Photonic devices and original probes for terahertz near-field microscopy

In the field of photonics and biophotonics, the need for higher resolution for microscopy and nanoscopy is of prime interest for many applications like the semiconductors industry (carrier density) or biological studies and diagnostics. After a detailed description of the free space approach, using tips just like those used for AFM or original ones that we proposed a few years ago, we will focus on the guided wave approach and particularly on a solution for microscopy-on-chip with an integrated photonic source that generates terahertz waves. Both approaches with free space or guided waves are presented with an original topology in each case. For free space infrared and terahertz waves, the shape of the tip plays a key role for an antenna-like coupling with the sample. For the guided mode approach, the electromagnetic confinement around a single conductor, which acts as a plasmonic circuit, is exploited to efficiently bring the sensing wave to the sample. Concerning biological studies, we will also see how the proposed approaches are compatible with liquid media, opening many areas of biophotonic application. The key point is the on-chip-integration of the active photonic device, the UTC-PD (Uni-traveling-carrier Photodiode), that can generate millimetre and terahertz waves with an ultrabroad behaviour that is useful for hyperspectral imaging.