Figure 1: Active region design and light-voltage-current (L-V-I) characteristics of the terahertz QCL in cw mode.
From: Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation
(a) Conduction band structure and the contour plot of the moduli squared of the wave functions of the hybrid active region at an electric field of 6 kV/cm. The layer sequence of one period, from right to left, is 4.1/3.8/1/23.6/1/13.8/2.1/11.8/3.1/9.6/3.1/8.7/3.1/7.7/3.1/17.2/3.4/14.8 nm, where Al0.25Ga0.75As layers are in bold, GaAs in normal font, and the underlined layers are doped to 2 × 1011 cm−2. (b) Measured L-V-I characteristics of a 6-mm long and 150-μm wide laser in cw mode at a heat sink temperature of 15 K. The vertical dashed line shows the voltage corresponding to the onset of the negative differential resistance (NDR) region, where the current and voltage are oscillating and the horizontal dashed line indicates the current density Jmax. The grey pattern on the “Current density” axis shows the laser dynamic range, defined as the current density range from the threshold to Jmax.
