferometer, the interference optical path does not overlap, and it is flexible and changeable. Etc.

Further, the periodic signal output by the signal source is input into piezoelectric ceramics to control the reflector in one optical path of the quantum interferometer, thereby changing the optical path difference between the two beams of the interferometer. Similar to LIGO’s principle of measuring gravitational waves: one beam of laser light is transformed into two laser beams through a beam splitter, and the distance between the two arms is increased through two 4-kilometer resonators, and then the two beams of light are combined into one beam through a beam splitter, and finally measurement; when the arms are equal in length, the two beams interfere destructively, but if a gravitational wave passes through the detector at that moment, it distorts time and space, causing the relative lengths of the two tubes to vary minutely. , thus changing the way the two beams interfere, which eventually leads to a change in the signal on the photodetector. Since the gravitational wave source is quite far from the earth observation point, and the gravitational wave signal is small, it is necessary to supplement with F-P cavity, vibration isolation and other technologies to further improve the sensitivity of the system; and the optical path difference caused by piezoelectric ceramics is large enough to make the In a fundamental physics laboratory environment, the measurement of gravitational waves is simulated with the help of a small quantum interferometer.

Further, use the electro-optic modulator to give a certain controllable signal, such as a signal with a known size of one micron, observe the spectrum analyzer, and know the signal-to-noise ratio; thus obtain the displacement measurement limit of the system, that is, it is possible to measure the signal minimum signal-to-noise ratio. When the signal size is equal to the noise size, it is possible to measure the signal; if the signal is smaller than the noise, the system cannot measure the signal.

The beneficial effects of the invention are: based on the principle of gravitational wave measurement, a small and portable quantum interferometer is built by using piezoelectric ceramics to change the optical path difference of two beams of the quantum interferometer. Demonstrating the application of the basic principles of quantum mechanics in precision measurements, such as the measurement of gravitational waves, can further analyze the limitation of vacuum noise on measurement accuracy. Realize and deepen students' understanding of the basic principles of quantum mechanics, and realize the differences between quantum mechanics and classical physics. Through the application experiment of gravitational wave measurement, students' interest in the field of quantum mechanics will be stimulated. Up to now, experimental teaching instruments involving interferometers are usually used to understand the interference phenomenon of the light field and test the light interference formula by observing the spatial interference fringes and counting the number of fringes. Few of them involve quantum measurement technology.

The small-scale quantum interferometer using piezoelectric ceramics to simulate gravitational waves of the present invention uses lasers, optical elements and measuring instruments that are commonly used in laboratories. The technology is mature and has been commercially produced. The invention is simple and easy to implement, has the characteristics of small volume and low cost, and is a new type of small quantum interferometer.

Description of drawings

Fig. 1 is a schematic diagram of the basic principles of the present invention;

Fig. 2 is a structural representation of the present invention;

Fig. 3 is the embodiment of the present invention, the signal source amplitude is 2V, the frequency is the triangular wave signal of 5Hz, after being amplified by the amplifier, it is input to the piezoelectric ceramic as a driving signal, and the incident light intensity is 250μW, and the spectrum analyzer waveform obtained picture;

Fig. 4 is the embodiment of the present invention, under the condition of different incident light intensities, the linear relationship curve between the spectrogram fitting coefficient |α| ² and the incident light intensity.

Detailed ways

As shown in Figure 1, the schematic diagram of the basic principle includes: two 50:50 BS beam splitters 11 and 13, a mirror 121 and a piezoelectric ceramic 122 with a mirror, photodetectors 141 and 142 and a spectrometer 15.

