Complex and Polarized Light Sensing/Imaging

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 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 change over time, leading to a notable increase in the rate of phase twist, effectively observed as phase retardation of the OAM. 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 to preserve the initial helical phase even propagating through the turbid tissue-like multiple scattering medium. The results confirm fascinating opportunities for 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.

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.

Our research on Orbital Angular Momentum (OAM) of light interacting with complex scattering media has been featured in a special issue of Optics & Photonics News. This prestigious issue highlights groundbreaking peer-reviewed optics research from 2024. We are thrilled that our work has been recognized for contributing valuable insights of significant interest to the global optics community.

1. Meglinski, I., Lopushenko, I., Sdobnov, A., & Bykov, A. (2024). Phase preservation of orbital angular momentum of light in multiple scattering environment. Light: Science & Applications. 13(214), 2047-7538. DOI:10.1038/s41377-024-01562-7.
2. Khanom. F., Mohamed, N., Lopushenko, I., Sdobnov, A., Doronin, A., Bykov, A., Rafailov, E., Meglinski, I. (2024.) Twists through turbidity: propagation of light carrying orbital angular momentum through a complex scattering medium. Scientific Reports, 14, 20662. DOI: 10.1038/s41598-024-70954-x
3. 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.
4. 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.