CN1614495A - Method for optical communicating waveband single photon high-efficient detection - Google Patents
Method for optical communicating waveband single photon high-efficient detection Download PDFInfo
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- CN1614495A CN1614495A CN 200410084623 CN200410084623A CN1614495A CN 1614495 A CN1614495 A CN 1614495A CN 200410084623 CN200410084623 CN 200410084623 CN 200410084623 A CN200410084623 A CN 200410084623A CN 1614495 A CN1614495 A CN 1614495A
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Abstract
A method for detecting single photon in optical communication waveband includes placing nonlinear crystal in active resonant cavity of pumping light, shooting single photon acting as signal light into nonlinear crystal pumped by light, making the pumping light frequency be larger than single photon source frequency and generating sum frequency of signal light with pumping light, using silicon APDs to carry out detection after near infrared waveband single photon signal light being filtered.
Description
Technical field:
The present invention relates to the quantum optics application, be applied in the quantum secret communication system, concrete is the optical communicating waveband single photon signal is realized single photon high-efficient detection by conversion on the non-linear frequency method.
Technical background:
1.3 μ m that the signal of optical communicating waveband is meant in middle-infrared band and the flashlight of 1.5 μ m, because compare with other wave band, optical fiber is to the minimum that influences of the loss of these two wave bands and chromatic dispersion, so can be applicable to the Optical Fiber Transmission of single photon signal long-distance especially.Yet in quantum secret communication system, we need be reduced to signal light intensity the single photon level, because not good in the performance of the single-photon detector of optical communicating waveband, the superiority of optical communicating waveband signal is weakened greatly.Now, that be used for single photon detection mainly is avalanche semiconductor photodiode detector APDs, and APDs is the avalanche photodide detector.When being used for single photon detection, avalanche photodide is operated under the Geiger pattern, and its operating voltage is greater than the avalanche voltage of APDs.What use at present optical communicating waveband (comprising 1.3 μ m and 1.5 μ m) is germanium avalanche photodiode or indium gallium arsenic avalanche photodide, and their performance classes seemingly.With indium gallium arsenic avalanche photodide is example, and generally the quantum efficiency of the indium gallium arsenic APDs detector of Shi Yonging is usually less than 10%, and dark counts is up to per second 10
4-10
5In addition, indium gallium arsenic APDs detector has very serious afterpulse, this disadvantages affect its performance in high repetition frequency work, therefore can only be operated in usually under the thresholding pattern of low-repetition-frequency.In order to reduce the dark counts of indium gallium arsenic APDs as far as possible, also under cryogenic conditions, work usually with semiconductor cooling device or liquid nitrogen refrigerating control APDs.By contrast, the silicon avalanche photodiode that is operated in near-infrared band highlight its simply, advantage efficiently.The detection efficiency of silicon APDs generally can reach 70%--80%, and dark counts is less than per second 100 times, and the afterpulse that produces during work can suppress.Therefore, the APDs detector of silicon can be realized the high efficiency detection of two-forty to the single photon signal, and the work repetition frequency can reach more than the 10MHz.
Can predict, if optical communicating waveband can be got up in the advantages aspect the detection in advantage aspect the transmission and silicon avalanche photodiode, will make the transmission range of quantum secret communication, performances such as the one-tenth code check of quantum key distribution all are significantly improved.One of them the most key problem is exactly how the single photon flashlight of optical communicating waveband to be transformed into visible light wave range (changing on the single photon non-linear frequency) expeditiously.At optical field, utilize nonlinear effect (as non-linear and frequency or difference frequency etc.) to realize the conversion of light frequency usually.Can prove that in theory application heavy pumping light and single photon flashlight act on, and can realize that the optical communicating waveband single photon signal is transferred to the near-infrared band signal in nonlinear crystal.Can prove that also when conversion efficiency reaches maximum, also realized the transfer of Quantum Properties when shifting on realizing frequency in the process of changing on frequency, it also is very important that this point is applied to quantum secret communication system for the present invention.
In order to realize changing on the effective non-linear frequency, the pump light intensities that as far as possible improves effective incident nonlinear crystal is necessary.Normally used method is, pump light is injected an external resonator cavity, with feedback servo control system control one side chamber mirror wherein, makes the resonance frequency of resonator cavity and pumping light frequency be complementary, and reaches the effect of intracavity power enhancing.The nonlinear crystal that is placed in this exocoel can obtain effective incident intensity that number decuples pump light.Yet this method has a significant disadvantage: because external resonator cavity is a passive cavity, in order to realize the locking of resonance frequency and pump light frequency, just must rely on the resonance frequency of servo-drive system latch well.Will increase the complexity of system so greatly and adjust difficulty, the stability of system also is difficult to be improved.
