CN110187586A - The thin chamber of compact monocrystal and the entangled photons source system for using the thin chamber - Google Patents
The thin chamber of compact monocrystal and the entangled photons source system for using the thin chamber Download PDFInfo
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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
- G02F1/3515—All-optical modulation, gating, switching, e.g. control of a light beam by another light beam
- G02F1/3517—All-optical modulation, gating, switching, e.g. control of a light beam by another light beam using an interferometer
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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
- G02F1/3544—Particular phase matching techniques
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- G—PHYSICS
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- 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
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3551—Crystals
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- G—PHYSICS
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- 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
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- G02F1/3551—Crystals
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- 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
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3558—Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM]
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Abstract
The present invention relates to laser technology, nonlinear optical physical technique, quantum optices and Technique on Quantum Communication fields, more particularly to the thin chamber of compact monocrystal and the entangled photons source system with the thin chamber, the free spectrum journey FSR and line width Δ υ of the thin chamber of compact monocrystal meet formula respectively:WithThe invention uses very thin nonlinear crystal single cavity structure, it is simple with manipulation small in size, and by choosing the long l of suitable chamber and filming parameter, wherein filming parameter adjusts transmitance T, it is only necessary to which meeting formula (2) can the photon line width wanted of free design.And due to the resonant interaction of the thin chamber of compact monocrystal, spectrum brightness when the spectrum brightness of the photon of generation is relative to once-through is greatly enhanced, theoretical calculation surface, the enhancement factor of the general brightness when spectrum brightness of the photon pair generated by the thin chamber of compact monocrystal is relative to once-through are proportional to square (F of the fineness of the thin chamber of compact monocrystal2)。
Description
Technical field
The present invention relates to laser technology, nonlinear optical physical technique, quantum optices and Technique on Quantum Communication fields, especially relate to
And a kind of thin chamber of compact monocrystal and the entangled photons source system with the thin chamber.
Background technique
Quantum entangled source is the foundation stone for studying quantum information technology, and high brightness minimizes and the quantum light source of high degree of entanglement will
For quantum communications, measures and calculates correlative study and bring great convenience.The photon wave that remote fiber optic communication needs to transmit
In the long communication window for being located at optical fiber, the photon line width needs furthermore transmitted are relatively narrow, to effectively avoid fibre-optical dispersion to light
The broadening of subpulse influences.On the other hand, remote quantum communications need to use quantum repeater, and the core of Quantum repeater is
Quantum memory, the useful photon line width of quantum memory within GHz, therefore the photon of narrow linewidth high brightness to be realize it is remote
Apart from the essential critical component of quantum communications.It is traditional based on the narrow linewidth photon converted under intracavitary Spontaneous Parametric to having
Volume is big, and system complexity is high, and needs additional resonant cavity just and can obtain the photon pair of narrow linewidth, photon huge in this way
Generation system is unable to satisfy the following requirement for minimizing highly integrated Quantum control system.
Summary of the invention
In order to overcome the deficiencies in the prior art described above, it is somebody's turn to do for this purpose, the present invention provides the thin chamber of compact monocrystal and uses
The entangled photons source system of thin chamber.
To achieve the above object, the invention adopts the following technical scheme:
The thin chamber of compact monocrystal includes the monocrystal of cavity and setting in the cavity, the thin chamber of compact monocrystal
Free spectrum journey FSR and line width Δ υ meet formula respectively:
Wherein l is that the chamber of the thin chamber of compact monocrystal is long, nyAnd nzRefractive index of the crystal in y-axis and z-axis is respectively indicated,
Wherein Fa=2 π/γa(a=y, z), γyAnd γzIndicate photon in the dissipation of intracavitary y-axis and z-axis, wherein γaIt is plated by output end face
The transmitance T of film and intracavitary absorbed inside, which dissipate, to be formed, and can be ignored in the absorption loss of communication band crystal, therefore can obtain
To γa=Ta, c is the light velocity, constant.
