Frequency conversion using stacked strontium tetraborate plates

A method for generating a laser output light beam having an output frequency with a corresponding wavelength in the range of approximately 125 nm to approximately 183 nm, said method comprising:

• generating one or more fundamental light beams such that each said fundamental light beam has a corresponding fundamental frequency with a corresponding fundamental wavelength between about 1 μm and 1.1 μm;
• utilizing a plurality of intermediate frequency conversion stages collectively configured to generate one or more intermediate light beams using said one or more fundamental light beams, each of said one or more intermediate light beams having an associated intermediate frequency;
• utilizing a final frequency conversion stage to pass said one or more intermediate light beams through a nonlinear crystal,
• wherein said nonlinear crystal includes a plurality of Strontium tetraborate SrB4O7 (SBO) crystal plates disposed in a stacked configuration such that each said SBO crystal plate forms an interface surface with at least one adjacent said crystal plate, and
• wherein said plurality of SBO crystal plates are cooperatively configured to form a periodic structure that achieves quasi-phase-matching (QPM) of said one or more intermediate light beams such that light exiting the nonlinear crystal includes said laser output light beam having said output frequency.

An inspection system configured to inspect a sample using a laser output light beam having an output frequency with a corresponding wavelength in the range of approximately 125 nm to approximately 183 nm, wherein said laser output light beam is generated by a laser assembly comprising:

• one or more fundamental lasers respectively configured to generate a fundamental light beam having a corresponding fundamental frequency;
• a plurality of intermediate frequency conversion stages collectively configured to generate one or more intermediate light beams using said one or more fundamental light beams, each of said one or more intermediate light beams having an associated intermediate frequency;
• a final frequency conversion stage configured to pass said one or more intermediate light beams through a nonlinear crystal,
• wherein said nonlinear crystal includes a plurality of Strontium tetraborate SrB4O7 (SBO) crystal plates disposed in a stacked configuration such that each said SBO crystal plate forms an interface surface with at least one adjacent said crystal plate, and
• wherein said plurality of SBO crystal plates are cooperatively configured to form a periodic structure that achieves quasi-phase-matching (QPM) of said one or more intermediate light beams such that light exiting the nonlinear crystal includes said laser output light beam having said output frequency.