TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

ACQUISITION PROGRAM: PMS 435, Periscope and Mast Venerability to operate Submarine at Periscope depth at littoral water

OBJECTIVE: Develop an Optical Emulator of complex Electromagnetic Maneuverability (EM) systems with Nanophotonics structure.

DESCRIPTION: Electromagnetic (EM) properties such as EM cross section (EMCS) or antenna gain are often measured in anechoic chambers. However, for very large structures such as submarine or other highly complex platforms, this could be expensive or impractical due to the sheer size of the structure. Computer simulation is a very helpful tool, but the processing time increases exponentially with the scale of the model about the wavelength, making the solution intractable for large systems. Also, these complex codes can easily diverge or present artifacts that should be identified by other means. This is new innovative technology of using Nanostructure and optics to determine periscope venerability. Currently, this is not commercially available.

Considering Maxwell's equations are invariant under dilatation transformation, it is possible to make the measurement on reduced size models and using proportionally higher frequencies. By conserving the scale factor between model and wavelength, the solution is identical. In the past, scale models of the structure of interest have been used with a reduced factor of the interested structure of a few tens in scale and kept into the radio frequency (RF) domain. Today, with the emergence of nanophotonics and the access to sub-micron 3D printing machines, it is possible to measure all the EM properties of complex RF systems in the near infrared (NIR) (1 micron) by reducing the size by a factor 105. At that scale, an entire Virginia-class submarine (~150 meters) can be recreated to a length of 1.5 cm� and can easily fit in a tabletop measurement setup. The advantages of this approach are faster computation (1/365) and much cheaper than the full-scale measurement (1/250). Using such a large-scale factor also means that it is possible to reproduce large radar clutter such as sea clutter to measure the Radar Cross Section (RCS) measurement of the submarine near marine wave boundary.

The NIR wavelength range provides critical advantages over other spectral regions. First, there are many transparent dielectric materials available in the NIR, such as organic polymers, that can be used and engineered to reproduce the complex permittivity of the material observed at RF. Second, there are many optical sources such as femtosecond pulsed fiber laser that can be used for ranging, or supercontinuum laser that can be used for spectral analysis. Third, by using 2D detector, it is possible to determine the specific part of the structure: periscope, communication antenna, stabilizer fin, conning tower, hull, or even wake pattern that is responsible for the RCS signal. This imaging technique gives information similar to Inverse Synthetic Aperture Radar (ISAR), which is a radar technique using Radar imaging to generate a two-dimensional high-resolution image of a target. It is analogous to conventional SAR, except that ISAR technology utilizes the movement of the target rather than the emitter to create the synthetic aperture and without the back projection computation (and artifact).

The proposer will demonstrate, at its company location, a femtosecond pulsed laser to perform holographic time-of-flight measurements, which allows retrieving the 3D information of the prototyped Naval platform (10�s of mm in size) model. This type of holographic measurement is similar to the ranging mode of operation of RADAR. In addition, the proposer will demonstrate the capability of immediately identifying the location and the nature of the strongest scatters and glints from the proposed Navy structure of interest. This ability allows for an intuitive interaction with the structure model to eliminate these sources of unwanted scattering and minimize the RCS from visible to RF range. The proposer should identify the RF permittivity of conductors and dielectrics like concrete and vegetation that will be reproduced as nanoparticles. The proposer should develop plasmonic nano-antennas that behave as their RF counterpart using current technology.

