National Science Foundation     |     Directorate for Engineering  (ENG)
Division of Chemical, Bioengineering, Environmental, & Transport Systems  (CBET)
 
CBET Research Highlights 
Notable Accomplishments from CBET Awards
 
 
1414 - Part A - Guiding Light at the Nanoscale
 
Huizhong Xu  -  Saint John's University, Queens, New York

Outcome or Accomplishment:  Researchers at St. John's University have found a new approach of guiding light efficiently on the nanoscale.  Their approach is based on filling a silver nanowaveguide with zinc oxide nanorods of 40 nanometers in diameter.  The results can be used to develop technologies for high-resolution imaging and sensing applications.

Huizhong Xu Image 1
  Figure 1.  Strong transmission of light through a nanowaveguide filled with zinc oxide, as revealed by computer simulations.  The color denotes the intensity of light in a logarithmic scale with red a million times stronger than blue.  As a result of filling the hole with zinc oxide, 40% of the incident light is guided through the waveguide.




 
Huizhong Xu Image Image 2
  Figure 2.  Transmission electron microscopy images of zinc oxide nanorods grown on glass substrates.
(a)  A bundle of nanorods.
(b)  A single nanorod.
(c)  High magnification image of the rod shown in (b).
      Inset shows electron diffraction pattern.
 
Credit for All Images:  Huizhong Xu, St. John's University, Queens, NY

Impact:  The study of guiding light on the nanoscale has a broad impact in both basic science and various technological applications.  Research of nanowaveguides will advance understanding of optics on the nanoscale as a whole.  The results in this research can also be utilized to make devices providing an efficient nanocopic light source demanded by a variety of applications such as super-resolution imaging and sensing, and high-resolution lithography.  These devices will enable innovative technologies that could expand how science, engineering, and medicine are explored.

Explanation/background:  Light, which is electromagnetic waves by its nature with a wavelength of around 500 nanometers for visible light, cannot pass through holes with sizes smaller than half of its wavelength according to conventional electromagnetic wave theory.  However, recent discovery has shown that light can transmit through subwavelength holes efficiently when they are arranged in periodic arrays in a metal.  It has also been found that light can be efficiently guided through a single isolated hole with sizes as small as one tenth of the incident wavelength if the hole is filled with dielectric materials matching the optical properties of the metal.  Such a structure thus becomes an efficient waveguide to transmit light waves on the nanoscale.  However, the mechanism underlying strong transmission of light through dielectric-filled nanowaveguides is not fully understood.  Furthermore, dielectric-filled nanowaveguide devices optimized for applications such as super-resolution imaging and sensing have not been designed and experimentally realized.
 
In this NSF-funded research, Professor Xu and his team at St. John's University in Queens, NY conduct computer simulations as well as experiments to understand the optical properties of a nanometer-sized waveguide and use these properties to develop novel imaging and sensing devices.  Their study has shown that efficient guiding of light through a nanowaveguide can be achieved by filling a silver nanowaveguide of 40 nanometers in diameter with a zinc oxide nanorod (Figure 1).  This finding provides a framework for the development of high-resolution imaging and sensing devices.



CBET Research Highlight - Part B - Engineering Technical Information

7236 - Guiding Light at the Nanoscale

Huizhong Xu  -  Saint John's University

Background:  The behavior of light on the nanoscale can be drastically different from predictions by conventional theory.  For example, light cannot pass through holes with sizes smaller than half of its wavelength according to conventional electromagnetic wave theory.  However, recent discovery has shown that light can efficiently transmit through subwavelength holes when they are arranged in periodic arrays.  It has also been found that light can be efficiently guided through a single isolated hole with sizes as small as one tenth of the wavelength if the hole is filled with dielectric materials of appropriate index of refraction.  However, the mechanism underlying strong transmission of light through dielectric-filled nanowaveguides is not fully understood.  Furthermore, dielectric-filled nanowaveguide devices, which can be very useful in a variety of applications such as high-resolution lithography and super-resolution imaging, are yet to be designed and fabricated.  In this NSF-supported research, Professor Xu and his team at St. John's University in Queens, NY conduct computer simulations and experiments to study the behavior of light in a nanometer-sized waveguide with the goal of building novel devices for high resolution imaging and sensing.

Results:  (1)  By simulating optical transmission through nanowaveguides made of different materials for the cladding metal and the core dielectric material, the team has identified silver and zinc oxide as one optimum material combination for building a nanowaveguide.  The team's analysis has shown that 40% of the incident light is guided through a zinc oxide-filled nanowaveguide of 40 nanometers in diameter (Figure 1).  Further investigation by the team has revealed that the strong transmission results from matching of the dielectric constants between silver and zinc oxide as well as the resonantly excited surface plasmons on the two end interfaces of the waveguide.
 
