High-efficiency superconducting nanowire single-photon detector without polarization selection and preparation method thereof
Technical Field
The invention relates to a superconducting nanowire single-photon detector and a preparation method thereof, in particular to a high-efficiency superconducting nanowire single-photon detector without polarization selection and a preparation method thereof, belonging to the technical field of optical signal detection.
Background
The Superconducting Nanowire Single Photon Detector (SNSPD) is an important high-sensitivity Single Photon Detector, compared with the traditional semiconductor Detector, the SNSDP has the advantages of high response speed, low background noise and small time jitter, and the detection wave band covers from visible light to infrared light.
The working principle of the superconducting nanowire single photon detection device is as follows: the SNSPD is placed in a low-temperature environment (<4K) to be in a superconducting state, meanwhile, a bias current Ib (Ib is slightly smaller than a switching current Iswitch for switching the device to a normal state) is applied to the SNSPD, when a single photon or a plurality of photons are incident on the superconducting nanowire and absorbed, a Kuebu electron pair in the superconducting state can be formed in a scattered mode, a large number of hot electrons are formed, the hot electrons are diffused to form a local hot spot, joule heat is generated under the action of the bias current Ib, then the nanowire is enabled to form a resistance area, a fast voltage pulse signal (namely a photon signal) is generated at two ends of the device at the moment, and finally detection is achieved. SNSPD has been widely used in important fields such as quantum communication, quantum optics and biological single molecule fluorescence spectroscopy.
At present, the traditional SNSPD device consists of a periodic superconducting nanowire with a winding curve shape, is close to a grating in optical response, has obvious polarization selectivity on the absorption of incident light, and has uniform distribution and high absorptivity in the superconducting nanowire when the polarization direction of the incident light is parallel to the superconducting nanowire; when the polarization direction of the incident light is perpendicular to the superconducting nanowire, the incident light is absorbed less at the two side edges of the superconducting nanowire and more at the center of the superconducting nanowire, and the overall absorption rate is much smaller than that of the incident light with parallel polarization. The selective absorption depending on the polarization direction of incident light is a disadvantage of the superconducting nanowire single photon detector, and the performance and the application of the detector are severely limited. Chinese patent document CN104091883A discloses a superconducting nanowire single photon detector based on a dielectric thin film mirror, but the distributed bragg mirror has a complex structure process, and only has an enhancement effect on incident light in a specific incident direction and a specific wavelength range, and meanwhile, the arrangement mode of the superconducting nanowires (the superconducting nanowires typically have a thickness of 5 nm and a width of 100 nm, and are of a zigzag meandering periodic structure) only deviates from the incident light of which the absorption polarization direction is parallel to the superconducting nanowires, and the absorption efficiency is relatively low.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a high-efficiency superconducting nanowire single photon detector without polarization selection and a preparation method thereof. The detector utilizes the medium nanowires to modulate the electromagnetic field distribution of incident light, and uses the medium layer and the metal film reflecting mirror with simple preparation process, thereby solving the problem that the existing detector has difference in the absorption of the incident light in different polarization directions, and simultaneously ensuring that the absorption efficiency of the device on the incident light in each polarization direction reaches about 90 percent.
The technical scheme of the invention is as follows:
a high-efficiency superconducting nanowire single-photon detector without polarization selection comprises:
a substrate;
a metal film reflecting mirror combined with the surface of the substrate;
the dielectric layer is combined on the surface of the metal thin film reflector;
a superconducting nanowire bonded to a surface of the dielectric layer;
and the dielectric nanowire is combined on the surface of the superconducting nanowire and the surface of the dielectric layer.
According to the present invention, preferably, the substrate is at least one of a silicon substrate, a gallium arsenide substrate, a silicon carbide substrate, a magnesium oxide substrate, and a sapphire substrate;
preferably, the thickness of the substrate is 300-500 microns.
According to the present invention, preferably, the metal thin film mirror includes a first thin film layer and a second thin film layer;
preferably, the material of the first thin film layer is titanium or indium, and the first thin film layer is combined on the surface of the substrate;
preferably, the material of the second thin film layer is one of gold, silver or aluminum, and the second thin film layer is combined on the surface of the first thin film layer; the first thin film layer can increase bonding of the second thin film layer to the substrate.