Summary of the invention
The present invention is the method that proposes a kind of optical communicating waveband single photon high-efficient detection for the deficiency that overcomes external resonator cavity in the above-mentioned prior art, this method is realizing under the prerequisite that Quantum Properties shifts, utilize nonlinear optical process, the single photon flashlight of optical communicating waveband is transformed into near-infrared band on the frequency expeditiously, realizes the high-efficient detection of single photon signal at last with silicon avalanche photodiode.By such disposal route, we just can combine the transmission advantage of optical communicating waveband and the detection advantage of silicon avalanche photodiode, make single photon frequency inverted efficiently, sensitive detection application in the quantum secret communication field, thereby develop the sensitive Detection Techniques of the efficient single photon that to be applicable to quantum secret communication system.
The object of the invention realizes being finished by following technical scheme:
A kind of method of optical communicating waveband single photon high-efficient detection, it is characterized in that this method at first puts into nonlinear crystal the active resonant cavity of pump light, to advance nonlinear crystal as the single-photon incident of flashlight, this nonlinear crystal is optically pumped, pumping light frequency wherein is greater than the frequency of single-photon source, adjusting flashlight then overlaps in nonlinear crystal with intracavity pump light, and satisfy phase-matching condition, feasible single-photon source and pump light generation and frequency as flashlight, again with each frequency spectrum composition of emergent light separately with dispersion element, leach the near-infrared band single photon flashlight composition after the conversion, survey with silicon APDs afterwards.
Single photon as flashlight refers to optical communicating waveband single photon.Nonlinear crystal has referred to second order nonlinear effect, and logical optical band comprises pump light, the nonlinear crystal of incoming signal light and conversion back signal light wavelength.Described phase-matching condition is meant angular phase coupling or accurate phase matching, angular phase coupling wherein is to select specific nonlinear crystal cutting angle, make that in nonlinear crystal pump light equates with the wave vector of conversion back flashlight with the wave vector stack back of incoming signal light; Accurate phase matching wherein is nonlinear crystal to be made period polarized, specific polarization cycle can correspondingly realize the pump light of specific wavelength and the phase matching of incoming signal light.
Advantage of the present invention is, success the nonlinear optics frequency inverted is introduced quantum secret communication system, by conversion on the frequency with the flashlight frequency translation of single photon level to near-infrared band, the controllable frequency conversion efficiency is near 100%.Replace indium gallium arsenic avalanche photodide to survey with silicon avalanche photodiode, can improve detection performance greatly.The raising meeting of detection performance is to the operating technology index of quantum secret communication system, such as communication distance, and the one-tenth code check of quantum key distribution, traffic rates etc. bring the raising of great-leap-forward.Nonlinear crystal is placed in the resonator cavity that produces pump light, can overcomes the difficulty of system debug on the one hand, also can improve the stability of frequency inverted simultaneously.
Summary of drawings
Accompanying drawing 1 is the embodiment schematic block diagram of continuous light for pump light of the present invention
Accompanying drawing 2 is the embodiment schematic block diagram of pulsed light for pump light of the present invention
Accompanying drawing 3 is the basic index path of the embodiment of the invention 1;
Accompanying drawing 4 is the basic index path of the embodiment of the invention 2;
Accompanying drawing 5 is the basic index path of the embodiment of the invention 3;
Concrete technical scheme
Feature of the present invention and other correlated characteristic are described in further detail by embodiment below in conjunction with accompanying drawing, so that technician's of the same trade understanding:
Optical communicating waveband 1.5 μ m are example with 1550nm in the present embodiment, and 1.3 μ m are example with 1310nm, and near its all band is consistent with the implementation method of these two wave bands; Pump light source is an example with the solid neodymium ion laser instrument of semiconductor diode pump among the present invention, and typical wavelengths is 1064nm and 1342nm, and the other types pumping source is consistent with implementation method in pump light wavelength and the inventive embodiments.The phase-matching condition of nonlinear crystal mainly contains the cutting angle of crystal, the working temperature of crystal; If it is the PPLN crystal, also relevant with returing cycle of crystal etc.
Produce the resonator cavity of pump light, the transmissivity of its outgoing mirror is generally a few percent or tens percent, and then the light intensity in the resonator cavity can reach tens times even tens times of output intensity.Nonlinear crystal is placed in this resonator cavity, can obtain being higher than effective incident intensity of 1-2 the order of magnitude of emergent light intensity.Because nonlinear crystal is placed the active cavity of pump light, the device that does not need to add just can obtain the incident pumping light power of high stable, and this also can improve the degree of stability of frequency inverted greatly.
In the present embodiment scheme, because nonlinear crystal is placed in the active resonant cavity of pump light, pump light continuous or pulse can be applied to frequency inverted of the present invention.In order to realize sufficient frequency inverted, flashlight and pump light also will be realized overlapping in time.If pump light is continuous, so the flashlight before the frequency inverted of incident can be continuous also can be pulse; If pump light is pulse, the single photon signal of incident also can only be pulse, so just might realize temporal coincidence.The rough schematic that technology realizes is as shown in Figure 1, 2:
(1) pump light is a continuous light:
According to shown in Figure 1, pump light is included in the converting system 2.At this moment, because pump light is continuous, so the single photon signal of continuous or pulse can be realized frequency inverted.But, because continuous pump light is difficult to reach very high power, so this moment, the effective nonlinear coefficient to the nonlinear crystal of use in the converting system 2 required than higher, as the accurate phase matching non-linear crystal of cycles such as PPLN (period polarized lithium niobate) crystal, PP-MgO:LN (lithium niobate of period polarized doped with magnesia) crystal polarization.
