Dual Picosecond Research Articles

Correlative Imaging of Motoneuronal Cell Elasticity by Pump and Probe Spectroscopy

Because of their role of information transmitter between the spinal cord and the muscle fibers, motor neurons are subject to physical stimulation and mechanical property modifications. We report on motoneuron elasticity investigated by time-resolved pump and probe spectroscopy. A dual picosecond geometry simultaneously probing the acoustic impedance mismatch at the cell-titanium transducer interface and acoustic wave propagation inside the motoneuron is presented. Such noncontact and nondestructive microscopy, correlated to standard atomic force microscopy or a fluorescent labels approach, has been carried out on a single cell to address some physical properties such as bulk modulus of elasticity, dynamical longitudinal viscosity, and adhesion.

Inside Cover: Label‐free multi‐parametric imaging of single cells: dual picosecond optoacoustic microscopy (J. Biophotonics 8/2019)

Sub‐picosecond light pulses are used to launch high‐frequency ultrasound in cells. The dual detection of acoustic echoes and of the time‐domain Brillouin scattering allows mapping remotely and in a single run experiment the cell adhesion, thickness, storage modulus and mass density, all with micron resolution. The dual picosecond opto‐acoustic microscope is demonstrated with the multiple imaging of a mitotic macrophage‐like cell. This novel modality is compatible with simultaneous fluorescence imaging.Further details can be found in the article by Liwang Liu, Laurent Plawinski, Marie‐Christine Durrieu, Bertrand Audoin (e201900045). image

Picosecond laser timing by rf phase shifting

Generation of picosecond and nanosecond time-scale time delays in a pump-probe laser system has been implemented without the use of an optical delay line, by rf-phase shifting of the mode-locking rf-signal. The system consists of dual picosecond dye lasers pumped by synchronized mode-locked, Q-switched, cw Nd:YAG lasers. The phase shifter operates with better than 10-ps precision and generates time delays from 0 to 26 ns.

Dual picosecond dye lasers pumped by synchronized mode-locked and Q-switched Cw Nd:YAG lasers

We have constructed a picosecond laser system with two Q-switched, mode-locked Nd:YAG lasers synchronously pumping two dye lasers. The Nd:YAG lasers are driven from the same rf source, and therefore produce synchronized pulse trains. Cross-correlation measurements of the two Nd:YAG lasers and of the two dye lasers are described, and the mode-locked pulses are found to be correlated to a high degree. Timing jitter between dye-laser pulses was determined to be ca. 50 ps. The phase relationship between the Nd:YAG lasers is found to be sensitive to cavity length detuning. The phase varies linearly with cavity length in a region ±0.02 mm about the optimum length. The laser system generates time-delays between pump and probe dye-laser pulses of up to milliseconds with picosecond resolution.

Dual picosecond dye lasers synchronously pumped by a mode locked cw yag laser

The performance of a novel dual dye laser system synchronously pumped by the frequency doubled output of a mode-locked CW-YAG laser is evaluated in relation to pulsewidth, pulse substructure, pulse spectral width and timing jitter. The behavior of the system is adequately described by a theoretical model which includes the time dependent gain and losses due to frequency bandwidth, cavity length mismatch and output coupler. The jitter is significantly reduced from that obtained with CW gas laser pumping as a result of the shorter pump pulse (50 ns instead of ≈100 ps). A routine operating condition uses 2-plate birefringen filters, 0.8 W pump power at 532 nm, to yield two 2.0 ps pulses having a cross correlation width of 3.8 ps, and 30 mW average power from each laser.