Further, the thin chamber output of compact monocrystal is divided into vertical polarization photon and horizontal polarization by polarization beam apparatus
Photon sets vertical polarization photon as signal photon, and horizontal polarization photon is idler photon, vertical polarization photon and horizontal polarization
The cluster frequency interval of photon is defined as:
The spontaneous radiation bandwidth of crystal is determined by phase matched function, that is, sets phase matched function are as follows:
sinc2(Δkl/2) (4)
Assuming that the full width at half maximum of phase matched function is Δ Ω, the thin chamber of compact monocrystal meets:
ΔΩc>ΔΩ (5)
Wherein Δ k is phase mismatch, and Δ k=kp-ks-ki+ 2 π/Λ, wherein kp、ks、kiRespectively indicate pump light, signal
The wave vector of photon, idler photon, FSRsAnd FSRiRespectively indicate the free spectrum journey of signal photon and idler photon, kp、ks、ki?
Coincidence formula kb=2 π nb/λb(b=p, s, i), wherein nbFor the refractive index of corresponding light, λbFor the wavelength of corresponding light, Λ is monocrystalline
The polarization cycle of body, sets pump light and signal photon is moved along the y-axis of the optical axis of crystal, Z axis of the idler photon along the optical axis of crystal
Movement, the y-axis of the optical axis of crystal are the length direction of crystal, and Z axis is the short transverse after crystal is placed.
Further, the monocrystal is the periodic polarized phosphoric acid hydrogen-oxygen potassium PPKTP of two type phase matcheds.
Further, the thin chamber of the compact monocrystal is arranged in crystal temperature controlling stove.
Further, monocrystal entrance face is provided with the anti-film of light of the anti-reflection film and first wave length light beam of pump light, out
Mouth end face is provided with the anti-reflection film of pump light and the part reflectance coating of first wave length light beam.
A kind of entangled photons source system with the above-mentioned thin chamber of compact monocrystal, including what is set gradually in optical path
Light laser Laser is pumped, for issuing the pump light of setting wavelength, and exports laser linewidth < 10MHz；
First mating plate component, for adjusting the polarization of pump light and reducing spot diameter；
Dichroic mirror DM is generated thin for reflected pump light input when photon for separating pumping wavelength and first wave length
Crystal intracavity, when characterizing the parameter of chamber, for transmiting the detection laser of first wave length；
Second mating plate component, for by the photon of output to the spot size for being integrated into setting；
Be divided transmission assembly, for filter out pumping laser and by the photon of polarized orthogonal to be divided into vertical polarization photon and
The output of horizontal polarization photon；
Two unequal arm fibre optic interferometers are respectively used to vertical polarization photon and the progress pair of horizontal polarization photon to generation
Photon Franson interferometry；
Coincidence counting component carries out time energy to the two-photon of two unequal arm fibre optic interferometer outputs and tangles measurement；
The thin chamber of compact monocrystal is arranged in the optical path between dichroic mirror DM and the second mating plate component.
Further, the first mating plate component is successively set on wave plate unit and the first lens unit in optical path.
Further, the light splitting transmission assembly includes the second lens unit set gradually in optical path, long pass filter
Device LPF, polarization beam apparatus PBS further include two optical fiber being accordingly arranged on the two-beam road separated through polarization beam apparatus PBS
Collimator.
Further, the coincidence counting component respectively corresponds two unequal arm fibre optic interferometers outputs of reception including 2
The superconducting single-photon detector SNSPD of photon signal is held, the output photon of 2 superconducting single-photon detector SNSPD is input to symbol
In total number instrument &.
A kind of entangled photons source system with the above-mentioned thin chamber of compact monocrystal, system includes correction component, described
Correcting component includes quickly pop one's head in PD, oscillograph OSC, detection laser, further includes the pumping light laser set gradually
Laser, the first mating plate component, dichroic mirror DM, the second mating plate component, half-wave plate HWP2, polarization beam apparatus PBS, the compact
The thin chamber of monocrystal is arranged in the optical path between dichroic mirror DM and the second mating plate component, and the quick probe PD is arranged in dichroic mirror
DM rear end face receives first wave length light beam, and the oscillograph OSC is used to receive the signal that quickly probe PD is obtained and shows state,
The detection light that the detection laser issues enters from a delivery outlet of light splitting transmission assembly reverses through the second mating plate component
It is thin intracavitary to compact monocrystal.
