Prototype Microspectrometer Suitable for Lab-on-a-Chip Technologies

By passing a beam of light through a silicon chip pierced with randomly scattered holes investigators have developed a sensitive microspectrometer that may be adaptable for "lab-on-a-chip" applications.

Investigators at Yale University (New Haven, CT, USA) reported in the July 28, 3013, online edition of the journal Nature Photonics that they had built a spectrometer based on multiple light scattering in a silicon-on-insulator chip featuring a random structure. A probe signal diffused through the chip generating wavelength-dependent speckle patterns, which were detected and used to recover the input spectrum after calibration. A spectral resolution of 0.75 nanometers at a wavelength of 1,500 nanometers in a 25-micrometer-radius structure was achieved.

“The largest dimension of our spectrometer, which we built on a silicon chip, is about the width of a human hair,” said first author Dr. Brandon Redding, a postdoctoral associate in applied physics at Yale University. “It could open up a whole new range of uses, a lot of them outside the lab.”

The microspectrometer can detect a change in wavelength of less than one nanometer, roughly matching the capability of macroscopic spectrometers about the size of a hard drive. “We were taking a very different approach,” said Dr. Redding. “The idea of using disorder and multiple scattering is a fairly unexplored concept. Normally, disorder is something you want to overcome or avoid. In this case, it is what lets us make the device so small. We get a much longer path length for our light relative to the size of the device, because the light bounces around many times.”

The authors maintain that a compact, high-resolution spectrometer, such as that described in this study, is well suited for lab-on-a-chip spectroscopy applications.

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