Notched microring resonator senses individual nanoparticles and their properties

Oct. 1, 2010
Nanoparticles such as quantum dots, nanoshells, and "functionalized" polymer nanoparticles (which means they have active biological molecules attached to them) have become important in biophotonics research and medical therapies.

Nanoparticles such as quantum dots, nanoshells, and "functionalized" polymer nanoparticles (which means they have active biological molecules attached to them) have become important in biophotonics research and medical therapies. Photonically detecting and characterizing a single nanoparticle is thus a key goal in optical sensing. One present-day technique, sensing the evanescently induced changes of a nanoparticle on the optical resonance of a microsphere cavity, produces spectral shifts only in the picometer range (determined using an expensive narrow-linewidth tunable laser), and is thus difficult to perform.

Scientists at the Massachusetts Institute of Technology (Cambridge, MA), New York University, and CUNY (both of New York, NY) are instead using a 4 μm diameter on-chip microring resonator as the sensor; they create a 100 nm notch in the ring so that the particle couples strongly to the ring's resonance mode. As a result, spectral shifts (determined using an ordinary non-narrow-linewidth tunable laser) are in the nanometer range and thus easily detectable. In a first test, the presence of a 20 nm silicon nanoparticle (placed on an atomic force microscope tip for easier positioning) was easily distinguished from the presence of a separately tested 20 nm gold nanoparticle; the spectral shifts induced on the ring resonance by the two nanoparticles differed by 2.2 nm. Contact Yasha Yi at [email protected].

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Request a quote: Micro 3D Printed Part or microArch micro-precision 3D printers

April 11, 2024
See the results for yourself! We'll print a benchmark part so that you can assess our quality. Just send us your file and we'll get to work.

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Precision Motion Control for Sample Manipulation in Ultra-High Resolution Tomography

April 10, 2024
Learn the critical items that designers and engineers must consider when attempting to achieve reliable ultra-high resolution tomography results here!

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!