The present invention has the advantages that
(1) present invention uses very thin nonlinear crystal single cavity structure, has manipulation small in size simple, and pass through selection
The suitable long l of chamber and filming parameter, wherein filming parameter adjusts transmitance T, it is only necessary to which meeting formula (2) can freely set
Photon line width required for counting.And due to the resonant interaction of the thin chamber of compact monocrystal, the spectrum brightness of the photon of generation is opposite
Spectrum brightness when once-through is greatly enhanced, theoretical calculation surface, the photon generated by the thin chamber of compact monocrystal
Pair spectrum brightness relative to once-through when general brightness enhancement factor be proportional to the thin chamber of compact monocrystal fineness it is flat
Side (F2)。
(2) the thin chamber of compact monocrystal generates first wave length light beam, due to the resonant interaction of the thin chamber of compact monocrystal, pump
Pu laser generates the vertical polarization photon and level that spontaneous parametric down conversion generates first wave length in the thin chamber of compact monocrystal
The photon pair of polarized photon, the photon of generation realize resonant check output in intracavitary roundtrip.
(3) the thin chamber that one piece of two type phase matched PPKTP crystal of pumping laser once-through is constituted, due under Spontaneous Parametric
Conversion process, intracavitary while generating the photon pair of a pair of of polarized orthogonal, the filming parameter by designing crystal can allow generation
Photon to from the rear end face of thin chamber export, only with thin chamber resonance photon could be exported from thin chamber.Crystal is in setting wave band
It can guarantee that the spacing of the frequency cluster of the photon of intracavitary polarized orthogonal is greater than the spontaneous radiation gain bandwidth of photon, so as to
Guarantee to export with the thin chamber resonance of compact monocrystal in the photon of intracavitary only a pair of of the frequency of the radiation bandwidth of crystal, thus
Single longitudinal mode operating may be implemented.The thin chamber of compact monocrystal for generating the photon pair of single longitudinal mode is tied relative to traditional based on space
The scheme of structure chamber have it is small in size, it is easy to operate, be easily integrated, have great importance for remote quantum communications.
(4) crystal temperature controlling stove is used in the present invention, is maintained at crystal within the temperature range of setting, to influence monocrystal
Refractive index change phase-matching condition.
(5) in the present invention setting of two terminal membrane of monocrystal it is different so as to adjusting line width Δ υa。
(6) vertical polarization photon and horizontal polarization photon are passed through two not by the entangled photons source system in the present invention respectively
Equiarm interferometer carries out two-photon Franson interferometry to characterize time energy Entanglement, the orthogonal polarized light of generation
Son passes through the unequal arm interferometer as two arm difference delays, the time met in this way in two-photon with horizontal polarization photon respectively
It is selected after being carried out on window, coincidence measurement is carried out on middle window, when a pair of of vertical polarization photon and horizontal polarization photon are same
When walk unequal arm interferometer galianconism it is consistent with long-armed time delay, meeting undistinguishable in window, therefore generate double
Photon time energy Entangled State can be write as
(7) pump light is adjusted to horizontal polarization by the wave plate unit, and first lens unit is for reducing spot diameter.
(8) second lens unit is used to entirely arrive the photon of output setting spot size, and long pass filter LPF is used
In filtering out pumping laser, polarization beam apparatus makes the photon of output be divided into vertical polarization photon and horizontal polarization photon, vertical polarization
It is dry that photon and horizontal polarization photon are transferred to corresponding unequal arm optical fiber by optical fiber after corresponding optical fiber collimator respectively
In interferometer.
