CN113568242A - Photon frequency conversion device - Google Patents
Photon frequency conversion device Download PDFInfo
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- CN113568242A CN113568242A CN202110850006.8A CN202110850006A CN113568242A CN 113568242 A CN113568242 A CN 113568242A CN 202110850006 A CN202110850006 A CN 202110850006A CN 113568242 A CN113568242 A CN 113568242A
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
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Abstract
The invention is suitable for the technical field of nonlinear photophysics and quantum optics, and provides a photon frequency conversion device, which comprises: the first laser is used for outputting first pump light; the beam processing module is used for generating a photon pair according to the first pump light and separating the photon pair into first horizontal polarized light and first vertical polarized light; the orbit angular momentum loading module is used for loading orbit angular momentum information on the first vertical polarized light to obtain an orbit angular momentum light beam; and the frequency conversion module is arranged at the output end of the orbital angular momentum loading module and is used for converting the light frequency of the orbital angular momentum light beam. According to the technical scheme, the orbit angular momentum loading module and the frequency conversion module are arranged, the orbit angular momentum information can be loaded on the first vertical polarized light output by the light beam processing module, the light frequency of the light beam carrying the orbit angular momentum information is converted through the frequency conversion module, and therefore the quantum systems with two different working wavelengths can be connected through the device provided by the scheme.
Description
Technical Field
The invention belongs to the technical field of nonlinear photophysics and quantum optics, and particularly relates to a photon frequency conversion device.
Background
Photons are very important information carriers for transferring quantum states between remote physical systems, such as atomic systems, ionic and solid state systems, acting as quantum memories and quantum information processors. In quantum communication, due to the inherent infinite dimensionality of orbital angular momentum, photons encoded in an orbital angular momentum space can significantly improve the information channel capacity of quantum key distribution. Photons in the telecommunications band or free space communication window are critical to building long-distance high-capacity quantum communication networks. Light beams carrying orbital angular momentum have attracted great research interest in the fields of classical optics and quantum optics.
At present, photon and orbital angular momentum of quantum memories has been realized recently, but most quantum memories operate in the visible wavelength range, and most quantum memories for quantum repeaters operate at different wavelengths, and no connection can be established between different quantum systems operating at different wavelengths.
Disclosure of Invention
An object of the embodiments of the present invention is to provide a photon frequency conversion device, which aims to solve the technical problem that in the prior art, no connection can be established between different quantum systems operating at different wavelengths.
The embodiment of the present invention is realized in such a way that the photon frequency conversion device includes:
a first laser for outputting a first pump light;
the beam processing module is arranged at the output end of the first laser and used for generating a photon pair according to the first pump light and separating the photon pair into first horizontal polarized light and first vertical polarized light;
the orbital angular momentum loading module is arranged at the output end of the first vertical polarized light of the light beam processing module and is used for loading orbital angular momentum information on the first vertical polarized light to obtain an orbital angular momentum light beam; and
and the frequency conversion module is arranged at the output end of the orbital angular momentum loading module and is used for converting the light frequency of the orbital angular momentum light beam.
According to the photon frequency conversion device provided by the embodiment of the invention, the first laser, the beam processing module, the orbital angular momentum loading module and the frequency conversion module are arranged in the device, a photon pair can be obtained by processing the first pump light output by the first laser through the beam processing module, the photon pair is separated to obtain the first horizontal polarized light and the first vertical polarized light, then the orbital angular momentum loading module can load the upper orbital angular momentum information on the first vertical polarized light, and finally the frequency conversion module converts the light frequency of the orbital angular momentum beams carrying the orbital angular momentum information, so that the conversion of the photon frequency is realized, and further the photon frequency conversion device can be connected with two quantum systems with different working wavelengths.
Drawings
Fig. 1 is a block diagram of a photon frequency conversion device according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a light beam processing module according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an orbital angular momentum loading module according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a frequency conversion module according to an embodiment of the present invention;
fig. 5 is a block diagram of a photonic frequency conversion apparatus provided with a first measurement module according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a first measurement module according to an embodiment of the present invention;
fig. 7 is a block diagram of a photon frequency conversion device provided with a second measurement module according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a second measurement module according to an embodiment of the present invention.
