Semiconductor Photonic Nanocavities on Paper Substrates
Professor Yong-Hoon Cho of the Department of
Physics and his team at KAIST have developed a semiconductor photonic nanocavity laser that can operate
on a paper substrate.
The researchers hope that this novel method, which involves transferring nano-sized photonic crystal
particles onto a paper substrate with high absorptiveness, will enable the diagnoses of various diseases by using high-tech semiconductor
sensors at low cost.
The results of this research were published
in the November 17th, 2016, issue of Advanced Materials.
Photonic crystals, which utilize light as a medium
to provide high bandwidths, can transfer large amounts of information. Compared
with their electronic counterparts, photonic crystals also consume less energy to operate.
Normally, semiconductor photonic particles
require substrates, which play only a passive role in the assembly and endurance of individual,
functional photonic components. These substrates, however, are bulky and environmentally hazardous as they are made up of
The research team overcame these two
shortcomings by replacing a semiconductor substrate with standard paper. The
substrate’s mass was reduced considerably, and because paper is made from trees, it degrades. Paper can be easily and cheaply acquired from our
surroundings, which drastically
reduces the unit cost of semiconductors.
In addition, paper possesses superior mechanical
characteristics. It is flexible and can be repeatedly folded and unfolded
without being torn. These are traits that have long been sought by researchers for existing
The research team used a micro-sized stamp
to detach photonic crystal nanobeam cavities selectively from their original
substrate and transfer them onto a new paper substrate. Using this technique,
the team removed nanophotonic crystals that had been patterned (using a process of selectively etching circuits
onto a substrate) onto a semiconductor substrate with a high degree of
integration, and realigned them as desired on a paper substrate.
The nanophotonic crystals that the team
combined with paper in this research were 0.5 micrometers in width, 6
micrometers in length, and 0.3 micrometers in height—about one-hundredth of the
width of a single hair (0.1 millimeter).
The team also transferred their photonic
crystals onto paper with a fluid channel, which proved that it could be used as
a refractive index
sensor. As can be seen in current commercial pregnancy diagnosis kits, paper has high absorptiveness. Since photonic crystal particles
have high sensitivity, they are highly suitable for applications such as sensors.
Professor Cho stated that “by using paper
substrates, this technology can greatly contribute to the rising field of
producing environmentally-friendly photonic particles” and “by combining inexpensive paper and high-performance
photonic crystal sensors, we can obtain low prices as well as designing
appropriate technologies with high performance.”
Dr. Sejeong Kim of the Department of Physics
participated in this study as the first author, and Professor Kwanwoo Shin of Sogang University and
Professor Yong-Hee Lee of KAIST also took part in this
research. The research was supported by the National Research Foundation’s
Mid-Career Researcher Program, and the Climate Change Research Hub of KAIST.
Figure 1. Illustration of photonic crystal
lasers on paper substrates
Figure 2. Photonic crystal resonator laser
and refractive index sensor operating on paper substrates