Fabrication of tellurite glass microdisks with thermal pressing method

Abstract

In this work, we report a two-step thermal pressing method of fabricating microdisk lasers that are suitable for processing thermally stable glass materials, and we utilize a tellurite glass (TeO₂-ZnO-Na₂O) to demonstrate the feasibility of this method. Compared with the conventional microdisk fabricating methods that rely on a series of complicated procedures, such as lithography, etching, thermal reflow, and ion implantation, this thermal pressing method involves only two heating procedures and can be accomplished with simple laboratory resistive heating furnaces. In the first heating procedure, we crush bulk tellurite glass into powders and drop those powders through a vertical heating furnace. Glass powders are transformed into microspheres by surface tension in the furnace. In the second heating procedure, microspheres are placed between two flat/smooth surfaces and are thermally treated when being pressed with suitable weights. With this procedure, the “flattened” microspheres turn into the microdisks. In this work, we demonstrate that our fabricated tellurite glass microdisks possess diameters of 100－400 μm, thinnest thickness of ～ 8 μm, and typical quality-factor (<i>Q</i>-factor) of ～ 10⁵. We also dope tellurite glass with active dopants such as Nd³⁺ and Tm³⁺ to fabricate the active microdisk resonators. We couple those active microdisk resonators with fiber tapers and demonstrate that with appropriate pump power, apparent fluorescence whispering gallery mode and laser mode can be obtained. Taking a 105.74-μm-diameter, 10.4-μm-thickness, and Nd³⁺-doped tellurite glass microdisk for example, we show that as the pump power increases above a threshold of 1.364 mW, a lasing peak near 1.06 μm can be obtained. We also show that lasing peaks near 1.9 μm can be obtained by coupling/pumping Tm³⁺ doped microdisks.