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Microfluidic mixing tunes dye-laser in real-time

05 Apr 2006

Researchers shrink a dye-laser set-up into a tiny polymer package suitable for lab-on-a-chip microsystems.

Scientists in Denmark have come up with a compact, liquid light source for applications such as dynamic spectral analysis. Featuring an integrated microfluidic mixer, the optically-pumped dye laser boasts a response time of just 110 s, allowing its output wavelength to be tuned over 10 nm in real-time. (Journal of Applied Physics 99 023102)

According to the team from the Technical University of Denmark, the micro-fluidic platform can be made using the same UV lithography process developed to manufacture other polymer-based components such as waveguides.

"It means that we can add and pre-align a tunable laser source to another polymer microchip without adding further steps to the process," Anders Kristensen of the University's Institute for Micro and Nanotechnology told Optics.org. "Another benefit of microfluidic tuning is that it allows us to vary the lasing wavelength without applying heat or stress, which could interfere with other functionalities on the chip."

The group's polymer chip is sandwiched between pyrex glass wafers and features a 200 micron wide mixing channel connected to a laser resonator. Diluted solutions of rhodamine 6G form the gain medium and are created by introducing ethanol into the dye. Thanks to the chip's small dimensions (overall length = 50 mm), mixing takes place quickly and precisely, and gives operators real-time control over the emitted wavelength.

Tests showed that the laser's peak output wavelength could be moved continuously from 573 to 583 nm by adjusting the relative flow rates of the two input streams. Here, light was collected by an optical fiber positioned 10 mm above the cavity.

Encouraged by performance of its microfluidic device in the lab, the team is now integrating the tiny dye-laser with on-board sensors to create a complete microsystem for undisclosed commercial applications.

Author
James Tyrrell is News Editor on Optics.org and Opto & Laser Europe magazine.

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