Method and system for generating tunable ultrafast optical pulses
A system and a method for generating tunable ultrafast optical pulses, the method comprising spectral broadening of a laser input beam by propagating the laser input beam in a nonlinear medium of a third-order nonlinear susceptibility χ (3) , yielding an output laser spectrum; and one of: i) selecting at least one portion of the output laser spectrum, yielding an output pulse different than the input pulse and centered at a different frequency; ii) temporal compensation and spatial spreading of spectral components of the output laser spectrum; selecting two pulses at two different frequencies; and nonlinearly mixing the two pulses together in a first second-order nonlinear susceptibility χ (2) nonlinear crystal into a third pulse centered at a frequency which is a difference between the frequencies of the first two pulses; and iii) dividing output laser spectrum into a pump beam and a probe beam, directing a pump pulse to a third second-order nonlinear crystal for THz radiation generation; and directing a probe pulse to a third second-order nonlinear crystal for THz radiation reconstruction.
1. A system for generating tunable ultrafast optical pulses, comprising a laser source, a gas-filled hollow-core fiber selected for spectrally broadening an input laser pulse by self-phase modulation or Raman effect and a filter unit, wherein an input pulse is spectrally broadened by propagation within said gas-filled hollow-core fiber, and said filter unit selects at least a spectral lobe of a broadened pulse output spectrum, yielding an output pulse shorter than the input pulse and centered at a different frequency.
2. The system of claim 1 , wherein said input pulse has a pulse energy of at least 1 nJ and pulse duration at most 1 ns, said gas-filled hollow-core fiber is filled with a gas of a third-order nonlinear susceptibility χ (3) >10 −27 m 2 /V 2 .
3. The system of claim 1 , comprising an optical unit adjusting a size of a beam from the laser source to a matching optical intensity in the gas-filled hollow-core fiber.
4. The system of claim 1 , wherein the gas-filled hollow-core fiber is filled with a gas of a third-order nonlinear susceptibility χ (3) larger than 10 27 m 2 /V 2 .
5. The system of claim 1 , wherein said gas-filled hollow-core fiber guides the input pulse over a selected distance at least once.
6. The system of claim 1 , said system comprising an optical unit adjusting the beam from the laser source to a matching main mode of the gas-filled hollow-core fiber.
7. The system of claim 1 , wherein said gas-filled hollow-core fiber is filled with one of: Argon, Nitrogen, Helium, Krypton, Xenon, and carbon dioxide.
8. The system of claim 1 , wherein said gas-filled hollow-core fiber is filled with a molecular Raman-active gas.
9. The system of claim 1 , wherein the laser source is selected with a laser input energy of at least 1 micro joule and pulse duration of at most 10 picoseconds.
10. The system of claim 1 , wherein at least one of i) a length and ii) a diameter of the gas-filled hollow core fiber is selected according to the laser source.