In the drawings: 10. a first laser; 20. a light beam processing module; 21. a first half wave plate; 22. a first lens; 23. a first nonlinear crystal; 24. a second lens; 25. a first optical filter; 26. a first polarizing beam splitter; 30. an orbital angular momentum loading module; 311. a first fiber coupling head; 312. a second fiber coupling head; 321. a first quarter wave plate; 322. a third half-wave plate; 33. a second polarizing beam splitter; 341. a first reflector; 342. a second reflector; 343. a third reflector; 35. swirling the phase plate; 36. a second half-wave plate; 40. a frequency conversion module; 41. a second laser; 42. a collimating lens; 431. a coupling mirror; 432 a fourth mirror, 433 a first concave mirror; 434. a second concave mirror; 44. a third lens; 45. a second nonlinear crystal; 46. a second optical filter; 471. a second quarter wave plate; 472. a third polarizing beam splitter; 473. a first photodetector; 474. a second photodetector; 475. a differential amplifier; 476. a piezoelectric ceramic actuator; 50. a first measurement module; 51. a third fiber coupling head; 52. a fourth fiber coupling head; 53. a first single photon detector; 54. a second single photon detector; 55. a coincidence counter; 60. a second measurement module; 61. a charge coupled device.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Specific implementations of the present invention are described in detail below with reference to specific embodiments.
As shown in fig. 1, a block diagram of a photon frequency conversion device according to an embodiment of the present invention is provided, where the photon frequency conversion device includes:
a first laser 10 for outputting first pump light;
a beam processing module 20, disposed at an output end of the first laser 10, and configured to generate a photon pair according to the first pump light, and separate the photon pair into a first horizontally polarized light and a first vertically polarized light;
an orbital angular momentum loading module 30, disposed at an output end of the first vertically polarized light of the light beam processing module 20, and configured to load orbital angular momentum information on the first vertically polarized light to obtain an orbital angular momentum light beam; and
and the frequency conversion module 40 is arranged at the output end of the orbital angular momentum loading module 30 and is used for converting the light frequency of the orbital angular momentum light beam.
In the embodiment of the present invention, the specific structure of the first laser 10 is not limited, for example, the first laser 10 may be a semiconductor laser, the first laser 10 is a 780nm laser, the center wavelength of the output beam is 780nm, the line width is less than 1MHz, and the output power is 120 mW.
In the embodiment of the present invention, the beam processing module 20 is disposed at the output end of the first laser 10, so that the first pump light output by the first laser 10 can be incident on the beam processing module 20. The specific structure of the light beam processing module 20 is not limited in this embodiment, for example, as shown in fig. 2, the light beam processing module 20 may include a first half-wave plate 21, a first lens 22, a first nonlinear crystal 23, a second lens 24, a first optical filter 25 and a first polarization beam splitter 26 that are sequentially disposed along a light path, where an operating waveband of the first half-wave plate 21 is also 780nm, a first pump light beam output from the first laser 10 is incident to the first half-wave plate 21, and an included angle between a fast axis of the first half-wave plate 21 and a polarization direction of the incident first pump light beam is set, that is, the pump light is converted into a horizontally polarized light by rotating the wave plate 21, so as to satisfy a type II parametric down-conversion condition; the light beam emitted from the first half-wave plate 21 enters the first lens 22, the surface of the first lens 22 is coated with AR @780nm, and the focal length of the first lens 22 is f1@775nm, the light beam emitted from the first half-wave plate 21 can be focused on the center of the first nonlinear crystal 23 through the first lens 22; the first nonlinear crystal 23 may be a type ii periodically poled KTP crystal, for example, specifically, PPKTP, the size of the first nonlinear crystal 23 may be 1mm × 2mm × 10mm, the poling period thereof is 46.2 μm, the phase matching temperature is 23.6(± 0.002) ° c, and both side surfaces of the first nonlinear crystal 23 are coated with films of AR @780nm and AR @1560 nm; the first pumping light generates a pair of orthogonally polarized photons after being acted by the first nonlinear crystal 23, and the photon pair is a signal photon and an idle photon at 1560 nm; the photon pair beam emitted from the first nonlinear crystal 23 is emitted into the second lens 24, the surface of the second lens 24 is coated with an AR @1560nm film, and the focal length f of the second lens 242@1550nm, and the focal length of the first lens 22 is the same as that of the second lens 24, the second lens 24 can collimate the light beam emitted from the first nonlinear crystal 23; the light beam emitted from the second lens 24 enters a first optical filter 25, and the surface of the first optical filter 25 is coated with films of AR @1560nm and HR @780nm, so that the first optical filter 25 can filter the first pumping light of 780nm in the light beam passing through the first optical filter 25 and only retain the first pumping light passing through a first non-filter 251560nm photons generated after the linear crystal 23 acts; the light beam emitted from the first filter 25 is incident on the first pbs 26, the surface of the first pbs 26 is coated with AR @1560nm, the first pbs 26 can separate the orthogonally polarized photon pair generated by the first nonlinear crystal 23 into a first horizontally polarized light and a first vertically polarized light, the first horizontally polarized light is emitted from the Port1 along the direction of the light beam incident on the first pbs 26, and the first vertically polarized light is emitted from the Port2 after being bent by 90 ° based on the direction of the light beam incident on the first pbs 26.
