Optical system employing terahertz radiation

An optical system, comprising:

• a source for emitting radiation in a range of frequencies within from 100 Ghz to 20 Thz wherein the source includes a dipole emitter formed on a first surface of a substrate;
• a first coupling lens structure for coupling radiation emitted by said source into free space wherein the coupling lens structure includes a substrate lens formed on a second surface of said substrate, the substrate lens having an optical axis through its center which intersects said dipole emitter and wherein the substrate lens is aplanatic and has a hyperhemispherical shape and wherein the center of said substrate lens and the first surface of said substrate are separated by a distance not greater than the substrate lens radius divided by the refractive index of the lens;
• at least one optical element for focusing received coupled radiation onto a diffraction limited focal spot;
• and
• a detector for detecting the radiation focused by said at least one optical focusing element.

A method of investigating an object with radiation emitted by source over a range of frequencies within from 100 GHz to 20 THz, comprising the steps of:

• coupling, with a first coupling lens structure, the radiation emitted by the emission source such that the wavelength of the coupled radiation is greater than 1/100th of the beam diameter at an exit pupil of the coupling lens structure;
• collimating received coupled radiation into a beam having a substantially frequency independent diameter and substantially no wavefront curvature;
• directing the collimated radiation at a medium under investigation;
• and
• detecting one of radiation reflected by and transmitted through the medium during the directing step.