A mechanically-adjustable variable optical attenuator includes an
azimuthally-tapering, rotatable beam attenuator. In a plane perpendicular
to the light beam to be attenuated, the projection of the beam attenuator
comprises a sharp distal tip, a proximal region, and a concave curved
light-blocking surface narrowing from the proximal region to the distal
tip. The extent of the beam attenuator obstructing the light beam is
varied by rotating the beam attenuator about a rotation axis perpendicular
to the light beam direction. The beam attenuator geometry allows achieving
high resolutions while limiting the beam attenuator size. The attenuated
light beam can be a single-mode or multi-mode light beam.
