The problem of focusing multimode radiation of high-power semiconductor lasers and light-emitting diodes (LEDs) has been studied. In these sources, low spatial quality of the output beam determines theoretical limit of the focal spot size (one to two orders of magnitude exceeding the diffraction limit), thus restricting the possibility of increasing power density and creating optical field gradients that are necessary in many practical applications. In order to overcome this limitation, we have developed a method of superfocusing of multimode radiation with the aid of interference. It is shown that, using this method, the focal spot size of high-power semiconductor lasers and LEDs can be reduced to a level unachievable by means of traditional focusing. An approach to exceed the theoretical limit of power density for focusing of radiation with high propagation parameter M is proposed.
Sokolovskii, G. S., Dudelev, V. V., Losev, S. N., Deryagin, A. G., Kuchinskii, V. I., Sibbett, W., & Rafailov, E. U. (2012). Superfocusing of mutimode semiconductor lasers and light-emitting diodes. Technical Physics Letters, 38(5), 402-404. https://doi.org/10.1134/S1063785012050136