Abstract-Diffraction-limited ultrabroadband terahertz spectroscopy.

Baillergeau M1, Maussang K1, Nirrengarten T1, Palomo J1, Li LH2, Linfield EH2, Davies AG2, Dhillon S1, Tignon J1, Mangeney J1.

http://www.ncbi.nlm.nih.gov/pubmed/27142959

• 1Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université P. et M. Curie, Université D. Diderot, 75231 Paris Cedex 05, France.
• 2School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS29JT, UK.

Diffraction is the ultimate limit at which details of objects can be resolved in conventional optical spectroscopy and imaging systems. In the THz spectral range, spectroscopy systems increasingly rely on ultra-broadband radiation (extending over more 5 octaves) making a great challenge to reach resolution limited by diffraction. Here, we propose an original easy-to-implement wavefront manipulation concept to achieve ultrabroadband THz spectroscopy system with diffraction-limited resolution. Applying this concept to a large-area photoconductive emitter, we demonstrate diffraction-limited ultra-broadband spectroscopy system up to 14.5 THz with a dynamic range of 10(3). The strong focusing of ultrabroadband THz radiation provided by our approach is essential for investigating single micrometer-scale objects such as graphene flakes or living cells, and besides for achieving intense ultra-broadband THz electric fields.