Up- and Downconversion Luminescence in Ho³⁺,Yb³⁺-Co-Doped Y₂O₃ Transparent Ceramics Prepared by Spark Plasma Sintering

Abstract

We employed spark plasma sintering (SPS) in the presence of sintering aids to fabricate highquality Ho 3+ ,Yb 3+-co-doped Y 2 O 3 transparent ceramics suitable for use as a laser gain medium, and analyzed their microstructure and optical properties. Ho 3+ ,Yb 3+-co-doped Y 2 O 3 transparent ceramics with different contents of Yb 3+ were fabricated by SPS and exhibited high transparency in both near-infrared and visible regions. All specimens showed high transparency in both the near-infrared and visible-light regions, and sample microstructure was almost unaffected by the amount of doped Yb 3+. The transmission spectra of 1 mol% Yb 3+ doped specimens exhibited transmissivities of 73.4 and 81.0% at wavelengths of 700 and 1500 nm, respectively. Relatively high transmissivity was quickly achieved through the addition of a sintering aid (1 mol% La 2 O 3) which accelerated mass transport during sintering. The effect of Yb 3+ doping on the upconversion photoluminescence of Y 2 O 3 :Ho 3+ ,Yb 3+ was examined. Irradiation at 980 nm resulted in strong green photoluminescence (552 nm) and weak red photoluminescence (669 nm). Excitation at 447 and 980 nm resulted in strong green emission (5 F 4 , 5 S 2 → 5 I 8) from Ho 3+. The effects of Yb 3+ content and laser input power on emission intensity and luminescence decay were investigated in detail. Under excitation at 980 nm, the presence of Yb 3+ increased emission intensity over the entire range, while the opposite behavior was observed under excitation at 447 nm.

Fabrication and Luminescence Properties of Highly Transparent Green-Emitting Ho:Y2O3 Ceramics for Laser Diode Lighting

“…For example, Ho 3+ -ion-doped polycrystalline transparent ceramics have been widely studied in 2000 nm solid-state lasers due to their 5 I 7 → 5 I 8 energy-level transitions [12][13][14]. The Ho 3+ ion is also a suitable active ion for the up-conversion laser and many researchers have focused on up-conversion emissions (for example, highly efficient up-conversion luminescence in a Ho 3+ -Yb 3+ system) [15]. Furthermore, under the excitation of ultraviolet and visible light, Ho 3+ ions produce a high-intensity green light emission, especially in the green region, and can, therefore, be used as an element in white light production due to their green emission.…”