Invention Disclosure

ARL 23-11

TITLE OF INVENTION: Passive optical retro reflective identification tagging for optical positioning

EXECUTIVE SUMMARY OVERVIEW:

(The purpose of this overview is to provide a brief summarized overview of the invention as described in this invention disclosure document and a direct explanation on what is new about the invention and information about potential military and commercial uses)

1. What is this Invention?

(e.g., a short 3-sentence “summarized” description as a more “detailed” description will be required further into this invention disclosure)

It is a completely passive optical retro reflective identification tagging device made by multiple optical metasurface layers atop a retroreflective layer for the application of free-space optical positioning, navigation, and timing as well as object identification, locating, and tracking.

2. What is the basic premise of the design?

A thin retro-reflective device created by a two-dimensional array of subwavelength structures provides a unique spectral signature to the reflected optical signal. The main idea is to create barcode-like patterns in the frequency domain using the engineered high-frequency electromagnetic response and the angularly-stable features of a new type of artificial optical materials, namely nonlocal metasurfaces. In this design, an optical transmitter/receiver device will be used to interrogate this passive retroreflecting device for tracking and identification. In operation, the information code can made by both frequency modulation and intensity modulation in time, so it can be received in either frequency domain or time domain.

3. What is new about this Invention?

The existing passive tagging devices operate with RF microwave signals, which are subject to various security threats such as jamming, sniffing, spoofing, and eavesdropping, and have limitations on resolution. The proposed optical bar-coding tagging technology relies on a highly-directional optical beam for the communication between the transmitter and the retro-reflective tag, which will greatly reduce the security risks of the conventional RF-based tagging technologies. The novel aspects of this invention include 1) the technical approach to create barcode-like patterns in the frequency domain using thin dielectric films, 2) the retro-reflective tags do not require a battery and are completely passive, 3) the operation range of this device can be few kilometers, much longer than that of existing RF-based systems, 4) a large number of unique spectral bar-code patterns can be generated by vertically stacking multiple metasurface thin films, and 5) use of a simple, low-cost spectral-barcode reader using a diffraction grating film and a CCD camera.

4. Has this Invention been verified?

(e.g., does it exist, is it factual, is there a test module)

No

5. Identify Potential Military Uses of the Invention:

(if CTI exists, please mark accordingly)

It can be a key building block for an optical positioning, navigation system without GPS. Without RF transmission, it cannot be jammed, spoofed, or located. It can provide covert operation. It can provide combat ID for friendly force. It can work at any (or multiple) optical frequency range(s), including the infrared (for transparency in fog).

6. Identify Potential Commercial Uses of the Invention:

Optical tagging with longer distance operation.

Highly secure contactless payment Long-distance cargo tracking Secure access management

PUBLICATION OF THE INVENTION:

If a description of the invention has been published (publicly disclosed, verbally or in writing), list the type of publication and the dates. Please also provide a detailed explanation of the circumstances surrounding this external disclosure (e.g., what are the provisions of a funding agreement, etc.). Also, identify any further planned reports or publications. If none, so state.

none

LIST ANY KNOWN RELATED PATENTS, PUBLICATIONS or PATENT

APPLICATIONS:

Also identify any previous reports, drawings, publications, or correspondence describing or showing the invention. List any known closely related patents, patent applications, reports, publications, devices, or methods. If none, so state.

US Patent application: S/N:17/500,092

IS AN EMBODIMENT OF THE INVENTION AVAILABLE FOR INSPECTION?

If so, where?

No

NATURE AND EXTENT OF PAST USE, PRESENT USE, AND FUTURE USE

AS WELL AS APPLICATIONS AND ADVANTAGES OF THIS INVENTION:

Past: RF Tagging, Optical barcoding, ID

Present: RF Tagging, Optical barcoding, ID

Future: Optical Positioning and navigation system in GPS denial environment;

long distance optical tagging/barcoding for ID.

DETAILED DESCRIPTION OF THE INVENTION:

Provide the following information concerning the disclosed invention and in the indicated sequence (or reference other submitted papers that contain the requested information – please do not cut and paste):

A. Specifically describe the invention and its operation. You may use and attach copies of sketches, prints, photographs, paper, and illustrations, all of which should be signed, witnessed and dated. Alternatively, this form should be signed, witnessed and dated if the invention description is incorporated into this form. Use numbers and descriptive names in descriptions and drawings. For inventions that are methods list the steps involved in the method.

For inventions that are apparatus describe all the elements.

Figure 1 sketches the essential operation of the passive tagging system. A ‘user’ emits a broadband optical pulse in the direction of the passive optical retroreflecting tagging device (‘tag’) operating within a matching frequency range (Fig. 1a). The pulse is retroreflected back to the user with a high degree of directionality, but with a series of spectral dips peculiar to the optical tag. Figure 1b sketches the basic composition and functionality of the tag: a pulse from the user is successively filtered by a stack of nonlocal metasurfaces, and then redirected back to the user by a retroreflector.

Figure 1. (a) User communicating with tag. (b) Tag composed of cascaded nonlocal metasurfaces atop a retroreflector.

