US 7,627,008 B2Granted

Laser apparatus and method for harmonic beam generation

OwnerChoong Bum Parkinventor

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Abstract

A second harmonic laser beam is generated by passing a fundamental frequency laser beam through a single second harmonic generator (SHG) crystal more than two and preferably four times, to increase the amount of power converted from the fundamental beam into the second harmonic beam and to increase the overall efficiency of the conversion.

Claims21

Dependent claims

A laser apparatus for generating a second harmonic laser beam at a second harmonic frequency of a fundamental frequency of a fundamental frequency laser beam, for use with a laser source that generates the fundamental laser beam at the fundamental frequency, the laser apparatus comprising:

a second harmonic generator (SHG) crystal receptive of the fundamental beam which converts a portion of the light energy of the fundamental beam into a second harmonic beam of light energy at the second harmonic frequency with each pass of the fundamental beam through the SHG crystal;
the SHG crystal having a characteristic angle for propagation of the fundamental beam and second harmonic beam which achieves critical phase matching of the fundamental and second harmonic beams;
and
an optical transmission element oriented with respect to the SHG crystal to propagate the fundamental beam through the SHG crystal in four parallel optical passes and to propagate the fundamental beam and the second harmonic beam resulting from each pass in an optical path;
the optical transmission element propagating each pass of the fundamental beam and the second harmonic beam through the SHG crystal at the characteristic angle to achieve critical phase matching of the fundamental and the second harmonic beams;
the optical transmission element including a plurality of mirrors positioned in the optical path to reflect the fundamental beam to the SHG crystal in first, second, third and fourth passes of the fundamental beam through the SHG crystal and to reflect the second harmonic beam resulting from passing the fundamental beam through the SHG crystal coincidentally with the fundamental beam;
the optical transmission element also including a dichroic device oriented with respect to the SHG crystal to filter the second harmonic beam from the fundamental beam;
and wherein:
the portion of the fundamental frequency beam converted to the second harmonic beam adds energy of the second harmonic beam with each pass of the fundamental beam through the SHG crystal.

6 more elements

A method for generating a second harmonic laser beam from a fundamental laser beam in which the second harmonic beam has a frequency twice the frequency of the fundamental beam, comprising:

generating the second harmonic beam coincident with the fundamental beam by passing the fundamental beam through a second harmonic generator (SHG) crystal to convert light energy at the fundamental frequency into light energy in the second harmonic beam at the second harmonic frequency with each pass of the fundamental beam through the SHG crystal;
propagating the fundamental beam and the second harmonic beam through the SHG crystal in an optical path which extends through the SHG crystal at a characteristic angle which achieves critical phase matching of the fundamental and second harmonic beams;
increasing the light energy of the second harmonic beam above the light energy of the second harmonic beam obtained from the previous pass through the SHG crystal with each additional parallel pass of the fundamental beam through the SHG crystal;
using a plurality of mirrors to define the optical path through the SHG crystal;
passing the fundamental beam through the SHG crystal in at least four parallel passes;
and
filtering the second harmonic beam from the optical path of the fundamental beam.

4 more elements

Dependencies are inferred from the claim text.

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Abstract

a second harmonic generator (SHG) crystal receptive of the fundamental beam which converts a portion of the light energy of the fundamental beam into a second harmonic beam of light energy at the second harmonic frequency with each pass of the fundamental beam through the SHG crystal;
the SHG crystal having a characteristic angle for propagation of the fundamental beam and second harmonic beam which achieves critical phase matching of the fundamental and second harmonic beams;
and
an optical transmission element oriented with respect to the SHG crystal to propagate the fundamental beam through the SHG crystal in four parallel optical passes and to propagate the fundamental beam and the second harmonic beam resulting from each pass in an optical path;
the optical transmission element propagating each pass of the fundamental beam and the second harmonic beam through the SHG crystal at the characteristic angle to achieve critical phase matching of the fundamental and the second harmonic beams;
the optical transmission element including a plurality of mirrors positioned in the optical path to reflect the fundamental beam to the SHG crystal in first, second, third and fourth passes of the fundamental beam through the SHG crystal and to reflect the second harmonic beam resulting from passing the fundamental beam through the SHG crystal coincidentally with the fundamental beam;
the optical transmission element also including a dichroic device oriented with respect to the SHG crystal to filter the second harmonic beam from the fundamental beam;
and wherein:
the portion of the fundamental frequency beam converted to the second harmonic beam adds energy of the second harmonic beam with each pass of the fundamental beam through the SHG crystal.

6 more elements