According to the invention, preferably, the thickness of the metal thin film reflector is 100-300 nanometers; wherein, the thickness of the first thin film layer is 10-50 nanometers, and the thickness of the second thin film layer is 90-250 nanometers.
According to the present invention, preferably, the dielectric layer material is Si, SiO2、Si3N4At least one of;
preferably, the thickness of the dielectric layer is 50-500 nm.
According to the present invention, preferably, the superconducting nanowire material is at least one of WSi, MoSi, MoGe, NbN, Nb, TaN, NbTiN;
preferably, the thickness of the superconducting nanowire is 4-10 nanometers, and the width of the superconducting nanowire is 50-500 nanometers.
According to the invention, preferably, the superconducting nanowires are periodically arranged in a zigzag shape with a right angle, and the distance between adjacent superconducting nanowires is 0.5-2 times the width of the nanowires.
According to the invention, preferably, the dielectric nanowire material is Si, SiO2、Si3N4At least one of them, the thickness is 10 to 100 nm.
According to the present invention, preferably, the dielectric nanowire bonded to the surface of the superconducting nanowire is located in the middle of the surface of the superconducting nanowire and aligned with the center of the superconducting nanowire, and the width of the dielectric nanowire is 20 nm to the width of a single superconducting nanowire.
According to the present invention, it is preferable that the dielectric nanowires bonded to the surface of the dielectric layer are filled between adjacent superconducting nanowires, and the width of the dielectric nanowires is equal to the distance between the adjacent superconducting nanowires.
According to the invention, the preparation method of the high-efficiency superconducting nanowire single photon detector without polarization selection comprises the following steps:
(1) evaporating a metal film reflecting mirror on the pretreated substrate by electron beam evaporation or magnetron sputtering;
(2) depositing a dielectric layer on the metal film reflector by Plasma Enhanced Chemical Vapor Deposition (PECVD);
(3) depositing a layer of superconducting thin film on the dielectric layer through magnetron sputtering, preparing an electrode through ultraviolet lithography, and etching periodically arranged meandering and right-angled superconducting nanowires on the superconducting thin film through electron beam exposure and reactive ion etching;
(4) depositing a layer of dielectric film on the device through Plasma Enhanced Chemical Vapor Deposition (PECVD), removing the dielectric film at the edge of the surface of the superconducting nanowire through electron beam exposure and reactive ion etching processes, and reserving the dielectric film between the middle part of the surface of the superconducting nanowire and the superconducting nanowire to form the dielectric nanowire.
According to the preparation method of the present invention, preferably, the pretreatment step in the step (1) is: and cleaning the substrate by using acetone, ethanol and deionized water respectively for 5 minutes in sequence, and finally drying by using nitrogen.
The invention has the following technical characteristics and beneficial effects:
1. the high-efficiency superconducting nanowire single photon detector without polarization selection has the advantages of no incident light polarization absorption difference and high overall absorption rate. The medium nanowire in the single photon detector can modulate the electromagnetic field distribution of incident light, so that the absorption distribution of the incident light in each polarization direction in the superconducting nanowire tends to be uniform; the medium layer and the metal film reflecting mirror in the single photon detector can improve the absorption rate of incident light in each polarization direction.
2. The high-efficiency superconducting nanowire single photon detector without polarization selection is simple in preparation process, simple in medium layer and metal film reflecting mirror process relative to a full medium layer reflecting mirror (distributed Bragg reflector), and capable of effectively reflecting light in all incident directions.
Drawings
Fig. 1 is a schematic structural cross-sectional view of a superconducting nanowire single photon detection device with a front-incident structure in the prior art.
FIG. 2 is a schematic structural cross-sectional view of a high-efficiency superconducting nanowire single photon detector without polarization selection according to the present invention.