In the embodiment of the present invention, the specific structure of the orbital angular momentum loading module 30 is not limited, for example, as shown in fig. 3, an input Port3 of the orbital angular momentum loading module 30 is connected to a Port2, the orbital angular momentum loading module 30 may include a coupling unit, a polarization adjusting unit, a second polarization beam splitter 33, an optical path folding unit, a vortex phase plate 35, and a second half-wave plate 36, wherein the coupling unit may couple the first vertically polarized light input from the Port3 into the free space, and the embodiment is not limited to the specific structure of the coupling unit, for example, the coupling unit may include a first fiber coupling head 311 and a second fiber coupling head 312, the input end of the first fiber coupling head 311 is connected to the Port3, the output end of the first fiber coupling head 311 is connected to the input end of the second fiber coupling head 312 through a single-mode fiber, the first fiber coupling head 311 may couple the first vertically polarized light input from the Port3 into a single-mode fiber, the working wavelength of the single-mode fiber is 1560nm, and a light beam entering the first fiber coupling head 311 is transmitted to the second fiber coupling head 312 through the single-mode fiber and then coupled to a free space through the second fiber coupling head 312; the light beam coupled to the free space through the coupling unit is incident into the polarization adjustment unit, and the specific structure of the polarization adjustment unit is not limited in this embodiment, for example, the polarization adjustment unit may include a first quarter-wave plate 321 and a third half-wave plate 322, the operating wavelengths of the first quarter-wave plate 321 and the third half-wave plate 322 are the same and are 1560nm, and the first quarter-wave plate 321 and the third half-wave plate 322 are sequentially disposed between the coupling unit and the second polarization beam splitter 33 along the optical path, and the polarization adjustment unit is configured to adjust the polarization characteristic of the light beam output by the coupling unit, so that the probability of splitting photons from the second polarization beam splitter 33 is equal; the light beam emitted from the third half-wave plate 322 enters the second polarizing beam splitter 33, the surface of the second polarizing beam splitter 33 is coated with an AR @1560nm film, the second polarizing beam splitter 33 separates the light beam entering the second polarizing beam splitter into a second horizontal polarized light and a second vertical polarized light, the second horizontal polarized light directly exits from the second polarizing beam splitter 33 along the direction of the light beam entering the second polarizing beam splitter 33, and the second vertical polarized light exits from the second polarizing beam splitter 33 after being bent by 90 degrees; the second horizontally polarized light and the second vertically polarized light are emitted from the second pbs 33, and then refracted to the vortex phase plate 35 through the optical path deflecting unit, and pass through the vortex phase plate 35 and then refracted to the second pbs 33 through the optical path deflecting unit, which is not limited in the present embodiment, for example, the optical path deflecting unit may include a first reflecting mirror 341, a second reflecting mirror 342, and a third reflecting mirror 343, the first reflecting mirror 341 and the second reflecting mirror 342 are disposed between the second horizontally polarized light emitting end of the second pbs 33 and the vortex phase plate 35, the third reflecting mirror 343 is disposed between the second vertically polarized light emitting end of the second pbs 33 and the vortex phase plate 35, and the surfaces of the first reflecting mirror 341, the second reflecting mirror 342, and the third reflecting mirror 343 are coated with films of HR @1560 nm; the second horizontal polarized light