(9) present invention corrects the thin chamber of compact monocrystal by the PD that quickly pops one's head in, oscillograph OSC, detection laser device
Effect, can be removed from whole system after detection.Since level can be generated after the thin chamber of compact monocrystal
Polarized photon and vertical polarization photon, in order to use quickly PD and oscillograph OSC of probe, by long pass filter LPF
It is substituted for half-wave plate HWP2, it, will half after detecting a kind of photon to the change detection of horizontal polarization photon and vertical polarization photon
Wave plate HWP2 rotates 90 degree of states for obtaining detecting another photon.
Detailed description of the invention
Fig. 1 is the light channel structure schematic diagram of entangled photons source of the present invention system.
Fig. 2 is the characterization structure chart that the present invention is chamber.
Fig. 3 is the transmission spectrum of the polarization of crystal single-chamber H used in the present invention and V polarization.
Fig. 4 is that the single channel of photon in the present invention counts the relational graph with coincidence counting with pump power.
Fig. 5 is the relational graph of the coincidence counting of characterization photon and the ratio C AR secretly met with power.
Fig. 6 is the two-photon Franson interference curve of time energy entangled photons provided in an embodiment of the present invention.
Specific embodiment
Embodiment 1
As shown in Figs. 1-2, the thin chamber of compact monocrystal includes cavity and crystal, and the thin chamber output of compact monocrystal is by inclined
Vibration beam splitter is divided into vertical polarization photon and horizontal polarization photon.Vertical polarization photon is set as signal photon, horizontal polarization light
Son is idler photon.The monocrystal is the periodic polarized phosphoric acid hydrogen-oxygen potassium PPKTP of two type phase matcheds, the compact list
The thin chamber of crystal is arranged in crystal temperature controlling stove.Wherein the operating temperature range of temperature controlling stove is in 15 to 70 degrees Celsius, temperature-controlled precision
2mK。
The monocrystal entrance face is provided with the anti-reflection film of pump light and the film that is all-trans of first wave length light beam, exit end face
It is provided with the anti-reflection film of pump light and the part reflectance coating of first wave length light beam.In this embodiment, it is respectively with wavelength
For the pump light and first wave length light beam of 780nm, 1560nm.That is the film of crystal entrance face include 780nm anti-reflection film and
The film that is all-trans of 1560nm, the film of exit end face include the anti-reflection film of 780nm and the part reflectance coating of 1560nm, the part reflectance coating
Reflectivity be 95%, i.e., transmitance be 5%.The long l of chamber of the thin chamber of compact monocrystal is 0.85mm.
The free spectrum journey FSR and line width Δ υ of the thin chamber of compact monocrystal meet formula respectively:
Wherein l is that the chamber of the thin chamber of compact monocrystal is long, nyAnd nzRefractive index of the crystal in y-axis and z-axis is respectively indicated,
Wherein Fa=2 π/γa(a=y, z), γyAnd γzIndicate photon in the dissipation of intracavitary y-axis and z-axis, wherein γaIt is plated by output end face
The transmitance T of film and intracavitary absorbed inside, which dissipate, to be formed, and can be ignored in the absorption loss of communication band crystal, therefore can obtain
To γa=Ta, c is the light velocity, constant.
