Fluorescence light suppression in Raman Spectroscopy using ultrafast time gated CCD camera

A high level of fluorescence background signal rejection was achieved for solid and powder samples by using a combination of simple low-resolution spectrograph and ultrafast intensified/gated CCD camera. The unique timing characteristics of CCD camera match exceptionally well characteristics of Ti:sapphire oscillator allowing fast gated light detection at a repetition rate of up to 110 MHz, making this approach superior in terms of duty cycle in comparison with other time-resolved Raman techniques. The achieved temporal resolution was about 150 ps under 785 nm Ti:sapphire laser excitation. At an average excitation power up to 300 mW there was no noticeable sample damage observed. The strong Hexobenzocoronane (HBC) fluorescence with a lifetime about 2.1 ns was efficiently rejected and Raman spectrum revealed. The combination of spectrometer and ultrafast gated CCD camera allows simultaneous study of spectral and temporal characteristics of emitted light for the fluorophores with a fluorescence lifetime in nanosecond range. It is particularly important in biomedical spectroscopy, since the majority of endogenous fluorophores has a relatively short lifetime of about 1-5 ns. This capability opens an exciting possibility to build a universal instrument for solving multitask problems in applied laser spectroscopy.