Advances in optoelectronic technology and industry development : proceedings of the 12th International Symposium on Photonics and Optoelectronics (SOPO 2019), August 17-19, 2019, Xi'an, China /: proceedings of the 12th International Symposium on Photonics and Optoelectronics (SOPO 2019), August 17-19, 2019, Xi'an, China. ([2020])