is refracted by the first reflector 341 and the second reflector 342 and then enters the vortex phase plate 35, the second horizontal polarized light is refracted by the third reflector 343 and then enters the second polarizing beam splitter 33 after being emitted from the vortex phase plate 35, the second vertical polarized light is refracted by the third reflector 343 and then enters the vortex phase plate 35, the second vertical polarized light is refracted by the second reflector 342 and the first reflector 341 and then enters the second polarizing beam splitter 33 after being emitted from the vortex phase plate 35, wherein the operating waveband of the vortex phase plate 35 is 1560nm, the light beams passing through the vortex phase plate 35 are all loaded with the upper orbital angular momentum L (L1, 2, 3 … n), the horizontal polarized light loaded with the upper orbital angular momentum is refracted back to the second polarizing beam splitter 33 and then directly transmitted out, the vertical polarized light loaded with the upper orbital angular momentum is refracted back to the second polarizing beam splitter 33 and then refracted by 90 degrees and then emitted, the second horizontally polarized light and the second vertically polarized light loaded with the orbital angular momentum exit from the second pbs 33 and reach the second half-wave plate 36, and the light beams are in a superimposed state.
In the embodiment of the present invention, the superimposed state of the superimposed light beam entering the second half-wave plate 36 depends on the polarization state of the light beam after the first quarter-wave plate 321 and the third half-wave plate 322 act, and the orbital angular momentum L of the vortex phase plate to load the light beam. For example, if the polarization state of the light beam is horizontal polarization and l is 1, the superimposed state of the light beam is expressed as: i1 >; the polarization state of the light beam is 45 ° polarization, and l is 1, the superimposed state of the light beam is written as: l 1> + |1 >; the polarization state of the light beam is horizontal polarization, and l is 2, the superimposed state of the light beam is expressed as: i2 >; the polarization state of the light beam is 45 ° polarization, and l is 2, the superimposed state of the light beam is written as: l 2> + | -2 >.
In the embodiment of the invention, the operating band of the second half-wave plate 36 is 1560nm, the polarization direction of the rotating light beam can be controlled by setting the included angle between the fast axis of the second half-wave plate 36 and the polarization direction of the incident light, and the light beam emitted from the second half-wave plate 36 passes through the Port4 to exit the orbital angular momentum loading module.
In the embodiment of the present invention, the specific structure of the frequency conversion module 40 is not limited, for example, as shown in fig. 4, the frequency conversion module 40 may include a second laser 41, a collimating lens 42, an optical cavity structure, a third lens 44, a second nonlinear crystal 45, and a second optical filter 46, wherein an input Port5 of the third lens 44 is connected to a Port4, which is coated with an AR @1560nm film, and the third lens 44 may focus a 1560nm light beam incident from the Port5 on the center of the second nonlinear crystal 45; the specific structure of the second laser 41 is not limited in this embodiment, for example, the second laser 41 is a semiconductor laser, the second laser 41 is a 795nm laser, the center wavelength of the second laser is 795nm, the line width is less than 1MHz, the output power is 100mW, and the second laser 41 is configured to output a second pump light; the collimating lens 42 is disposed at the beam output end of the second laser 41, and an AR @795nm film is coated on the surface of the collimating lens 42, and is used for collimating the second pump light and then emitting the collimated second pump light to the second nonlinear crystal 45 through the optical cavity structure.
