Laser Sources

Our lab is equipped with about twenty state-of-the-art research lasers and numerous other major scientific instruments. A comprehensive list of lasers can be found below. The most advanced lasers in our lab include:

1. A femtosecond Ti:Sapphire laser amplifier system (Clark MXR, CPA). To the best of our knowledge, this is the only femtosecond laser amplifier system in the Commonwealth of Kentucky. The laser system is combined with frequency conversion units and a transient absorption system (Clark MXR, ShapeShifter) to study ultrafast energy and charge transfer in solar cell materials;

2. A high-power, widely tunable continuous-wave (CW) optical parametric oscillator (OPO) system (Toptica Photonics, TOPO). It was developed by Toptica and the Liu Group. This is a one-of-its-kind cw OPO system that can be used to record high-resolution spectra of molecules in the mid-infrared “fingerprints” region. (See Dr, Liu’s recent interview with Toptica for more information).

3. CW “ ring” Ti:Sapphire laser (MSquared, SolsTiS) and dye laser (Sirah, Matisse) laser systems. These two “ring” lasers are the most precise lasers that are commercially available and indispensable tools for high-resolution and high-precision spectroscopy. These two lasers are combined with frequency conversion units and amplifiers. Together they cover the wide spectral range from mid-infrared to ultraviolet.

List of Lasers:

(1) Equipment in the High-Resolution Spectroscopy Lab:

The existing laser systems in our high-resolution lab can cover mid-IR, near-IR, visible, and UV ranges almost continuously.

Lasers and other major instruments:

· Nd:YAG lasers x5 (Spectra-Physics: Quanta-Ray Pro250, Quanta-Ray Pro270 x2; Continuum: Powerlite Precision II 8000; Big Sky);

· Excimer lasers x3 (Lambda-Physik: Compex 110, EMG103-MSC, LPX-120-1);

· Pulsed dye lasers x2 (Sirah: PrecisionScan, Cobra-Stretch) with frequency doubling and difference-frequency mixing units);

· Ar⁺ laser (Coherent: Innova Sabre);

· Diode-pumped solid-state laserx2 (Coherent: Verdi-V10: Sirah: Millennia eV);

· Continuous-wave (cw) ring lasers x2 (MSqured: SolsTiS Ti:Sapphire with TeraScan automation system and ECD frequency doubling unit; Sirah: Matisse 2 DS);

· Home-built Ti:Sapphire amplifier;

· Raman shift cells x3 (single-pass x2, multi-pass);

· CW optical parametric oscillator (OPO, TOPTICA: TOPO) with the diode pump laser and a home-built automation system;

· Wavemeters x2 (HighFinesse: WS/6-200-VIS/IR 2, WS7);

· Cavity ring-down cells x3 (single-wavelength x2, dual-wavelength).

The Doppler-free saturated absorption spectrum of methane obtained in our lab (shown below) demonstrates the narrow linewidth of the OPO system.

Specifications of cw lasers available for the proposed two-photon spectroscopy experiments:

(2) Equipment in the Ultrafast Laser Spectroscopy Lab

The Ultrafast Transient Absorption Spectroscopy (UTAS) system consists of a Clark-MXR Ti:Saphire regenerative amplifier seeded by a SErF fiber laser and pumped by a Nd:YAG laser, two non-collinear optical parametric amplifiers (NOPAs) and a frequency-doubling system that together cover a wavelength range of 225-1600 nm, and a transient absorption (pump-probe) spectrometer. The system is designed to carry out ultrafast spectroscopy measurements with either white-light or single-wavelength laser sources, using a high speed linear array detector or a single-channel detector with balanced detection scheme, respectively. The laser pulse duration is as narrow as 30 femtoseconds.

The ultrafast laser spectroscopy lab also has a Coherent Vitesse 800 ultrafast laser system and a MenloSystems TERA K8 Time-Domain terahertz (THz) spectrometer.