New Scheme of Microlens for High-Yield Laser Coupling to PMF by Calibrated Glass Coating

Abstract

A new scheme of oriented hyperboloid microlens (OHM) for high-yield lasers coupled to polarization-maintaining-fibers (PMFs) employing calibrated spin-on-glass (SOG) coating, automatic grinding, and electric field techniques is proposed. The results showed that the OHMs were precisely controlled to achieve the required minor radius of curvature of 4–4.9 $\mu \text{m}$ for achieving high-average coupling efficiency of 81.7% and high-average polarized extinction ratio of 31.5 dB from lasers to PMFs. In comparison with the fabricated OHMs by multiple fusing techniques, the SOG coating significantly reduced the fabrication time from more than 20 fusing times to a single time of electric field, decreased the average OHM offset from 0.59 to 0.47 $\mu \text{m}$ , resulting in the increased tolerance of the required radius of curvature of the OHMs from 4.0–4.2 to 4.0–4.9 $\mu \text{m}$ , and hence the OHMs with high-yield coupling efficiency to an average of 81.7% from laser to PMF. This is due to the OHM structure by SOG coating layer integrated with a uniform electric field to provide a simple process for adjusting the required minor radius of curvature. In addition, the OHM offset was minimized due to the balance of the electrostatic pulling force and the surface tension of the SOG liquid. The newly developed OHMs with unique SOG coating technique is beneficial for the applications of laser/PMF modules use in high-precision fiber optic gyroscopes as well as many low-cost and high-performance lightwave interconnection applications.