FIG. 3 is a calculation result of spatial distribution of absorption of two polarized lights in a single superconducting nanowire in the high efficiency superconducting nanowire single photon detector without polarization selection provided in example 1, wherein the horizontal axis represents the direction across the width of the single superconducting nanowire of 150 nm width, the vertical axis represents the value of light absorption efficiency, and the solid line and the short transverse line represent absorption distribution of polarized light parallel to the superconducting nanowire (solid line) and polarized light perpendicular to the superconducting nanowire (short transverse line) without a dielectric nanowire and a metal thin film mirror; the dotted and dotted lines represent the absorption profiles of polarized light parallel to the superconducting nanowire (dotted lines) and polarized light perpendicular to the superconducting nanowire (dotted and transverse lines) in the presence of the dielectric nanowire and the metal thin film mirror.
Description of the element reference numerals
10 a substrate; 11 distributed bragg mirrors; 111SiO 22A thin film layer; 112Si thin film layer; 12 superconducting nanowires; 13 a dielectric layer; 14 a grating structure; 20 a substrate; 21 a metal thin film mirror; 22 a dielectric layer; 23 superconducting nanowires; 24 dielectric nanowires; 241 a dielectric nanowire bonded to the surface of the dielectric layer; 242 to the surface of the superconducting nanowire.
Detailed Description
The embodiments of the present invention are illustrated below by specific examples, and other advantages of the present invention can be easily understood by those skilled in the art from the contents of the present specification. The invention is capable of other and different embodiments and its several details are capable of modifications and various obvious aspects, all without departing from the spirit and scope of the present invention. Please refer to fig. 2 to fig. 3. It should be noted that the drawings shown in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number of components and the shape and size in the actual implementation, and the type, the number and the proportion of the components in the actual implementation can be changed freely, and the layout of the components can be more complicated.
Example 1
As shown in fig. 2, the present embodiment provides a high-efficiency superconducting nanowire single photon detector without polarization selection, which includes:
a substrate 20;
a metal thin film mirror 21 bonded to the surface of the substrate 20;
a dielectric layer 22 combined with the surface of the metal thin film reflector 21;
a superconducting nanowire 23 bonded to the surface of the dielectric layer 22;
the dielectric nanowires 24 are combined on the surfaces of the superconducting nanowires 23 and the dielectric layer 22, wherein the dielectric nanowires 241 are combined on the surface of the dielectric layer 22 and filled between the adjacent superconducting nanowires 23; the dielectric nanowire 242 is bonded to the surface of the superconducting nanowire 23, is positioned in the middle of the surface of the superconducting nanowire 23, and is aligned with the center of the superconducting nanowire 23.
Wherein, the substrate 20 is a silicon substrate with a thickness of 300 μm;
the metal film reflector 21 comprises a titanium film and a gold film, and the thicknesses of the titanium film and the gold film are 20 nanometers and 90 nanometers respectively;
the dielectric layer 22 is SiO, and the thickness of the dielectric layer is 50 nanometers;
the superconducting nanowires 23 are NbN, the width of the superconducting nanowires is 150 nanometers, the thickness of the superconducting nanowires is 4 nanometers, the spacing between the nanowires is 150 nanometers, and the superconducting nanowires 23 are arranged in a periodic winding right-angle zigzag manner;
the medium nanowire 24 is Si and has the thickness of 10 nanometers; the width of the medium nanowire 241 which is combined on the surface of the medium layer 22 and filled between the adjacent superconducting nanowires 23 is 150 nanometers; the width of the dielectric nanowire 242, which is combined with the surface of the superconducting nanowire 23, is 20 nm, and is located at the middle of the surface of the superconducting nanowire 23 and aligned with the center of the superconducting nanowire 23.
The preparation method of the high-efficiency superconducting nanowire single photon detector without polarization selection comprises the following steps:
(1) washing the substrate with acetone, ethanol and deionized water for 5 minutes respectively in sequence, and finally drying the substrate with nitrogen to obtain a pretreated substrate; evaporating a metal film reflecting mirror on the pretreated substrate by electron beam evaporation or magnetron sputtering;
(2) depositing a dielectric layer on the metal film reflector by Plasma Enhanced Chemical Vapor Deposition (PECVD);
(3) depositing a layer of superconducting thin film on the dielectric layer through magnetron sputtering, preparing an electrode through ultraviolet lithography, and etching periodically arranged meandering and right-angled superconducting nanowires on the superconducting thin film through electron beam exposure and reactive ion etching;
(4) depositing a layer of dielectric film on the device through Plasma Enhanced Chemical Vapor Deposition (PECVD), removing the dielectric film at the edge of the surface of the superconducting nanowire through electron beam exposure and reactive ion etching processes, and reserving the dielectric film between the middle part of the surface of the superconducting nanowire and the superconducting nanowire to form the dielectric nanowire.
