Ultra-Fast modulation of mid infrared buried heterostructure quantum cascade lasers

We present the first direct observation of 26.5 GHz direct modulation of mid infrared buried heterostructure quantum cascade laser (QCL) emitting at 9 μm. For these measurements we have used an ultra-fast QWIP detector with 65 GHz bandwidth. As expected the modulation frequency bandwidth increases by increasing the laser driving DC current. Finally, we demonstrate that the laser cavity round trip frequency, f
_rt
, can be injection locked by direct modulation of laser driving current hinting to mode-locked operation.