Modulation of the dephasing time for a magnetoplasma in a quantum well

We investigate the femtosecond kinetics of optically excited 2D magneto-pla sma. We calculate the femtosecond dephasing and relaxation kinetics of the laser pulse excited magneto-plasma due to bare Coulomb potential scattering , because screening is under these conditions of minor importance. BY takin g into account four Landau subbands in both the conduction band and the val ence band, we are now able to extend our earlier study [Phys. Rev. B 58, 19 98, in press] to lower magnetic fields. We can also fix the magnetic field and change the detuning to further investigate the carrier density-dependen ce of the dephasing time. For both cases, we predict strong modulation in t he dephasing time. (C) 1998 Published by Elsevier Science Ltd. All rights r eserved.