BACKGROUND OF THE INVENTION

This invention relates, generally, to pyroelectric detectors. More specifically, it relates to detectors using a pyroelectric detective device capable of detecting electromagnetic radiation in the terahertz (THz) range.

Electromagnetic radiation detectors have existed and are designed specifically to detect certain wavelengths. For example, there exist detectors adapted to intercept electromagnetic radiation in the mid-wave and long-wave infrared spectral regions. Those devices, however, are designed for the infrared spectral regions and the described geometries are not adaptable to terahertz wavelengths.

Additionally, other alternative detectors require multiple optical components to achieve similar parameters, with lower effectiveness. Two alternatives are bolometers, that require liquid helium cooling to achieve similar performance characteristics, and hydrogen isotope enriched deuterated triglycine sulfate detectors paired with a spectrometer to provide wavelength/frequency selectivity.

Terahertz detectors are particularly useful in detecting objects with specific optical qualities within the terahertz range of wavelengths. One such example is the extremely dangerous narcotic, fentanyl. Fentanyl is a powerful opioid and norepinephrine inhibitor that binds to μ-opioid receptors in the body. At the moment, there are several fentanyl analogs and derivates that exist and bind to μ, δ, or, κ opioid receptors. Metabolism of fentanyl primarily takes place through liver and intestinal CYP3A4 N-oxidative dealkylation. This process also includes several additional metabolization steps before being excreted from the body through the urine.

Fentanyl is a dangerous narcotic that enters the body through multiple methods, including dermal, inhalation, and injection. The danger of this narcotic has been illustrated in rat studies. The data shows that, in rats, the lethal dose (LD50) of fentanyl is 3.1 mg/kg, an eighth of the LD50for heroin. In addition, carfentanil, a synthetic opioid, and analog of fentanyl, has a 100 times higher effective dose (ED50) and lower LD50than fentanyl, making it substantially more dangerous when misused.

The lethality of fentanyl and related compounds has resulted in a sharp increase in the number of deaths resulting from illicit drug use. In addition, fentanyl-related incidents have become increasingly more problematic for first responders arriving at an opioid-related event as fentanyl uptake through inhalation is frequently being reported.

To combat the rise in fentanyl-related deaths and curb the importation of fentanyl from countries around the world, police, federal officers, paramedics, and others must have a safe and reliable device and method for detecting illicit drugs—such as fentanyl. Such a detector must be contact free to keep personnel safe, simple to operate and interpret results with minimal training, capable of providing results in seconds, accurate to prevent false positives, and able to detect fentanyl and its derivatives.

Accordingly, what is needed is a device and method adapted to detect objects with specific optical quality within the terahertz wavelength, including but not limited to the illicit drug fentanyl, that is quick, safe, accurate, and effective. However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome.

All referenced publications are incorporated herein by reference in their entirety. Furthermore, where a definition or use of a term in a reference, which is incorporated by reference herein, is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

While certain aspects of conventional technologies have been discussed to facilitate disclosure of the invention, Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects discussed herein.

The present invention may address one or more of the problems and deficiencies of the prior art discussed above. However, it is contemplated that the invention may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the claimed invention should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.

In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.

SUMMARY OF THE INVENTION

In various embodiments, the pyroelectric detection device of the present invention has a combination of material and geometric parameters that are unique and tunable, enabling resonating frequencies (spectral selectivity) in the THz range (0.1-15) with ultra-narrow channel widths (0.01-0.10 THz) full width half max (FWHM) and minor secondary absorption bands. Dependent upon configuration, the device may either act as a large area resonator to collect weak/diffuse signals or as a constituent of an array able to capture pictures within the spectrum for which they are sensitive.

Various embodiments include plasmonic near-perfect absorbers, comprised of metal films with a periodic array of subwavelength openings deposited on the surface of pyroelectric materials to create wavelength-selective far-infrared detectors. Similar work has focused on detectors for mid-wave and long-wave infrared spectral regions, but none for far-infrared. The present invention focuses on wavelengths beyond 20 μm, which was motivated by a long felt need for specific aerospace, security, and contraband sensing applications.

