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We present narrow-band polarization-sensitive reflectance of GaN/AlGaN heterostructures in the mid-infrared range. Experimental measurements performed at 15° angle of incidence show the excitation of a Berreman mode at the interface between GaN and sapphire substrate. A transfer matrix method for anisotropic layers has been used to analyze the obtained results. The contribution of the two-dimensional electron gas at the interfaces of the heterostructures has been included by proper modelization of an effective thin layer.

In this contribution we will discuss the experimental application of 3D chiral metamaterials as high sensitivity biosensors, exploiting circular dichroism in transmission. 3D metamaterials with chiral features can be realized by highly accurate and highly localized bottom-up nanofabrication approach. Large chiroptical effects can be engineered, originating from the single element optical resonances, but collective interactions in arrayed configurations can play a significant role, further enhancing these effects. Capability of biomarker detection in the femtomolar range is demonstrated even in complex biofluid matrix.