Generation of kilovolt, picosecond electric pulses by coherent combining in optoelectronic system
Résumé
Nowadays, interactions between pulsed electromagnetic field and biological cells and tissues are particularly investigated to prevent any noxious effects and/or to develop therapeutic processes able to improve cancer treatment. Electrochemotherapy is an example which allows drugs delivery improvement thanks to local pulsed electric field application. Consequently, high voltage electrical nanosecond pulse generation has received great interest from the researchers working in the bioelectromagnetic domain. In that framework, we demonstrated that picosecond kilovolt generator activated by a nanosecond and femtosecond laser sources can be coupled with a Multiplex Coherent Anti-Stokes Raman Scattering system (M-CARS) to study the impact of electric pulses on biological cells. We generated kilovolt picosecond electric pulses by using a frozen-wave generator which integrated silicon PhotoConductive Semiconductors Switches (PCSSs). Because of the linear switching regime no temporal jitter is observed during the optical switching thus, coherent combining of short electric pulses can be obtained. Two semiconductors are activated with adjustable time delay, generating unipolar pulses with less than 60 ps rise time (pulse duration 100 ps). Balanced and unbalanced bipolar pulses have been also obtained with a peak to peak voltage of 1.4 kV and a total duration of 244 ps. The initial optical pulse may be used to produce a supercontinnum extended from the visible and up to infrared domain (2.4 µm). Thus synchronized M-CARS diagnosis can be realized when nanosecond and picosecond electric pulse excitation is applied to biological samples.
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