US-12618711-B2 - Single photon detector device for detecting an optical signal

US12618711B2US 12618711 B2US12618711 B2US 12618711B2US-12618711-B2

Abstract

The invention relates to a single photon detector device ( 10 ) for detecting an optical signal ( 36 ), comprising at least one optical waveguide ( 12 ) and a nanowire ( 18 ), wherein: the at least one waveguide ( 12 ) is designed to guide the optical signal ( 36 ) along an optical axis ( 14 ) in two opposing directions ( 16 a, 16 b ); the nanowire ( 18 ) is curved at least in some parts within a region ( 20 ) defined by the at least one waveguide ( 12 ); the nanowire ( 18 ) is shaped in such a way that within a region ( 20 ) defined by the at least one waveguide ( 12 ) the nanowire ( 18 ) a) is substantially mirror-symmetrical with respect to a plane ( 24 ) perpendicular to the optical axis ( 14 ), or b) is substantially point-symmetrical with respect to a point ( 26 ) within the region ( 20 ) defined by the at least one waveguide ( 12 ); within the region ( 20 ) defined by the waveguide ( 12 ) deviations of up to ±5% in each spatial direction and/or of up to ±10 μm along the optical axis are possible.

Inventors

Nicolai Walter
Wolfram Pernice
Fabian Beutel
Wladick Hartmann
Martin Wolff

Assignees

Pixel Photonics GmbH

Dates

Publication Date: 20260505
Application Date: 20220728
Priority Date: 20210802

Claims (9)

