Terahertz transfer onto a telecom optical carrier

In a GaAs crystal, owing 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-laser and telecom technologies by injecting a telecom beam into a suitably designed THz quantum-cascade laser. Within the optical cavity, the phase and amplitude of the THz wave are recorded onto the near-infrared 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 up-conversion technique opens up new possibilities in the optical treatment of THz, by taking advantage of the highly developed telecom technology.