John Zeller

Optical correlator based target detection, recognition, classification, and tracking

A dedicated automatic target recognition and tracking optical correlator (OC) system using advanced processing technology has been developed. Rapidly cycling data-cubes with size, shape, and orientation are employed with software algorithms to isolate correlation peaks and enable tracking of targets in maritime environments with future track prediction. The method has been found superior to employing maximum average correlation height filters for which the correlation peak intensity drops off in proportion to the number of training images. The physical dimensions of the OC system may be reduced to as small as 2 in. × 2 in. × 3 in. (51 mm × 51 mm × 76 mm) by modifying and minimizing the OC components.

ZnMgO solar blind detectors: from material to systems

Zinc oxide (ZnO) is a unique wide bandgap biocompatible material system exhibiting both semiconducting and piezoelectric properties that has a diverse group of growth morphologies. Bulk ZnO has a bandgap of 3.37 eV that corresponds to emissions in the ultraviolet (UV) spectral band. Highly ordered vertical arrays of ZnO nanowires (NWs) have been grown on substrates including silicon, SiO2, GaN, and sapphire using a metal organic chemical vapor deposition (MOCVD) growth process. The structural and optical properties of the grown vertically aligned ZnO NW arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. Compared to conventional UV sensors, detectors based on ZnO NWs offer high UV sensitivity and low visible sensitivity, and are expected to exhibit low noise, high quantum efficiency, extended lifetimes, and have low power requirements. The photoresponse switching properties of NW array based sensing devices have been measured with intermittent exposure to UV radiation, where the devices were found to switch between low and high conductivity states at time intervals on the order of a few seconds. Envisioned applications for such sensors/FPAs potentially include threat detection and threat warning.

Near-marine boundary layer atmospheric and turbulence measurement and modeling

Currently there are extensive modeling and measurement capabilities for the region extending from 100 ft above sea surface to space, but few such capabilities exist for the region extending up to 10 ft above the sea surface. By measuring and characterizing conditions in the marine boundary layer existing below 30 ft above the sea surface such as turbulence and extinction, the optical communication capabilities of maritime vessels when operating at or near the surface may be extended and enhanced. Key physical parameters such as absorption, scattering, and turbulence strength (Cn 2) along the propagation path have a degree of variability on meteorological conditions as well optical wavelength. Modeling of the atmospheric environment is thus critical in order to generate a good understanding of optical propagation through the atmosphere. NUWC is utilizing software provided by MZA to model Cn 2 and resultant beam propagation characteristics through the near-marine boundary layer. We are developing the capability of near-marine boundary layer atmospheric and turbulence measurements and modeling as well as optical laser link testing at outdoor test sites. Measurements are performed with optical laser links (e.g., bit rate error), scintillometer, and particle image velocimetry (PIV) cameras, while turbulence and propagation modeling is achieved using MODTRAN5, ATMTools, NSLOT, LEEDR, and WaveTrain modeling and simulation code. By better understanding the effects of turbulence on optical transmission in the near-marine boundary layer through modeling and experimental measurements, measures can be implemented to reduce the bit error rate and increase data throughput, enabling more efficient and accurate communication link capabilities.

Development of nanostructured antireflection coatings for infrared technologies and applications

Infrared (IR) sensing technologies and systems operating from the near-infrared (NIR) to long-wave infrared (LWIR) spectra are being developed for a variety of defense and commercial systems applications. Reflection losses affecting a significant portion of the incident signal limits the performance of IR sensing systems. One of the critical technologies that will overcome this limitation and enhance the performance of IR sensing systems is the development of advanced antireflection (AR) coatings. Magnolia is actively involved in the development and advancement of ultrahigh performance AR coatings for a wide variety of defense and commercial applications. Ultrahigh performance nanostructured AR coatings have been demonstrated for UV to LWIR spectral bands using various substrates. The AR coatings enhance the optical transmission through optical components and devices by significantly minimizing reflection losses, a substantial improvement over conventional thin-film AR coating technologies. Nanostructured AR coatings are fabricated using a tunable self-assembly process on substrates that are transparent for a given spectrum of interest ranging from UV to LWIR. The nanostructured multilayer structures have been designed, developed and optimized for various optoelectronic applications. The optical properties of the AR-coated optical components and sensor substrates have been measured and fine-tuned to achieve a predicted high level of performance of the coatings. In this paper, we review our latest work on high quality nanostructure-based AR coatings, including recent efforts towards the development of nanostructured AR coatings on IR-transparent substrates.