(2) pump light is a pulsed light
According to shown in Figure 2, pulse pump light is included in converting system 2
*In.At this moment, the single photon signal 1 of incident
*It is pulse.In order to make pump light, flashlight and detector reach synchronous in time, here control the triggering of single photon signal with clock 5, the triggering of pulse pump light and the triggering of detection system are constantly, and consider the priority that incident takes place, add time-delay, purpose is assurance pump light pulse and signal pulse time to go up inregister, guarantees the also punctual response of detector.Because pulse pump light can have very high peak power, correspondingly, the effective nonlinear coefficient of nonlinear crystal does not need very high, as BIBO (bismuth boracic acid) crystal.
Shown in Fig. 3-5, label 1-20 is respectively:
Optical fiber collimator 1: collimator distance satisfies the gauss light beam waist make behind the collimation and drops on the nonlinear crystal center;
Planar laser cavity reflection mirror 2: two sides plating anti-reflection film @ incoming signal optical band, simultaneously plate high-reflecting film @ pump light wave band near nonlinear crystal;
Nonlinear crystal 3: satisfy phase-matching condition, can realize the nonlinear crystal of the flashlight frequency translation that needs among the present invention, such as BIBO crystal, PPLN crystal or PP-MgO:LN crystal etc., working temperature is accurately controlled;
Amici prism 4: Brewster angle quartz prism;
Pumping source 5: the LD (semiconductor laser diode laser instrument) of optical fiber coupling output.Emission wavelength is 808nm, peak power output 20W.Be coupled on the gain medium by optical focusing system;
Concave surface laser cavity catoptron 6: two sides plating Zeng Toumo @808nm, curved surface plating high-reflecting film @ pumping laser wavelength, radius of curvature R=-100mm;
Laser gain crystal 7: mix Nd
3+The ion laser gain media is (as Nd
3+: GdVO
4, Nd
3+: YVO
4) length is 3mm, two sides plating anti-reflection film @ intracavity pump laser wavelength, doping content is 1%;
Concave surface laser cavity catoptron 8: two sides plating anti-reflection film @ incoming signal optical band, curved surface plating high-reflecting film @ intracavity pump optical band, reflectivity is 98%, radius of curvature R=-500mm;
Diaphragm 9: slit diaphragm;
Filter system 10: comprise that to change the back signal light wavelength be that the bandwidth at center is each a slice of plane mirror of interference filter and 0 ° of incident high-reflecting film @ pump light wavelength of plating and the two sides anti-reflection film @ conversion back signal light wavelength of 10nm;
Detector 11: silicon avalanche photodiode is operated under the single photon counting pattern;
Optical fiber polarization controller 12: the polarization direction that is used to control the optical fiber emergent light;
Collecting lens 13: about focal length 50mm, flashlight wave band anti-reflection film after the two sides plating frequency inverted;
Optoisolator 14: the device that only allows the light folk prescription to pass through to (clockwise or counterclockwise), operation wavelength is at the pump light wave band;
Active Q switched element 15: the acousto-optic of operation wavelength and pump light consistent wavelength or electric-optically Q-switched switch;
Active mode element 16: be used to realize the acousto-optic or the electrooptic modulator of active mode in the chamber, operation wavelength @ pump light wavelength.
Planar cavity mirror 17: pump light wave band of laser high reflective mirror, reflectivity is greater than 99.9%.Two surfaces are coated with the anti-reflection film of pumping source 808nm;
Coupling input cavity mirror 18: the planar laser catoptron, at pump light wave band reflectivity 95%;
Concave surface laser mirror 19: radius of curvature R=-75mm, the high-reflecting film of curved surface plating pump light wave band, R＞99.9%, the anti-reflection film of two sides plating frequency translation front signal optical band;
Concave surface laser mirror 20: radius of curvature R=-75mm, the high-reflecting film of curved surface plating pump light wave band, R＞99.9%, the anti-reflection film of flashlight wave band after the two sides plating frequency translation;
Embodiment 1.1:
The structural representation of realizing present embodiment as shown in Figure 3, resonator cavity comprises two sides plane mirror and two sides concave mirror, constitutes a ring resonator, satisfies the resonator cavity stable condition.This ring resonator is the active cavity that is used to produce pump light, has both obtained pump light in the chamber, also realizes frequency inverted simultaneously in the chamber.The pump light of 1064nm is produced by solid neodymium ion laser instrument.It is that the 808nm laser 5 of 20W is focused on the neodymium ion laser gain crystal 7 by optical system that the semiconductor diode laser of optical fiber coupling output produces maximum emergent power, realizes laser generation in ring-like laserresonator.Interpolation is gone into optoisolator in the chamber, can realize the single longitudinal mode traveling wave oscillation of pump light like this in ring cavity.The size of 1064nm laser power can be regulated by changing 808nm pump light 5 power that sent by LD in the chamber.The long nonlinear crystal PPLN of the 40mm that uses in this scheme, the two sides is coated with Zeng Toumo @631nm﹠amp; 1064nm﹠amp; 1550nm both in order to reduce low light level loss of signal, also is the insertion loss that reduces resonator cavity.
