The demonstration of femtosecond pulse generation in fiber lasers [4] and the follow-on development of ultrafast fiber laser technology has moved ultrafast laser applications such as THz time-domain spectroscopy from the optical table into hand-portable find more information systems allowing for stand-off sensing in field applications.Interest in ultrafast lasers for sensing arises primarily from their high time resolution at the timescale of chemical or electronic and vibrational processes and from the high peak power achieved in the pulses. Typically, these lasers operate in a very limited wavelength range, around 800 nm for Ti:sapphire or 1,550 nm for Erbium doped fiber lasers. The high peak power, though, allows conversion of the laser light to a wide range of different wavelengths.

It makes non-linear frequency conversion very efficient, and multiple-harmonic generation has been used to generate coherent deep-UV and soft X-ray pulses [2]. Optical parametric amplification Inhibitors,Modulators,Libraries allows generation of femtosecond pulses at wavelengths in the near and mid infrared to 20 ��m covering the fingerprint area of the IR spectrum which is especially useful for chemical sensing applications. To continue the Inhibitors,Modulators,Libraries spectral coverage, optical rectification allows generation of THz pulses from the mid-IR region (30 THz = 10 ��m) to mm-waves at tens of GHz.Beyond narrow bandwidth pulses, at high laser intensities the refractive index of any material, including air, becomes a function of the intensity, with the optical Kerr effect being the strongest, non-vanishing nonlinearity that occurs in all media.

Inhibitors,Modulators,Libraries When properly controlled, this nonlinearity can give rise to a time-dependent phase shift and associated spectral broadening in the ultrashort pulse. This allows the generation of so-called white-light continuum pulses with significant powers and wavelengths ranging between 400 nm to 4.5 ��m from a 800 nm fs pulse after traveling through short glass or Inhibitors,Modulators,Libraries sapphire fibers [5,6]. This type of source can be a valuable broadband ultrafast laser light source for sensing and spectroscopy applications.Other nonlinear effects resulting from high power Anacetrapib femtosecond laser interactions with air include filament generation [7,8], Raman signatures [9], laser-induced fluorescence [10] or stimulated backscattered emission [11,12] from these filaments that can also be used for sensing applications.

The applications discussed in depth in this article are Laser-induced breakdown spectroscopy (LIBS), coherent anti-Stokes Raman spectroscopy (CARS), and THz time-domain spectroscopy. For LIBS, the high power and short duration of the laser pulse shifts the emission spectra from atomic emissions to molecular selleck chem inhibitor emissions. The spectral width of an ultrashort laser allows CARS to be performed with a single laser, reducing complexity for many sensing applications.