First Step Toward Laser Micromachining Realization by Photonic Nanojet in Water Medium

Abstract

In the recent period of the miniaturization of devices, there has been a high demand for high-resolution, flexible, and fast machining technique to accommodate high production volumes. Conventional laser machining with a focused laser beam has been widely used to fabricate small devices for various applications. However, this process is limited by the optical diffraction limit of the laser beam. Therefore, the photonic nanojet (PNJ) machining technique is a promising solution to tackle this problem. This technique is based on the near-field focusing of light waves with a high-energy laser power below the surface of an irradiated dielectric microsphere. We introduce water as a medium in the proposed PNJ machining technique so that the pattern could be fabricated more efficiently, faster, and with better quality. We evaluate the characteristics of the generated PNJ in water; further, we estimate the PNJ machining results numerically using the FDTD method and confirm them experimentally. To the best of our knowledge, this is the first ever to do so. All the holes obtained from the PNJ machining experiment were consistently in the sub-micrometer order and below the optical diffraction limit value of the constructed setup.