Key Highlights
- Pulse width adjustment from < 180 up to 500 ps
- Improved coherence length and spectral width close to transform limit
- Sub-ns pulse shaping
- Selection of spectrally broader rising slope or narrow pulse tail
- Ideally suited for Time-Domain Diffussive Correlation Spectroscopy (TD-DCS)
Description
Inspired by the TD-DCS community‘s need for having high-power picosecond pulses that are also coherent, PicoQuant developped a respective upgrade for the VisIR. By integrating an electro-optic modulator (EOM) into the VisIR laser platform, the temporal shape of the optical pulse can be adjusted. The EOM is driven by PicoQuant‘s programmable electric pulse generator PPG 512 and is able to generate optical pulses between < 180 and 500 ps with a resolution better than 25 ps.
Optical pulses based on gain-switching or modulated laser diodes exhibit nonlinear spectral chirp and varying spectral linewidth over the temporal pulse width. Typically, the spectral linewidth decreases towards the falling slope of the pulse to nearly the transformation limit. Suppressing the rising slope via EOM enables the creation of highly coherent sub-ns optical pulses with the extra benefit of ideal extinction ratio between optical pulses in comparison to EOM shaping of CW signals.
Such a shaping process is of great interest for time-domain diffuse coherence spectroscopy (TD-DCS), as the improved laser pulse coherence will result in drastically improved quality of the speckle-based TD-DCS. Shaping the VisIR laser pulses by EOM represents a drastic improvement for brain vessel sensitive blood flow monitoring.
Interested in learning more about this upgrade and its application? Then watch Mario Gerecke’s webinar on “Shaping nanosecond laser pulses via electro optical modulators and PicoQuant‘s PPL 512”.
