  Time-resolved optical measurements of electron-spin dynamics in a (110) GaAs
quantum well are used to study the consequences of a strongly anisotropic
electron g-tensor, and the origin of previously discovered all-optical nuclear
magnetic resonance. All components of the g-tensor are measured, and a strong
anisotropy even along the in-plane directions is found. The amplitudes of the
spin signal allow the study of the spatial directions of the injected spin and
its precession axis. Surprisingly efficient dynamic nuclear polarization in a
geometry where the electron spins are injected almost transverse to the applied
magnetic field is attributed to an enhanced non-precessing electron spin
component. The small absolute value of the electron g-factor combined with
efficient nuclear spin polarization leads to large nuclear fields that dominate
electron spin precession at low temperatures. These effects allow for sensitive
detection of all-optical nuclear magnetic resonance induced by periodically
excited quantum-well electrons. The mechanism of previously observed Delta m =
2 transitions is investigated and found to be attributable to electric
quadrupole coupling, whereas Delta m = 1 transitions show signatures of both
quadrupole and electron-spin induced magnetic dipole coupling.

Mesoscale and Nanoscale Physics;Materials Science