Graphene harmonic oscillator, and phonon exciter and method based on graphene harmonic oscillator
Technical Field
The invention relates to the technical fields of preparation of two-dimensional material harmonic oscillators, cavity optomechanics, phonon information devices, precision measurement and the like, in particular to a method and a device for realizing a phonon exciter by utilizing a graphene harmonic oscillator.
Background
In recent years, the rapidly developed laser technology makes great contribution in the field of optical quantum information, and the cognition of people on quantum physics is greatly promoted. Phonons (lattice vibrational energy quanta) have several unique advantages over photons: the phonon has shorter wavelength under the same frequency, namely the phonon is more localized, and compared with microwave and photon, the transmission speed on a chip is slower, so that the phonon is easier to control and can realize higher resolution in the application of imaging, precision machining and the like; secondly, the coherence time of the phonons is longer, and the phonons have significance for classical coherent information transmission and processing and quantum information processing; and thirdly, in a solid system, phonons are strongly coupled with a plurality of physical systems (such as electrons), and the method can be used in the fields of expansion, control and the like of a composite quantum system. Therefore, there is a great interest in the application of phonon exciters in both classical and quantum information processing fields. However, the phonon lasing phenomenon based on the laser principle has been difficult to effectively push practical application of phonon lasers. With the rapid development of micro-nano electromechanical systems in recent years, an optical electromechanical system composed of a mechanical vibrator and a laser becomes an effective means for searching phonon lasers. The mechanical oscillator prepared based on the graphene has the advantages of small mass, high frequency, large quality factor and the like, and the advantages are favorable for basic and application research of phonon lasing by using the mechanical oscillator. The graphene mechanical oscillator and the micropores on the chip form an optical resonant cavity, when laser enters the optical resonant cavity, the light radiation pressure generated by blue detuned laser on the graphene influences the phonon dissipation of the harmonic oscillator along with the increase of laser power, so that the phonon dissipation degree is gradually reduced until zero. And then, phonons in the graphene mechanical vibrator can generate a stimulated radiation process similar to photons in laser, and the phonon number shows an obvious threshold effect along with the increase of the pump laser power, namely, a phonon lasing phenomenon is generated. Along with the vibration of graphene mechanical harmonic, the intensity of laser light reflected by the optical resonant cavity is synchronously modulated in a high-frequency state, the laser light is converted into an electric signal through a photoelectric detector and then processed by a spectrum analyzer, and then the resonant mode of the mechanical vibrator can be extracted, and the phenomenon of phonon lasing is explored.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a graphene harmonic oscillator, and a phonon exciter and an operating method based on the graphene harmonic oscillator
In order to achieve the purpose, the technical scheme of the invention is as follows:
the utility model provides a graphite alkene harmonic oscillator, includes the substrate chip, the substrate chip prepare through the sculpture silicon wafer, the substrate chip includes the silicon layer of bottom, there is the silicon dioxide layer at both ends about the silicon layer upper surface, is equipped with the recess in the middle of the silicon dioxide layer, covers the graphite alkene film directly over the recess, the graphite alkene film obtains through the cubic graphite of mechanical stripping, the both ends of graphite alkene film cover part silicon dioxide layer, constitute an optical resonator between substrate chip and the graphite alkene film.
As a preferable mode, when laser is incident to the optical resonant cavity, the light radiation pressure generated by the blue detuned laser on the graphene is increased along with the increase of the laser power, so that the phonon dissipation in the graphene harmonic oscillator is reduced until zero; and then, phonons in the graphene harmonic oscillator show a photon stimulated radiation process similar to that of laser, and the number of the phonons shows an obvious threshold effect along with the increase of the power of the pump laser, namely, a phonon lasing phenomenon occurs, so that the phonon lasing device is obtained.
