Siddhartha Lahon

Nonlinear interband and intersubband transitions in quantum dots for multiphoton photodetectors

Accurate nonperturbative Floquet theory is used to study nonlinear multiphoton transitions in quantum dot involving interband and intersubband states. The interband transitions generate electron-hole pairs, which in turn give rise to photocurrent useful for making multiphoton photodetector. We find the direct role of multiphoton absorption processes over the single photon absorption in enhancing the sensitivity of the photodetector for photon energy equal to or less than the half of the bandgap energy.

LASER-INDUCED ADIABATIC POPULATION TRANSFER IN ASYMMETRIC QUANTUM WELLS

The basic technique of stimulated Raman adiabatic passage for laser-induced adiabatic population transfer between discrete quantum states of an asymmetric double quantum well has been used in our study. The results show that the proper time-delay, overlap, and detuning of two pulses allows the coherent transfer between the states of a double quantum well system, leading to the possibility of implementation of semiconductor–based quantum logic gates and high efficiency optical switches. The impact of phase relaxation on the population transfer efficiency is also studied.