Patent ID: 7807942

Claim:
A laser processing method comprising the steps of: emitting ultrashort light pulses having a wavelength λ, an FWHM diameter Δi and an FWHM pulse width Δt from a pulse laser, wherein the FWHM diameter Δi is a full width of a peak of laser power distribution at a height of half of the maximum and the FWHM width Δt is a full width of a peak of pulse width distribution at a height of half of the maximum; and converging the ultrashort light pulses by a diffractive lens having a focal length f to a work piece placed at the focal point of the diffractive lens, wherein the focal length f, the FWHM diameter Δi and the FWHM pulse width Δt are adjusted so that a Z-parameter defined by Z p =2fcΔt/Δi 2 satisfies an inequality Z p =2fcΔt/Δi 2 ≦1, where c is the light velocity in vacuum.