Tip preparation for near-field ablation at mid-infrared wavelengths

A fabrication method for high-throughput, fiber-based tips for near-field scanning microscopy (NSOM) in the mid-infrared (λ ~ 3 μm) has been developed. Several fiber materials have been investigated and recipes for wet-chemical etching have been varied to produce tips that are physically robust and are capable of low-loss transmission of high-power pulses of mid-infrared light. Ultimately, wet-chemical etching techniques are used on glass fibers to produce tips capable of focusing mid-infrared light to ablate material from sub-micron-sized regions of organic films. The power throughput of the tips is significantly increased by using a novel material, previously unreported for NSOM applications: germanate fibers. The tips produced are mechanically strong and capable of transmitting high light fluence without sustaining physical damage. Here, the development of these tips and their performance are described.