- Vibrational mid-IR spectroscopy
- CEO-free frequency comb
- High harmonic generation
- Difference frequency generation (DFG)
- DFG generating 3 - 15 µm
The spectral region between optics and electronics lying in the mid-Infrared is difficult to access. Nevertheless it is of great spectroscopic interest because it hosts the majority of molecular finger prints: This important vibrational modes with energies in the spectral range of 670 cm-1 to 3400 cm-1 can be accessed by exciting the sample at wavelengths of 3 µm to 15 µm.
TOPTICA’s ultrafast fiber laser FemtoFiber dichro midIR generates powerful radiation tunable between 3 µm – 15 µm that is ideally suited for spectroscopy and (nearfield) microscopy applications. Based on difference frequency generation (DFG) of two optically synchronized laser pulses at tunable wavelengths of 1 – 2 µm a highly stable broadband emission of approximately 400 cm-1 is generated. Here, the powerful fundamental output at 1560 nm of an Erbium doped ultrafast fiber laser is superimposed with the long or short wavelength part of a supercontinuum which is efficiently generated in a highly non-linear optical materials.
A welcomed side effect of the DFG approach is the elimination of the carrier envelope offset (CEO) of the mode-locked laser: The CEO-free mid-IR laser pulses are therefore applied to attosecond spectroscopy where the extreme UV pulses consist of only a few optical cycles. The conversion of mid-IR radiation to extreme UV is accomplished by high harmonic generation. First, the mid-IR pulses are amplified by several orders of magnitude with optical parametric chirped amplification (OPCPA). Then, the intense laser fields are launched into an atomic beam or a gas-filled hollow core fibre to generate extreme UV attosecond laser pulses via high harmonics