In a particular embodiment, the novel pyroelectric detective device is incorporated into a THz reflectance spectroscope, which may be configured as a portable handheld unit. The unit may additionally include a broadband mercury source, stereoscopic detection scheme for localization, and a visible camera for overlaying images, such as an active pixel sensor.

In one embodiment, the present invention provides a pyroelectric detection device comprising a pyroelectric element comprising a first surface and an opposite second surface, a first conductive layer adjacent to the first surface of the pyroelectric element, the first conductive layer comprising a periodic array of plasmonic absorbers to transfer energy of terahertz (THz) frequency range electromagnetic radiation incident on the first conductive layer into heating of the pyroelectric element and a second conductive layer adjacent to the second surface of the pyroelectric element.

The plasmonic absorbers of the periodic array simultaneously provide capacitive and inductive coupling of the electromagnetic radiation and each of the plasmonic absorbers of the periodic array includes a cross-shaped inset of the first conductive layer and a cross-shaped aperture in the first conductive layer dimensioned to surround the cross-shaped inset.

The pyroelectric detection device of claim1, wherein the pyroelectric element includes one or more of, LiTaO3, BaTiO3, LiNbO3, SrNb1-xBaxNb2O6, where 0.2<x<0.7, PbxMeyMe′zO3, where x+y+z=2, Me is selected from a divalent ion and Me′ is selected from a pentavalent ion, and HfxMe(1-x)O2, where Me is selected from a combination of Zr, Ti, Pb, Ba, Si, or Al and triglycine sulfate.

The pyroelectric detection device may further include measurement circuitry coupled to the first conductive layer and to the second conductive layer, the measurement circuitry to measure an electrical signal generated in the pyroelectric element in response to the heating of the pyroelectric element.

In an additional embodiment, the present invention provides a method for detecting terahertz (THz) frequency range electromagnetic radiation. The method includes positioning a pyroelectric detection device to receive THz frequency range electromagnetic radiation, the pyroelectric detection device comprising a pyroelectric element comprising a first surface and an opposite second surface, a first conductive layer comprising a periodic array of plasmonic absorbers adjacent to the first surface of the pyroelectric element and a second conductive layer adjacent to the second surface of the pyroelectric element. The method further includes, absorbing energy of the THz frequency range electromagnetic radiation by the periodic array of plasmonic absorbers, transferring the energy absorbed by the periodic array of plasmonic absorbers to heat the pyroelectric element and measuring an electrical generated in the pyroelectric element in response to the heating of the pyroelectric element. In particular, each of the plasmonic absorbers of the periodic array utilized in the method of the present invention includes a cross-shaped inset of the first conductive layer and a cross-shaped aperture in the first conductive layer dimensioned to surround the cross-shaped inset.

In another embodiment, the present invention provides a non-contact terahertz (THz) reflectance spectroscope for identifying a compound of interest. The spectroscope includes a light source to emit far-infrared wavelength electromagnetic radiation focused on a target of interest, a camera focused on the target of interest, one or more pyroelectric detection devices to receive electromagnetic radiation reflected from the target of interest, each of the one or more pyroelectric detection devices comprising. In particular, each of the one or more pyroelectric detection devices includes a pyroelectric element comprising a first surface and an opposite second surface, a first conductive layer adjacent to the first surface of the pyroelectric element, the first conductive layer comprising a periodic array of plasmonic absorbers to transfer energy of terahertz (THz) frequency range from the electromagnetic radiation incident on the first conductive layer into heating of the pyroelectric element, a second conductive layer adjacent to the second surface of the pyroelectric element, measurement circuitry coupled to the first conductive layer and to the second conductive layer, the measurement circuit to measure an electrical signal resulting from the heating of the pyroelectric element to generate reflectance spectra and analysis circuitry to compare the reflectance spectra to known spectra to identify a compound of interest present in the target of interest. In particular, each of the plasmonic absorbers of the periodic array utilized in the spectrometer of the present invention includes a cross-shaped inset of the first conductive layer and a cross-shaped aperture in the first conductive layer dimensioned to surround the cross-shaped inset.