In order to achieve the above object, the present invention further provides a phonon exciter based on a graphene harmonic oscillator, including the graphene harmonic oscillator 8, which includes: along the optical path direction, the device sequentially comprises a driving laser source 1, a first optical fiber coupler 21 aligned with the center of the driving laser source 1, a second optical fiber coupler 22 connected with the first optical fiber coupler 21 through optical fibers, a first half wave plate 31 aligned with the center of the second optical fiber coupler 22, a first high-reflection mirror 41 aligned with the center of the first half wave plate 31 and forming an included angle of 45 degrees with the first half wave plate 31, a first polarization beam splitter prism 51 aligned with the emergent light of the first high-reflection mirror 41, a second half wave plate 32 aligned with the emergent light of the first polarization beam splitter prism 51, a second polarization beam splitter prism 52 aligned with the emergent light of the second half wave plate 32, a quarter wave plate 6 aligned with the emergent light of the second polarization beam splitter 52, an objective lens 7 aligned with the center of the quarter wave plate 6, a graphene harmonic oscillator 8 aligned with the center of the objective lens 7, and the graphene harmonic oscillator 8 which are fixed on a nanometer electric displacement table 9, the light source device comprises a beam splitter 10 aligned with the emergent light of a second polarization beam splitter 52, a part of emergent light of the beam splitter 10 and the center of a CCD camera 11 are aligned, the other part of emergent light and the center of a second high-reflection mirror 42 are aligned, a filter plate 12 aligned with the emergent light of the second high-reflection mirror 42, a photoelectric detector 13 aligned with the center of the filter plate 12, and a spectrum analyzer 14 electrically connected with the photoelectric detector 13, wherein an illumination light source 15 is arranged on one side, away from a second half-wave plate 32, of a first polarization beam splitter 51, and the illumination light source 15 is aligned with the emergent light of the first polarization beam splitter 51.
As a preferred mode, the pump laser of the driving laser source 1 is simultaneously used for measuring the vibration mode of the harmonic oscillator by laser interference, the laser is focused and irradiated on the surface of the graphene harmonic oscillator 8 through an objective lens in the form of free space light, an optical resonant cavity is formed between the graphene harmonic oscillator 8 and the silicon substrate chip, the light intensity of the laser reflected by the optical resonant cavity is synchronously modulated along with the vibration of the graphene harmonic oscillator 8, the laser is converted into an electric signal through a photoelectric detector, and the electric signal is processed by a spectrum analyzer to extract the resonance mode of the graphene harmonic oscillator.
Preferably, the beam splitter 10 is a 10:90 beam splitter.
Preferably, the nano electric displacement table 9 is a three-axis displacement table, and moves along a three-dimensional direction in space, and initially, the center of the objective lens 7 and the center of the graphene resonator 8 are aligned through the movement of the displacement table.
Preferably, the driving laser source is a 633nm single-mode continuous light laser.
Preferably, the white LED is used as an illumination light source for CCD imaging;
in order to achieve the above object, the present invention further provides a working method of the phonon exciter based on the graphene harmonic oscillator, including: the driving laser source 1 emits laser, the laser is collimated and collected by the first optical fiber coupler 21 and is re-collimated by the second optical fiber coupler 22, the laser enters the first half-wave plate 31 in parallel, the emergent light of the first half-wave plate 31 is changed in polarization by the half-wave plate, the light path direction is changed by the first high reflecting mirror 41, the laser is made to vertically enter the first polarization beam splitter prism 51, the first polarization beam splitter prism 51 reflects the laser with vertical polarization direction, the emergent light of the first polarization beam splitter prism 51 vertically passes through the center of the second half-wave plate 32, the laser with polarization state changed by the second half-wave plate 32 enters the second polarization beam splitter prism 52, the laser penetrates the second polarization beam splitter 52 and is changed in polarization state by the quarter-wave plate 6, the emergent light of the quarter-wave plate 6 is focused by the objective lens 7 to irradiate the graphene resonator 8 vertically fixed on the nano electric displacement table 9, and the laser reflected by the graphene resonator 8 is collected by the objective lens 7, After the polarization state is changed again by the quarter-wave plate 6, the laser passes through the second polarization beam splitter prism 52 for the second time, the second polarization beam splitter prism 52 reflects the polarized laser, the laser enters the beam splitter 10, the beam splitter 10 splits the laser beam, one beam enters the CCD camera for imaging, the other beam changes the direction of the light path through the second high-reflection mirror 42, the laser is filtered by the filter 12, the laser with the same wavelength as the driving laser source 1 is ensured to enter the photoelectric detector 13, the photoelectric detector 13 converts the received optical signal into an electric signal, the electric signal extracts the resonance mode of the graphene harmonic oscillator 8 through the spectrum analyzer 14, and all the half-wave plates and the quarter-wave plates are also used for adjusting the power of the laser of each part in the light path; the nanometer electric displacement platform 9 is used for adjusting the position of the graphene harmonic oscillator, so that laser spots can be accurately focused on the target position of the graphene harmonic oscillator.