                 (2)  The team has successfully synthesized zinc oxide nanorods using a hydrothermal process and characterized their morphology and crystalline properties using X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy.  The zinc oxide nanorods are single crystals, and have typical diameters of 40-50 nanometers and lengths of several hundred nanometers (Figure 2).  These zinc oxide nanorods are very suitable for their use as the core material of a dielectric-filled nanowaveguide.
 
Summary:  Efficient guiding of light through a dielectric-filled nanowaveguide with sizes down to one tenth of the incident wavelength can be achieved by matching the dielectric constants of the cladding metal and the core material.  For an optimized zinc oxide-filled nanowaveguide in silver, 40% of the incident light at wavelength 488 nanometers can be transmitted.  Zinc oxide nanorods with diameters 40-50 nanometers were successfully fabricated and will be used as the core material of a dielectric-filled nanowaveguide.

Scientific Uniqueness:  This NSF-funded research is unique because it advances a novel approach for guiding light efficiently on the nanoscale by utilizing the unique optical properties of dielectric-filled nanowaveguides.  The properties enable the development of innovative devices and technologies for high-resolution imaging and sensing applications.

Strategic Outcome Goals include:
 
- 1Discovery:  This NSF-funded research aims to understand the optical transmission properties of dielectric-filled nanowaveguides and advance knowledge and understanding of optics on the nanoscale in general.  In addition, the project is aimed at utilizing the unique properties of dielectric-filled nanowaveguides to build novel devices for high-resolution sensing and imaging.
 
- 2Learning:  This educational goal of this project is to make science and engineering education more accessible to all students, especially underrepresented groups.  The research and training activities have provided students at St. John's University as well as in the local community experiences and skills that will pave the way for their careers in science, engineering, and medicine.

Transformative Research:  The research is potentially transformative because the results obtained in this project can be utilized to develop novel imaging and sensing devices.  Such devices can find a variety of applications in semiconductor industry and basic biomedical research such as high-resolution lithography and cellular imaging at the single molecule level.  The innovative technologies enabled by this research could expand how science, engineering, and medicine are explored.

Intellectual Merit:  The study of behavior of light in dielectric-filled nanowaveguides will advance knowledge and understanding of optics on the nanoscale.  The new approach of guiding light efficiently on the nanoscale found by this research and new technologies enabled by this finding could be potentially useful in a variety of applications in science, engineering, and medicine.

Broader Impacts of this research include:
 
- 1Benefits to society:  The new approach of guiding light efficiently on the nanoscale found by this NSF-funded research can be used to build novel devices for high-resolution imaging and sensing.  The innovative technologies enabled by this research could facilitate the solving of challenging problems in basic science, engineering, and medicine.  For example, the nanowaveguide devices developed by this research will allow high-resolution nanofabrication in semiconductor industry, and cellular imaging at the single molecule level in biomedical research.
 
- 2Broadening participation of underrepresented groups:  The project has made opportunities in science and engineering education more accessible to all students, especially underrepresented groups in science and engineering.  Among the eleven students who have worked on the project, three are women undergraduate students, and two are from underrepresented minorities.  In addition, Professor Xu has been active in promoting science and engineering education among local high school students via the Science & Technology Entry Program at St. John's University.
 
- 3Advancing discovery and understanding while promoting teaching, training, and learning:  A total of eleven undergraduate students from St. John's University, which is a primarily undergraduate institution, have participated in this research project.  The students come from a variety of majors including biology, chemistry, mathematics, physics, and physical sciences.  In addition, a total of four high school students from the New York Metropolitan area have worked on the project through the Harlem Children Society Summer Internship Program.  The research and training activities have provided students experiences rich in critical thinking and problem solving that will pave their way to become the nation's next generation of scientists and engineers.
 
- 4Results disseminated broadly to enhance scientific and technological understanding:  The findings of this research are being disseminated broadly in international scientific journals as well as through presentations made at research symposiums and international conferences.


 
Program Director:
 
 
 
Leon Esterowitz
CBET Program Director - Biophotonics
     
NSF Award Number:   0953645
     
Award Title:   CAREER: Dielectric-Filled Nanowaveguides for Advanced Imaging and Sensing
     
Principal Investigator:   Huizhong Xu
     
Institution Name:   Saint John's University
     
Program Element Code:   7236
     
CBET Research Highlight:   Fiscal Year 2012
     
Approved by CBET on:   30 March 2012
     
     


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This Award Achievement was Updated on 24 July 2012.