ZnO nanowire growth and characterization for UV detection and imaging applications

Zinc oxide (ZnO) is a unique wide bandgap biocompatible material system exhibiting both semiconducting and piezoelectric properties that has a diverse group of growth morphologies. Bulk ZnO has a bandgap of 3.37 eV that corresponds to emissions in the ultraviolet (UV) spectral band. Highly ordered vertical arrays of ZnO nanowires (NWs) have been grown on substrates including silicon, SiO2, GaN, and sapphire using a metal organic chemical vapor deposition (MOCVD) growth process. The structural and optical properties of the grown vertically aligned ZnO NW arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. Compared to conventional UV sensors, detectors based on ZnO NWs offer high UV sensitivity and low visible sensitivity, and are expected to exhibit low noise, high quantum efficiency, extended lifetimes, and have low power requirements. The photoresponse switching properties of NW array based sensing devices have been measured with intermittent exposure to UV radiation, where the devices were found to switch between low and high conductivity states at time intervals on the order of a few seconds. Furthermore, NW based UV sensors and focal plane arrays (FPAs) show promise for imaging in the near marine boundary layer, an area extending up to about six meters above the ocean surface characterized by a relatively high degree of aerosols and turbulence. Envisioned applications for such sensors/FPAs potentially integrated into submarine photonic masts (which would maintain their effectiveness even in bright daylight conditions) include threat detection and threat warning.

MOCVD growth of ZnO nanowire arrays for advanced UV detectors

Zinc oxide (ZnO) is a biocompatible and versatile functional material having a bandgap of 3.37 eV that exhibits both semiconducting and piezoelectric properties and has a diverse group of growth morphologies. We have grown highly ordered vertical arrays of ZnO nanowires (NWs) using a metal organic chemical vapor deposition (MOCVD) growth process on various substrates. The NWs were grown on p-Si (100), SiO2, and m-plane sapphire substrates. The structural and optical properties of the grown vertically aligned ZnO NW arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. The unique diffraction pattern for ZnO (002) concurred with the SEM inspection indicating vertical orientation of the NWs. UV detectors based on ZnO NWs offer high UV sensitivity and low visible sensitivity for applications such as missile plume detection and threat warning. Compared to the photomultiplier tubes (PMTs) prevalent in current missile warning systems, the NW detector arrays are expected to exhibit low noise, extended lifetimes, and low power requirements for UV detector applications.

Growth and characterization of nanowires and nanorods on Al 2 O 3 (110), Si(111) and SiO 2 /p-Si(100) by MOCVD

We report growth of ZnO nanowires and nanorods using an atmospheric pressure, horizontal MOCVD, without any metal catalyst. The ZnO structures were grown on sapphire (110), Si(111) and SiO2/p-Si(111) substrates by controlling the ZnO precursor flow, growth temperature and distance from the injector. Prior to the growth of the nanostructure, a thin film of ZnO was grown at 400°C for 2 mins, DeZ was used as ZnO precursor with a flow rate of 200 sccm, N2O was used as oxygen source with a flow rate of 50 sccm and N2 was used as the carrier gas.

EO/IR sensor development using nanostructures for unattended ground sensor applications

Next Generation EO/IR focal plane arrays using nanostructure materials are being developed for a variety of Defense Applications including Unattended Ground Sensor Applications. Several different nanomaterials are being evaluated for these applications. These include ZnO nanowires that have demonstrated large signal to noise ratio as a wide band gap nanostructure material in the UV band. Similarly, the work is under way using Carbon Nanotubes (CNT) for a high speed detector and focal plane array as bolometer for IR bands of interest, which can be implemented for the unattended ground sensor applications. In this paper, we will discuss the sensor design and model predicting performance of an EO/IR focal plane array that can cover the UV to IR bands of interest. The model can provide a robust means for comparing performance of the EO/IR FPAs and Sensors that can operate in the UV, Visible-NIR (0.4-1.8 μm), SWIR (2.0-2.5 μm), MWIR (3-5 μm), and LWIR bands (8-14 μm). This sensor model can be used as a tool for predicting performance of nanostructure arrays under development. We will also discuss our results on growth and characterization of ZnO/MgZnO nanowires and CNTs for the next generation sensor applications.

Effect of atmosphere on free-space optical communication networks for border patrol

Free-space optics (FSO) communication links for relaying video from cameras are investigated in relation to atmospheric attenuation. Through MODTRAN-based modeling of transmission bands across the NIR to MWIR (1.5-4.2 μm) portion of the infrared spectrum in atmospheric conditions including clear maritime, desert extinction, and various levels of rain and fog, we seek to identify which wavelength ranges are the most practical for minimizing transmission losses in both ideal and unfavorable conditions. Atmospheric, free-space, and scintillation losses are investigated for various FSO configurations and atmospheric conditions to determine incident beam power required for successful data transmission in view of a 2 km FSO link at various path elevation angles from the horizon. In addition, FSO transmitter and receiver circuits were designed to optically relay an analog video signal at IR wavelengths. Using advanced tunable laser sources to provide illumination across wavelength ranges from visible to mid-wave infrared, it should be possible to overcome transmission limitations associated with adverse weather and atmospheric conditions for communication networks to benefit border protection.

Wideband lasers on manned/unmanned platforms under poly-environment

Compact and robust high power eye-safe laser sources are required for rapidly deployable free-space optical (FSO) communication networks. Such systems have been demonstrated using essentially telecom-based lasers in a relatively narrow bandwidth window around 1.5 μm. Here we discuss additional wavelength transmission bands within the mid-IR. Using advanced laser sources to provide illumination across wide wavelength ranges, particularly within the 2-5 μm it may be possible to overcome transmission limitations associated with adverse weather and atmospheric conditions.