Fluorescence suppression in resonance Raman spectroscopy using a high‐performance picosecond Kerr gate

Abstract

A high-performance Kerr gate designed for the suppression of fluorescence in both time-resolved and steady-state resonance Raman spectroscopy is described and its performance illustrated. This is an improved version of a system described recently, with superior extinction ratio, higher throughput and wider usable spectral range. Specially designed polarizers are an essential feature of the system. The gate opens for ∼4 ps at 1 kHz repetition rate, throughput in the open state is up to ∼40% (excluding Fresnel losses on optical elements), the extinction ratio in the closed state is 10 −5 and the usable spectral range is 300-700 nm with a single set of polarizers. The Kerr gate is driven by ∼500 µ µJ, 1 kHz, 1 ps laser pulses at 800 nm and we believe that it is currently the most powerful device in operation for the temporal rejection of fluorescence from Raman spectra. It increases the general applicability of Raman spectroscopy as illustrated by picosecond time-resolved resonance Raman spectra of the intramolecular charge transfer state of 4-dimethylaminobenzonitrile and by the ground-state Raman spectrum of unleaded petrol at 400 nm probe wavelength.

Laser Raman spectroscopy as a technique for identification of seafloor hydrothermal and cold seep minerals

“…For example, fluorometers designed to measure chlorophyll a excite in the blue region (~440-470 nm) and detect fluorescence in the red (~685 nm). Methods for overcoming fluorescence are discussed by Ferraro et al (2003) and include: changing the excitation wavelength (into the red); using pulsed lasers to discriminate the signals by time (Raman scattering is faster in response and shorter-lived than fluorescence (Matousek et al, 2001;Matousek et al, 1999)); and exposing the sample to prolonged laser irradiation to bleach out fluorescent impurities.…”

Mineral–microbe interactions in deep-sea hydrothermal systems: a challenge for Raman spectroscopy

“…microbial mats). Fluorescence mitigation techniques include (i) time gating with a pulsed excitation source to differentiate between the faster, shorter Raman signal and the fluorescence signal (Matousek et al 2001), (ii) basing measurements on the anti-Stokes (blue-shifted) half of the Raman spectrum that is less affected by fluorescence (which is predominantly red-shifted), and (iii) shifting to a longer wavelength excitation source (Ferraro et al 2003). Of these fluorescence-mitigating approaches, time gating would significantly increase system complexity and cost, and would require higher laser powers or longer exposure times.…”

Direct measurement of the Raman enhancement factor of rhodamine 6G on graphene under resonant excitation

“…This fluorescence background is not a problem for R6G on graphene because of the fluorescence suppression effect of graphene [11]. Among the several kinds of techniques developed to suppress the fluorescence background [11][12][13], FSRS [10] and polarization-difference resonance Raman spectroscopy (PD-RRS) [14] have so far been able to measure the resonance Raman (RR) spectra of R6G. The FSRS requires considerable experimental complexity and the spectral resolution is limited by the ultrashort laser pulse, but PD-RRS exhibits splendid adaptability for use with a standard Raman system and provides the same spectral resolution as the standard system.…”