We develop a theory of time-resolved pump–probe optical spectroscopy for modelling interband absorption by an anisotropic semiconductor nanodumbbell. By considering three transition schemes where the pump and probe pulses are nearly resonant to a dipole-allowed interband transition of different elements of the nanodumbbell, and assuming that the populations of the exited states are coupled through the nonradiative relaxation processes, we analytically calculate the absorption efficiency of the probe as a function of its delay from the pump for relatively short pulses. The obtained functional dependency, being the sum of exponentials with exponents proportional to the energy relaxation rates of the excited electronic states, is useful for the analysis of experimental absorption spectra aiming at retrieving the relaxation parameters of the nanodumbbell’s electronic subsystem.
We develop a theory of time-resolved pump–probe optical spectroscopy of intraband absorption of a probe pulse inside
an anisotropic semiconductor nanorod. The absorption is preceded by the absorption of the pump pulse resonant to an
interband transition. It is assumed that the resonantly exited states of the nanorod are interrelated via the relaxation
induced by their interaction with a bath. We reveal the conditions for which the absorption of the probe’s pulse is
governed by a simple formula regardless of the pulse’s shape. This formula is useful for the analysis of the experimental
data containing information on the relaxation parameters of the nanorod’s electronic subsystem.
We develop a theory of secondary emission from a single quantum dot, when the lowest-energy states of its
electron–hole pairs are involved in the photoluminescence process. For the sake of definiteness, our model allows
for two states contributing to the luminescence. We analyze the dependency of secondary emission intensity on
the energy gap between the states, while considering that the gap is determined by the quantum dot’s size. An
analytical expression for the time-dependent signal of thermalized luminescence is obtained using an analytical
solution to the kinetic Pauli equation. This expression yields the signal of stationary luminescence as the spectral
width of the excitation pulse tends to zero.