2D IR spectroscopy with phase-locked pulse pairs from a birefringent delay line.

Julien Réhault,Margherita Maiuri,Giulio Cerullo,Daniele Brida,Cristian Manzoni,Jan Helbing

doi:10.1364/oe.22.009063

Abstract

We introduce a new scheme for two-dimensional IR spectroscopy in the partially collinear pump-probe geometry. Translating birefringent wedges allow generating phase-locked pump pulses with exceptional phase stability, in a simple and compact setup. A He-Ne tracking scheme permits to scan continuously the acquisition time. For a proof-of-principle demonstration we use lithium niobate, which allows operation up to 5 μm. Exploiting the inherent perpendicular polarizations of the two pump pulses, we also demonstrate signal enhancement and scattering suppression.

Highlights

Since its first demonstration by Hamm et al [1], two-dimensional infrared spectroscopy (2D IR) has developed as an important technique to describe molecular structure, measure couplings between vibrational modes of a molecule and track structural dynamics on the picosecond timescale [2, 3]
We introduce a new scheme for two-dimensional IR spectroscopy in the partially collinear pump-probe geometry
While 2D IR was first realized in the frequency domain [1], time domain techniques are usually preferred [4,5,6,7,8,9], as they have better spectral resolution in the pump frequency axis, and because they maintain the time resolution afforded by the spectral bandwidth of the laser pulses [10]

Summary

Introduction

Since its first demonstration by Hamm et al [1], two-dimensional infrared spectroscopy (2D IR) has developed as an important technique to describe molecular structure, measure couplings between vibrational modes of a molecule and track structural dynamics on the picosecond timescale [2, 3]. The heterodyne photon-echo configuration is the most versatile and sensitive and the most complex way of performing 2D spectroscopy It requires the overlap of four independent beams at the sample, two pumps, one probe and one heterodyning pulse, and interferometric stabilization of the pulses in pairs, the two pumps and the probe with the heterodyning pulse. This configuration is in principle less flexible and sensitive than the heterodyne photon-echo, but control of the polarization and intensity of the four fields interactions is still possible by the use of polarizers in both the pump and probe beams [12,13,14] If we compare it to standard pump-probe spectroscopy, the additional requirement of 2D spectroscopy is to resolve the frequency of the pump pulses. It is possible to use the two perpendicularly polarized pulses to remove scattering and enhance signal with the use of polarizers in the probe beam [13, 14, 18, 19]

Measurement principle

Continuous scanning with He-Ne delay tracking

Polarization measurements

Findings

Discussion and conclusion