Intersubband transitions from the second subband in a coupled quantum wells structure

Asymmetrical coupled quantum wells structures with energy separation between the first two subbands of the order of 10-50 meV are key structures in the design of optically pumped intersubband lasers. In these structures the population of the second subband is not negligible and intersubband transitions from the second to higher excited subbands can be observed. In this work we investigate the temperature dependency of the intersubband transitions from the second subband in an asymmetrical coupled quantum wells structure. We show that this approach provides a direct way to measure the energy separation between the second subband and the Fermi energy which is a crucial parameter in the design of optically pumped intersubband lasers.