3D holograms may soon make their way into our daily lives. Until now, 3D holograms based on phase shifting holo­graphy method could be captured using a large, specialized camera with a polari­zing filter. However, a Korean research group has just developed techno­logy that can acquire holograms on mobile devices, such as smartphones.

The Korea Institute of Science and Techno­logy (KIST) recently announced that a research team led by Min-Chul Park and Do Kyung Hwang of the Center for Opto-Elec­tronic Materials and Devices, in colla­boration with a research team led by Seongil Im of the Department of Physics at Yonsei University, was successful in developing a photodiode that detects the polari­zation of light in the near-infrared region without additional polari­zation filters and thus, the realization of a minia­turized holographic image sensor for 3D digital holograms, using the 2D semi­conductor materials: rhenium diselenide and tungsten dise­lenide.

Photo­diodes, which convert light into current signals, are essential components within the pixels of image sensors in digital and smartphone cameras. Introducing the ability to sense the polariz­ation of light to the image sensor of an ordinary camera provides a variety of new infor­mation, enabling the storage of 3D holograms. Previous polari­zation-sensing cameras have an additional polari­zation filter, several hundred micrometers in size, attached to an ultra-small optical diode image sensor, less than a micrometer in size. Thus, they could not be imple­mented into portable electronic devices because of their inability to be integrated and minia­turized.

The research group developed a photodiode by stacking an n-type semi­conductor, rhenium diselenide, which exhibits a dif­ference in light absorption dependent on the linear polari­zation angle of light in the near-infrared region, and a p-type semi­conductor, tungsten diselenide, which exhibits no difference in photo-response depen­dent on polari­zation, but enables superior per­formance. The device is excellent in the photo­detection of various wavelengths from ultra­violet to near-infrared, even capable of selectively detecting the polari­zation charac­teristics of light in the near-infrared region. The research group utilized the device to create a digital holo­graphic image sensor that records polarization charac­teristics to success­fully capture holograms.

Do Kyung Hwang said, “Research on the downsizing and inte­gration of individual elements is required to ultimately minia­turize holo­graphic systems. The results of our research will lay the founda­tion for the future develop­ment of miniaturized holo­graphic camera sensor modules.” In addition, Min-Chul Park remarked, “The new sensor can further detect near-infrared light, as well as previously undetectable visible light, opening up new oppor­tunities in various fields such as 3D night vision, self-driving, biotechno­logy, and near-infrared data acqui­sition for analyzing and restoring cultural assets.” (Source: KIST)

Reference: J. Ahn et al.: Near-Infrared Self-Powered Linearly Polarized Photodetection and Digital Incoherent Holography Using WSe₂/ReSe₂ van der Waals Heterostructure, ACS Nano 15, 17917 (2021); DOI: 10.1021/acsnano.1c06234

Link: Center of Optoelectronic Materials and Devices, Post-Silicon Semiconductor Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea