Raman-Microsampling Technique Applying Optical Levitation by Radiation Pressure

We report on a new Raman microprobe technique where micron-sized solid particles are trapped in stable optical potential wells using only the force of radiation pressure from a continuous gas laser. We demonstrate this technique with Raman spectra from spherical and non-spherical particles of sizes ranging between 10–30 μm. The particles are stably supported by a vertical directed focused TEM 00 -mode cw argon ion laser of ∼500 mW. The latter simultaneously serves as the exciting light source. Several suggestions for improvements of this technique are made.