1 . A single photon detector device for detecting an optical signal, comprising: at least one optical waveguide and a nanowire, wherein the at least one waveguide is designed to guide the optical signal along an optical axis in two mutually opposite directions, wherein the nanowire is at least partly curved within a region defined by the at least one waveguide, and wherein the nanowire is shaped in such a way that within the region defined by the at least one waveguide the nanowire a) is substantially mirror-symmetrical relative to a plane-perpendicular to the optical axis, or b) is substantially point-symmetrical relative to a point within the region defined by the at least one waveguide, wherein, within the region defined by the waveguide, deviations from symmetry of up to ±5% in each spatial direction and/or of up to ±10 μm along the optical axis are possible; and a coupler, wherein the coupler is connected to two ends of the at least one waveguide and is designed in such a way that an optical signal is able to be incoupled into different ends of the at least one waveguide depending on its polarization, and wherein the nanowire is arranged in a region between the two ends of the at least one waveguide.
2 . The single photon detector device as claimed in claim 1 , wherein the nanowire is shaped according to feature a) and wherein two ends of the nanowire outside the region defined by the waveguide are on the same side of the at least one waveguide.
3 . The single photon detector device as claimed in claim 1 , wherein the nanowire is shaped according to feature b) and wherein two ends of the nanowire outside the region defined by the waveguide are each on mutually opposite sides of the at least one waveguide.
4 . The single photon detector device as claimed in claim 1 , wherein within the region defined by the at least one waveguide the nanowire has a meandering shape, an S-shape and/or an oval shape.
5 . The single photon detector device as claimed claim 1 , wherein the single photon detector device comprises a plurality of waveguides crossing one another, wherein the plurality of waveguides are designed to guide the optical signal along a respective optical axis in two mutually opposite directions.
6 . The single photon detector device as claimed in claim 5 , wherein two ends of the nanowire are in each case on the same side of each waveguide of the plurality of waveguides.
7 . The single photon detector device as claimed in claim 5 , wherein the plurality of waveguides cross one another in a common region.
8 . The single photon detector device as claimed in claim 1 , wherein the nanowire is curved in each case within the region defined by each waveguide, and wherein the nanowire is shaped in such a way that in each case within the region defined by each waveguide the nanowire is mirror-symmetrical relative to a plane perpendicular to the optical axis of the respective waveguide, wherein within the region defined by each waveguide in each case deviations from symmetry of up to ±5% in each spatial direction and/or of up to ±10 μm along the respective optical axis are possible.
9 . The single photon detector device as claimed in claim 1 , wherein the nanowire is applied on the optical waveguide or is integrated into the waveguide.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a § 371 national stage entry of International Application No. PCT/EP2022/071278, filed on Jul. 28, 2022, which claims priority to German Patent Application No. 10 2021 119 979.4, filed on Aug. 2, 2021, the entire contents of which are incorporated herein by reference. The invention relates to a single photon detector device for detecting an optical signal, comprising at least one optical waveguide and a nanowire. Waveguide-integrated superconducting photon detectors, and in particular their subtype superconducting nanowire single photon detectors (SNSPDs), highly efficiently detect broadband light which propagates in a waveguide on which they are integrated. SNSPDs have a nanowire as the actual detector element, said nanowire being superconducting at sufficiently low temperatures. In the case of SNSPDs known in the prior art, as are illustrated in FIG. 1, the nanowire 1 extends either in a U-shape or W-shape along an optical axis 2 of the waveguide 3. By virtue of the nanowire 1 extending along the optical axis 2, the absorption of the light guided in the waveguide 3 by the nanowire 1 is dependent on the length thereof, such that the absorption of the nanowire 1 and thus the efficiency of the detector can be defined by the length of the nanowire 1. These shapings have the disadvantage, however, that the efficiency of the SNSPD varies depending on the direction 4a, 4b from which the light is guided in the waveguide 3. SNSPDs having I-shaped nanowires 1 extending perpendicular to the optical axis 2 are additionally known in the prior art. However, on account of their extending perpendicular to the optical axis 2, these nanowires have only very low absorption, and so these SNSPDs do not allow highly efficient detection of light. Taking this as a departure point, it is an object of the invention to provide a single photon detector having a reduced difference in the detection efficiency for light having different propagation directions. In particular, it is an object of the invention to provide a single photon detector which detects light from different propagation directions with substantially equivalently high efficiency. This object is achieved by means of the features of the independent patent claim. Preferred developments are found in the dependent claims. The invention thus provides a single photon detector device for detecting an optical signal, comprising at least one optical waveguide and a nanowire, wherein the at least one waveguide is designed to guide the optical signal along an optical axis in two mutually opposite directions, wherein the nanowire is at least partly curved within a region defined by the at least one waveguide, and wherein the nanowire is shaped in such a way that within the region defined by the at least one waveguide the nanowire a) is substantially mirror-symmetrical relative to a plane perpendicular to the optical axis, orb) is substantially point-symmetrical relative to a point within the region defined by the at least one waveguide, wherein within the region defined by the waveguide deviations from symmetry of up to ±5% in each spatial direction and/or of up to ±10 μm along the optical axis are possible. The heart of the invention is to shape the nanowire within the region defined by the waveguide in a specific shape having at least one curvature and a substantially mirror-symmetrical or substantially point-symmetrical design. This makes it possible, firstly, that the single photon detector device can highly efficiently detect the optical signal guided in the waveguide and, secondly, that the differences in the efficiency with which the single photon detector device detects the optical signal depending on the propagation direction of the optical signal are greatly reduced. Particularly preferably, the single photon detector device can detect the optical signal with substantially the same efficiency independently of the propagation direction of said optical signal. In other words, the single photon detector device does not have a preferred direction in which the optical signal is detected with higher efficiency, as is the case in the prior art. The waveguide of the single photon detector device is designed in such a way that the optical signal can propagate along the optical axis of the waveguide. In this case, it is provided that the optical signal can propagate in the two mutually opposite directions along the optical axis. The optical waveguide is preferably a planar optical waveguide structure that is used in integrated optics. In principle, the nanowire can be applied on the optical waveguide, can be integrated into the waveguide, or can be arranged in the optical near field of the waveguide, preferably at a distance of not more than 1 μm from the optical waveguide, with respect to the optical waveguide. Particularly preferably, the nanowire is integrated into the waveguide structure directly during production of