Abstract:We demonstrate a new kind of optical spectrometer employing photonic crystal patterns to outcouple waveguided light from a transparent substrate. This spectrometer consists of an array of photonic crystal patterns, nanofabricated in a polymer on a glass substrate, combined with a camera. The camera captures an image of the light outcoupled from the patterned substrate; the array of patterns produces a spatially resolved map of intensities for different wavelength bands. The intensity map of the image is converted into a spectrum using the photonic crystal pattern response functions. We present a proof of concept by characterizing a white LED with our photonic crystal spectrometer.

Ionizing radiation poses a significant challenge to the operation and reliability of conventional silicon-based devices. Here, we report the effects of gamma radiation on graphene field-effect transistors (GFETs), along with a method to mitigate those effects by developing a radiationhardened version of our back-gated GFETs. We demonstrate that activated atmospheric oxygen from the gamma ray interaction with air damages the semiconductor device, and damage to the substrate contributes additional threshold voltage instability. Our radiation-hardened devices, which have protection against these two effects, exhibit minimal performance degradation, improved stability, and significantly reduced hysteresis after prolonged gamma radiation exposure. We believe this work provides an insight on graphene's interactions with ionizing radiation that could enable future graphene-based electronic devices to be used for space, military, and other radiation-sensitive applications.

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