A secure border necessitates the development of new technology for remote sensing and surveillance. We investigate
and develop wireless sensor network systems consisting of spatially distributed sensor nodes that can monitor various
environmental parameters including temperature, humidity, motion, and vibration, etc. The sensors, nodes and
transceivers have low-power consumption and are powered by solar energy so that the systems can work over long time
periods with minimal human intervention and maintenance. This paper presents the technology development, wireless
sensor integration, power management, and communication architecture, as well as a demonstration of environmental
monitoring.
Fabry-Perot etalons using electro-optic (EO) organic materials can be used for devices such as tunable
filters and spatial light modulators (SLM's) for wavelength division multiplexing (WDM) communication
systems1-5 and ultrafast imaging systems. For these applications the SLM's need to have: (i) low insertion
loss, (ii) high speed operation, and (iii) large modulation depth with low drive voltage. Recently, there have
been three developments which together can enhance the SLM performance to a higher level. First, low
loss distributed Bragg reflector (DBR) mirrors are now used in SLM's to replace thin metal mirrors, resulting
in reduced transmission loss, high reflectivity (>99%) and high finesse. Second, EO polymer materials
have shown excellent properties for wide bandwidth optical modulation for information technology due to
their fabrication flexibility, compatibility with high speed operation, and large EO coefficients at
telecommunication wavelengths. For instance, the EO polymer AJL8/APC (AJL8: nonlinear optical
chromophore, and APC: amorphous polycarbonate has recently been incorporated into waveguide
modulators and achieved good performance for optical modulation. Finally, very low loss transparent
conducting oxide (TCO) electrodes have drawn increasing attention for applications in optoelectronic devices.
Here we will address how the low loss indium oxide (In2O3) electrodes with an absorption coefficient
~1000/cm and conductivity ~204 S/cm can help improve the modulation performance of EO polymer
Fabry-Pérot étalons using the advanced electro-optic (EO) polymer material (AJL8/APC). A hybrid etalon
structure with one highly conductive indium tin oxide (ITO) electrode outside the etalon cavity and one
low-absorption In2O3 electrode inside etalon cavity has been demonstrated. High finesse (~234), improved
effective applied voltage ratio (~0.25), and low insertion loss (~4 dB) have been obtained. A 10 dB
isolation ratio and ~10% modulation depth at 200 kHz with only 5 V applied voltage have been achieved.
These results indicate that such etalons are very promising candidates for ultrafast spatial light modulation in
information technology.
We report a systematic investigation on organic-inorganic hybrid sol-gels doped with nonlinear optical chromophores. The host is based on photosensitive sol-gels prepared from precursor of 3-(methacryloxy)propyl trimethoxysilane-zirconium (or aluminum) oxide (MAPTMS-Zr(Al)) hybrid system. The chromophores are incorporated into the hybrid sol-gels as both guest and side-chain. Second harmonic generation experiment has been conducted to optimize the poling parameters for the active sol-gel films and examine the stability of the second-order nonlinear optical coefficients. Electro-optic channel waveguides have been fabricated by direct ultra-violet (UV) exposure, direct blue laser writing, and reverse-mesa methods. Electro-optic effect of the waveguides is measured at 1550 nm. All the results show that the hybrid sol-gels are promising media for electro-optic devices for integrated optics in both performance and fabrication flexibility.
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