Under the premise of determining the length and filming parameter of the thin chamber of compact monocrystal, seek to determine generation in next step
Whether photon is under conditions of single longitudinal mode operating, and for the intracavitary parameter of two types, single longitudinal mode operating needs to meet spoke
The frequency cluster interval of the vertical polarization photon and horizontal polarization photon penetrated is greater than the spontaneous radiation gain half-breadth of crystal, specifically
, the cluster frequency interval of vertical polarization photon and horizontal polarization photon is defined as:
The spontaneous radiation bandwidth of crystal is determined by following phase matched function:
sinc2(Δkl/2) (4)
Assuming that the full width at half maximum of phase matched function is Δ Ω, the thin chamber of compact monocrystal meets:
ΔΩc> Δ Ω (5)
Wherein Δ k is phase mismatch, and Δ k=kp-ks-ki+ 2 π/Λ, wherein kp、ks、kiRespectively indicate pump light, vertical
The wave vector of polarized photon, horizontal polarization photon, FSRsAnd FSRiThe free spectrum journey of signal photon and idler photon is respectively indicated,
kp、ks、kiEqual coincidence formula kb=2 π nb/λb(b=p, s, i), wherein nbFor the refractive index of corresponding light, λbFor the wavelength of corresponding light,
Λ is the polarization cycle of monocrystal.Pump light and signal photon are moved along the y-axis of the optical axis of crystal, and idler photon is along the optical axis of crystal
Z axis movement, the y-axis of the optical axis of crystal are the length direction of crystal, and Z axis is the short transverse after crystal is placed.In present example
In, it is divided into 1075.1GHz between the frequency cluster of signal photon and idler photon, greater than the spontaneous radiation bandwidth 914GHz of crystal, because
This can satisfy single longitudinal mode operating condition.
The program has manipulation small in size simple, and pass through choosing due to using very thin nonlinear crystal single cavity structure
It selects suitable chamber length and filming parameter be free to the photon line width that design is wanted.Furthermore the core of the design scheme is certainly
The spacing for sending out the frequency cluster of parameter photon is greater than the gain line width of crystal spontaneous radiation, thereby may be ensured that single longitudinal mode exports.
This programme has small in size, and easy to operate, spectrum brightness is high, tangles quality height, and photon line width can be designed freely, is suitble to all Multiple-quantums
Information technology related application.
Embodiment 2
As shown in Figure 1, a kind of entangled photons source system with the thin chamber of compact monocrystal described in embodiment 1, this is
System include the pumping light laser Laser set gradually in optical path, the first mating plate component, dichroic mirror DM, the second mating plate component,
It is divided transmission assembly, two unequal arm fibre optic interferometers, coincidence counting component.
Wherein pumping light laser Laser is used to issue the pump light of setting wavelength, exports laser linewidth < 10MHz；To
Ensure narrow linewidth, in this embodiment, chooses the pump light that wavelength is 780nm.
First mating plate component is used to adjust the polarization of pump light and reduces spot diameter；The first mating plate component is successively set
Set wave plate unit and the first lens unit in optical path.Specifically, the first mating plate component includes setting gradually in optical path
Half-wave plate HWP1 and quarter-wave plate QWP adjusts pump light to horizontal polarization state, to meet periodic polarized phosphoric acid
Conversion process under the Spontaneous Parametric of hydrogen-oxygen potassium PPKTP.First lens unit includes the first lens L1 and second for setting gradually saturating
Mirror L2, the first lens L1 and the second lens L2 are the lens of 780nm.The pump light of 780nm is tuned into level by wave plate unit
After polarization, the effect then in turn through the first lens L1 and the second lens L2 reduces spot diameter to being sized.
It is thin intracavitary that pump light after adjusting is input to compact monocrystal by dichroic mirror DM, when characterizing to chamber, instead
It is transmitted after intracavitary transmission, then from dichroic mirror DM by quick probe detection to the detection laser of input cavity.
The thin chamber of compact monocrystal is arranged in the optical path between dichroic mirror DM and the second mating plate component, compact list
The thin chamber of crystal generates first wave length light beam, and first wave length is 1560nm in this embodiment.Due to the thin chamber of compact monocrystal
Resonant interaction, it is the vertical of 1560nm that pumping laser, which generates spontaneous parametric down conversion in the thin chamber of compact monocrystal and generates wavelength,
The photon pair of polarized photon and horizontal polarization photon, the photon of generation realize resonant check output in intracavitary roundtrip.
Second mating plate component includes the third lens L3 and the 4th lens L4 being successively set in optical path, for what will be exported
Photon is to the spot size for being integrated into setting, so as to efficiently be coupled into subsequent single mode optical fiber SMF.
