Terahertz Field Induced Second Harmonic coherent detection scheme based on a biased nonlinear micro-slit

We demonstrated coherent Terahertz characterization based on Terahertz Field Induced Second Harmonic effect in few microns thick Silica (SiO₂) samples that can be easily operated with 10-100 V sources. Our sample is an infinitely long 30 μm slit written in gold. The underlying idea of our work is that of exploiting the large breakdown voltage and the high nonlinearity of glass to achieve a large signal to noise ratio detection with a very weak optical probe at moderate bias fields, thus drastically reducing the electrodes gap. Our results pave the way to a novel approach towards broadband THz detection.