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(Color online) Scheme of the multiplexed single-beam CARS approach. The excitation field can be thought of as superposition of two parts: A broadband part with a hole in its spectrum and a narrowband part that fills this hole. Each one of these parts of the excitation spectrum has a different phase (ϕn−ϕb) as the scheme shows (dashed lines).
(Color online) Simulation of the multiplexed single-beam CARS scheme: (a) Broadband excitation spectrum with a phase-gate (dashed line) with a width of 2 cm−1 and 30 cm−1, respectively. (b) Modulus of the third-order susceptibility . (c) Resulting single beam CARS spectrum. (d) Processed signal intensities according to Eq. (6) for the two gate widths of 2 cm−1 (lower black line) and 30 cm−1 (upper red line). The line for a gate width of 30 cm−1 is vertically shifted for clarity.
(Color online) (a) Measured spectral intensity of the used Ti:Sa-oscillator. The dashed vertical line indicates the position of the phase gate. (b) CARS spectra measured with the four phases used in the DQSI operation. (c) Resulting CARS spectra after DQSI without division by the local oscillator. (d) CARS spectra on acetonitrile using the DQSI operation is shown as a black line (Eq. (6)). The lower blue line is a MCARS measurement of pure acetonitrile for comparison using the setup described in Ref. 6.
(Color online) CARS spectra on toluene using the DQSI operation is shown as a black line (Eq. (6)). The lower red line is the extracted imaginary part with the MEM, which shows the usability of the measured spectrum for this analysis method (Ref. 6). The blue line in the middle is a MCARS measurement of pure acetonitrile for comparison using the setup described in Ref. 6.
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