Light splitting transmission assembly for filter out pumping laser and by the photon of polarized orthogonal to be divided into vertical polarization photon and
The output of horizontal polarization photon；Specifically, light splitting transmission assembly includes that be divided transmission assembly include the set gradually in optical path
Two lens units, long pass filter LPF, polarization beam apparatus PBS further include accordingly being arranged in separate through polarization beam apparatus PBS
First optical fiber collimator FC1 of two-beam road and the second optical fiber collimator FC2, the first optical fiber collimator FC1 and second
Optical fiber collimator FC2 is used to the photon after shaping pass through the first optical fiber collimator FC1 and second to effectively being collected
Optical fiber collimator FC2 is output in corresponding single mode optical fiber SMF, is used for subsequent interference and measurement & characterization.Due to compact list
The plated film of the thin chamber of crystal only allows rear end output parameter photon, with the photon of the polarized orthogonal of the thin chamber resonance of compact monocrystal from
After the output of rear end, the pump light that wavelength is 780nm is filtered out by long pass filter LPF, then using polarization beam apparatus PBS
It separates.
Two unequal arm fibre optic interferometers are respectively that the first unequal arm fibre optic interferometer UMI1 and the second unequal arm optical fiber are dry
Interferometer UMI2.The coincidence counting component includes 2 and respectively corresponds reception the first unequal arm fibre optic interferometer UMI1 and second not
The superconducting single-photon detector SNSPD of equiarm fibre optic interferometer UMI2 output end photon signal, 2 superconducting single-photon detectors
The output photon of SNSPD is input in coincidence counting instrument &.2 superconducting single-photon detector SNSPD are respectively the first superconduction monochromatic light
Sub- detector SNSPD1 and the second superconducting single-photon detector SNSPD2.Coincidence counting component is to the first unequal arm fibre optic interferometer
The two-photon of UMI1 and the second unequal arm fibre optic interferometer UMI2 output carries out time energy and tangles measurement analysis.Described first is not
Two-photon of the equiarm fibre optic interferometer UMI1 and the second unequal arm fibre optic interferometer UMI2 for the narrow linewidth photon pair of generation
Franson interferometry, the horizontal polarization photon of generation and vertical polarization photon pass through the as two arm differences delays respectively
One unequal arm fibre optic interferometer UMI1 and the second unequal arm fibre optic interferometer UMI2, in this way on the time window that two-photon meets
It is selected after progress, coincidence measurement is carried out on middle window, when a pair of of photon walks the first unequal arm fibre optic interferometer UMI1 simultaneously
It is consistent with long-armed time delay with the galianconism of the second unequal arm fibre optic interferometer UMI2, meeting undistinguishable in window, because
This two-photon time energy Entangled State generated can be write as
The photon pair generated is collected in order to efficient, needs first to be carried out the characteristic of resonant cavity with the laser of photonic band
Characterization and measurement, need to determine at the same time the direction of incident pumping laser by the intracavity frequency doubling of two types.Specifically, as schemed
Shown in 2, system includes correction component, and the correction component includes quickly pop one's head in PD, oscillograph OSC, detection laser, further includes
The pumping light laser Laser that sets gradually, the first mating plate component, dichroic mirror DM, the second mating plate component, half-wave plate HWP2, partially
Shake beam splitter PBS, and the thin chamber of compact monocrystal is arranged in the optical path between dichroic mirror DM and the second mating plate component, described
Quickly probe PD setting receives first wave length light beam in dichroic mirror DM rear end face, and the oscillograph OSC is for receiving quick probe
The signal of PD acquisition simultaneously shows state, and a delivery outlet of the detection light that the detection laser issues from light splitting transmission assembly is anti-
It is thin intracavitary to compact monocrystal is entered by the second mating plate component.It, will when detecting the performance of the thin chamber of compact monocrystal
Transmission assembly, unequal arm fibre optic interferometer, coincidence counting component is divided in embodiment 2 to remove, and long pass filter LPF is replaced
Change half-wave plate HWP2 into.The change detection to horizontal polarization photon and vertical polarization photon may be implemented in half-wave plate HWP2, is examining
After surveying a kind of photon, it is the state for obtaining detecting another photon that half-wave plate HWP2, which is rotated 90 degree,.The quick probe PD is set
It sets and receives first wave length light beam in dichroic mirror DM rear end face, the oscillograph OSC is used to receive the signal that quickly probe PD is obtained
And showing state, the detection light that the detection laser issues is from reversely successively by single mode optical fiber SMF, the second optical fiber collimator
FC2, that the second mating plate component enters compact monocrystal is thin intracavitary.I.e. the parameter characterization of the thin chamber of compact monocrystal passes through reversed
The laser of incident a branch of tunable wave length, is then used in combination by the quick probe PD after dichroic mirror DM come the transmission spectrum of detection cavity
Oscillograph OSC monitors the resonance state of chamber, so that it is determined that spectrum free path and line width of the chamber two polarization directions.Fig. 3 is to make
With the transmission spectral curve for the polarization direction H and V that scanning 1560nm Laser Measuring obtains, the spectrum free path of chamber can be determined by being fitted
And line width.
