Fig. 1. (a) Diagram of Er:Ta₂O₅ coating and mixed Er₂O₃/Ta₂O₅ target. (b) Fabricated 4-inch Er:Ta₂O₅ film and thickness profile of the deposited Er:Ta₂O₅ film.

Fig. 2. (a) Optical micrograph where the dark central region represents the SiO₂ pillar underneath, and the outer pale region corresponds to the microdisk. (b) Top view SEM image. (c) Oblique SEM image. Inset: AFM image of the Ta₂O₅ thin film surface. (d) Photograph of the Er:Ta₂O₅ waveguide chip. (e) Optical micrograph of the Er:Ta₂O₅ waveguide. (f) False color SEM image of the waveguide end face.

Fig. 3. (a) Experimental setup for measuring the microdisk resonator laser. CTL, continuously tunable laser; FPC, fiber polarization controller; PM, power meter; OSA, optical spectrum analyzer; PD, photodetector; SG, signal generator; OSC, oscilloscope. (b) The microdisk resonator emits intense green upconversion fluorescence when pumped by a 980-nm tunable laser. (c) Quality factor of the microdisk at 951 nm. (d) Quality factor of the microdisk at 1566 nm. (e) Evolution of the emission spectrum of the Er:Ta₂O₅ microdisk as the input pump power increases. (f) Output power of lasing as a function of input pump power.

Fig. 4. (a) Experimental setup used to characterize the Er:Ta₂O₅ waveguide amplifier; the inset shows a simplified energy diagram of Er:Ta₂O₅ with the pump at 980 and 1480 nm, and the signal at 1550 nm. FPC, fiber polarization controller; OSA, optical spectrum analyzer; WDM, wavelength division multiplexer. (b) Optical image of an intensely pumped Er:Ta₂O₅ waveguide amplifier chip butt-coupled with lensed fibers. (c) Measured spectra from the OSA at a wavelength of 1550 nm pumped at different 980-nm LD powers. (d) On-chip gains of the Er:Ta₂O₅ waveguide amplifier as a function of the launched 980-nm LD pump power for a signal wavelength of 1550 nm. (e) Measured spectra from the OSA at a wavelength of 1550 nm pumped at different 1480-nm LD powers. (f) On-chip gains of the Er:Ta₂O₅ waveguide amplifier as a function of the launched 1480-nm LD pump power for a signal wavelength of 1550 nm.