We report the observation of cw laser-excited visible luminescence at the E1 - E1, + Δ1 direct gaps in n-type Ge with Ne >≈ 1018 cm-3 . The phenomenon appears to be induced by participation of the high density of free electrons in the E1 - E1 + Δ1 transitions at the L-point (2.1 and 2.3 eV) since the luminescence is not observed in either pure or p-type Ge. We have used this luminescence to investigate the effect of doping on the band structure of bulk doped and also of phosphorus implanted laser annealed Ge. Shifts and broadening of the E1 - E1 + Δ1 energies and also Burstein-Moss-Fermi energy shifts have been observed. The results for bulk Ge go over smoothly and overlap with the results for the laser annealed material.