The PPLN crystal has utilized accurate phase matching to interact, and has selected specific polarization cycle to realize pump light 1064nm and incoming signal light 1550nm and interact frequently obtaining changing back flashlight 631nm, and effective nonlinear coefficient is about 16pm/V.The polarization cycle of the PPLN crystal that adopts in the present embodiment is 11.80 μ m or 12.0 μ m.The single photon signal of 1550nm is exported by optical fiber, adjusts through optical fiber polarization controller 12 and is polarized in 1064nm laser light field polarization unanimity in the resonator cavity, satisfies I class phase-matching condition.Through after the collimating apparatus 1, incide on the nonlinear crystal 3 centre position of dropping on nonlinear crystal with a tight waist of collimation.The temperature of nonlinear crystal is accurately controlled, and deviation is less than 0.1 ℃.The careful position of adjusting the 1550nm incident light, make incident light in nonlinear crystal with resonator cavity in the 1064nm light field well overlap.Like this, strong 1064nm pump light and weak 1550nm flashlight interact in nonlinear crystal, are converted to the flashlight of 631nm on the flashlight frequency of the 1550nm of incident.The pump light intensities of effective incident nonlinear crystal in the control chamber makes conversion efficiency reach the maximum quantum state transfer that also realized simultaneously.In order to reduce low light level signal (comprising 1550nm signal before the frequency inverted and the 631nm signal after the frequency inverted) loss, on the element of its process, all be coated with corresponding anti-reflection film.631nm flashlight after the conversion and the pump light of 1064nm are together outside the output cavity, spatially separate through Amici prism, by filter system and diaphragm the flashlight of 631nm is separated, and flashlight is collected with collecting lens, guarantee to be mapped to effective light-sensitive surface of APDs, just can survey then with silicon APDs.
Embodiment 1.2:
Compare with embodiment 1.1, the single photon signal of incident in the present embodiment is at the 1310nm wave band, and corresponding conversion back signal in band is 587nm.The laser mirror that relates among the embodiment 1.1 is at the anti-reflection film of the corresponding 1310nm of the being adjusted into wave band of the anti-reflection film of 1550nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1064nm, incoming signal light 1310nm and outgoing flashlight 587nm wave band.The phase-matching condition of nonlinear crystal also is adjusted into 1310nm and 1064nm and obtains 587nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 587nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 587nm, and catoptron anti-reflection film wavelength is adjusted into 587nm.Other elements, implementation method and step are identical with embodiment 1.1.
Embodiment 1.3:
Compare with embodiment 1.1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm, and the operation wavelength of optoisolator is adjusted to 1342nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1550nm and outgoing flashlight 719nm wave band.The phase-matching condition of nonlinear crystal is adjusted to 1550nm and 1342nm and is obtained 719nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 719nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 719nm, and catoptron anti-reflection film wavelength is adjusted into 719nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are identical with embodiment 1.1.
Embodiment 1.4:
Compare with embodiment 1.1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm, and the operation wavelength of optoisolator is adjusted to 1342nm.The wave band of incident single photon flashlight is 1310nm, and at the single photon signal input part, the anti-reflection film wave band at the laser mirror of 1550nm among the embodiment 1.1 is adjusted to 1310nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1310nm and outgoing flashlight 663nm wave band.The phase-matching condition of nonlinear crystal is adjusted to 1310nm and 1342nm and is obtained 663nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 663nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 663nm, and catoptron anti-reflection film wavelength is adjusted into 663nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are with identical with embodiment 1.1.
Embodiment 2.1:
As shown in Figure 4, among the embodiment, the pump light of 1064nm is produced by solid neodymium ion laser instrument.It is that the laser 5 of 20W is focused on the neodymium ion laser gain crystal 7 by optical system that the semiconductor diode laser of optical fiber coupling output produces maximum emergent power, realizes laser generation in the laserresonator of L type.The laserresonator of L type is to be made of two sides concave surface laser cavity catoptron 6 and 8 and planar laser cavity reflection mirrors 2, and the angle between two arms is approximately 18 °.Laser cavity structure satisfies stable resonator cavity condition.The reflectivity of 8 pairs of 1064nm laser of concave surface laser cavity catoptron is 98%, owing to along the direction of resonator cavity two arms laser emitting is arranged all, its total coupling output rating is about 3%, and endovenous laser is a linear polarization.When if the 1064nm Output optical power of resonator cavity is 3W, then the power in the chamber is 100W.The size of 1064nm laser power can be regulated by changing 808nm pump light 5 power that sent by LD in the chamber.Because the spot size of resonator cavity inner light beam is smaller on the close position of planar laser cavity reflection mirror 2, nonlinear crystal 3 is positioned over obtains bigger incident optical power density herein.The long nonlinear crystal PPLN of the 40mm that uses in this scheme two sides is coated with Zeng Toumo @631nm﹠amp; 1064nm﹠amp; 1550nm both in order to reduce low light level loss of signal, also is the insertion loss that reduces resonator cavity.
