Patent for third harmonic generation

The patent PAT.220359 for the third harmonic generation entitled 
"Optical system, generator and method for generating the third harmonic 
impulses of laser light" invented by Czesław Radzewicz and Tomasz 
Kardaś, has been published on the 30th October 2015 by the Polish 
Patenting Office.
The related patent application P.395808 was submitted on 29.07.2011.

Application summary: The optical set-up (7) contains elements in the form of the first crystal and the second crystal
with a second order nonlinearity, a birefringent plate, and half-wave plate for the base frequency,
positioned in a sequence inside a housing, through which elements passes the optical path of laser
pulses, wherewith the positioning order of these elements in the housing is the following:
the first crystal, followed by the birefringent wave-plate, followed by the half-wave plate
for the base frequency, followed by the second crystal with second order nonlinearity. The third
harmonic generator for laser pulses includes the optical set-up (7) located in between the laser
source (8), and the optical splitter (9). The method of third harmonic generation from laser pulses
is based on that the generated laser beam (12) with pulses of the base frequency is directed onto
the optical set-up (7), where the second harmonic beam (13) of pulses is generated, the relative
retardation between laser pulses of base frequency and second harmonic frequency is compensated,
the polarization state of base frequency pulses is rotated by 90°, which is followed by summing
the base frequency pulses (12) and second harmonic beam (13) pulses and by this means creating
the third harmonic laser pulses beam (14), and following the beam (12), beam (13) and beam (14)
in a form of a beam group (15) are directed onto an optical splitter (9) in which the third
harmonic beam (14) is selected out of other beams.

Patent PAT.220359