With Millionths of a Meter Technique for Measurements Using Light

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Rodolfo Cortés Martínez (Source: Investigación y Desarrollo)

Certain scientists, researchers and scholars from disciplines such as biology, mechanical engineering, or the pharmaceutical industry, use elements of the nanoscale (nano corresponds to a billionth of a meter) for their projects. Handling these compounds requires extreme precision tools, as well as high accuracy measurements.

Responding to this need is the professional work of Rodolfo Cortés Martínez, member of the Center for Scientific Research and Higher Education (CICESE) in Monterrey, north of Mexico, who has developed a measurement process based on the interference of evanescent fields in the far field.

“This is a noninvasive technique able to measure objects or compounds of nanometric dimensions without doing any damage. So that an object to be measured is placed between the light sources and the separation among them is considered, then we quantify the generated fringes through their periodicity and take account of our observation distance, so that we can determine the diameters and thicknesses of objects that are susceptible to damage by using other mechanical instruments.

“Another way to achieve this is to use just one light source instead of two, placing specific objects on it so that they scatter light and capture its overlaping with a specialized camera, so the interference fringes will give us a measure of the dimensions or separation between the objects immersed in the field of light”.

Physicist Cortés Martinez explains the application of interferometric techniques to sense the relative nanoscale displacement of objects as is to move a tapered optical fiber closer to a sample. To make this kind of approach at these scales a series of steps are required, “a mechanical kind, which uses a micrometer screw, and closing in at a microns distance approximate to 300 nanometers, for which we developed an optical technique based in light interference that gives us a measure of approximation to the surface of the tip of what we want to characterize.

“Our technique uses the reflection of light through the tip of an optical fiber, and the reflection causes interference with itself in space. That light is captured by a specialized camera and shows us the interference pattern of the two sources of light, and then the approach of these bands is the value we can look for. ”

So far this technique has been used in a joint project between the NanoOptics Group at CICESE Monterrey and Héctor Rafael Siller Carrillo from the Technological Institute of Superior Studies in Monterrey (ITESM), which was complemente by so called fuzzy logic; the combination of both systems has been employed for a device named near field microscope.

The optics specialist refers that the concept of interference of light as a means of approach has resulted in a publication that describes how two light sources were created on the surface of a prism, so that the light that spreads on the surface is captured far from the surface using a camera, so that superposition of light interference fringes again give the information required.

Cortés Martínez has been scientifically trained in Plasmon, the branch of optics at the nanoscale which is based on the study of the processes of interaction with light.

He notes that Metrology techniques with needs of nanoscale approach or non-invasive neither destructive measurement is performed in specialties such as mechanical engineering, precision measuring the wear of mechanical tools, among many other applications.

The projects that have used the technique of Cortés Martínez have led to the publication of two scientific papers on international journals. (Source: Investigación y Desarrollo)

Links: Center for Scientific Research and Higher Education (CICESE)

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