As shown in Figure 1, a beam of laser light (called beam- ), after passing through a 50:50 beam splitter 11, it is divided into two to obtain beam two and beam three Then each propagates in different paths, and is reflected by the reflector 121 and the piezoelectric ceramic 122 with the reflector, then spatially merges the beam on the second beam splitter 13, and finally outputs from the two output ports, that is, the interference output and interference output It is detected by two photodiodes 141 and 142 and subtracted, that is, the balanced zero-beat detection method in quantum optics is adopted, and the subtracted signal is amplified and input to the spectrum analyzer 15 for analysis.

a laser beam After the first BS beam splitter 11 is divided into two, the beam two and beam three The light intensities are:

in, is the quantum operator of the electric field intensity of beam A, is a quantum operator The complex conjugate operator of . is the quantum operator of the electric field intensity of beam B, is a quantum operator The complex conjugate operator of . while beam two and beam three The expressions are respectively:

In the above formula is the vacuum field energy operator incident on the beam splitter, is the quantum operator of the laser electric field intensity emitted by the laser. The phase factor e ^iθ is brought about by the vibration displacement of the piezoelectric ceramic 122 . After passing through the second BS beam splitter 13, the interference output and interference output They are:

here and Beam and beam The quantum operator of the electric field strength of . Therefore, the interference output The strength of is:

here quantum operator and The complex conjugate operator; i is a complex number, (i square = negative 1).

After the signal C is directly detected by the photodetector 141, it is analyzed by the spectrum analyzer 15 to obtain the noise size under each phase, and the final output variance of the spectrum analyzer 15 is:

Example

As shown in FIG. 2 , the laser light source used in this embodiment is a continuous 632.8nm laser.

As shown in Figure 2, after the laser light source 21 is collimated, it is divided into two paths by the 50:50 beam splitter 24, and one path passes through a set of mirrors 251, 261, 271, and then enters another 50:50 beam splitter 28 for transmission; The other path is reflected by the piezoelectric ceramic 262 with a mirror, and reflected again in the beam splitter 28 . The optical paths of the two beams are equal, and they are merged on the outgoing beam splitter 28; they are then focused on the detection surface of the photodetector 210, and the focal length of the focusing lens 29 is 100 mm. One set of reflectors includes three reflectors 251, 261 and 271 placed at an angle of 45° to the optical path, and the three reflectors can be easily adjusted to make the two beams combine perfectly.

As shown in FIG. 2 , a polarization beam splitter 22 and a polarizer 23 are used to form a light attenuation system before the interferometer system, which can be used to change the light intensity of the incident laser light. By using the adjustable attenuation sheet 252 in one optical path after beam splitting, the light intensity of the two split optical paths can be made approximately the same, further improving the interference contrast.

As shown in Figure 3, the periodic expansion and contraction of the piezoelectric ceramic 262 simulates the phase θ. If the input signal is a triangular wave, then within half a cycle, the phase θ provided by the piezoelectric ceramic 262 satisfies:

θ=kt (7)

The k value is a proportional coefficient, which is proportional to the amplitude of the triangular wave and inversely proportional to the period of the triangular wave. Bring the above formula into the variance Available:

This formula is the relationship between the signal detected on the spectrum analyzer and the time in half a cycle. In this embodiment, the signal generator 211 generates a triangular wave signal with an amplitude of 2V and a frequency of 5Hz, which is amplified by the amplifier 272 and then input to the piezoelectric ceramic 262 as a driving signal. The piezoelectric ceramic 262 provides a small optical path difference in the beam splitting branch to simulate small changes such as gravitational waves. The triangular wave signal causes the optical path difference between the two paths of the interferometer to change linearly and reciprocally. Although the movement of the fringes in the interference pattern generated after beam combining cannot be directly observed, through the photodetector 210, the oscilloscope 212 and the spectrum analyzer 213, the sinusoidal form of the signal curve.

As shown in Figure 4, in the embodiment of the present invention, the total incident light intensity is changed, and 7 data points are selected in the interval of 100-250 μW incident light intensity, and the corresponding waveform diagram is obtained. ^The sine function fitting coefficient |α| The light intensity satisfies a good linear relationship.

The optimization scheme of the present invention also includes the following aspects:

The invention is applicable to various laser light sources, and has no special requirements on wavelength, repetition frequency and pulse width. Since the light intensity of the incident interference system can significantly improve the amplification signal-to-noise ratio of tiny signals, it is easier to observe a good sinusoidal signal on a spectrometer for a laser source with a higher power. If the laser light source is changed to a light source of other wavelengths, it is only necessary to change the reflector, attenuation sheet, photodetector, etc.