In the embodiment of the present invention, the specific structure of the optical cavity structure is not limited, and the optical cavity structure may be used to enhance the intensity of the light beam passing through the second nonlinear crystal 45. For example, the optical cavity structure includes a coupling mirror 431, a fourth reflecting mirror 432, a first concave mirror 433, and a second concave mirror 434, wherein the second nonlinear crystal 45 is disposed between the first concave mirror 433 and the second concave mirror 434, and a light beam emitted from the collimating lens 42 enters the optical cavity structure and then passes through the coupling mirror 431, the fourth reflecting mirror 432, the first concave mirror 433, the second nonlinear crystal 45, and the second concave mirror 434 in sequence, and can be refracted to the coupling mirror 431 from the second concave mirror 434. The surface of the coupling mirror 431 is coated with a film which ensures that the transmittance at 795nm is 3%, on one hand, the coupling mirror 431 can ensure that the light beam collimated by the collimating lens 42 can smoothly pass through to the fourth reflecting mirror 432, on the other hand, the light beam with 3% intensity in the light beam reflected by the second concave mirror 434 can be ensured to be transmitted through the coupling mirror 431 and emitted, and the light beam with 97% intensity is reflected to the fourth reflecting mirror 432; the surface of the fourth reflecting mirror 432 is plated with an HR @795nm film, so that a 795nm light beam can be efficiently reflected on the surface of the fourth reflecting mirror 432; the curvature of the first concave mirror 433 is 80mm, and a film of AR @1560nm and HR @795nm is plated on the surface of the first concave mirror, so that the first concave mirror 433 can ensure that a light beam of 1560nm wave band emitted from the third lens 44 can smoothly pass through to reach the second nonlinear crystal 45; the curvature of the second concave mirror 434 is 80mm, the surface of the second concave mirror 434 is coated with a film with the wavelength of R @525nm and HR @795nm, on one hand, the second concave mirror 434 can ensure that a light beam with the wavelength of 525nm emitted from the second nonlinear crystal 45 can smoothly pass through and is emitted from a Port6 through the second optical filter 46, on the other hand, the light beam with the wavelength of 795nm reflected from the first concave mirror 433 can be effectively reflected to the coupling mirror 431 on the surface of the second concave mirror, wherein the surface of the second optical filter 46 is coated with films with the wavelength of AR @525nm, HR @795nm and HR @1560nm, the second concave mirror can be used for further filtering light beams with other wavelength bands, and only idle photons at the position of 525nm generated after the action of the first nonlinear crystal 23 are reserved.
In an embodiment of the present invention, preferably, the optical cavity structure further includes a control adjusting unit, where the control adjusting unit is configured to adjust the length of the optical cavity structure, and the specific structure of the control adjusting unit is not limited in this embodiment, for example, the control adjusting unit may include a second quarter-wave plate 471, a third polarization beam splitter 472, a first photodetector 473, a second photodetector 474, a differential amplifier 475, and a piezoelectric ceramic actuator 476, where the operating wavelength of the second quarter-wave plate 471 is 795nm, an included angle between a fast axis of the second quarter-wave plate and a polarization direction of incident light is set to pi/2, the incident light is changed into circularly polarized light, the second quarter-wave plate 471 is disposed on a side of the coupling mirror 431, where the light beam with 3% intensity of the coupling mirror 431 is emitted through the coupling mirror 431, and the incident light of the second quarter-wave plate 471 is the light beam emitted through the coupling mirror 431; the light beam emitted from the second quarter-wave plate 471 is incident on a third pbs 472, the surface of the third pbs 472 is coated with an AR @795nm film, the third pbs 472 is used for separating circularly polarized light into a third horizontally polarized light and a third vertically polarized light, wherein the third horizontally polarized light is directly transmitted from the third pbs 472 to reach the first photodetector 473, and the third vertically polarized light reaches the second photodetector 474 after being refracted by 90 °; the first photodetector 473 and the second photodetector 474 are photoelectric conversion devices that convert light intensity signals into electric signals, output different voltage signals when different light beam intensities irradiate the surfaces thereof, and change as the light beam intensities change, and the first photodetector 473 and the second photodetector 474 convert the third horizontally polarized light and the third vertically polarized light into first electric signals and second electric signals, respectively; the outputs of the first photodetector 473 and the second photodetector 474 are respectively connected to the input of a differential amplifier 475 by wires, so that the first electrical signal and the second electrical signal are transmitted to the differential amplifier 475, the output of the differential amplifier 475 is connected to a piezoceramic actuator 476 by wires, the differential amplifier 475 is configured to compare the magnitudes of the first voltage signal and the second voltage signal and output a control signal to the piezoceramic actuator 475, and the piezoceramic actuator 475 is disposed on the fourth mirror 432, and is capable of adjusting the length thereof according to the applied voltage value, thereby adjusting the position of the fourth mirror 432. By providing the optical cavity structure and the control and adjustment unit in the optical cavity structure, the light beam at 795nm can be circulated in the optical cavity structure many times, thereby increasing the intensity of the light beam passing through the second nonlinear crystal 45, and in addition, when the state of the optical cavity is changed, the first photodetector 473 and the second photodetector 474 can detect the changed signal and transmit it to the differential amplifier, and then the differential amplifier 475 controls the piezoelectric ceramic actuator to change the cavity length, thereby restoring the optical cavity to the previous state, and thus, through the above feedback process, the optical cavity can be stably operated in an ideal state at all times.
