Measurement of far-infrared intersubband spontaneous emission from optically pumped quantum wells

We present the results of an experiment to measure far-infrared intersubband spontaneous emission from optically pumped quantum wells. A four-level laser design scheme was implemented using a coupled triple quantum well structure for optical pumping from E1 to E4 with a CO2 laser. The phonon scattering rates were designed to optimize the far-infrared emission efficiency and population inversion between E3−E2∼30 meV. The spontaneous emission spectrum was successfully resolved to reveal an emission peak at 30.8 meV with a linewidth of 7 meV.