Apparatus for frequency conversion of light, the apparatus comprises: a
light-emitting device for emitting a light having a first frequency, the light-emitting
device being an edge-emitting semiconductor light-emitting diode having an extended
waveguide selected such that a fundamental transverse mode of the extended waveguide
is characterized by a low beam divergence. The apparatus further comprises a light-reflector,
constructed and designed so that the light passes a plurality of times through
an external cavity, defined between the light-emitting device and the light-reflector,
and provides a feedback for generating a laser light having the first frequency.
The apparatus further comprises a non-linear optical crystal positioned in the
external cavity and selected so that when the laser light having the first frequency
passes a plurality of times through the non-linear optical crystal, the first frequency
is converted to a second frequency being different from the first frequency.
