Exploiting the magneto-optics of quantum wires for designing optical amplifiers

This report aims at a core issue related with the magnetoplasmon excitations in the quantum wires
characterized by the confining harmonic potential and subjected to a longitudinal electric field and a
perpendicular magnetic field in the symmetric gauge. Despite the substantive complexity, we obtain the
exact analytical expressions for the eigenfunction and eigenenergy, using the scheme of ladder operators,
which fundamentally characterize the quantal system. Crucial to this inquiry is an
intersubband collective excitation that evolves into a magnetoroton -- above a threshold value of magnetic
field -- which observes a negative group velocity between maxon and roton. The evidence of negative group
velocity implies anomalous dispersion in a gain medium with the population inversion that forms the basis
for the lasing action of lasers. Thus, the technological pathway that unfolds is the route to devices
exploiting the magnetoroton features for designing the novel optical amplifiers and hence paving the way
to a new generation of lasers. [See, e.g., Phys. Rev. B {\bf 78}, 153306 (2008); J. Appl. Phys. {\bf 109},
106102 (2011); Europhys. Lett. {\bf 123}, 34001 (2018); Mod. Phys. Lett. B {\bf 33}, 1950062 (2019).]