The PPLN crystal has utilized accurate phase matching to interact, and has selected specific polarization cycle to realize pump light 1064nm and incoming signal light 1550nm and interact frequently obtaining changing back flashlight 631nm, and effective nonlinear coefficient is about 16pm/V.Polarization cycle is identical with embodiment 1.1.The single photon signal of 1550nm is exported by optical fiber, adjusts through optical fiber polarization controller 12 and is polarized in 1064nm laser light field polarization unanimity in the resonator cavity, satisfies I class phase-matching condition.Through after the collimating apparatus 1, incide on the nonlinear crystal 3 centre position of dropping on nonlinear crystal with a tight waist of collimation.The temperature of nonlinear crystal is accurately controlled, and deviation is less than 0.1 ℃.The careful position of adjusting the 1550nm incident light, make incident light in nonlinear crystal with resonator cavity in the 1064nm light field well overlap.Like this, strong 1064nm pump light and weak 1550nm flashlight interact in nonlinear crystal, are converted to the flashlight of 631nm on the flashlight frequency of the 1550nm of incident.The pump light intensities of effective incident nonlinear crystal in the control chamber makes conversion efficiency reach the maximum quantum state transfer that also realized simultaneously.In order to reduce low light level signal (comprising 1550nm signal before the frequency inverted and the 631nm signal after the frequency inverted) loss, on the element of its process, all be coated with corresponding anti-reflection film.631nm flashlight after 1064nm pump light and the conversion is through outside concave surface laser cavity catoptron 8 output cavities, and this moment, they spatially still overlapped basically.Through behind the Amici prism 4, pump light and flashlight spatially are separated, and collect by the flashlight of collecting lens 13 with 631nm, make it can get on effective plane of incidence of silicon ADPs.Filter 1064nm pump light composition with slit diaphragm 9 spaces, only allow the flashlight of 631nm to pass through.For further purified signal light, in order to avoid be subjected to the interference of other band of light, before entering silicon avalanche photodiode detector 11, the filtering system 10 that we form at narrow band filter slice and the plane high reflective mirror of 631nm with centre wavelength is further isolated the weak signal light of 631nm.
Embodiment 2.2:
Compare with embodiment 2.1, the single photon signal of incident in the present embodiment is at the 1310nm wave band, and corresponding conversion back signal in band is 587nm.The laser mirror that relates among the embodiment 2.1 is at the anti-reflection film of the corresponding 1310nm of the being adjusted into wave band of the anti-reflection film of 1550nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1064nm, incoming signal light 1310nm and outgoing flashlight 587nm wave band.The phase-matching condition of nonlinear crystal also is adjusted into 1310nm and 1064nm and obtains 587nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 587nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 587nm, and catoptron anti-reflection film wavelength is adjusted into 587nm.Other elements, implementation method and step are consistent with embodiment 2.1.
Embodiment 2.3:
Compare with embodiment 2.1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1550nm and outgoing flashlight 719nm wave band.The phase-matching condition of nonlinear crystal is adjusted to 1550nm and 1342nm and is obtained 719nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 719nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 719nm, and catoptron anti-reflection film wavelength is adjusted into 719nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are consistent with embodiment 2.1.
Embodiment 2.4:
Compare with embodiment 2.1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm.The wave band of incident single photon flashlight is 1310nm, and at the single photon signal input part, the anti-reflection film wave band at the laser mirror of 1550nm in the former scheme is adjusted to 1310nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1310nm and outgoing flashlight 663nm wave band.The phase-matching condition of nonlinear crystal is adjusted to 1310nm and 1342nm and is obtained 663nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 663nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 663nm, and catoptron anti-reflection film wavelength is adjusted into 663nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are consistent with embodiment 2.1.
