Abstract-Nanoscale terahertz scanning probe microscopy

 

T. L. Cocker, V. Jelic, R. Hillenbrand,  F. A. Hegmann 

Zooming in on surfaces with terahertz microscopy.

Scattering-type scanning near-field terahertz microscopy

Fig. 3: Alternate tip-based terahertz near-field nanoscopy techniques.

Fig. 4: Ultrafast THz-STM imaging at nano and atomic scales

https://www.nature.com/articles/s41566-021-00835-6

Terahertz radiation has become an important diagnostic tool in the development of new technologies. However, the diffraction limit prevents terahertz radiation (λ ≈ 0.01–3 mm) from being focused to the nanometre length scale of modern devices. In response to this challenge, terahertz scanning probe microscopy techniques based on coupling terahertz radiation to subwavelength probes such as sharp tips have been developed. These probes enhance and confine the light, improving the spatial resolution of terahertz experiments by up to six orders of magnitude. In this Review, we survey terahertz scanning probe microscopy techniques that achieve spatial resolution on the scale of micrometres to ångströms, with particular emphasis on their overarching approaches and underlying probing mechanisms. Finally, we forecast the next steps in the field.

Abstract-Enhancement of hot-carrier photoluminescence with intense terahertz pulses

D. N. Purschke, M. Na, A. Longman,   L. V. Titova,  F. A. Hegmann

http://aip.scitation.org/doi/abs/10.1063/1.5009470

Intense terahertz (THz) pulses have been shown to induce photoluminescence (PL) quenching in bulk semiconductors. We show that in addition to PL quenching near the bandgap, intense THz pulses enhance the high-energy tail of the PL in GaAs. Furthermore, we propose a simple model that accounts for both PL quenching and enhancement where THz-induced hot carriers directly enhance high-energy PL but reduce overall radiative efficiency due to ultrafast diffusion. Exploring the interplay between THz-induced PL enhancement and quenching over a range of excitation parameters reveals a reduction of integrated PL at low photoexcitation fluence, while at higher fluences, the amplitude of the PL quenching is balanced by that of the PL enhancement.