Preferably, the operating method further comprises: focusing a driving continuous light laser source with the wavelength of 633nm on an optical resonant cavity, dividing a laser beam reflected by a graphene harmonic oscillator 8 into two beams by using a 90:10 beam splitter, wherein one beam is used for imaging, the other beam is converted into an electric signal by a photoelectric detector, and extracting a resonant mode of the graphene mechanical oscillator by a spectrum analyzer after spectrum analysis to obtain frequency domain information of harmonic oscillator vibration; with the increase of laser power, phonons have obvious threshold effect and are subjected to lasing to form a phonon maser; the normal operation of the device is ensured, and after the mechanical vibration mode of the graphene harmonic oscillator 8 can be observed, the half-wave plate and the quarter-wave plate in the optical path are rotated to change the laser power focused on the graphene film; on the premise of not damaging the graphene film, the optical power of the incident laser is increased, and the realization condition of the phonon exciter is judged according to the amplitude change of the vibration mode in the frequency spectrum information. This amplitude variation is based on fig. 4, and if an amplitude variation similar to that in fig. 4 occurs, it can be judged that the phonon exciter is implemented.
The invention has the beneficial effects that: compared with the known phonon exciter device, the phonon exciter disclosed by the invention has the advantages of simple preparation process, low technical difficulty, easiness in chip integration and batch preparation and the like. The stable and controllable phonon exciter has important basic research significance and wide application prospect in the fields of developing acoustic quantum information devices, realizing information interaction among different quantum information systems, precision measurement and the like.
Drawings
Fig. 1 is a schematic diagram of an apparatus of a phonon exciter based on a graphene harmonic oscillator according to the present invention.
Fig. 2 is a schematic diagram of the measurement principle of the graphene harmonic oscillator laser pumping drive of the present invention.
Fig. 3 is a frequency domain display of a graphene harmonic oscillator photoreoscope, an electron microscope image, and a resonance mode of the present invention. The graphene harmonic oscillator is characterized by comprising a suspended graphene harmonic oscillator photo mirror diagram. (b) Electron microscopy of suspended graphene harmonic oscillator. (c) Suspended graphene harmonic oscillator measurement spectrogram.
FIG. 4 is a graph showing the variation trend of resonant mode information under different incident light powers. Wherein (a) is a waterfall plot of a certain vibration mode change under different incident light powers; the graph (b) shows the peak variation of a certain vibration mode under different incident light powers.
