A group of the Vrije Universiteit Amsterdam has just disclosed a new technique that might open up unprecedented possibilities in the development of optical fiber sensors: the align-and-shine photolithography (A. Petrušis, J. Rector, K. Smith, S. de Man, and D. Iannuzzi, J. Micromech. Microeng. 19 (2009) 047001).

 

Align-and-shine photolithography is a process that allows fabrication of arbitrary patterns on the facet of an optical fiber with a lateral resolution of a couple of microns. The technique relies on the combination of standard photolithography with the optomechanical tools developed for optical fiber fusion splicing and adapts well to low-cost batch fabrication. The process starts with the fabrication of a mask fiber - a multimode UV fiber coated with metal everywhere except for the pre-defined pattern that the user wishes to transfer to a large number of other fibers. A series of other fibers, called target fibers, is coated with photoresist. The mask fiber and one of the target fibers are then mounted on a splicing machine, which is used to automatically align and bring to contact the facet of the mask fiber with the facet of the target fiber. Coupling UV light from the opposite side of the mask fiber, it is then possible to transfer the desired pattern to the photoresist layer deposited on the target fiber. The photoresist layer is finally developed according to standard photolithography processes. The process can be then repeated for an arbitrary number of target fibers without changing the mask fiber.

 

The authors believe that align-and-shine photolithography will allow a faster development of fiber-top technology - a new generation of optical fiber sensors that combines the optical properties of optical fibers with the mechanical properties of MicroElectroMechanical Systems (see D. Iannuzzi et al., Meas. Sci, Technol. 18 (2007) 3247, and references therein). The technique, in fact, may be used to fabricate miniaturized mechanical parts on the tip of a fiber following the common approach used in microtechnology, i.e., by growing and patterning alternate layers of structural and sacrificial materials. Furthermore, it should be possible to develop similar techniques (e.g., photo or thermoplastic nanoimprinting) that could push the lateral resolution in the submicron range, which could then be used to fabricate optical antenna arrays for optical fiber probes (see E. J. Smith et al., Nanoletters 9 (2009) 1132).

 

For more information, please contact Davide Iannuzzi:  iannuzzi@few.vu.nl .