Evaluation of penetration depth of near-infrared irradiation generated by tunable ultra-short pulsed laser in ex vivo samples of mouse head

Diana Galiakhmetova*, Viktor Dremin, Aleksandr Koviarov, Dmitrii Stoliarov, Neville Ngum, Rhein Parri, Sergei Sokolovski, Edik Rafailov

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


Optogenetic research has opened up the possibility to control neurons that will help detect and treat neurological diseases in the early stage. Treatment of dysfunctions requires exposure to a partial neural network accessible through the absorption of opsins or phytochromes expressed in the brain matter. The use of II-NIR USP lasers makes it possible to non-linear activate and deactivate photoactuators in neuronal cells through the skull. The possible obstacles for noninvasive stimulation are the limits in light penetration depth, scattering and absorption by biological tissues. This research aimed to investigate light propagation and penetration depth in skin, skull and brain matter of mouse head. To evaluate the light transmittance in brain tissues, we developed an experimental setup with a tunable ultra-short pulsed laser source operating at the wavelength range of 1.1-1.2 μm. This spectrum range corresponds to the spectra of nonlinear absorption of opsins/phytochromes and matches the second biological window where laser irradiation can penetrate the skin and skull bone without damaging and overheating them. The experimental results demonstrate that under certain conditions, the ultra-short pulsed laser radiation can reach a penetration depth with required power that will be sufficient for non-linear activation of opsins/phytochromes in the brain of living animals. These results could support applications of II-NIR USP laser in non-invasive optogenetics, photobiomodulation of the brain functioning and even neurological disorders diagnostics.

Original languageEnglish
Article number1214708
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 19 May 2022
EventTissue Optics and Photonics II 2022 - Virtual, Online
Duration: 9 May 202220 May 2022

Bibliographical note

Copyright 2022 SPIE. One print or electronic copy may be made for personal use only. Systematic reproduction, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Funding Information:
This work has been supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No.863214 – NEUROPA project. D.G. gratefully acknowledges funding by the Return to Research grant, Rank Prize.


  • light propagation
  • mouse head samples
  • tunable ultra-short pulsed laser


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