Wherein, 1 is the driving laser source, 21 is the first fiber coupler, 22 is the second fiber coupler, 31 is first half-wave plate, 32 is the second half-wave plate, 41 is first high reflection mirror, 42 is the second high reflection mirror, 51 is first polarization beam splitting prism, 52 is the second polarization beam splitting prism, 6 is quarter-wave plate, 7 is objective, 8 is the graphite alkene harmonic oscillator, 9 is the electronic displacement platform of nanometer, 10 is the beam splitter, 11 is the CCD camera, 12 is the filter, 13 photoelectric detector, 14 is the spectral analyser, 15 is illumination light source.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
The embodiment provides a graphene harmonic oscillator, which comprises a substrate chip, wherein the substrate chip is prepared by etching a silicon wafer, the substrate chip comprises a silicon layer at the bottom, silicon dioxide layers are arranged at the left end and the right end of the upper surface of the silicon layer, a groove is formed in the middle of the silicon dioxide layer, a graphene film covers the groove, the graphene film is obtained by mechanically stripping blocky graphite, the two ends of the graphene film cover the silicon dioxide layers, and an optical resonant cavity is formed between the substrate chip and the graphene film.
When laser is incident to the optical resonant cavity, the light radiation pressure generated on the graphene by the blue detuned laser is increased along with the increase of the laser power, so that the phonon dissipation in the graphene harmonic oscillator is reduced until the phonon dissipation is zero; and then, phonons in the graphene harmonic oscillator show a photon stimulated radiation process similar to that of laser, and the number of the phonons shows an obvious threshold effect along with the increase of the power of the pump laser, namely, a phonon lasing phenomenon occurs, so that the phonon lasing device is obtained.
As shown in fig. 1, this embodiment further provides a phonon exciter based on a graphene harmonic oscillator, including the graphene harmonic oscillator 8, which is: along the optical path direction, the device sequentially comprises a driving laser source 1, a first optical fiber coupler 21 aligned with the center of the driving laser source 1, a second optical fiber coupler 22 connected with the first optical fiber coupler 21 through optical fibers, a first half wave plate 31 aligned with the center of the second optical fiber coupler 22, a first high-reflection mirror 41 aligned with the center of the first half wave plate 31 and forming an included angle of 45 degrees with the first half wave plate 31, a first polarization beam splitter prism 51 aligned with the emergent light of the first high-reflection mirror 41, a second half wave plate 32 aligned with the emergent light of the first polarization beam splitter prism 51, a second polarization beam splitter prism 52 aligned with the emergent light of the second half wave plate 32, a quarter wave plate 6 aligned with the emergent light of the second polarization beam splitter 52, an objective lens 7 aligned with the center of the quarter wave plate 6, a graphene harmonic oscillator 8 aligned with the center of the objective lens 7, and the graphene harmonic oscillator 8 which are fixed on a nanometer electric displacement table 9, the light source device comprises a beam splitter 10 aligned with the emergent light of a second polarization beam splitter 52, a part of emergent light of the beam splitter 10 and the center of a CCD camera 11 are aligned, the other part of emergent light and the center of a second high-reflection mirror 42 are aligned, a filter plate 12 aligned with the emergent light of the second high-reflection mirror 42, a photoelectric detector 13 aligned with the center of the filter plate 12, and a spectrum analyzer 14 electrically connected with the photoelectric detector 13, wherein an illumination light source 15 is arranged on one side, away from a second half-wave plate 32, of a first polarization beam splitter 51, and the illumination light source 15 is aligned with the emergent light of the first polarization beam splitter 51.
Specifically, in this embodiment, the beam splitter 10 is a 10:90 beam splitter. The nanometer electric displacement table 9 is a three-axis displacement table and moves along the three-dimensional direction of the space, and a plurality of three-dimensional displacement tables appear in the prior art and can be used in the invention; the objective lens 7 and the graphene resonator 8 are initially centered by movement of the translation stage. The driving laser source adopts a 633nm single-mode continuous light laser. A 633nm single mode fiber and a fiber collimator to couple the laser into the free space optical path. The laser power of the laser was 35 mW. The white LED is used as an illuminating light source for CCD imaging;
the half-wave plate in the light path is fixed on the rotary mounting seat, the wave plate is rotated, and the laser intensity of the subsequent light path of the wave plate can be conveniently adjusted by utilizing the polarization characteristic of laser.
The high-reflection mirror can conveniently change the direction of a light path so as to reduce the occupied area of the whole system.
