Patent ID: 7688871

Claim:
A method of increasing the contrast of a high-intensity laser comprising: amplifying laser light outputted from a laser oscillator with an optical parametric chirped pulse amplifier as excited by laser light of a short pulse width, whereby the laser light is provided with an extremely high value of contrast which represents the intensity ratio between the pre-pulse as background light and the main pulse, both being contained in the temporal waveform of the laser light, wherein the laser light outputted from a laser oscillator is signal light and the laser light of a short pulse width is pump light, wherein excitation by pump light of a short pulse width enables efficient amplification by the short length of interaction in the optical parametric chirped pulse amplifier and, at the same time, the short length of interaction enables amplification of a wide spectral band, and wherein in a laser system comprising a laser oscillator, a pulse stretcher, a laser amplifier and a pulse compressor, signal light outputted from the laser oscillator has only the main pulse amplified selectively with an optical parametric chirped pulse amplifier as excited by pump light of a short pulse width and thereafter the amplified pulse is launched into an optical parametric chirped pulse amplifier as excited by pump light of a short pulse width or into another titanium-sapphire laser amplifier in the latter stage, whereby the amplified light can have a higher intensity.