Hyperspectral imaging provides a highly discriminative and powerful signature for target detection and discrimination. Recent literature has shown that considering additional target characteristics, such as spatial or temporal profiles, simultaneously with spectral content can greatly increase classifier performance. Considering these additional characteristics in a traditional discriminative algorithm requires a feature extraction step be performed first. An example of such a pipeline is computing a filter bank response to extract spatial features followed by a support vector machine (SVM) to discriminate between targets. This decoupling between feature extraction and target discrimination yields features that are suboptimal for discrimination, reducing performance. This performance reduction is especially pronounced when the number of features or available data is limited. In this paper, we propose the use of Supervised Nonnegative Tensor Factorization (SNTF) to jointly perform feature extraction and target discrimination over hyperspectral data products. SNTF learns a tensor factorization and a classification boundary from labeled training data simultaneously. This ensures that the features learned via tensor factorization are optimal for both summarizing the input data and separating the targets of interest. Practical considerations for applying SNTF to hyperspectral data are presented, and results from this framework are compared to decoupled feature extraction/target discrimination pipelines.
Space division multiplexing of optical beams has recently been demonstrated for improving the bandwidth of optical communication links. This paper will explore the use of space division multiplexing utilizing blue lasers for potential undersea applications. Experimental results will be shown for optical vortices utilizing a range of charge numbers corresponding to various Orbital Angular Momentum states.
The recent development and refinement of Gallium nitride (GaN) semiconductor devices has produced both blue light emitting diodes (LEDs) and laser diodes, which provide an efficient means to obtain high emission powers in the blue spectral range. Such sources have potential applications in both imaging and communication systems. However, many applications require precise control over the spectral emission from these devices and the current blue laser diodes lack this ability. In this paper, we demonstrate a method to control the spectral emission from GaN blue laser diodes. We present the simulation and subsequent fabrication of a guided-mode resonance filter (GMRF) that can be used to lock the output wavelength of a GaN blue laser diode. Successful locking of the emission wavelength with respect to fluctuations in the surrounding environment addresses challenges associated with communication systems. Our experiment uses an optical cavity with a GaN blue laser diode source and an on-axis narrowband GMRF fabricated for 445.2 nm. Based on spectral drift of the diode emission caused by an increase in input current, experimental measurements were taken with the GMRF installed to verify wavelength locking capability.
3D Meta-Optics are optical components that are based on the engineering of the electromagnetic fields in 3D dielectric
structures. The results of which will provide a class of transformational optical components that can be integrated at all
levels throughout a High Energy Laser system. This paper will address a number of optical components based on 2D
and 3D micro and nano-scale structures and their performance when exposed to high power lasers. Specifically, results
will be presented for 1550 nm and 2000 nm spectral bands and power densities greater than100 kW/cm2.
This paper highlights recent developments in resonant optical devices for infrared (IR) and mid-infrared (mid- IR) lasers. Sub-wavelength grating based resonant optical filters are introduced and their application in 2 μm thulium fiber laser and amplifier systems has been discussed. The paper focuses on applying such filtering techniques to 2.8 μm mid-IR fiber laser systems. A narrowband mid-IR Guided-Mode Resonance Filter (GMRF) was designed and fabricated using Hafnium(IV) Oxide film/quartz wafer material system. The fabricated GMRF was then integrated into an Erbium (Er)-doped Zr-Ba-La-Al-Na (ZBLAN) fluoride glass fiber laser as a wavelength selective feedback element. The laser operated at 2782 nm with a linewidth less than 2 nm demonstrating the viability of GMRF’s for wavelength selection in the mid-IR. Furthermore, a GMRF of narrower linewidth based on Aluminum Oxide/quartz wafer material system is fabricated and tested in the same setup. The potentials and challenges with GMRFs will be discussed and summarized.
We have developed an integrated Tm:fiber master oscillator power amplifier (MOPA) system
producing 100 W output power, with sub-nm spectral linewidth at -10 dB level, >10 dB
polarization extinction ratio, and diffraction-limited beam quality. This system consists of
polarization maintaining fiber, spliced together with fiberized pump combiners, isolators and
mode field adaptors. Recent advances in PM fibers and components in the 2 μm wavelength
regime have enabled the performance of this integrated high power system; however further
development is still required to provide polarized output approaching kilowatt average power.
We report on a Tm:fiber master oscillator power amplifier system producing 100 W output power, with
>10 dB polarization extinction ratio and diffraction-limited beam quality. To our knowledge, this is the
highest polarized output power from an integrated Tm:fiber laser. The oscillator uses polarization
maintaining (PM) single mode fiber with 10/130 μm core/cladding diameters, and the amplifier uses large
mode area PM fiber with 25/400 μm core/cladding diameters. The oscillator and amplifier are pumped
using 793 nm diodes spliced with pump combiners, and the oscillator is spliced to the amplifier via a
mode field adaptor.
This paper presents a narrow spectral filter based on a monolithic material system. Guided-mode resonance is
achieved by embedding a periodic array of air holes within a similar-index material. Microvoids created in the lowindex
substrate during deposition of the waveguide give a relatively high index contrast for guided-mode resonance.
One and two-dimensional gratings are used to examine polarization dependence of the device. Theoretical and
experimental results are provided, demonstrating a roughly six nanometer resonance at the full width half-maximum for
Micro-Optics has expanded to include a wide variety of applications for spectral filtering, polarization filtering and beam
shaping. Recently, a new class of optical elements have been introduced that can combine the spectral, polarization, and
beam conditioning into the same optical element. This engineered optical functionality results in a 3D Meta-Optic
structure that relies on sub-wavelength features to essentially engineer the electromagnetic fields within the structure;
thereby, resulting in highly dispersive structures that spatially vary across the optical element. This talk will summarize
recent results in the design, fabrication and applications of 3D Meta-Optics.
Large-scale fabrication of micro-optical Guided-Mode-Resonance (GMR) components using VLSI techniques is
desirable, due to the planar system integration capabilities it enables, especially with laser resonator technology.
However, GMR performance is dependent on within-wafer as well as wafer-to-wafer lithographic process variability,
and pattern transfer fidelity of the final component in the substrate. The fabrication of lithographs below the g-line
stepper resolution limit is addressed using multiple patterning. We report results from computational simulations,
fabrication and optical reflectance measurements of GMR mirrors and filters (designed to perform around the
wavelength of 1550nm), with correlations to lithographic parameter variability, such as photoresist exposure range and
etch depth. The dependence of the GMR resonance peak wavelength, peak bandwidth are analyzed as a function of
photolithographic fabrication tolerances and process window.