In order to characterize the quality of generated entangled light source, need to measure the following parameter in source of tangling.
Firstly the need of the relationship of measurement photon generation rate and pump power, as shown in figure 4, photon in this example generates
Rate can achieve 2 × 105.Then the coincidence counting for needing to characterize photon and the ratio C AR secretly met such as scheme with the relationship of power
Shown in 5, in this example we have found that ratio C AR can achieve 1400. finally under suitable power when 100mW is pumped,
Need to characterize the time energy Entanglement of entangled photons, Entanglement is portrayed by measurement Franson interference curve, by it
In a unequal arm interferometer be fixed on phase be 0 or π/4 under, change the phase of another unequal arm interferometer and survey
It measures compound counting and is achieved with two groups of interference curves, as shown in Figure 6.Experiment measures under two groups of phases of unequal arm interferometer
Interference visibility is respectively 91.49% and 90.80%, this proves the photon generated to good Entanglement.
The above is only the preferred embodiments of the invention, are not intended to limit the invention creation, all in the present invention
Made any modifications, equivalent replacements, and improvements etc., should be included in the guarantor of the invention within the spirit and principle of creation
Within the scope of shield.
Claims (10)
1. the thin chamber of compact monocrystal, which is characterized in that the thin chamber of compact monocrystal includes cavity and is arranged in the cavity
Monocrystal, the free spectrum journey FSR and line width Δ υ of the thin chamber of compact monocrystal meet formula respectively:
Wherein l is that the chamber of the thin chamber of compact monocrystal is long, nyAnd nzRefractive index of the crystal in y-axis and z-axis is respectively indicated, wherein
Fa=2 π/γa(a=y, z), γyAnd γzIndicate photon in the dissipation of intracavitary y-axis and z-axis, wherein γaBy output end face plated film
Transmitance T and intracavitary absorbed inside, which dissipate, to be formed, and can be ignored in the absorption loss of communication band crystal, therefore available
γa=Ta, c is the light velocity, constant.
2. the thin chamber of compact monocrystal according to claim 1, which is characterized in that the thin chamber output of compact monocrystal is passed through
Polarization beam apparatus is divided into vertical polarization photon and horizontal polarization photon, sets vertical polarization photon as signal photon, horizontal polarization
Photon is idler photon, the cluster frequency interval of vertical polarization photon and horizontal polarization photon is defined as:
The spontaneous radiation bandwidth of crystal is determined by phase matched function, that is, sets phase matched function are as follows:
sinc2(Δkl/2) (4)
Assuming that the full width at half maximum of phase matched function is Δ Ω, the thin chamber of compact monocrystal meets:
ΔΩc> Δ Ω (5)
Wherein Δ k is phase mismatch, and Δ k=kp-ks-ki+ 2 π/Λ, wherein kp、ks、kiRespectively indicate pump light, signal light
The wave vector of son, idler photon, FSRsAnd FSRiRespectively indicate the free spectrum journey of signal photon and idler photon, kp、ks、kiAccord with
Close formula kb=2 π nb/λb(b=p, s, i), wherein nbFor the refractive index of corresponding light, λbFor the wavelength of corresponding light, Λ is monocrystal
Polarization cycle, pump light and signal photon move along the y-axis of the optical axis of crystal, and idler photon is moved along the Z axis of the optical axis of crystal, brilliant
The y-axis of body optical axis is the length direction of crystal, and Z axis is the short transverse after crystal is placed.
