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Diameter limitations of microsphere and microbottle WGM microresonators fabricated using a low-cost fusion splicer

S. MOHD FARID1,2, N. A. MOHD YAHAYA1,2, S. N. F. AZAHAN1,2, M. K. MOHD YUSOF1,2, M. Z. ZULKIFLI1,2,*

Affiliation

  1. IIUM Photonics and Quantum Research Centre (iPQC), Department of Physics, Kulliyyah of Science, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang, Malaysia
  2. Physics Department, Kulliyyah of Science, International Islamic University Malaysia, 25200 Kuantan, Pahang, Malaysia

Abstract

This study investigates the diameter limitations and performance boundaries of microsphere and microbottle whispering gallery mode (WGM) microresonators fabricated using a low-cost fusion splicer. Diameter is a critical parameter governing mode confinement, free spectral range (FSR), and quality factor (Q), yet its practical limits under arc-discharge fabrication remain insufficiently explored. Both resonator types were fabricated from standard single-mode fibers using controlled electrical discharges and characterized via tapered fiber coupling. Microspheres are found to be constrained by thermal equilibrium, exhibiting saturation at 258.8 µm beyond 30 arc discharges, with high reproducibility (R² = 0.9657 and SD = 2.0 µm), a maximum Q-factor of 18,894, and an FSR of 2.44 nm. In contrast, microbottle resonators demonstrate linear and controllable radial growth to a maximum of 232.5 µm on the 50th discharges (R² = 0.9723), accompanied by reduced variability (SD from 4.84 µm to 0.97 µm). However, their diameter is ultimately limited by mechanical failure beyond 50 discharges. The microbottle geometry also exhibits axial contraction to 484.8 µm due to surface-tension-driven redistribution, resulting in a lower Q-factor (13,843) and narrower FSR (1.40 nm), while enabling enhanced axial mode control. These findings identify distinct limiting mechanisms which are thermal saturation for microspheres and structural failure for microbottles, providing a practical framework for optimizing WGM resonator design within low-cost fabrication environments..

Keywords

Whispering Gallery Mode (WGM) Microresonators, Microsphere, Microbottle, Fiber Fusion Splicer, Quality Factor (Q) and Free Spectral Range (FSR).

Submitted at: Sept. 25, 2025
Accepted at: June 2, 2026

Citation

S. MOHD FARID, N. A. MOHD YAHAYA, S. N. F. AZAHAN, M. K. MOHD YUSOF, M. Z. ZULKIFLI, Diameter limitations of microsphere and microbottle WGM microresonators fabricated using a low-cost fusion splicer, Journal of Optoelectronics and Advanced Materials Vol. 28, Iss. 5-6, pp. 216-224 (2026)