Dispersion-free continuum two-dimensional electronic spectrometer

Abstract

Electronic dynamics span broad energy scales with ultrafast time constants in the condensed phase. Two-dimensional (2D) electronic spectroscopy permits the study of these dynamics with simultaneous resolution in both frequency and time. In practice, this technique is sensitive to changes in nonlinear dispersion in the laser pulses as time delays are varied during the experiment. We have developed a 2D spectrometer that uses broadband continuum generated in argon as the light source. Using this visible light in phase-sensitive optical experiments presents new challenges in implementation. We demonstrate all-reflective interferometric delays using angled stages. Upon selecting an ~180 nm window of the available bandwidth at ~10 fs compression, we probe the nonlinear response of broadly absorbing CdSe quantum dots and electronic transitions of Chlorophyll a.

Ultrabroadband 2D electronic spectroscopy with high-speed, shot-to-shot detection

“…Of the four, the bottom two mirrors, which reflect beams 1 and 2, are mounted and translated on two mechanical stages at a small angle (∼0.3 • ) to the plane normal to the beam propagation. In this geometry, the effective increment (∆x) in τ is greatly reduced from the actual increment of the translational stage (∆d) when θ is small (∆x = ∆d sinθ) [27]. This gives us a much more precise control over the coherence time steps without approaching the mechanical limit of the precision of the stage (in our case, 100 nm).…”

“…The ultrabroadband excitation source is produced by supercontinuum generation through selfguided argon gas filamentation, as has been reported previously [27,29]. A 5-kHz Ti:sapphire regenerative amplifier (Coherent Libra) provides the initial input pulses that are centered at 800 nm (32-nm bandwidth) with a pulse duration of less than 40 fs.…”

“…To control the coherence time (τ) with interferometric precision but without introducing further dispersion, we have adopted the all-reflective interferometric delay (ARID) system reported by Zheng et al (Fig. 2) [27]. The system consists of four independent square mirrors arranged in a four-quadrant fashion [43].…”

“…This makes NOPA-based apparatuses unable to simultaneously probe the broad range of electronic and vibronic transitions that are typically seen in complex condensed-phase systems, which necessitates the use of a broadband light source to obtain a complete picture of the energy landscape and relaxation pathways. As such, several examples that demonstrate the applicability of few-cycle supercontinuum pulses to 2DES have been reported in recent years [27][28][29][30][31]. While there are several approaches to generate supercontinuum, [32,33] the most popular method of supercontinuum generation for 2DES is focusing a regenerative amplifier output into a chamber of pressurized argon gas, also known as gas filamentation [34,35].…”

Correlated Protein Environments Drive Quantum Coherence Lifetimes in Photosynthetic Pigment-Protein Complexes

“…46 For FMO, the coherence and waiting times were sampled from À1,001 to 2,002 fs in 3.5 fs steps, and from 0 to 1,860 fs in 30 fs steps, respectively. Rephasing times were obtained interferometrically.…”