Infrared Light Sources Group
The group of Assist. Prof. Markku Vainio develops new coherent light sources, in particular for high-resolution laser spectroscopy. We use the new light sources for highly sensitive and selective molecular spectroscopy, both in scientific and industrial applications.
Optical frequency combs
Direct optical frequency comb (OFC) spectroscopy, such as dual-comb spectroscopy, is one of the most powerful methods for real-time multispecies trace gas analysis. Frequency combs in the mid-infrared (wavelength > 3 µm) region, which occupies the strong fundamental vibrational transitions of most molecules, are needed to fully utilize the capabilities of OFC spectroscopy. We conduct research on infrared frequency comb generation by quadratic optical nonlinearities.
The most common method to produce optical frequency combs in the visible and near-infrared regions is to use mode-locked lasers. While direct mode-locked laser operation in the mid-infrared region is beyond the state-of-the-art, a near-infrared comb can be transferred to the mid-infrared region using nonlinear optics, such as a degenerate, synchronously pumped optical parametric oscillator (OPO). Using this technique, we have recently demonstrated a fully-stabilized OFC in the 3 µm molecular fingerprint region [Opt. Lett. 42, 2722-2725 (2017)].
Cascaded quadratic nonlinearities
We have discovered a promising new method for direct infrared frequency comb generation without femtosecond lasers [Opt. Lett. 38, 4281-4284, (2013)]. This method, which is based on cascaded quadratic nonlinearities, allows for OFC generation with simple CW laser pumping practically at any wavelength from visible to infrared. Our ongoing research of CW-pumped cascaded nonlinearities focuses on miniaturization of the OFC generators for field applications.