Laser Terahertz Emission Microscopy of Gold Nanorods forming a Coffee-stain Ring on a Semiconductor Surface

We study the influence of resonant gold nanorod deposited on an InAs surface to enhance the terahertz (THz) emission induced by the photo-Dember effect. With the nanorods forming a coffee-stain ring, we observe a variation in the induced THz field, which we image with Laser THz Emission Microscopy (LTEM). Here, we observe an enhancement of up to 30% of the THz signal measured from a bare InAs surface. On the other hand, clustering of nanorods in the central region leads to a suppression of THz signal where less than 80% of the signal measured from the bare surface is obtained. By preparing several samples with the same method but varying the number of nanorods, we are able to study the correlation between the nanorod concentration and the THz signal enhancement.