Design of laser Michelson interferometer for the detection of nanolitre solution

By use of common optical equipment, a laser Michelson interferometer system that can be used for the detection of microfluidic chip is designed. A He-Ne laser beam (power of 0.5mW and diameter of about 0.7mm) is divided into a detection beam and a reference beam by a beam splitter. The reference beam is slightly expanded with a lens and has a diameter of about 1.5mm. A microfluidic chip with channel diameter of 60μm is placed in the detection arm of the interferometer. The detection beam falls on the channel of the chip. On the screen 1.6 meters far from the splitter, an interesting pattern containing both circular fringes and linear fringes is observed. Experiment shows obviously that the patterns on the screen are different when the channel is filled with air, pure water and the sodium hydroxide solution (with a refractive index of 1.343). It is indicated that the interferometer is effective for the detection of solutions as tiny as 3 nano liters with different refractive indices.

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