Young-Gu Ju works at the Department of Physics Education, KyungPook National University, Daegu, Korea. He received the B.S., M.S., and Ph.D. degrees from the Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, in 1992, 1994, and 1998, respectively. During his Ph.D. work, he studied the design, fabrication, and characterization of vertical-cavity surface-emitting laser (VCSEL). He was a Visiting Engineer at the University of California at Santa Barbara (1998~1999) and developed a coarse wavelength-division multiplexing VCSEL array. From 2000 to 2004, he continued his research at the Electronics and Telecommunication Research Institute (ETRI), Daejeon. During his stay at ETRI, he worked on long-wavelength VCSELs. He joined KyungPook National University in 2004. His research interests include optics, physics education, and semiconductor optics. His major research achievements include a scalable optical computer based on free-space optics using lens arrays and a spatial light modulator and scalable optical convolutional neural networks based on free-space optics using lens arrays and a spatial light modulator.