The first polarization beam splitter prism 51 changes the direction of the optical path by its polarization beam splitting characteristic and allows the white auxiliary illumination light source to be easily coupled into the optical path.
The second polarization beam splitter prism 52 and the quarter wave plate 6 form an optical isolator, so that the laser with polarization characteristics cannot return along an incident light path, and the imaging and the photoelectric detection are facilitated to extract the resonance mode of the graphene harmonic oscillator.
Laser is focused on the graphene harmonic oscillator 8 through an objective lens to form a light spot with the size of 1um, wherein the objective lens with the magnification of 100 times, the working distance of 0.9mm and the Numerical Aperture (NA) of 0.8 is selected.
The graphene harmonic oscillator 8 is vertically fixed on the electric nanometer displacement table, as shown in fig. 1. The graphene harmonic oscillator 8 is formed by suspending a graphene film in a circular hole of a 5um silicon substrate chip.
The electric nanometer displacement platform is used for accurately moving a load sample, the step pitch is 100nm, and the movable range is 5mm, so that the accurate focusing of a laser spot to a target position on the graphene mechanical vibrator is ensured.
After the light beam passes through the objective lens for the first time, the light beam reflected by the surface of the graphene harmonic oscillator interferes with the light beam reflected by the surface of the silicon substrate chip below the graphene, and the focused laser generates radiation pressure on the graphene, as shown in fig. 2. The interference beam passes through the objective lens again, changes the optical path direction by the polarization beam splitter prism, and irradiates on the 90:10 optical beam splitter.
The optical beam splitter of 90:10 divides the laser beam reflected by the optical resonant cavity into two beams, and one beam is used for imaging; the other beam is used for a photodetector, which converts the optical signal into an electrical signal. A free-space photodetector with a responsivity of 0.3A/W and a coverage of 633nm was selected here.
The spectrum analyzer processes the electrical signals to obtain vibration information of each mode of the graphene harmonic oscillator, as shown in fig. 3, (a) diagram, (b) diagram is a schematic diagram of a test sample optical mirror and an electron microscope, and (c) diagram is a measurement spectrogram of the suspended graphene harmonic oscillator. Fig. 3(c) shows different ranges of vibration information due to the selection of the spectrum range, which is only an example, and the appropriate spectrum range is selected according to the specific experimental requirements. If no similar vibration information is available, it should be checked: 1. whether the preparation of the graphene harmonic oscillator is successful or not; 2. whether the laser spot is shot at the correct position on the graphene harmonic oscillator or not; 3. whether the system noise overwhelms the resonant mode information.
Adjusting a half-wave plate and a quarter-wave plate in a light path to enable the laser power focused on the suspended graphene to be stably changed from 300uW to 6.3mW, dividing the power at proper power intervals in the process of power change, repeatedly recording frequency spectrum data and image information under each power condition, integrating and drawing multiple groups of result data similar to the result data shown in the figure 3, and observing the change of a resonance mode in the frequency spectrum. As shown in fig. 4, when the incident light power is increased, the resonance mode of the graphene harmonic oscillator changes: obvious resonance peak appears, the line width of the resonance peak is gradually reduced, and the peak value is gradually increased. In the process, the phonon dissipation is gradually reduced to zero, and the phonon shows obvious threshold effect, namely, the phenomenon of lasing of the phonon occurs.
The pump laser of the driving laser source 1 is used for laser interferometry to resonate the harmonic oscillator vibration mode at the same time, the laser irradiates the surface of the graphene harmonic oscillator 8 in the form of free space light through the focusing of an objective lens, an optical resonant cavity is formed between the graphene harmonic oscillator 8 and a silicon substrate chip, the laser light intensity reflected by the optical resonant cavity is synchronously modulated along with the vibration of the graphene harmonic oscillator 8, the laser light intensity is converted into an electric signal through a photoelectric detector, and the electric signal passes through a spectrum analyzer to extract the resonance mode of the graphene harmonic oscillator.
