Method of generating terahertz emission using an ink
There is disclosed a method of generating terahertz radiation which comprises: (a) depositing an ink on a substrate ( 2 ), wherein the ink comprises particles ( 3 ) of a semiconductor; (b) allowing the ink to form a coating; (c) shining a laser onto the coating so as to generate terahertz radiation.
1 . A method of generating terahertz radiation which comprises:
(a) depositing an ink on a substrate, wherein the ink comprises particles of a semiconductor;
(b) allowing the ink to form a coating;
(c) shining a laser onto the coating so as to generate terahertz radiation.
2 . The method of claim 1 , wherein the semiconductor has a bandgap energy from about 2 to about 5 times lower than the excitation wavelength; and/or wherein the semiconductor material has a bandgap in the range from about 0.18 eV to about 0.5 eV.
3 . The method of claim 1 , wherein the semiconductor is a III-V semiconductor material.
4 . The method of claim 1 , wherein the semiconductor is n-doped or p-doped.
5 . The method of claim 1 , wherein at least about 50 wt. %, of the semiconductor particles have a hydrodynamic diameter within the range from about 500 nm to about 2000 nm.
6 . The method of claim 1 , wherein the semiconductor particles have an aspect ratio greater than 1.
7 . The method of claim 1 , wherein the ink comprises a carrier selected from water and an organic solvent.
8 . The method of claim 1 , wherein the ink further comprises a binder.
9 . The method of claim 1 , wherein, in step (c), at least a part of the coating is at a first temperature, the method further comprising heating or cooling said at least a part of the coating to a second temperature different than the first temperature.
10 . The method of claim 9 , wherein the generated terahertz radiation in step (c) comprises a first distribution of terahertz radiation, the method comprising generating a second distribution of terahertz radiation different to the first distribution of terahertz radiation by heating or cooling said at least a part of the coating to a second temperature different than the first temperature.
11 . The method of claim 1 , wherein the method comprises exposing the coating to a magnetic field after step (b).
12 . The method of claim 11 , wherein the method comprises removing the magnetic field before shining a laser onto the coating.
13 . The method of claim 1 , wherein the substrate comprises a metal, a plastic, a cellulose-based product, glass, a ceramic, carbon fibre, or a combination thereof.
14 . The method of claim 1 , wherein the ink further comprises magnetic contaminant particles.
15 . The method of claim 14 , wherein the generated terahertz radiation in step (c) comprises a first distribution of terahertz radiation, the method further comprising generating a second distribution of terahertz radiation different to the first distribution of terahertz radiation by exposing the coating to a first magnetic field.
16 . The method of claim 15 , wherein the step of exposing the coating to the first magnetic field comprises: exposing the coating to the first magnetic field after step (b) and removing the first magnetic field before shining a laser onto the coating; or exposing the coating to the first magnetic field after step (b) and maintaining the first magnetic field during step (c).
17 . The method of claim 14 , wherein the method further comprises generating a third distribution of terahertz radiation, different to and in place of the second distribution of terahertz radiation, by exposing the coating to a second magnetic field in place of the first magnetic field, preferably wherein the second magnetic field is perpendicular to the first magnetic field.
18 . The method of claim 1 , wherein the ink further comprises contaminant particles wherein the material of the contaminant particles is different from the semiconductor, wherein the contaminant particles absorb THz radiation and/or are configured to change the temperature of the particles of the semiconductor when exposed to radiation.