Two terahertz quantum cascade lasers based on GaAs∕Al0.1Ga0.9As heterostructures are reported. Pulsed mode operation up to 84K and continuous wave (cw) power of 0.36mW at 10K are demonstrated for the laser which emits from 1.34to1.58THz. The other laser shows emission from 1.2to1.32THz with pulsed mode operation up to 69K and cw power of 0.12mW at 10K.

In this paper we review recent progress in obtaining laser action from semiconductor quantum cascade structures covering the low THz region of the electromagnetic spectrum, from 2 THz (λ 155 μm) down to the sub-THz region (λ > 300 μm). Particularly, laser active region designs based on bound-to-continuum transition and magnetically assisted intra-well transition are presented. The wide scalability of active region designs is discussed and illustrated with experimental data. Latest results including the demonstration of laser action from quantum heterostructure at 950 GHz are presented.THz quantum cascade lasers are based on semiconductor heterostructures and cover a wide spectral window which now extends below 1 THz.

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We present the development of a broad gain quantum cascade active region. By appropriate cascade design and using a symmetric active region arrangement, we engineer a flat gain and increase the total modal gain in the desired spectral range. Grating-coupled external cavity quantum cascade lasers using this symmetric active region are tunable from 7.6 to 11.4 μm with a peak optical output power of 1 W and an average output power of 15 mW at room-temperature. With a tuning of over 432 cm−1, this single source covers an emission range of over 39% around the center frequency.

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