Future state of the 3D printing technique will be able to create any structure in nano scale, in only a few hours, compared to current manufacturing technology to create a scale model submarine or other structure, which currently takes more than couple of months. Since the RCS measurement by itself can take only a few minutes, this technique offers an extremely fast turnaround between Computer Added Design (CAD) modification and measuring the impact of the change on the RCS signature. This fast turn-around provides a critical advantage on the ability to create a RADAR in stealth structure. The proposer shall demonstrate such antennas by benchtop emulator and can include active emitters, so that antenna placement as well as interferences should evaluate at their far field emission and be measured.
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The long-term Navy vision is an electromagnetic �wind tunnel� system where, from a CAD model of the structure of interest, a scale model can be manufactured by 3D printing. By integrating different materials, conductor and dielectrics, the model will accurately reproduce the RF properties of the original structure. Active antennas will then be added to specific locations to test for obstruction and interferences. The electromagnetic signature will be obtained with 2D sensors all around the model for a fast and high-resolution measurement. Turnaround time from CAD file to measurement has been proven to be less than a day.

PHASE I: Provide a concept for an Optical Emulator of complex EM systems with nanophotonics to solve the Navy�s problem, and demonstrate the feasibility of that concept based on model-based engineering (MBE), simulation, and modeling. Conduct a feasibility study that includes manufacturing, source, detector, and material scaling. Develop a Phase II plan. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Build and demonstrate a prototype design of the system from the proof of concept of EMCS technology. Provide a compact demonstration of the prototype�s ability to measure the EMCS of a submarine model in near marine boundary as well as sea clutter as defined in Phase I and Phase II Statement of Work (SOW). Ensure that the RCS measured data compares to the simulation for accuracy and reliability. Ensure that the range demonstrates the ability to identify the structure responsible for the EMCS signal. Deliver a small, compact, desk top, field-operational prototype optical emulator to the Navy. Demonstrate femtosecond pulsed laser to perform holographic time-of-flight measurements at company location, which allows retrieving the 3D information of the model. This type of holographic measurement is similar to the ranging mode of operation of RADAR. In addition, demonstrate the capability of immediately identifying the location and the nature of the strongest scatters and glints from the proposed Navy structure of interest. This ability allows for an intuitive interaction with the structure model to eliminate these sources of unwanted scattering and minimize the RCS from visible to Radio Frequency range. Deliver a bench-top, prototyped RCS measurement instrument and related software and Actual training or training materials/manuals to the Navy for the transition this technology.

PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the technology. RCS range prototype delivered to the Navy will be used for Submarine, Littoral Combat Ship (LCS), DDG, or any other NAVAL Platform.

This technology can be used to scale down and test many different commercial structures such as buildings, cruise ships, and other structures.

REFERENCES:

1. Knott, E. F. �Radar Cross Section Measurements.� Springer Science & Business Media, 2012, https://www.springer.com/us/book/9781468499063

2. Coulombe, M., Horgan, T., Waldman, J., Szatkowski, G. and Nixon, W. �A 524 GHz Polarimetric Compact Range for Scale Model RCS Measurements.� Tech. Rep., DTIC Document, 1999, https://www.uml.edu/docs/Coulombe%2C%20Antenna%20mess_tcm18-42196.pdf

3. Goyette, T. M., Dickinson, J. C., Waldman, J. and Nixon, W. E. �A 1.56-thz compact radar range for W-band imagery of scale-model tactical targets.� https://www.uml.edu/docs/Goyette%2C%20radar%20range%20tac_tcm18-42363.pdf

4. Rosenberg, L. and Watts, S. �High Grazing Angle Sea-Clutter Literature Review.� Electronic Warfare and Radar Division, Defence Science and Technology Organisation, Edinburgh South Australia 2013), https://pdfs.semanticscholar.org/20b7/9bf18d96ba26b519cca5b979d165c9d5aea1.pdf

5. A. Marandi et al., �Network of time-multiplexed optical parametric oscillators as a coherent Ising machine.� Photonics Nature, Vol 8, 937 (2014)

6. S. Utsunomiya et al., �Mapping of Ising models onto injection-locked laser system.� Optics Express, Vol 19, 18091 (2011)

KEYWORDS: Radar Cross-section; Meteorological Instrumentation; Laser Beam Propagation; Maritime Environment; Turbulent Boundary Layer; Nano Photonics