Microscopic second harmonic generation (SHG) from tilt-placed collagen fibrils

Chang, Y.; Wei, H.; Jin, Y.; Liu, H.; Deng, X., 2011: Microscopic second harmonic generation (SHG) from tilt-placed collagen fibrils. General Physiology and Biophysics 30(2): 175-185

We report a theoretical study of second-harmonic generation (SHG) from the collagen fibrils which have a tilt angle Φ between their axes with the plane of the polarization angle α of the linearly polarized focused light. The effects of Φ as well as α on SHG emission have been investigated. Our results show that the total strength of SHG electrical field (E(2ω)) and power (P(2ω)) reach their maximal values as Φ locates at a certain angle, here it is around 27° under all demonstrated α. When Φ < 27°, E(2ω) and P(2ω) gradually increase to their maximal value, while when Φ > 27°, they quickly drops. Specially, E(2ω) and P(2ω) are almost undetectable when Φ ≥ 45°. Also, Φ influences the distribution pattern of E(2ω), P(2ω) and their parallel (E(2ω,p), P(2ω,p)) and perpendicular (E(2ω,s), P(2ω,s)) components, such as the number of emission lobes and shape. α has unevenly impact on E(2ω) and P(2ω), the far deviation of α from x axis induce much great decrease of E(2ω) and P(2ω). α = 45° has special influence on the distribution pattern of E(2ω,s), E(2ω), P(2ω,s) as well as P(2ω) compared to those of α = 0° and 90°.