Embodiment 3.1:
As Fig. 5, to compare with embodiment 2, present embodiment has adopted the working method of pulse.Cavity resonator structure that adopts in the present embodiment and embodiment 2 are in full accord.For pump light is moved under pulse mode, we have inserted the Q switched element (can be acousto-optic Q modulation element or electric-optically Q-switched element) of 1064nm in the chamber.Q switched element can be used for regulating the loss of laser cavity.Transfer the process of Q to be described below: in laser pump (ing) just at first, Q switched element produces very high loss, makes the laser output of can't vibrating.Because continue pumping, energy is stored.This moment, Q switched element reduced the wastage suddenly, in the extremely short time energy stored was discharged, and promptly formed a strong laser pulse.The Q pulse has very high peak power, short pulse width.The repetition frequency of the triggering frequency lock 1064nm pump light Q impulse of Q switched element is consistent with the repetition frequency of flashlight.The 1550nm single photon flashlight of incident also is pulse, and pulsewidth is about 1 ns (10
-9S).As described in Figure 3, the triggering of flashlight, Q-switch element and detector is all by a time clock control, and suitably introducing time-delay, guarantees the trigger pulse coincidence in time of flashlight, pump light pulse and detector.
Nonlinear crystal 3 can use the low slightly crystal of effective nonlinear coefficient, BIBO crystal such as length 10mm, the cutting angle of crystal is: θ=7.7 °, the angular phase matching condition that obtains 631nm outgoing flashlight when 1064nm pump light and the incident of 1550nm incoming signal light positive the time with frequency is satisfied in =0 °.The crystal two sides is coated with Zeng Toumo @631nm﹠amp equally; 1064nm﹠amp; 1550nm.Q impulse width in the chamber is at 10ns (10
-9Second) magnitude, pulse width than the big magnitude of signal pulse about with bonding photon signal light fully by frequency inverted.Adjusting the power of 808nm pumping source and the width (adjusting Q-switch) of Q pulse makes the peak power (several kW magnitude) of pumping pulse satisfy the requirement of frequency inverted.The single photon signal of 1550nm is exported by optical fiber, adjusts through optical fiber polarization controller 12 and is polarized in 1064nm laser light field polarization unanimity in the resonator cavity, satisfies I class phase-matching condition.Through after the collimating apparatus 1, incide on the nonlinear crystal 3 centre position of dropping on nonlinear crystal with a tight waist of collimation.The careful position of adjusting the 1550nm incident light, make incident light in nonlinear crystal with resonator cavity in the 1064nm light field well overlap.On the flashlight frequency of the 1550nm of incident under non-linear and the effect frequently, be converted to the flashlight of 631nm.In order to reduce low light level signal (comprising 1550nm signal before the frequency inverted and the 631nm signal after the frequency inverted) loss, on the element of its process, all be coated with the anti-reflection film of corresponding wave band.631nm flashlight after 1064nm pump light and the conversion is through outside concave surface laser cavity catoptron 8 output cavities, and this moment, they spatially still overlapped basically.Through behind the Amici prism 4, pump light and flashlight spatially are separated, and collect by the flashlight of collecting lens 13 with 631nm, make it can get on effective plane of incidence of silicon ADPs.Filter 1064nm pump light composition with slit diaphragm 9 spaces, only allow the flashlight of 631nm to pass through.Filter system 10 comprises narrow band filter slice and the plane high reflective mirror of centre wavelength at 631nm, can further isolate the flashlight of 631nm.
Embodiment 3.2:
Compare with embodiment 3.1, the single photon signal of incident in the present embodiment is at the 1310nm wave band, and corresponding conversion back signal in band is 587nm.The laser mirror that relates in the scheme 3.1 is at the anti-reflection film of the corresponding 1310nm of the being adjusted into wave band of the anti-reflection film of 1550nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1064nm, incoming signal light 1310nm and outgoing flashlight 587nm wave band.The phase-matching condition of nonlinear crystal also is adjusted into 1310nm and 1064nm and obtains 587nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 587nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 587nm, and catoptron anti-reflection film wavelength is adjusted into 587nm.Other elements, implementation method and step are consistent with scheme 3.1.
Embodiment 3.3:
Compare with embodiment 3.1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm.The operation wavelength of Q-switch is adjusted into 1342nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1550nm and outgoing flashlight 719nm wave band.The phase-matching condition of nonlinear crystal is adjusted to 1550nm and 1342nm and is obtained 719nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 719nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 719nm, and catoptron anti-reflection film wavelength is adjusted into 719nm, and high anti-wavelength is adjusted to 1342nm.Other elements, implementation method and step are consistent with embodiment 3.1.
Embodiment 3.4:
Compare with embodiment 3.1, the pump light wavelength that uses in this programme is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm.The wave band of incident single photon flashlight is 1310nm, and at the single photon signal input part, the anti-reflection film wave band at the laser mirror of 1550nm in the former scheme is adjusted to 1310nm.The operation wavelength of Q-switch is adjusted into 1342nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1310nm and outgoing flashlight 663nm wave band.The phase-matching condition of nonlinear crystal is adjusted to 1310nm and 1342nm and is obtained 663nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 663nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 663nm, and catoptron anti-reflection film wavelength is adjusted into 663nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are consistent with embodiment 3.1.
