Abstract: A beam homogenizer for surface modification comprises: a first lens array configured to split a laser beam, irradiated from a laser beam irradiation unit, into a plurality of beamlets; a second lens array configured to transmit the plurality of beamlets and comprising a plurality of lenslets corresponding to the first lens array; and a focusing lens configured to focus the plurality of beamlets, transmitted through the second lens array, onto a surface of a target. The beam homogenizer further comprises: a plasma generation-preventing unit disposed between the first and second lens arrays and configured to prevent plasma from being generated in the focal zone of the beamlets; or a damage-preventing unit disposed between the focusing lens and the target and configured to prevent the focusing lens from being damaged by energy generated when the plurality of beamlets is irradiated onto the target.

Abstract: A laser output device includes: a laser oscillator for oscillating a source laser pulse; a pulse extender for temporally extending the source laser pulse oscillated by the laser oscillator; an amplifier for amplifying the laser pulse temporally extended by the pulse extender; the laser pulse filter for filtering a pre-pulse and a post-pulse contained in the amplified laser pulse; and a pulse compressor for temporally compressing the laser pulse which has passed through the laser pulse filter.

Abstract: A beam homogenizer for surface modification comprises: a first lens array configured to split a laser beam, irradiated from a laser beam irradiation unit, into a plurality of beamlets; a second lens array configured to transmit the plurality of beamlets and comprising a plurality of lenslets corresponding to the first lens array; and a focusing lens configured to focus the plurality of beamlets, transmitted through the second lens array, onto a surface of a target. The beam homogenizer further comprises: a plasma generation-preventing unit disposed between the first and second lens arrays and configured to prevent plasma from being generated in the focal zone of the beamlets; or a damage-preventing unit disposed between the focusing lens and the target and configured to prevent the focusing lens from being damaged by energy generated when the plurality of beamlets is irradiated onto the target.

Abstract: Apparatus for stabilizing carrier-envelope phase (CEP) of laser pulse generated by mode locked pulsed laser based on direct locking method includes laser oscillator, interferometer, detector and double feedback circuit. The laser oscillator includes the mode locked pulsed laser generating the laser pulse. The interferometer generates laser pulses having first and second frequency components from the laser pulse generated by the mode locked pulsed laser to generate first and second interference signals that substantially correspond to each other in time domain and space domain. The detector receives the first and second interference signals to output third and fourth interference signals by inverting phase of the second interference signal. The double feedback circuit controls the laser oscillator so that the CEP of the laser pulse generated by the mode locked pulsed laser has substantially constant value with respect to time using CEP signal obtained from the third and fourth interference signals.

Abstract: Provided is a high-repetition-rate femtosecond regenerative amplification system. The regenerative amplification system includes: a laser oscillator emitting pulses; a stretcher stretching the pulses with negative dispersion; a regenerative amplifier amplifying the pulses, the regenerative amplifier comprising an acousto-optic modulator for pulse switching, a pulsed pump laser for pumping a gain medium, a resonator for reciprocating the pulses between a plurality of mirrors, and at least one chirped mirror for providing negative dispersion; and a glass compressor compressing the pulses. Accordingly, the 100 kHz-class high-repetition-rate femtosecond regenerative amplification system can produce an output energy of tens of ?J, higher than a few ?J provided by a conventional system.

Abstract: Apparatus for stabilizing carrier-envelope phase (CEP) of laser pulse generated by mode locked pulsed laser based on direct locking method includes laser oscillator, interferometer, detector and double feedback circuit. The laser oscillator includes the mode locked pulsed laser generating the laser pulse. The interferometer generates laser pulses having first and second frequency components from the laser pulse generated by the mode locked pulsed laser to generate first and second interference signals that substantially correspond to each other in time domain and space domain. The detector receives the first and second interference signals to output third and fourth interference signals by inverting phase of the second interference signal. The double feedback circuit controls the laser oscillator so that the CEP of the laser pulse generated by the mode locked pulsed laser has substantially constant value with respect to time using CEP signal obtained from the third and fourth interference signals.