A luminaire with directional side-light extraction comprises a light pipe
with a light-carrying core. The light pipe has light-extraction structure
along a first longitudinal side of the luminaire, which is confined to a
radial swath of the luminaire, along the longitudinal axis of the
luminaire, of substantially less than 180.degree.. For efficiency, the
second end has light-saving structure for directing saved light from the
second end towards the first end, at redirection angles other than an
excluded range of redirection angles, so long as the photon content of
light at so-called alpha redirection angles is at least 10 percent of the
photon content of light at so-called beta redirection angles, where the
excluded range of redirection angles is defined by:
|.beta..sub.r|<=20.degree. and |.alpha..sub.r|<|.beta..sub.r|/10,
where .beta..sub.r is the beta redirection angle and .alpha..sub.r is the
alpha redirection angle.