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<p>Recent years have seen a huge progress in the
development of phase sensitive second order
laser spectroscopy which has proven to be a
very powerful tool for the investigation of interfaces. These interferometric techniques involve the nonlinear interaction between three
short laser pulses with the sample. In order
to obtain accurate phase information, the relative phases between the pulses must be stabilized and their timings precisely controlled.
Despite much progress made, fulfilling both requirements remains a formidable experimental
challenge. The two common approaches employ
different beam geometries which each yields its
particular advantages and deficiencies. While
non-collinear spectrometers allow for a relatively simple timing control they typically yield
poor phase stability and require a challenging
alignment. Collinear approaches in contrast
come with a simplified alignment and improved
phase stability but typically suffer from a highly
limited timing control. In this contribution we
present a general experimental solution which
allows for combining the advantages of both approaches while being compatible with most of
the common spectrometer types. Based on a
collinear geometry we exploit different selected polarization states of the light pulses in well-
defined places in the spectrometer to achieve a
precise timing control. The combination of this
technique with a balanced detection scheme al-
lows for the acquisition of highly accurate phase
resolved nonlinear spectra without any loss in
experimental flexibility. In fact, we show that
the implementation of this technique allows us
to employ advanced pulse timing schemes inside
the spectrometer, which can be used to sup-
press nonlinear background signals and extend
the capabilities of our spectrometer to measure
phase resolved sum frequency spectra of inter-
faces in a liquid cell.</p>
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