3D digital holograms on smartphones?
3D holograms, previously reserved for sci-fi movies, may soon find their way into our daily lives. Until now, 3D holograms based on the phase shift holography method could be captured using a large specialized camera with a polarizing filter. However, a Korean research group has just developed a technology to acquire holograms on mobile devices, such as smartphones.
The Korea Institute of Science and Technology (KIST, Director Seok-jin Yoon) recently announced that a research team led by Dr Min-Chul Park and Dr Do Kyung Hwang of the Center for Opto-Electronic Materials and Devices, in collaboration with a research team led by Prof. Seongil Im from the Physics Department of Yonsei University, succeeded in developing a photodiode that detects the polarization of light in the near infrared without additional polarization filters and thus, the realization of ‘a miniaturized holographic image sensor for 3D digital holograms, using 2D semiconductor materials: rhenium diselenide and tungsten diselenide.
Photodiodes, which convert light into current signals, are essential components of the pixels of image sensors in digital cameras and smartphones. The introduction of the ability to detect the polarization of light on the image sensor of an ordinary camera provides a variety of new information, enabling the storage of 3D holograms. Previous polarization detection cameras have an additional polarization filter, several hundred microns, attached to an ultra-small optical diode image sensor, less than one micrometer. Thus, they could not be implemented in portable electronic devices due to 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 depending on the linear polarization angle of light in the near infrared region ( 980 nm), and a p-type semiconductor, tungsten diselenide, which exhibits no difference in photo-response as a function of polarization, but allows superior performance. The device is excellent in photodetecting 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 used the device to create a digital holographic image sensor that records polarization characteristics to successfully capture holograms.
KIST’s Dr Hwang said, “Research on downsizing and integrating individual elements is needed to ultimately miniaturize holographic systems. The results of our research will lay the foundation for the future development of miniaturized holographic camera sensor modules. Further, Dr Park remarked, “The new sensor can detect more near infrared light, as well as previously undetectable visible light, opening up new opportunities in various fields such as 3D night vision, autonomous driving, biotechnology and the acquisition of infrared data for the analysis and restoration of cultural property.