In the embodiment of the present invention, the second nonlinear crystal 45 is a type 0 periodic polarized KTP crystal, specifically PPKTP, with a size of 1mm × 2mm × 10mm, a polarization period of 9.375 μm, the degenerate phase matching temperature for the 1560nm light beam is 39.4(± 0.002) ° c, and both side surfaces of the second nonlinear crystal 45 are coated with films of AR @525nm, AR @795nm, and AR @1560nm, and the converged 1560nm light beam generates a pair of orthogonally polarized photons after being acted by the second nonlinear crystal 45, where the photon pair is a signal photon at 795nm and an idle photon at 525 nm.
According to the device provided by the embodiment of the invention, the first laser 10, the beam processing module 20, the orbital angular momentum loading module 30 and the frequency conversion module 40 are arranged, a photon pair can be obtained by processing the first pump light output by the first laser through the beam processing module, the photon pair is separated to obtain the first horizontal polarized light and the first vertical polarized light, then the orbital angular momentum loading module can load the upper orbital angular momentum information on the first vertical polarized light, and finally the frequency conversion module converts the light frequency of the orbital angular momentum beams carrying the orbital angular momentum information, so that the conversion of the photon frequency is realized, and further the photon frequency conversion device can be used for connecting two quantum systems with different working wavelengths. And the coherence of single photons is maintained during the conversion process.
As shown in fig. 5 to 6, in the embodiment of the present invention, the photon frequency conversion device further includes a first measurement module 50, and the first measurement module 50 is used for measuring the spatial structure of the light beam.
In the embodiment of the present invention, the first measuring module 50 may include a third optical fiber coupling head 51, a fourth optical fiber coupling head 52, a first single-photon detector 53, a second single-photon detector 54, and a coincidence counter 55, wherein an input Port7 of the third optical fiber coupling head 51 is connected to an output Port1 of the first horizontally polarized light in the optical beam processing module 20, an input Port8 of the fourth optical fiber coupling head 52 is connected to an output Port6 of the frequency conversion module 40, output ends of the third optical fiber coupling head 51 and the fourth optical fiber coupling head 52 are respectively connected to input ends of the first single-photon detector 53 and the second single-photon detector 54 through single-mode optical fibers, output ends of the first single-photon detector 53 and the second single-photon detector 54 are respectively connected to two input ends of the coincidence counter 55, wherein the third optical fiber coupling head 51 and the fourth optical fiber coupling head 52 may connect photons emitted from ports 7 and 8 to single-mode optical fibers of which output ends are connected, the working waveband of the single-mode fiber connected with the output end of the third fiber coupling head 51 is 1560nm, and the working waveband of the single-mode fiber connected with the output end of the fourth fiber coupling head 52 is 525 nm; the first single-photon detector 53 and the second single-photon detector 54 are used for detecting photon signals, the quantum efficiency is 20%, and the time delay is less than 5 mu s. The principle is that when a photon reaches the surface of the single photon detector, the single photon detector outputs an electric signal to the coincidence counter. The second single-photon detector is arranged on a one-dimensional adjusting platform and can be adjusted in position along the vertical direction of a light path, and the first single-photon detector is arranged on a fixed platform; the coincidence counter 55 is used for coincidence counting, and the output signals of the first single-photon detector 53 and the second single-photon detector 54 are sent to the coincidence counter 55 with a coincidence window of 0.4 ns. The principle is that when the signals output by the first single-photon detector 53 and the second single-photon detector 54 are received at the same time, the count is increased by 1, that is, the number of photons reaching the first single-photon detector 53 and the second single-photon detector 54 at the same time can be recorded. The spatial structure of the light beam can be measured in a coincidence counting mode by adjusting the one-dimensional adjusting platform of the first measuring module.
