Improving the signal-to-noise ratio of femtosecond luminescence upconversion by multichannel detection

Abstract

We have improved the sensitivity and signal-to-noise ratio of a luminescence upconversion experiment, using a charge-coupled device (CCD) as the detector. We show experimentally and numerically that the bandwidth of a 1-mm-thick ␤-barium borate crystal is large enough to take full advantage of the multichannel capabilities of the CCD. The improvement is significant in a standard experiment with a single laser as well as in experiments with resonant excitation that use two synchronized femtosecond pulse sources at different wavelengths. The characteristics of the two-color scheme are discussed in detail.

Initial Photoinduced Dynamics of the Photoactive Yellow Protein

“…Hence, evolution such as shifting and narrowing can be more clearly observed without the need for spectral reconstruction techniques from the single-wavelength traces. [36,37] Recently, the upconversion technique has been expanded to include the near-simultaneous collection of multiple wavelengths, [38,39] which combines high time resolution (< 150 fs) with dispersed wavelength detection. Vengris et al used this technique to contrast the fluorescence dynamics in the PYP protein and in isolated model chromophores in solution.…”

Femtosecond Pulse Propagation through a Quantum Wire Optical Waveguide Observed by Cross-Correlation Frequency-Resolved Optical Gating Spectroscopy

“…Since the wavelengths of the sum-frequency signal and the SHG signal from each of the pulses are different, the sumfrequency signal can be easily resolved by a spectrometer. 14) The waveguide sample was fixed on the cold finger of a high-stability transmission-type helium cryostat (Axess Tech) for the low-temperature experiment. The drift of the sample position with respect to the support of the cryostat in all dimensions was less than 1 micron for at least over 3 h. CCD cameras were used in order to visualize the waveguide facet on both input and output sides.…”

Linear and nonlinear femtosecond pulse propagation through a quantum nano-structure optical waveguide observed with XFROG spectroscopy

“…One is a two-color sum-frequency generation configuration. The combination of a Ti:sapphire laser and an optical parametric oscillator (OPO) provide a background-free measurement because the wavelength of the sum-frequency signal and the SHG signal from each pulses are different [3]. The other is a one-color type-2 SHG configuration.…”