Structural Health Monitoring (SHM) is required for early detection of damage in structural components to improve the
safety, reduce the cost, and increase the performance and efficiency of aircrafts. Currently available techniques have a
number of deficiencies prohibiting wide spread of SHM in aerospace applications. In this contribution we will present
the initial results of development at Luna Innovations of an all-fiber optic ultrasonic airframe SHM system that will be
able to address the deficiencies of solutions suggested/developed to date. In this contribution we will present the details
on design, development and testing of the prototype fiber optic SHM system.
Photovoltaic technology will have a substantial impact on the nation's wealth and economy in 21st century. The main
obstacle for widespread use of PV energy at present is the higher cost of PV energy generation equipment compared to
that of fossil fuels. Improved in-line diagnostics can reduce the cost and increase the productivity by significantly
improving the yield of the process. Here we present the first results of development of a high-throughput PV
(Photovoltaic) characterization system, which can provide fast and accurate data on the spatial uniformity of thickness,
refractive indices, and birefringence of the thin films comprising the solar cell in a single scan over the entire solar cell
area. The unmatched throughput, the amount of retrieved information, and the unique capability of characterization of
both plane and structured surfaces and interfaces of such a system will provide the opportunity to use this system and
develop in-situ, real time process diagnostics/prognostics capabilities that would result in improved yield and reduced
cost of solar cell manufacturing. Here we provide the modeling results, demonstrate applicability of the technique for
characterization of organic solar cells and discussing the modifications of the system that would permit characterization
of structured solar cell surfaces.
Continuously tunable optical true time-delay (TTD) modules based on dispersion-enhanced photonic crystal fibers (DEPCFs) are demonstrated to provide continuous microwave squint-free beam scanning for an X-band (8 to 12 GHz) phased-array antenna (PAA) system. The dispersion of the fabricated photonic crystal fibers (PCFs) is as high as –600 ps/nm km at 1550 nm. By employing PCFs to increase the dispersion, the TTD module size can be proportionally reduced. The time delay is continuously tunable from –31 ps to 31 ps between adjacent delay lines by tuning the laser wavelength continuously from 1528 to 1560 nm. The far-field radiation patterns of a 1×4 subarray were measured from –45 to 45 deg scanning angles. Squint-free operation is experimentally confirmed. Wavelength conversion is also demonstrated to confirm that time-delay information can be successfully transferred from one wavelength to the other without being changed, which is suitable to be implemented in 2-D phased-array antenna systems. The TTD formation idea presented is suitable for not only the X band, but also the other higher microwave frequencies, such as the K band.
A wavelength-controlled continuous beam-steering four-element X-band (8- to 12-GHz) phased array antenna system is presented. The system is based on the continuously tunable optical true-time-delay technique. Dispersion-enhanced waveguide holograms were proposed and used to fabricate the optical true-time-delay devices. The devices are characterized both theoretically and experimentally. The wavelength of a laser was tuned within the system to get continuously tunable true time delay. The time delay was measured for a wavelength tuning range from 1537 to 1547 nm in 10-nm steps. The far-field radiation patterns of the antenna system were measured at 9 and 10.3 GHz, and they showed no beam squint. The true-time-delay formation idea presented here is suitable for not only X-band, but also for higher microwave frequencies, such as K-band.
•A two-dimensional optically controlled phased array antenna (PAA) system is proposed. The system employs highly dispersive photonic crystal fibers (HDPCFs) to provide the true-time-delays (TTD). Independent azimuth and elevation control is obtained through a mid-stage optical wavelength conversion process. The dispersion of the fabricated is as high as -600 ps/nmkm around 1550 nm which is 33 times of conventional telecom SMF. By employing the PCFs to increase the dispersion, the TTD module size can be proportionally reduced. A 64-element (8x8) PCF-based PAA system is under construction. Simulation results operating at X-band are shown in this paper.
The holographic-grating based wavelength-controlled true-time-delay devices are presented in the paper. The optical true-time-delay can be continuously controlled by continuously tuning the wavelength of a single laser within the devices. The dispersion ability of the devices is greatly enhanced by increasing the diffraction angles of the holographic gratings. The fabricated true-time-delay devices work within 1550nm region. The loss performance of the devices were calculated and measured. The wavelength-controlled true-time-delay was also characterized both theoretically and experimentally.
To find the optimal driving voltage and bandwidth for electro-optic polymer-waveguide-based directional couplers, four electrode structures are investigated. They are the microstrip line (MSL), the asymmetric coplanar waveguide with ground (ACWG), the coplanar waveguide with ground (CPWG), and the edge-coupled microstrip line (CMSL). UV15:Polymethyl methacrylate/dispersed-red 1:UV11-3-based directional couplers are evaluated. The CPWG and the ACWG have almost the same driving voltages, which are about twice the driving voltage of the CMSL. The MSL has the largest driving voltage, which is 20 to 25% higher than the diving voltages of the CPWG and ACWG. Simulation results further conclude that the MSL has the largest bandwidth, and its bandwidth is about 1.6 times that of the bandwidth of the CMSL, which has the narrowest bandwidth. The bandwidths of the ACWG and CPWG are 1.4 and 1.2 times that of the CMSL, respectively. The driving voltages for the four different devices are experimentally confirmed.
Wavelength-controlled true-time delay modules based on the dispersive hologram-waveguide are presented here to provide continuous beam-scanning for a X-band phased-array antenna system. The true-time delay modules operating in the 1550nm region were fabricated with continuously tunable time delays from 5ps to 64ps. All-optical wavelength conversion in the semiconductor optical amplifiers was proposed in the system to extend the beam-scanning scope from one dimension to two dimensions. The wavelength-controlled time delays were measured across the x-band (8-12GHz) in the experiment.
Communication between computing systems is recognized as the main limitation to increasing the speed of all-electronic systems beyond levels currently achieved in existing supercomputers. Optical interconnects hold great promise in eliminating current communication bottlenecks because of properties that stem from optics inherent parallelism. Wavelength-division multiplexing (WDM) technology, by which multiple optical channels can be simultaneously transmitted at different wavelengths through a single optical transmission medium is a useful means of making full use of optics parallelism over a wide wavelength region. In this talk, we review the working principles of wavelength division (de) multiplexers (WD(D)M) for optoelectronic interconnection in high-throughput optical links and address the optical design issues of Wd9D)Ms. Several grating-based WD9D)M structures are analyzed. We report experimental data for several versions of WD(D)Ms which exhibit low insertion loss, high reliability, and low cost.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.