Professor Yong - Hoon Cho’s research team from the Department of Physics has discovered a method of integrating semiconductor photonic nanocavities with a paper substrate, which provides the interconnections for electric circuits.Photonic nanocavities allow lasing actions on paper substrates, useful in creating more eco-friendly electronics, affordable electronic sensors, and medical diagnostic equipment. PhD student Sejeong Kim has been cited as the lead author for this research paper in the scientific journal Advanced Materials on November 17.

Photonic integrated circuits (PICs) are anticipated to replace electronic circuit boards as they provide high bandwidth and allow for low loss of energy during operation. As they are based on semiconductors, PICs need semiconductor substrates in order to maintain their shapes. However, the semiconductor substrate not only limits the volume of the electronic device, but also acts as a source of pollution as they are not biodegradable, calling for a need for “green photonics”.

Thus, Professor Cho’s research team utilized paper, a biodegradable and easily obtainable material, as a substrate, which provides the interconnections for electric circuits. After transferring photonic nanocavities onto paper using a microsized stamp, high precision patterning is used to embed the nanocavities. The study shows the first time semiconductor nanocavity laser has operated on a paper substrate, which shows that paper can support the function of optical components. In addition, the study demonstrated that their substrate can be utilized as a high-sensitivity sensor as paper was seen to have a low refractive index. The photonics component on the paper substrate had a width of 0.5 μm, length of 6 μm and height of 0.3 μm. Furthermore, the research team showed that if the PICs are embedded on paper with fluid channels, the circuit could be used as a refractive index sensor. Professor Cho stated that “This technique, which allows the use of paper as a substrate in PICs, will make a large contribution to the eco-friendly movement.”