Tapered fiber coupler serves as biosensor

Oct. 1, 2007
In the interests of developing a simple, low-cost, sensitive optical biosensor, researchers at Sumitomo Electric Industries (Yokohama, Japan) created something that is not much different from a telecommunications-style fused, tapered fiber coupler (including the use of a telecom C-band laser), except that the peak-to-valley pitch of the sinusoidal transmission spectrum was made narrower (35 nm) than that for a standard telecom coupler.

In the interests of developing a simple, low-cost, sensitive optical biosensor, researchers at Sumitomo Electric Industries (Yokohama, Japan) created something that is not much different from a telecommunications-style fused, tapered fiber coupler (including the use of a telecom C-band laser), except that the peak-to-valley pitch of the sinusoidal transmission spectrum was made narrower (35 nm) than that for a standard telecom coupler. Because the evanescent field surrounding the tapered portion of the coupler produces a transmission that varies with the refractive index of the surrounding medium, biosubstances that stick to the sensor are easily detected.

After initial tests with ethanol-water solutions of 0.1, 1, and 10 wt% (showing a refractive-index sensitivity of 4 × 106), the researchers prepared the sensor by silanizing it, then coating it with biotin. The sensor was then immersed in a solution of streptavidin at a concentration of 0.5, 1, or 2 µg/ml; over time, the avidin (a protein found in egg white) contained in the solution binds to biotin. The sensor’s response was proportional to the avidin concentration (although temperature drift was observed). Contact Hidehisa Tazawa at [email protected].

Sponsored Recommendations

Ask the Expert: Building Better Laser Micromachining Systems

Dec. 8, 2023
Dr. Cliff Jolliffe, Head of Strategic Marketing, Industrial Automation, Physik Instrumente (PI), fields questions about integrating controls for different motion systems and lasers...

Video: December 8, 2023 Photonics Hot List

Dec. 8, 2023
In this episode, we cover a microscopy method that hits uncharted cell territory, drone-based imaging for solar farm inspection, soliton microcombs that boost conversion efficiency...

China’s industrial laser market shows steady growth in turbulent times

Dec. 8, 2023
This in-depth market update focuses on trends in laser processing and industrial lasers while touching on what to expect in the ultrafast laser, fiber laser, LiDAR, and handheld...

What does it take to land venture capital for photonics-driven startups?

Dec. 7, 2023
Capital to grow a startup company can come from many sources: contract and non-recurring engineering (NRE) funding, angels and friends, customer upfront payments, and venture ...

Voice your opinion!

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