Abstract
Terahertz technologies recently emerged as outstanding candidates for a variety of applications in such sectors as security, biomedical, pharmaceutical, aero spatial, etc. Imaging the terahertz field, however, still remains a challenge, particularly when sub-wavelength resolutions are involved. Here we demonstrate an all-optical technique for the terahertz near-field imaging directly at the source plane. A thin layer (<100 nm-thickness) of photo carriers is induced on the surface of the terahertz generation crystal, which acts as an all-optical, virtual blade for terahertz near-field imaging via a knife-edge technique. Remarkably, and in spite of the fact that the proposed approach does not require any mechanical probe, such as tips or apertures, we are able to demonstrate the imaging of a terahertz source with deeply sub-wavelength features (<30 μm) directly in its emission plane.
Highlights
Terahertz technologies recently emerged as outstanding candidates for a variety of applications in such sectors as security, biomedical, pharmaceutical, aero spatial, etc
A thin layer (,100 nm-thickness) of photo carriers is induced on the surface of the terahertz generation crystal, which acts as an all-optical, virtual blade for terahertz near-field imaging via a knife-edge technique
We propose an all-optical KE characterization technique and we demonstrate its working principle by characterizing the sub-l features of a spatially modulated THz source directly on the nonlinear crystal employed for the THz generation
Summary
In our experiment an ultraviolet (UV) optical beam is projected on the output facet of a generation crystal (featuring sub-l thickness) where it induces a thin layer (,100 nm) of photo-excited carriers Such conductive mask blocks THz radiation, acting as the blade in a KE measurement, directly on the THz source plane. It is worth noticing that the OKE enables us to characterize the emission geometry inside the generation crystal, overcoming the significant refractive index mismatch between the crystal and the air, well known for filtering out the high frequency components of the field spatial spectrum We employ this approach to demonstrate the imaging of a THz source with sub-l features (,30 mm) directly in its emission plane. This is the first example, to the best of our knowledge, in which a THz source has been mapped inside the generating crystal, as the clipping of the field physically occurs before the output interface, normally characterized by a very large refractive index mismatch between the air and the crystal at THz frequencies
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