The piezoelectric ceramics of the present invention for simulating gravitational wave signals can also work under driving signals of other frequencies, amplitudes, and waveforms (such as sine waves). That is to say, regardless of the frequency and magnitude of the gravitational wave signal, the system can measure any signal within the measurement limit range.

Using the electro-optic modulator to give a certain controllable signal, if the signal size is known, such as one micron, observe the spectrum analyzer to know the signal-to-noise ratio; thus the displacement measurement limit of the system can be obtained. The displacement measurement limit is one of the important characterization parameters of the system measurement accuracy. When the signal size is equal to the noise size, the signal can be measured; if the signal is smaller than the noise, the system cannot measure the signal.

It can be seen from the above analysis that the present invention builds a small quantum interferometer based on the principle of gravitational wave measurement. The construction of this experimental instrument can be realized in the basic physics laboratory, and the quantum mechanics experiment is incorporated into the undergraduate experimental course system , can further carry out more quantum precision measurement explorations, and the present invention has high in-depth research and application value.

Claims (3)

1. The small quantum interferometer for simulating gravitational waves by using piezoceramics is characterized by comprising a helium-neon laser (21), a polarization beam splitter (22), a polarizing plate (23), a first beam splitter (24), a first reflecting mirror (251), a second reflecting mirror (261), a third reflecting mirror (271), a second beam splitter (28), a converging lens (29), a photoelectric detector (210), an attenuation sheet (252), piezoceramics (262) with reflecting mirrors, a signal generator (211), a voltage amplifier (272) and a frequency spectrograph (213) or an oscilloscope (212), wherein the helium-neon laser (21), the polarization beam splitter (22), the polarizing plate (23), the first beam splitter (24), the first reflecting mirror (251), the second reflecting mirror (261), the third reflecting mirror (271), the second beam splitter (28), the converging lens (29), The photoelectric detectors (210) are connected in turn by optical paths; the first beam splitter (24), the attenuation sheet (252) and the piezoelectric ceramic (262) with the reflecting mirror are connected in sequence through an optical path; the signal generator (211), the voltage amplifier (272) and the piezoelectric ceramics (262) with the reflector are sequentially connected by a circuit; the piezoelectric ceramic (262) with the reflecting mirror is connected with the optical path of the second beam splitter (28); the photoelectric detector (210) is in circuit connection with the frequency spectrograph (213) or the oscilloscope (212);

continuous laser emitted by the helium-neon laser (21) enters a polarization beam splitter (22) and a polaroid (23) to modulate light intensity, and enters a beam splitter (24) for splitting to obtain two beams, and one beam enters a beam splitter (28) through a first reflector (251), a second reflector (261) and a third reflector (271); the other beam of light enters an attenuation sheet (252) for attenuation, enters piezoelectric ceramics (262) with a reflecting mirror to adjust the optical path length of the beam of light, and is reflected to enter a beam splitter (28); the two beams of light entering the beam splitter (28) are combined again, converged by a converging lens (29), then converted into electric signals by a photoelectric detector (210), and enter a frequency spectrograph (213) or an oscilloscope (212) for signal analysis; the signal generator (211) sends out signals, and the signals are regulated and controlled by the piezoelectric ceramics (262) after passing through the voltage amplifier (272) so as to simulate the influence of gravitational waves on one optical path.

2. The small-scale quantum interferometer using piezoceramic simulation gravitational wave of claim 1, wherein the electrical signal generated by the signal generator (211) is of any amplitude and any frequency, and is biased when amplified by the voltage amplifier (272) to ensure that the signal input to the piezoceramic (262) is positive; the piezoelectric ceramic (262) drives the reflector to generate a certain displacement, thereby generating phase change on one arm.

3. The compact quantum interferometer using piezoceramics for simulating gravitational waves according to claim 1, characterized in that the interference contrast is observed with an oscilloscope (212); the interferometer output signal and noise are detected and analyzed by a spectrum analyzer (213).