In another embodiment of the present invention, as shown in fig. 7-8, the photon frequency conversion device further comprises a second measuring module 60, wherein the second measuring module 60 is used for measuring the cross-sectional shape of the display beam.
In the embodiment of the present invention, the second measurement module 60 includes a charge coupled device 61, and an input Port9 of the charge coupled device 61 is connected to an output Port4 of the orbital angular momentum loading module 30. The charge coupled device 61(CCD) can directly convert the optical signal into an analog current signal, and the current signal is amplified and analog-to-digital converted to realize acquisition, storage, transmission, processing and reproduction of an image, so as to display details of the cross-sectional shape of the light beam. In actual operation, the Port9 of the second measurement module 60 is connected to the Port4 to measure the state of the beam before passing through the frequency conversion module; then, the Port9 of the second measurement module is connected to the Port6 to measure the beam status after passing through the frequency conversion module.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A photon frequency conversion device, characterized in that the photon frequency conversion device comprises:
a first laser for outputting a first pump light;
the beam processing module is arranged at the output end of the first laser and used for generating a photon pair according to the first pump light and separating the photon pair into first horizontal polarized light and first vertical polarized light;
the orbital angular momentum loading module is arranged at the output end of the first vertical polarized light of the light beam processing module and is used for loading orbital angular momentum information on the first vertical polarized light to obtain an orbital angular momentum light beam; and
and the frequency conversion module is arranged at the output end of the orbital angular momentum loading module and is used for converting the light frequency of the orbital angular momentum light beam.
2. The photon frequency conversion device according to claim 1, wherein the beam processing module comprises a first half-wave plate, a first lens, a first nonlinear crystal, a second lens, a first optical filter and a first polarization beam splitter, which are sequentially arranged along the optical path;
the first half-wave plate is used for controlling the polarization direction of the first pump light;
the first lens is used for focusing the light beam output by the first half wave plate on the first nonlinear crystal;
the first nonlinear crystal is used for generating the photon pair from the light beam output by the first lens, and the photon pair comprises a signal photon and an idle photon;
the focal length of the second lens is the same as that of the first lens, and the second lens is used for collimating the light beam output by the first nonlinear crystal;
the first optical filter is used for filtering the first pump light in the light beam passing through the second lens;
the first polarization beam splitter is configured to split the photon pair into the first horizontally polarized light and the first vertically polarized light.
3. The photon frequency conversion device according to claim 1, wherein the orbital angular momentum loading module comprises a coupling unit, a polarization adjusting unit, a second polarization beam splitter, an optical path folding unit, a vortex phase plate and a second half-wave plate;
the coupling unit is used for coupling the first vertically polarized light into free space;
the polarization adjusting unit is used for adjusting the polarization characteristic of the light beam output by the coupling unit;
the second polarization beam splitter is used for separating the light beam output by the polarization adjusting unit into a second horizontal polarized light and a second vertical polarized light;
the optical path deflection unit is used for refracting the second horizontal polarized light and the second vertical polarized light to the vortex phase plate respectively, and refracting the second horizontal polarized light and the second vertical polarized light which pass through the vortex phase plate back to the second polarization spectroscope;
the vortex phase plate is used for loading orbital angular momentum on the second horizontally polarized light and the second vertically polarized light which are emitted into the vortex phase plate;
the second half-wave plate is used for controlling the polarization direction of the light beam loaded with orbital angular momentum emitted from the second polarizing beam splitter.
4. A photon frequency conversion device according to claim 3, wherein the polarization adjustment unit comprises a first quarter wave plate and a third half wave plate, the first quarter wave plate and the third half wave plate have the same operating wavelength, and the first quarter wave plate and the third half wave plate are sequentially arranged between the coupling unit and the second polarization beam splitter along the optical path.