The calculation result of the spatial distribution of the absorption of two polarized lights in a single superconducting nanowire in the high-efficiency superconducting nanowire single photon detector without polarization selection provided by this embodiment is shown in fig. 3, where the horizontal axis represents the direction of the width of the single superconducting nanowire spanning 150 nm, and the vertical axis is the value of the light absorption efficiency. Wherein the solid and short transverse lines represent the absorption profiles of polarized light parallel to the superconducting nanowire (solid line) and polarized light perpendicular to the superconducting nanowire (short transverse line) without the dielectric nanowire and the metal thin film mirror; the dotted and dotted lines represent the absorption profiles of polarized light parallel to the superconducting nanowire (dotted lines) and polarized light perpendicular to the superconducting nanowire (dotted and transverse lines) in the presence of the dielectric nanowire and the metal thin film mirror. As can be seen from fig. 3, the existence of the dielectric nanowire and the metal thin film mirror not only improves the spatial uniformity of the absorption distribution of the vertically polarized incident light in the superconducting nanowire, but also improves the absorption efficiency of both polarized lights from less than 20% to about 90%.
Example 2
As shown in fig. 2, the present embodiment provides a high-efficiency superconducting nanowire single photon detector without polarization selection, which includes:
a substrate 20;
a metal thin film mirror 21 bonded to the surface of the substrate 20;
a dielectric layer 22 combined with the surface of the metal thin film reflector 21;
a superconducting nanowire 23 bonded to the surface of the dielectric layer 22;
the dielectric nanowires 24 are combined on the surfaces of the superconducting nanowires 23 and the dielectric layer 22, wherein the dielectric nanowires 241 are combined on the surface of the dielectric layer 22 and filled between the adjacent superconducting nanowires 23; the dielectric nanowire 242 is bonded to the surface of the superconducting nanowire 23, is positioned in the middle of the surface of the superconducting nanowire 23, and is aligned with the center of the superconducting nanowire 23.
Wherein, the substrate 20 is a gallium arsenide substrate, the thickness of which is 500 micrometers;
the metal film reflector 21 comprises an indium film and a silver film, and the thicknesses of the indium film and the silver film are respectively 50 nanometers and 200 nanometers;
the dielectric layer 22 is made of Si, and the thickness of the dielectric layer is 500 nanometers;
the superconducting nanowires 23 are WSi, the width of each superconducting nanowire is 500 nanometers, the thickness of each superconducting nanowire is 10 nanometers, the spacing between the nanowires is 500 nanometers, and the superconducting nanowires 23 are arranged in a periodic winding right-angle zigzag manner;
the medium nanowire 24 is SiO, and the thickness is 100 nanometers; the width of the medium nanowire 241 which is combined on the surface of the medium layer 22 and filled between the adjacent superconducting nanowires 23 is 500 nanometers; the width of the dielectric nanowire 242, which is combined with the surface of the superconducting nanowire 23, is positioned at the middle of the surface of the superconducting nanowire 23, and is aligned with the center of the superconducting nanowire 23, is 400 nm.
The preparation method of the high-efficiency superconducting nanowire single photon detector without polarization selection is as described in embodiment 1.
Example 3
The embodiment provides a high-efficiency superconducting nanowire single photon detector without polarization selection, and the basic structure and the preparation method of the detector are as described in embodiment 1, except that the substrate 20 is a silicon carbide substrate, and the superconducting nanowire 23 is MoSi.
Example 4
The embodiment provides a high-efficiency superconducting nanowire single photon detector without polarization selection, and the basic structure and the preparation method thereof are as described in embodiment 1, except that the substrate 20 is a sapphire substrate, and the dielectric layer 22 is Si3N4。