Beam moments of higher-order annular Gaussian beams in tissue turbulence

Beam moments of the laser beam at the receiver plane were analyzed using our previously developed formula for the average light intensity of a higher-order annular Gaussian (HOAG) beam in the presence of biological tissue turbulence. HOAG beam moments are examined for the entities of power-in-the-bucket (PIB) and kurtosis across various tissue types such as the upper dermis (human), liver parenchyma (mouse), intestinal epithelium (mouse), and deep dermis (mouse). Moreover, beam moments are explored considering factors like the strength coefficient of the refractive-index fluctuations and the propagation distance. The PIB values for all HOAG beam modes are found to decrease exponentially and steadily, behaving similar to Gaussian beams as tissue length increases. As turbulence intensity increases, higher-order HOAG beam modes transfer optical energy to the receiver more efficiently than the lower order modes. Kurtosis analysis shows that at intermediate distances, the beam energy is distributed toward the edges, while at longer distances, the energy concentration is lower at the edges than at the center. This trend is reflected in increasing kurtosis values across all HOAG modes and tissue types. Considering the changes in PIB and kurtosis, higher-order HOAG modes transfer energy more conservatively within the tissue. Furthermore, the tissue type with the best transfer of optical power was observed to be the deep dermis (mouse).