Optical media with gradually changing refractive index are commonly found in practical optical systems. The thermal effects either weak or strong are present in almost all cases. The non-negligible thermal usually give rise to a modulation of the refractive index, which functions as a graded-index (GRIN) medium. An efficient treatment based on the Runge-Kutta method has been developed as a regional solver for GRIN medium, and that enables the accurate evaluation of the system performance with e.g. the thermal lens effect into consideration.

Pic-GRIN Medium
Fig. 1: Modeling of thermal lens effect in the high-power laser system. With high-power illumination, the refractive index of the laser crystals may show vary with the temperature, and therefore leading to the thermal lens effect. The index modulation can usually be modeled as a function of input laser power, and then the output laser beam diameter can be investigated with respect to the input power. (rights: IAP)


H. Zhong, S. Zhang, R. Shi, C. Hellmann, F. Wyrowski, Fast propagation of electromagnetic fields through graded-index media, J. Opt. Soc. Am. A, 35(4), 661-668 (2018).

Links to examples

Gaussian Beam Focused by a Thermal Lens
Modeling of Graded-Index (GRIN) Multimode Fiber

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