Paper from the QUAD team to appear in Nature Photonics (july 2007) :
In a GaAs crystal, due to the anomalous dispersion introduced by optical phonon absorption, a phase-matched interaction is possible
between a near-infrared beam and a terahertz (THz) wave. We exploit this nonlinear optical process to allow the merging of THz
quantum cascade (QC) laser and telecom technologies by injecting a telecom beam into a suitably designed THz QC laser.
Within the optical cavity, the phase and amplitude of the THz wave are recorded onto the near-infrared (NIR) beam, which can
be transported through an optical fibre. We show that the process is phase-matched and can be tuned over the entire telecom
range by waveguide engineering. This nonlinear upconversion technique opens up new possibilities in the optical treatment of
THz, by taking advantage of the highly developed telecom technology.
