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\section{Photodectors and Sensors}  Spectrosocopy and imaging are important to provide insight into analysis, and characterization of a chemical physical processes. \cite{Dai_2014}Furthermore, optical data links, such as vertical cavity surface emitting lasers, rely on photodectors on the receiving end to be sensitive enough to detect different frequencies of light.\cite{Seyedi_2014} Therefore improvements of photodectors and other sensors are always desired.   Peng and coworkershave recently,  developed single GaAs nanowires as microscopic coherent THz sensors.\cite{Peng_2015} These single GaAs nanowire detectors were fabricated using a direct laster lithographic technique and were even used as a spectrometer to measure the transmission spectrum of a 290 GHz low pass filter. Dai and coworkers have developed a nanowire photodetector using a GaAs core and AlGaAs shell nanowires.\cite{Dai_2014} In typical III-V NW the large density of surface states pin the surface fermi energy, limiting carrier mobility. These surface states were "passivated" by placing a "shell" on top. The GaAsAl shell and GaAs was are  found to be significantly more sensitive as a photodetector than the GaAs nanowire alone. Low dark current and high photoresponsivity was found in the range of 300-890 nm. Seyedi and coworks also demonstrated the power of GaAs core and AlGaAs shell NW. They explain how NW based photodectors have detection limits based on active are area  diameter and GaAs nanowires have large active areas. A bandwidth sensitivity of several GHz was found for the NW.\cite{Seyedi_2014}