Terahertz quantum cascade laser sources based on ?erenkov difference-frequency generation

摘要

Room-temperature terahertz (THz) quantum cascade laser (QCL) sources based on intra-cavity difference-frequencygeneration (DFG) with record THz conversion efficiencies is reported. THz DFG QCLs reported previously are highlyinefficient since THz radiation produced more than ~100 μm away from the exit facet is fully absorbed due to high THzlosses in the QCL waveguide. Our lasers use a non-collinear ?erenkov DFG scheme to extract THz radiation from theactive region. Dual-color mid-infrared quantum cascade lasers with integrated giant optical nonlinearity are grown onsemi-insulating (S.I.) InP substrates. A lateral current extraction scheme is used. THz radiation is emitted at an angle intothe substrate with respect to the mid-infrared pumps. Since S.I. InP is virtually lossless to THz radiation, this schemeallows for efficient extraction of THz radiation along the whole waveguide length. As a result, our sources demonstratelarge mid-infrared-to-THz conversion efficiency and directional THz output. Experimentally, proof-of-principle devicesdemonstrate a conversion efficiency up to 70 μW/W2 and provide output across a 1.2 - 4.5 THz spectral range.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.