A Very Fast Single-Step Process for Optical Microfiber Long Period Gratings Fabrication

Optical microfiber long period gratings (MLPGs) with advantages such as low insertion loss, polarization independence, high resonance dip, and simple configuration are broadly involved in different applications, including fiber optics micro-scale components and sensors. However, it is still a grand challenge to fabricate MLPGs by using current long-time multistep processes. Herein, based on the typical arc-discharge fiber heating and pulling technique, a very fast single-step process for MLPGs fabrication is presented. In this process, the applied fiber heating arc-discharge is functionalized by a series of narrow OFF-pulses to simultaneously modulate the being pulled microfibers. Through the developed one-step technique, a low-loss adiabatic optical microfiber with a periodic array of micro-tapers along its waist region is implemented in less than 100 s, which is much faster than current methods. It is shown that the realized single-step MLPGs with the diameter of 20 μm are characterized by high resonance dip (>27 dB), low transmission loss (≤1.2 ± 0.2 dB), narrow FWHM (<20 nm), and high repeatability. The measured external refractive index (RI) sensitivity and temperature dependency of the gratings are 744 nm/RI-unit and 12 pm/°C, respectively. The results of this study could be of interest for the applications of the MLPGs for miniature fiber optics elements and sensors realization.