Integrated terahertz pulse generation and amplification in quantum cascade lasers

摘要

Integrated terahertz (THz) pulse generation and amplification in a THz quantum cascade laser (QCL) is demonstrated. Intracavity THz pulses are generated by exciting the facet of the QCL with an ultrafast Ti:Sapphire laser (～100 fs) and detected using electro-optic sampling. Maximum THz field emission is found with an interband transition of 1.535 eV (809 nm) and by narrowing the excitation laser bandwidth to ～3 THz. These resonance conditions correspond to the narrowband excitation of the quantum cascade miniband, indicating that the THz pulse is generated by the photoexcited carriers that are accelerated by the applied field. The generated pulse is subsequently amplified by the narrowband gain of the laser as it propagates through the QCL cavity.