5. A photon frequency conversion device in accordance with claim 2, wherein said frequency conversion module comprises:
a second laser for generating a second pump light;
the collimating lens is used for collimating the second pump light and then injecting the collimated second pump light into the second nonlinear crystal through the optical cavity structure;
the optical cavity structure is used for enhancing the intensity of the light beam passing through the second nonlinear crystal;
the third lens is used for focusing the light beam emitted by the orbital angular momentum loading module to pass through the optical cavity structure and enter the second nonlinear crystal;
the second nonlinear crystal is used for enabling the light beams with the specified wave bands to generate photon pairs; and
and the second optical filter is used for screening the optical frequency of idle photons in the photon pair generated by the first nonlinear crystal and outputting the optical frequency.
6. A photon frequency conversion device according to claim 5, wherein said optical cavity structure comprises a coupling mirror, a fourth reflecting mirror, a first concave mirror and a second concave mirror;
the second nonlinear crystal is disposed between the first concave mirror and the second concave mirror.
7. The photon frequency conversion device according to claim 6, wherein the optical cavity structure further comprises a control and adjustment unit;
the control and adjustment unit is used for adjusting the length of the optical cavity structure.
8. The photon frequency conversion device according to claim 7, wherein the control and adjustment unit comprises a second quarter wave plate, a third polarization beam splitter, a first photodetector, a second photodetector, a differential amplifier and a piezoelectric ceramic actuator,
the second quarter-wave plate is used for generating circularly polarized light from the light beam emitted from the coupling mirror;
the third polarization beam splitter is used for separating the circularly polarized light into third horizontally polarized light and third vertically polarized light;
the first photodetector is used for converting the third horizontally polarized light into a first electric signal;
the second photodetector is used for converting the third vertically polarized light into a second electric signal;
the input end of the differential amplifier is respectively connected with the first photoelectric detector and the second photoelectric detector through leads, the output end of the differential amplifier is connected with the piezoelectric ceramic actuator through leads, and the differential amplifier is used for comparing the magnitude of the first voltage signal and the magnitude of the second voltage signal and outputting a control signal to the piezoelectric ceramic actuator;
the piezoceramic actuator is used for adjusting the position of the fourth reflector according to the control signal so as to adjust the length of the optical cavity structure.
9. A photon frequency conversion device according to claim 1, further comprising a first measuring module for measuring the spatial configuration of the light beam;
the first measuring module comprises a third optical fiber coupling head, a fourth optical fiber coupling head, a first single-photon detector, a second single-photon detector and a coincidence counter, the third optical fiber coupling head is connected with the output end of the first horizontal polarized light in the light beam processing module, the fourth optical fiber coupling head is connected with the output end of the frequency conversion module, the output ends of the third optical fiber coupling head and the fourth optical fiber coupling head are respectively connected with the input ends of the first single-photon detector and the second single-photon detector through single-mode optical fibers, and the output ends of the first single-photon detector and the second single-photon detector are respectively connected with the two input ends of the coincidence counter.
10. The photon frequency conversion device according to claim 1, further comprising a second measuring module for measuring a cross-sectional shape of the display beam;
the second measurement module comprises a charge-coupled device, and the input end of the charge-coupled device is connected with the output end of the orbital angular momentum loading module.
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| CN110908216A (en) * | 2019-12-18 | 2020-03-24 | 青岛鲲腾量子应用技术有限公司 | Vector beam-based nonlinear frequency conversion device |
| CN213069366U (en) * | 2020-06-17 | 2021-04-27 | 青岛鲲腾量子应用技术有限公司 | Up-conversion imaging processing device based on field of view and edge enhancement |
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| CN110908216A (en) * | 2019-12-18 | 2020-03-24 | 青岛鲲腾量子应用技术有限公司 | Vector beam-based nonlinear frequency conversion device |
| CN213069366U (en) * | 2020-06-17 | 2021-04-27 | 青岛鲲腾量子应用技术有限公司 | Up-conversion imaging processing device based on field of view and edge enhancement |
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