Piezoacoustic modulation of gain and distributed feedback for quantum cascade lasers with widely tunable emission wavelength

Due to the piezoelectric properties of III–V materials, an acoustic wave propagating along the optical axis of a unipolar laser produces a periodic modulation of the carrier density and the optical gain, sufficient for providing distributed feedback ~DFB! with a mode suppression ratio exceeding 30 dB. In contrast to bipolar lasers, the piezoelectric modulation of unipolar carrier density is not accompanied by a degradation of the average gain. Inasmuch as the acoustic frequency can be easily changed, the wavelength of the main DFB mode can be tuned in a wide range. This property should be very attractive for spectroscopic applications of the quantum cascade laser. © 2003 American Institute of Physics. @DOI: 10.1063/1.1543232#