HgCdTe Metasurface-based Terahertz Source and Detector

Abstract

A Terahertz Source and Detector device is provided that includes a nanostructured metasurface configured to transmit fully into a layer of absorbing material below the metasurface to achieve transparent conductivity in the visible spectrum region, wherein the metasurface is composed of crystalline material with very high mobility. The crystalline material can be composed of HgCdTe. The HgCdTe material can have a bandgap of about 700 meV. The intrinsic carrier concentration can be 10.sup.12 cm.sup.−3 at 300K.

Claims

1. A Terahertz Source and Detector, comprising: a nanostructured metasurface configured to transmit fully into a layer of absorbing material below the metasurface to achieve transparent conductivity in the visible spectrum region; the metasurface composed of crystalline HgCdTe material.

2. The Terahertz Source and Detector according to claim 1, wherein the crystalline material is composed of HgCdTe with a bandgap of about 700 meV.

3. The Terahertz Source and Detector according to claim 1, wherein the intrinsic carrier concentration is 10.sup.12 cm.sup.−3 at 300K.

4. The Terahertz Source and Detector according to claim 1, wherein photocarrier density for an input power of 0.1 nW focused to 100 mm.sup.2 area and absorbed in 100 nm-thick material will produce a photocarrier density of ˜10.sup.20 cm.sup.−3.

5. The Terahertz Source and Detector according to claim 1, wherein the switching contrast in pure sample is ˜10.sup.8 at 300K.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic perspective view of a prior art Terahertz (THz) source and detector device;

[0024] FIG. 2a is a perspective view of a device according to an exemplary embodiment of the invention;

[0025] FIG. 2b is a fragmentary, enlarged perspective view of the device shown in FIG. 2;

[0026] FIG. 2c is a top view of the device of FIG. 2;

[0027] FIG. 2d is a side view of the device of FIG. 2;

[0028] FIG. 3a is a schematic perspective view of a first stage of manufacturing the device of FIG. 2;

[0029] FIG. 3b is a schematic perspective view of a second stage of manufacturing the device of FIG. 2;

[0030] FIG. 3b is a schematic perspective view of a third stage of manufacturing the device of FIG. 2; and

[0031] FIG. 3c is a schematic perspective view of a fourth stage of manufacturing the device of FIG. 2.

DETAILED DESCRIPTION

[0032] While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

[0033] This application incorporates by reference U.S. Provisional Application 63/108,298, filed Oct. 31, 2020.

[0034] An exemplary embodiment Terahertz Source and Detector device includes a large photocarrier density for the same input energy, which allows for 1550 nm wavelength for pump probe, for improved efficiency.

[0035] The device provides a low-cost THz source and detector. THz sources and detectors based on photoconductive materials are one of the most commonly used for both pulsed and continuous wave operation. With applications ranging from biomedical field (imaging, burn wound assessment, and dental tissue imaging) to high end defense.

[0036] FIGS. 2a-2d illustrate the device 10 which comprises a non-absorbing layer 14, and a metasurface 18 formed by a grid of pillars 19 formed by etching the surface of the non-absorbing layer 14. The device 10 includes an antenna 24 with metal contacts 24a, 24b and a center gap 24c therebetween, and an absorbing layer 30. The absorbing layer 30 is attached by a layer of adhesive or glue 34 to a quartz substrate 38.

[0037] FIG. 2c shows a length L of the antenna 24 and the exposed portion of the absorbing layer 30. According to one exemplary embodiment L can be 100 μm. FIG. 2c also shows the center gap 24c of the antenna 24 having a gap length g. The gap length g can be 5 μm.

[0038] FIG. 2d shows the stack arrangement of layers. The non-absorbing layer 14 can have a thickness of 1.1 μm. The absorbing layer 30 can have a thickness of 100 nm. The adhesive layer 34 and a low refractive index substrate such as a quartz layer 38 are shown.

[0039] The absorbing layer 30 can be composed of Hg.sub.0.7Cd.sub.0.3Te having a thickness of 100 nm and the metasurface 18 can be composed of Hg.sub.0.28Cd.sub.0.72Te having a thickness of 699 nm. This is a calculated composition for THz device operation at 180K.

[0040] Alternately, the absorbing layer 30 can be composed of Hg.sub.0.44Cd.sub.0.56Te having a thickness of 100 nm and the metasurface 18 can be composed of, Hg.sub.0.28Cd.sub.0.72Te having a thickness of 670 nm. This is a calculated composition for THz device operation at 300K.

[0041] FIGS. 3a to 3c illustrates three stages of manufacturing the device 10. FIG. 3a illustrates the quartz substrate 38 and the absorbing layer 30 and the non-absorbing layer 14 applied onto the quartz layer. FIG. 3b illustrates the device shown in FIG. 3a in a further stage of manufacturing. The pillars 19 of the metasurface 18 are formed by etching into the non-absorbing layer 14. FIG. 3c illustrates a further stage of manufacturing wherein the antenna 24 and metal contacts 24a, 24b are formed using lithography and metal deposition.

[0042] From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.