The embodiment also provides a working method of the phonon exciter based on the graphene harmonic oscillator, which includes: the driving laser source 1 emits laser, after collimated and collected by the first optical fiber coupler 21 and re-collimated by the second optical fiber coupler 22, the laser enters the first half-wave plate 31 in parallel, the emergent light of the first half-wave plate 31 is changed in polarization by the half-wave plate, the light path direction is changed by the first high reflecting mirror 41, the laser is made to vertically enter the first polarization beam splitter prism 51, the first polarization beam splitter prism 51 reflects the laser with the polarization direction, the emergent light of the first polarization beam splitter prism 51 vertically passes through the center of the second half-wave plate 32, the laser with the polarization state changed by the second half-wave plate 32 enters the second polarization beam splitter prism 52, at this moment, the laser is transmitted through the second polarization beam splitter prism 52 and is changed in polarization state by the quarter-wave plate 6, the emergent light of the quarter-wave plate 6 is focused into 1 μm light spot by the objective lens 7, and irradiates the graphene resonator 8 vertically fixed on the nano electric displacement, the laser reflected by the graphene harmonic oscillator 8 is collected by the objective lens 7, the polarization state of the laser is changed by the quarter-wave plate 6 again, the laser passes through the second polarization beam splitter prism 52 for the second time, the second polarization beam splitter prism 52 reflects the polarized laser, the laser enters the beam splitter 10, the beam splitter 10 splits the laser beam, one beam enters the CCD camera for imaging, the other beam changes the direction of the light path through the second high-reflection mirror 42, the laser is filtered by the filter 12, the laser with the same wavelength as the driving laser source 1 is ensured to enter the photoelectric detector 13, the photoelectric detector 13 converts the received optical signal into an electric signal, the electric signal is used for extracting the resonance mode of the graphene harmonic oscillator 8 through the spectrum analyzer 14, and all the half-wave plates and the quarter-wave plate are also used for adjusting the power of the laser in each part of the light; the nanometer electric displacement platform 9 is used for adjusting the position of the graphene harmonic oscillator, so that laser spots can be accurately focused on the target position of the graphene harmonic oscillator.
Further, a driving continuous light laser source with the wavelength of 633nm is focused on the optical resonant cavity, a 90:10 beam splitter is used for splitting a laser beam reflected by the graphene harmonic oscillator 8 into two beams, one beam is used for imaging, the other beam is converted into an electric signal by a photoelectric detector, and a frequency spectrum analyzer is used for extracting the resonance mode of the graphene mechanical oscillator after the frequency spectrum analysis to obtain frequency domain information of harmonic oscillator vibration; with the increase of laser power, phonons have obvious threshold effect and are subjected to lasing to form a phonon maser; the normal operation of the device is ensured, and after the mechanical vibration mode of the graphene harmonic oscillator 8 can be observed, the half-wave plate and the quarter-wave plate in the optical path are rotated to change the laser power focused on the graphene film; on the premise of not damaging the graphene film, the optical power of the incident laser is increased, and the realization condition of the phonon exciter is judged according to the amplitude change of the vibration mode in the frequency spectrum information.
Other harmonic oscillator embodiments of different two-dimensional materials can achieve phonon lasing.
The graphene harmonic oscillator has the characteristics of simple material preparation, small mass, stable physical performance and high quality factor. The graphene material is a layered graphene sample obtained by mechanically exfoliating bulk graphite. And transferring the few-layer graphene sample obtained by mechanical stripping to a silicon substrate chip with a microstructure by using a two-dimensional material transfer platform to suspend, so as to obtain the required graphene harmonic oscillator. In addition, other two-dimensional materials are transferred, e.g. MoS2、WSe2The prepared harmonic oscillator can also be coupled with laser and a microcircuit to prepare an optical machine and a micro electro mechanical system, and has wide research and application prospects.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.