Development and demonstration of table-top synchronized fast-scan femtosecond time-resolved spectroscopy system by single-shot scan photo detector array

Abstract

Ultrafast dynamics is generally studied by pump-probe method with laser pulse, which scans optical delay by motorized stage step by step. Using ultrashort laser pulse shorter than typical molecular vibration periods, the pump-probe measurement can study both of electronic dynamics and vibration dynamics simultaneously. The probe wavelength dependence of the ultrafast electronic and vibration dynamics (UEVD) helps us to distinguish the signal contributions from the dynamics of the electronic ground state and that of the electronic excited states, which elucidates primary reaction mechanism after photoexcitation. Meanwhile, the measurement time of UEVD spectroscopy takes too long time to be used in realistic application. In our previous work, we have developed multi-channel lock-in amplifying (MLA) detectors to study UEVD at all probe wavelengths simultaneously, and synchronized it with laser and fast-scan delay stage to scan the data in five seconds. It enabled us to study UEVD spectroscopy even for photo-fragile materials. However, the home-made MLA detectors required for the measurement is expensive and massive in size and weight, thus not suitable for general researchers in the field of ultrafast time-resolved spectroscopy. In the present work, we have developed a table-top synchronized fast-scan femtosecond time-resolved spectroscopy system using single shot scan line CCD. This system measures time-resolved trace at all probe wavelengths simultaneously in five seconds. The CCD-based fast-scan time-resolved spectroscopy system enables us to study ultrafast dynamics of various materials even biomaterials, which have been thought to be hard or even impossible to be studied in previous methods.

Perylene Diimide-Fused Dithiophenepyrroles with Different End Groups as Acceptors for Organic Photovoltaics

“…Parts a and b of Figure display the ΔA spectra for the four samples measured with time delays of 1 and 10 ps, respectively. The ΔA spectra revealed two main features: (i) For FhPDI-IO2F and FhPDI-IO2Cl (with IO end groups), positive ΔA signals appeared near 600 nm (locations indicated by the red arrow in Figure a), presumably because of photoinduced absorption (PIA) through singlet S 1 → S n transitions. , Similar PIA signals appeared for both FhPDI-IC2F and FhPDI-IC2Cl (with IC end groups) in the range above 525 nm (blue arrow in Figure a). (ii) For FhPDI-IO2F and FhPDI-IO2Cl (with IO end groups), the negative ΔA signals extended from 500 to 600 nm, due to ground state bleaching (GSB) centered near 540 and 550 nm, respectively.…”

Development of Ultrashort Pulse Lasers for Ultrafast Spectroscopy

“…We have developed two detection schemes: the multi-channel lock-in detector [18] and the diode array detection system [19,20].…”

“…The broadband spectroscopic data provide invaluable information of the species appearing in the time-resolved data. For example, they enable discrimination of the congested spectrum and separate the signal into IA, SE, and GSB from the wavelength dependent dynamics of the ultrafast TA signal [18][19][20].…”

“…Therefore, scan trace can be averaged without the artefacts. The details of this system are described elsewhere [19,20].…”

Development of Sub 10 fs Visible-NIR, UV, and DUV Pulses and Their Applications to Ultrafast Spectroscopy

“…The fastscan system has improved the reproducibility and reliability of time-resolved transient absorption spectrum measurements. Details regarding this method have been reported previously in [19,20].…”