Figure 2 discusses two implementations of the tag using a stack of nonlocal metasurfaces atop a retroreflective layer. Figure 2a defines the incident angle, In both embodiments, the nonlocal metasurfaces are transparent in the operating frequency range except for a single narrow bandwidth, wherein incident optical energy is rejected (a combination of reflection, scattering, and absorption). This optical ‘stopband’ (Fig. 2b, top) has completely customizable bandwidth, polarization response, and operating frequency, by manipulating geometric parameters of the nonlocal metasurface. The transparent response outside of this stopband enables cascading many nonlocal metasurfaces, to create a compound meta-optic with multifunctionality, here encoding a spectral barcode.

The transmitted light reaches the retroreflector (Fig. 2b, bottom), which redirects light directly back to the user. In the first embodiment (Fig. 2c), the nonlocal metasurfaces’ stopbands are independent of incident angle, yielding a constant barcode irrespective of the external users’ position. This is implemented by dispersion-engineered nonlocal metasurfaces supporting ‘flat bands’. In this first embodiment, the barcode may be instantiated as the spectral positions of the dips. In the second embodiment, the stopbands vary as a function of incident angle (called ‘dispersion’), but each nonlocal metasurface has an identical dispersion. In this second embodiment (Fig. 2d), the barcode is instantiated as the gaps between the spectral dips (and the lowest frequency spectral dip is used for registration of the barcode).

Figure 2. (a) onto the tag. (b) Functionality of the nonlocal metasurfaces (top) and retroreflector (bottom) layers. (c) Example embodiment where a stack of nonlocal metasurfaces is nondispersive, producing the same spectral barcode (dips in transmittance, T, as a function of frequency, ) Second embodiment where each nonlocal metasurface is dispersive, but with identical dispersion.

In certain embodiments, the polarization response of the nonlocal metasurfaces is independent of polarization. This may avoid polarization scrambling from fog between the user and the device. In other embodiments, the polarization response of the nonlocal metasurfaces may be customized for spectropolarimetric barcoding, further increasing the security of the system. In further embodiments, linearly polarized stopbands are utilized with circular polarized excitation from the user, guaranteeing successful barcoding irrespective of the orientation of the user and the tag.

There are two possible operation modes: (1) Frequency (wavelength) modulation coding mode and (2) time modulation mode.

(1) For the frequency modulation mode, the user-device sends a relative broad-band laser signal pulse to the remote metasurface tagging device.

The laser pulse will retroreflect back to the user-device with dips in the frequency spectrum as shown in Fig.1. The user-device receive the reflected signal with a spectrometer designed to resolve the missing frequencies which provide the code to identify the “tag”.

(2) For the time modulation mode, the user-device sends a pulsed laser signal that frequency modulated in time domain as shown in Fig.3. This can be done by a tunable semiconductor laser. The light is reflected back from the metasurface tagging device, the light will be intensity modulated in time since some of the frequency will be filter-out by the metasurface.

Therefore, a simple photodetector in the user-device can received a modulation code to identify the “tag”.

Fig.3. Time-modulation operating mode

B. State the advantages of the invention over presently known devices, systems or processes. Also discuss/provide a background of the prior art.

Compared to existing RFID systems, this invention offers multiple advantages including 1) low probability of unwanted detection due to the highly directional radiation of the interrogating optical beam, 2) long operational distance in a few kilometer range, 3) difficult to clone the invented devices, 4) completely passive and simple operation (i.e. this optical tagging technology does not require an internal battery).

Discuss the problems which the invention is designed to solve, referring to any prior invention of a similar nature with which you may be familiar (e.g limitations or disadvantages).

This invention will address several concerns in the existing RFID systems including 1) short working distance, 2) eavesdropping, and 3) malicious cloning & spoofing.

D. List all known and other possible uses for the invention.

Highly secure contactless payment/access management Massively distributed remote sensing applications Long distance and highly secure friendly fire and combat identification

E. List the features of the invention that are believed to be novel – how does this invention differ from present technology.

Use of barcode-like transmission spectra for identification Use of collective spectral response of subwavelength dielectric structures Use of cascaded optical metasurfaces that are mutually transparent

F. Please provide an abstract of your invention. This should be limited to no more than 250 words and will be used to facilitate discussion with the Invention Evaluation Committee.

A completely passive optical retro reflective identification tagging device made by multiple optical metasurface layers atop a retroreflective layer for the application of free-space optical positioning, navigation, and timing as well as object identification, locating, and tracking. The device created by a two-dimensional array of subwavelength structures provides a unique spectral signature to the reflected optical signal. The main idea is to create barcode-like patterns in the frequency domain using the engineered high-frequency electromagnetic response and the angularly-stable features of a new type of artificial optical materials, namely nonlocal metasurfaces. In this design, an optical transmitter/receiver device will be used to interrogate this passive retroreflecting device for tracking and identification. In operation, the information code can made by both frequency modulation and intensity modulation in time, so it can be received in either frequency domain or time domain.