Complex and Polarized Light Imaging

In recent years, special attention of scientific society has been paid to investigation of Laguerre-Gaussian (LG) beams carrying orbital angular momentum (OAM) (known also as ‘vortex’ light). It was shown that this ‘vortex’ light with OAM penetrates deeper into tissue-like scattering medium comparing to the Gaussian light. Therefore, ‘vortex’ light has a high potential for a purpose of biomedical diagnosis tissue biopsy.
We investigate how the light carrying OAM propagates through the turbid tissue-like scattering medium. The modified off-axis Mach–Zehnder interferometer is implemented and used extensively for this purpose.

Selected results

Phase Memory of Orbital Angular Momentum in Multiple Scattering Environment

Recent advancements in wavefront shaping techniques have facilitated the study of complex structured light’s propagation with orbital angular momentum (OAM) within various media. The introduction of a spiral phase modulation to the Laguerre–Gaussian (LG) beam during its paraxial propagation is facilitated by the negative gradient of the medium’s refractive index’s temporal change, resulting in an accelerated retardation in OAM twist. This approach attains remarkable sensitivity to even the slightest variations in the medium’s refractive index (∼ 10^(−6)). The phase memory of OAM is revealed as the ability of twisted light preserving initial helical phase even propagating through the turbid tissue-like multiple scattering medium. The results confirm fascinating opportunities of the exploiting OAM light in biomedical applications, e.g. such as non-invasive trans-cutaneous glucose diagnosis and optical communication through biological tissues and other optically dense media.

Monte Carlo simulation of light carrying orbital angular momentum propagated through turbid tissue-like scattering medium

We developed Monte Carlo (MC) model to trace the evolution of light carrying either OAM propagating within the biological tissue. MC modeling approach allows to study light propagation in the random scattering medium via simulating a large number of MC-photon trajectories (∼ 10^9), with the possibility of involving up to 103 scattering events along each trajectory. The tracing cut-off is conducted according to the Beer-Lambert-Bouguer law, whereas direction at each scattering event is defined via Henyey-Greenstein phase function. The highlighted modeling of OAM beams involves definition of the appropriate beam
intensity distribution LG ℓ, p, initial phase ψ0 and unique initial direction s for each MC-photon based on the corresponding trajectory of the Poynting vector. The developed model also allows us to track speckle formation. We consider light shaped in the form of Laguerre-Gaussian (LG) beams and investigate how sensitive LG beams are to subtle alterations in biological tissues. We show that when the LG beam propagates through normal and abnormal tissue samples the OAM is preserved with the noticeably different phase shift – twist of light.

Media appearance

To be updated

Selected publications

  1. Meglinski, I., Lopushenko, I., Sdobnov, A., & Bykov, A. (2023). Phase Memory of Orbital Angular Momentum in Multiple Scattering Environment. arXiv preprint arXiv:2312.08928.
  2. Sdobnov, A., Lopushenko, I., Bykov, A., & Meglinski, I. (2023, June). Preservation of orbital angular momentum of light along propagation through a turbid tissue-like scattering medium. In The European Conference on Lasers and Electro-Optics (p. cl_4_3). Optica Publishing Group.
  3. Lopushenko, I., Sdobnov, A., Bykov, A., & Meglinski, I. (2023, June). Propagation of shaped light carrying orbital angular momentum through turbid tissue-like scattering medium. In European Quantum Electronics Conference (p. ej_4_2). Optica Publishing Group.