Embodiment 4.1:
Mode locking pulse can obtain higher peak power equally, has replaced the method for the accent Q among the embodiment 3 in the present embodiment with the method for active mode.Active mode locking technique is to place a modulator in laser cavity, the modulation that this modulator produces an amplitude or phase place to endovenous laser, and purpose is to make the longitudinal mode spacing in the chamber equal fully.Realize coherence stack between each longitudinal mode that equates at interval, so obtain the laser pulse of high-peak power, short pulse width.Because the repetition frequency of mode locking pulse is by the length decision of laserresonator, when so we design cavity resonator structure, set the suitable cavity length value, make the pump light repetition frequency equal the flashlight repetition frequency, or the integral multiple of flashlight repetition frequency, we could guarantee that pump light pulse and signal pulse can be corresponding one by one like this, realize in time overlapping.Because pump light is pulse, also be pulse so be used for the flashlight of frequency inverted, realize synoptic diagram as shown in Figure 2.It is narrow that mode locking pulse has pulse width, and the characteristics that repetition frequency is high can realize the incoming signal light frequency conversion of high repetition frequency on the one hand, also require flashlight to have very narrow pulse width on the other hand.In this programme, the pulse width of pump light is about tens ps (10
-12S), repetition frequency tens MHz, the signal pulse width of incident is about several ps, and repetition frequency can be up to several MHz even tens MHz.
The structural representation of present embodiment and Fig. 5 basically identical, because the length setting of resonator cavity is a specific value, the radius-of-curvature of each concave surface laser mirror has also been done corresponding adjustment, what insert in the chamber in addition is not the Q-switch element, but can produce the acousto-optic or the electrooptic modulator 16 of locked mode modulation, the operation wavelength of modulator is at 1064nm.As described in Figure 2, the triggering of flashlight, electric light or acousto-optic modulator and detector is all by a time clock control, and suitably introducing time-delay, guarantees the trigger pulse coincidence in time of flashlight, pump light pulse and detector.
Nonlinear crystal is placed in the resonator cavity of solid neodymium ion laser instrument, as pumping source, produces the pump light mode locking pulse of 1064nm by the semiconductor diode laser of 808nm in the chamber.Because be operation under the high power, the same with embodiment 3, present embodiment also can use the lower crystal of effective nonlinear coefficient.The phase-matching condition of nonlinear crystal satisfies pump light 1064nm and flashlight 1550nm and frequently produces 631nm, and the crystal two sides is coated with anti-reflection film.The single photon signal polarisation of light of adjusting incident 1550nm makes it to satisfy I class phase matching.Adjust the output power of 808nm pumping source, make the pump light pulse peak power in the chamber satisfy the condition of frequency conversion efficiency maximum.All be coated with the anti-reflection film of corresponding wave band at flashlight (631nm after 1550nm before comprising conversion and the conversion) element surface of process.631nm flashlight after the conversion and the pump light of 1064nm are together outside the output cavity, spatially separate through Amici prism, by filter system and diaphragm the flashlight of 631nm is separated, and flashlight is collected with collecting lens, guarantee to be mapped to effective light-sensitive surface of APDs, just can survey then with silicon APDs.
Embodiment 4.2:
Compare with embodiment 4.1, the single photon signal of incident in the present embodiment is at the 1310nm wave band, and corresponding conversion back signal in band is 587nm.The laser mirror that relates among the embodiment 4.1 is at the anti-reflection film of the corresponding 1310nm of the being adjusted into wave band of the anti-reflection film of 1550nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1064nm, incoming signal light 1310nm and outgoing flashlight 587nm wave band.The phase-matching condition of nonlinear crystal also is adjusted into 1310nm and 1064nm and obtains 587nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 587nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 587nm, and catoptron anti-reflection film wavelength is adjusted into 587nm.Other elements, implementation method and step are consistent with embodiment 4.1.
Embodiment 4.3:
Compare with embodiment 4.1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1550nm and outgoing flashlight 719nm wave band.The operation wavelength of modulator is adjusted into 1342nm.The phase-matching condition of nonlinear crystal is adjusted to 1550nm and 1342nm and is obtained 719nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 719nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 719nm, and catoptron anti-reflection film wavelength is adjusted into 719nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are consistent with embodiment 4.1.
Embodiment 4.4:
Compare with embodiment 4-1, the pump light wavelength that uses in the present embodiment is 1342nm, and the solid neodymium ion laser instrument by semiconductor diode pump produces equally.The high anti-wave band of each laser cavity catoptron is adjusted to 1342nm.The wave band of incident single photon flashlight is 1310nm, and at the single photon signal input part, the anti-reflection film wave band at the laser mirror of 1550nm in the former scheme is adjusted to 1310nm.Nonlinear crystal two surface coatings are adjusted into the anti-reflection film of pump light 1342nm, incoming signal light 1310nm and outgoing flashlight 663nm wave band.The operation wavelength of modulator is adjusted into 1342nm.The phase-matching condition of nonlinear crystal is adjusted to 1310nm and 1342nm and is obtained 663nm output frequently.An end of flashlight output after conversion, the anti-reflection film of laser mirror and collecting lens is adjusted into the 663nm wave band.In the filter system, the centre wavelength of optical filter is adjusted into 663nm, and catoptron anti-reflection film wavelength is adjusted into 663nm, and the high-reflecting film wavelength is adjusted into 1342nm.Other elements, implementation method and step are consistent with embodiment 4.1.
