90. NON-DEGENERATE MULTIPHOTON MICROSCOPY FOR DEEP BRAIN IMAGING

Department: Electrical & Computer Engineering
Faculty Advisor(s): Y. Shaya Fainman

Primary Student
Name: Muhan Yang
Email: muy003@ucsd.edu
Phone: 858-534-7208
Grad Year: 2017

Abstract
In theory, non-degenerate 2-photon excitation (ND-2PE) of a fluorophore with two laser beams of different photon energies may offer independent degree of freedom in tuning of the photon flux (i.e., the power) for each beam. Here, using spatially and temporally aligned Ti:Sapphire laser and optical parametric oscillator (OPO) beams operating at near infrared (NIR) and short-wavelength infrared (SWIR) optical frequencies, respectively, we provide a practical demonstration that the emission intensity of a fluorophore excited in the ND-2PE regime in scattering medium is more efficient than the commonly used degenerate 2-photon excitation (D-2PE). The ND-2PE mechanism takes advantage of the infrared wavelengths used in 3-photon microscopy to achieve increased penetration depth, while preserving relatively high 2-photon excitation cross section, exceeding that achievable with the 3-photon excitation. Importantly, independent control of power for each beam implies that the flux requirement for the higher photon energy NIR beam, which experiences higher scattering in biological tissue, can be relaxed at the expense of increasing the flux of the lower photon energy SWIR beam which experiences lower scattering, thus promising deeper penetration with higher efficiency of excitation.

Industry Application Area(s)
Life Sciences/Medical Devices & Instruments

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