CC BY
15LS-I-2
Sub-100 fs OPA in the 6-10 ^m range pumped by a 100 kHz Yb laser, and its application to vibrational spectroscopy
Z. Heiner1
1Humboldt Universitat zu Berlin, School of Analytical Sciences Adlershof SALSA, Berlin, Germany
Nonlinear spectroscopy is one of the numerous applications being revolutionized by commercial diode-pumped (sub-)picosecond Yb-lasers exhibiting exceptional average power scalability. On the one hand, frequency down-conversion of Yb-laser pulses to the mid-infrared spectral region between 2.5 and 12.5 |im has an enormous potential in vibrational spectroscopic applications, especially vibrational sum-frequency generation (VSFG) and 2D-IR spectroscopy, where the high repetition rate can significantly improve the sensitivity and signal-to-noise ratio (SNR) even at drastically reduced acquisition times. On the other hand, standard Ti:Sapphire-pumped vibrational spectrometers operating beyond 5 |im rely on multiple frequency conversion stages, including a difference frequency generation stage, severely limiting the conversion efficiency. Employing an OPA with an output above 5 |im pumped directly at ~1 |im is a promising solution. This requires a nonlinear crystal that is both highly transparent at these long mid-IR wavelengths and also has sufficiently large bandgap and damage threshold.
Recently, we constructed the first high-resolution, broadband VSFG spectrometer operating at laser repetition rates up to 100 kHz between 2.8 and 3.6 |im but the long wavelength edge of the spectrum was limited by the absorption edge of the amplifying material to ~4.5 |im [1,2]. Here, we present the first 100-kHz VSFG spectrometer operating at an extended mid-IR spectral region. The MIR source is based on a single-stage OPA pumped directly at 1 |im delivering carrier-envelope-phase-stable, sub-100 fs, 0.5 J and spectrally tunable pulses in the region of 6-10 |im [3]. To demonstrate the capability and sensitivity of our 100-kHz VSFG spectrometer, vibrational spectra of biomolecules at air-solid and air-liquid interfaces will be demonstrated in the fingerprint region, yielding very high SNR's within short acquisition times (<<1 min). The obtained results can bring new insight into laser-matter interaction of biomolecules at high repetition rates up to 100 kHz.
References
[1] Z. Heiner, V. Petrov, M. Mero, APL Photonics 2, 066102 (2017).
[2] F. Yesudas, M. Mero, J. Kneipp, Z. Heiner, J. Chem. Phys. 148, 104702 (2018).
[3] Z. Heiner, L. Wang, V. Petrov, M. Mero, Opt. Exp. 27, 15289-15297 (2019).
