Astrolabe tabletop femtosecond SFG/CARS spectrometer

  • Femtosecond broadband combination SFG/CARS spectrometer
  • Unique vibrational spectroscopy tool for monitoring surface layers in real time
  • Modular quick-interchangeable sample holdes for flat samples, crystals, liquid and electrochemical cells
  • Cost-efficient: combines two powerful nonlinear probes, specifically designed to be shared among several research groups
  • Compact tabletop design

1. General

Astrolabe is table-top nonlinear spectroscopy setup designed to be installed on 4x8' (1200x2400mm) standard optical table. It consists of CPA (chirped-pulse amplification) Ti:Sapphire femtosecond laser source, femtosecond Optical Parametric Amplifier (OPA) as a source of tunable radiation, Air-spaced Fabry-Perot etalon for shaping 800nm pulses, beam delivery and conditioning system with computer-controlled delay line, gas-purged beams and sample boxes, with appropriate filters, attenuators and polarization control elements, modular sample holder and detection system consisting of spectrograph with CCD detector.

SFG spectroscopy: strengths of the method:

  • Specificity: probes surface layers but not the bulk of the substrate.
  • Sensitivity: readily detects surface concentrations less than a monolayer.
  • Uniqueness: optical probe with unmatched sensitivity to the surface symmetry, molecular orientation and disorder – determine the tilt of surface molecules, detect isomerisation such as kinking of molecular chains, surface disorder under pressure or due to chemical reaction, 2D phase-transitions and the like.
  • Reach: get to interfaces buried under layers of only partially IR-transparent material, enclosed in vacuum and liquid cells, easily relay the coherent SFG signal away from hard to reach areas without compromising sensitivity.

Where does our system stand out:

  • Measure FAST - acquire 1000 spectral points in the time you would otherwise measure just one point in "traditional" scanning SFG setup. This allows for real-time monitoring of surface concentrations with submonolayer sensitivity. Alternatively this provides enough time to register weak SFG signal even if the sample is short-lived.
  • Look WIDE: Simultaneously monitor multiple peaks and their evolution in real time over 200cm-1 frequency range; not just the amplitudes, but also bandwidths and peak shapes in general; record minutes of "vibrational spectral movie" of your process.
  • Time-tested tabletop Ti:Sapphire CPA system – spend time on your experiment, not on laser alignment.
  • Powerful IR beam capable of overcoming strong absorption and reaching interfaces covered with water, e.g. in electrochemical cell.
  • Powerful visible beam: split out portion of it and use it to provide a pump with SFG signal serving as a probe for pump-probe experiment with picosecond time resolution.
  • Unique sample positioning system with fixed base plane allowing for rapid changes of dissimilar samples and complete sample cells, all that without the need for major realignment of the optics – several research groups can share one installation reconfiguring it for new experiment in a matter of minutes.
  • Quickly change from vertical sample orientation (good for flat solid samples) to horizontal orientation (suitable for electrochemical cells).
  • Choose between copropagating IR-Visible beam geometry and on-sample crossing geometry – the former allowing for simple optical alignment; suitable for less experienced researches; use the latter if stray nonlinear optical effects has to be completely eliminated.
  • With minor realignment switch the system to CARS spectrometer mode, taking advantage of the same versatile sample holders and detection system. CARS, while not surface-sensitive, can complement SFG in cases where sample composition results in complicated vibrational spectra.Please read more on SFG in PDF section.

2. Specifications

3. Applications

Real time monitoring of:

  • Surface chemical reactions

  • 2-D phase transitions

  • Surface heating and pressurization

  • Effects of potential changes on the electrode in electrolyte

  • Measurements of surface concentration (after calibration)

Pump-probe measurements of laser-induced flash heating, shock compression and chemical reactions at surfaces with picosecond time resolution (with optional high-power laser source).