Glass Microspheres for Optics

Preparation and application of glass spheres as resonators are discussed. Surface-tension mold (StM) and localized-laser heating (LLH) techniques have been developed to fabricate glass super spheres and true spheres, respectively. These prepared glass spherical particles have been examined to evaluate their suitability for whispering gallery mode (WGM) oscillators or laser cavities. Super spherical glass acts as a WGM oscillator using its equatorial plane. An equatorial circle roundness > 0.99 provides a high Q-value to lead laser oscillation. LLH demonstrates its excellent capability to prepare “true spheres” on a transparent substrate under gravity. A tellurite glass sphere prepared by the LLH technique exhibits a few-mW-order threshold for lasing at the 1.06-μm region. An added-on terrace and an installed bubble in the sphere serve as an input/output gate and as a “non-WGM” coupling input gate for laser action, respectively. Glass is showed to have strong potential with respect to both preparation and utilization of spherical shapes for optics.