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A General Approach To Combine the Advantages of Collinear and Noncollinear Spectrometer Designs in Phase-Resolved Second-Order Nonlinear Spectroscopy
journal contribution
posted on 2019-12-12, 19:36 authored by Tobias Garling, R. Kramer Campen, Martin Wolf, Martin ThämerRecent 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. In these techniques, the
nonlinear interaction between two short laser pulses and the sample
yields a signal pulse which subsequently interferes with a third pulse,
the so-called local oscillator. To obtain accurate phase information,
the relative phases between the signal and local oscillator 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 noncollinear 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. On the basis of 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 allows 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 suppress nonlinear background
signals and extend the capabilities of our spectrometer to measure
phase-resolved sum frequency spectra of interfaces in a liquid cell.