Though below design and embodiment according to the object of the invention are described in detail with reference to accompanying drawing, but those of ordinary skills can recognize, under the precondition that does not break away from the claim limited range, still can make various improvement and conversion to the present invention, for example: the conversion of nonlinear crystal kind, the conversion of light path, meet the conversion or the like of the laser optical source category resonant cavity structure of request for utilization of the present invention.
Claims (5)
1, a kind of method of optical communicating waveband single photon high-efficient detection, it is characterized in that this method at first puts into nonlinear crystal the active resonant cavity of pump light, to advance nonlinear crystal as the single-photon incident of flashlight, this nonlinear crystal is optically pumped, pumping light frequency wherein is greater than the frequency of single-photon source, adjusting flashlight overlaps in nonlinear crystal with intracavity pump light, and satisfy phase-matching condition, feasible single-photon source and pump light generation and frequency as flashlight, again with each frequency spectrum composition of emergent light separately with dispersion element, leach the near-infrared band single photon flashlight composition after the conversion, survey with silicon APDs afterwards.
2, the method for a kind of optical communicating waveband single photon high-efficient detection according to claim 1 is characterized in that described single photon as flashlight refers to optical communicating waveband single photon.
3, the method for a kind of optical communicating waveband single photon high-efficient detection according to claim 1, it is characterized in that described nonlinear crystal has referred to second order nonlinear effect, and logical optical band comprises the nonlinear crystal of pump light, incoming signal light and conversion back signal light wavelength.。
4, the method for a kind of optical communicating waveband single photon high-efficient detection according to claim 1 is characterized in that described pumping light intensity should make nonlinear crystal produce nonlinear polarization at least, but can not surpass the damage threshold of nonlinear crystal.
5, the production method of a kind of communication band single-photon source according to claim 1 is characterized in that described phase-matching condition refers to angular phase coupling or accurate phase matching.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102147293A (en) * | 2010-11-18 | 2011-08-10 | 南京大学 | Single photon detector based on polarization unrelated frequency up-conversion |
| CN103488022A (en) * | 2013-09-11 | 2014-01-01 | 华东师范大学 | Polarization-independent quantum frequency upconversion method |
| CN108663870A (en) * | 2018-05-23 | 2018-10-16 | 中国电子科技集团公司第四十研究所 | One kind can forecast single-photon source generation device |
| CN113310574A (en) * | 2021-06-01 | 2021-08-27 | 中国电子科技集团公司第四十一研究所 | Superconducting single photon detector detection efficiency testing device and method |
| CN114486788A (en) * | 2021-09-29 | 2022-05-13 | 华东师范大学重庆研究院 | Large-view-field ultra-sensitive intermediate infrared frequency up-conversion imaging technology and device |
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| US6078052A (en) * | 1997-08-29 | 2000-06-20 | Picker International, Inc. | Scintillation detector with wavelength-shifting optical fibers |
| JP3682266B2 (en) * | 2002-03-28 | 2005-08-10 | 株式会社東芝 | Single photon generator |
| CN1228646C (en) * | 2003-07-18 | 2005-11-23 | 华东师范大学 | Single photon detector with high counting rate |
| CN1295896C (en) * | 2003-11-11 | 2007-01-17 | 中国科学院武汉物理与数学研究所 | Space quantum communication unit using atom light filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102147293A (en) * | 2010-11-18 | 2011-08-10 | 南京大学 | Single photon detector based on polarization unrelated frequency up-conversion |
| CN103488022A (en) * | 2013-09-11 | 2014-01-01 | 华东师范大学 | Polarization-independent quantum frequency upconversion method |
| CN103488022B (en) * | 2013-09-11 | 2016-04-06 | 华东师范大学 | Conversion method on the quantum frequency that a kind of polarization is irrelevant |
| CN108663870A (en) * | 2018-05-23 | 2018-10-16 | 中国电子科技集团公司第四十研究所 | One kind can forecast single-photon source generation device |
| CN113310574A (en) * | 2021-06-01 | 2021-08-27 | 中国电子科技集团公司第四十一研究所 | Superconducting single photon detector detection efficiency testing device and method |
| CN113310574B (en) * | 2021-06-01 | 2022-07-15 | 中国电子科技集团公司第四十一研究所 | Superconducting single photon detector detection efficiency testing device and method |
| CN114486788A (en) * | 2021-09-29 | 2022-05-13 | 华东师范大学重庆研究院 | Large-view-field ultra-sensitive intermediate infrared frequency up-conversion imaging technology and device |
| CN114486788B (en) * | 2021-09-29 | 2024-02-13 | 华东师范大学重庆研究院 | Mid-infrared frequency up-conversion imaging technology and device with large visual field and ultrasensitive function |
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