AN INVESTIGATION SYSTEM, A RECEIVER AND A METHOD OF INVESTIGATING A SAMPLE

摘要

A system for investigating a sample, the system comprising at least one source of radiation for producing a first beam of radiation having a first frequency and a second beam of radiation having a second frequency, wherein said first and second frequencies are both in the range from 25GHz to 100THz and are not equal to one another, the system further comprising a detector configured to perform heterodyne detection using the first and second beams, wherein said at least one source is a quantum cascade laser.