3. the thin chamber of compact monocrystal according to claim 1, which is characterized in that the monocrystal is two type phase matcheds
Periodic polarized phosphoric acid hydrogen-oxygen potassium PPKTP.
4. the thin chamber of compact monocrystal according to claim 1, which is characterized in that the thin chamber setting of compact monocrystal
In crystal temperature controlling stove.
5. the thin chamber of compact monocrystal according to claim 1, which is characterized in that monocrystal entrance face is provided with pumping
The anti-film of light of the anti-reflection film and first wave length light beam of light, exit end face are provided with the anti-reflection film and first wave length light beam of pump light
Part reflectance coating.
6. a kind of entangled photons source system with the thin chamber of compact monocrystal described in claim 1-5 any one, special
Sign is, including what is set gradually in optical path
Light laser Laser is pumped, for issuing the pump light of setting wavelength, and exports laser linewidth < 10MHz；
First mating plate component, for adjusting the polarization of pump light and reducing spot diameter；
Pump light is reflected and is input to that compact monocrystal is thin intracavitary by dichroic mirror DM, is made the light of first wave length high thoroughly, will be pumped
Light and the light of first wave length separate, the parameter measurement for the thin chamber of monocrystal；
Second mating plate component, for by the photon of output to the spot size for being integrated into setting；
It is divided transmission assembly, for filtering out pumping laser and by the photon of polarized orthogonal to being divided into vertical polarization photon and level
Polarized photon output；
Two unequal arm fibre optic interferometers are respectively used to vertical polarization photon and horizontal polarization photon to generation and carry out two-photon
Franson interferometry；
Coincidence counting component carries out time energy to the two-photon of two unequal arm fibre optic interferometer outputs and tangles measurement；
The thin chamber of compact monocrystal is arranged in the optical path between dichroic mirror DM and the second mating plate component.
7. entangled photons source according to claim 6 system, which is characterized in that the first mating plate component is successively set on
Wave plate unit and the first lens unit in optical path.
8. entangled photons source according to claim 6 system, which is characterized in that the light splitting transmission assembly is included in optical path
On the second lens unit, long pass filter LPF, the polarization beam apparatus PBS that set gradually, further include corresponding setting through polarization point
Two optical fiber collimators of the two-beam road that beam device PBS is separated.
9. entangled photons source according to claim 6 system, which is characterized in that the coincidence counting component includes 2 points
The superconducting single-photon detector SNSPD of two unequal arm fibre optic interferometer output end photon signals, 2 superconduction lists Dui Ying not received
The output photon of photon detector SNSPD is input in coincidence counting instrument &.
10. a kind of entangled photons source system with the thin chamber of compact monocrystal described in claim 1-5 any one, special
Sign is that system includes correction component, and the correction component includes quickly pop one's head in PD, oscillograph OSC, detection laser, also wraps
Include the pumping light laser Laser set gradually, the first mating plate component, dichroic mirror DM, the second mating plate component, half-wave plate HWP2,
Polarization beam apparatus PBS, the thin chamber of compact monocrystal are arranged in the optical path between dichroic mirror DM and the second mating plate component, institute
It states quickly probe PD setting and receives first wave length light beam in dichroic mirror DM rear end face, the oscillograph OSC is for receiving quick spy
The signal of head PD acquisition simultaneously shows state, a delivery outlet of the detection light that the detection laser issues from light splitting transmission assembly
It is thin intracavitary that compact monocrystal is entered reverses through the second mating plate component.
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