Ultralow-threshold laser and blue shift cooperative luminescence in a Yb3+ doped silica microsphere

Abstract

An experimental investigation on ultralow threshold laser and blue shift cooperative luminescence (CL) in a Yb3+ doped silica microsphere (YDSM) with continuous-wave 976 nm laser diode pumping is reported. The experimental results show that the YDSM emits laser oscillation with ultralow threshold of 2.62 μW, and the laser spectrum is modulated by the microsphere morphology characteristics. In addition, blue emission of YDSM is also observed with the increase of pump power, which is supposed to be generated by CL of excited Yb ion-pairs with the absorption of 976 nm photons and Si-O vibration phonons, and the process is explained with an energy level diagram. This property of the blue shift CL with phonons absorption in the Yb3+doped microcavity makes it attractive for the application of laser cooling based on anti-Stokes fluorescence emission, if the Yb3+doped microcavity made from with low phonon energy host materials.

Ultralow-threshold laser in a Nd 3+ doped silica microsphere

“…An ultralow-threshold Yb 3 þ doped SiO 2 glass microsphere laser has been reported by Vahala's team, which was about 1.8 mW [6]. Our team also observed a very low threshold multi-mode laser emission in 1064 nm band and blue shift cooperative luminescence in a Yb 3 þ doped SiO 2 microspheres, the threshold was about 2.6 mW [7,8]. Nd 3 þ is also one of the most popular laser active ions among all the REIs [9].…”

“…The experiment presented the characteristics of NDSM laser oscillation exactly. Compared to Yb 3 þ doped silica microsphere lasers which were pumped by a 976 nm laser diode [7], the Stokes shift is as large as 3000 cm À 1 which is the down conversion from the pumped laser (808 nm) to the output emission (1100 nm), and it is beneficial to get accurate signal separation and collection.…”

High efficiency white luminescence in Tm3+/Er3+/Yb3+ tri-doped oxyfluoride glass ceramic microsphere pumped by 976 nm laser

“…The detailed process of the cooperative UC luminescence of Yb 3 þ ion pairs has been explained in the previous paper [17,18]. The red emission is weak in the Er 3 þ /Yb 3 þ co-doped oxyfluoride glass ceramic microspheres [27], but it is significantly enhanced when Tm 3 þ is introduced into the system.…”

“…The microspheres were fabricated by the butane flame melting of the annealed glass filaments with diameter ranging from 20 to 50 μm. We also tried to form the microspheres by arc-melting the glass filaments with electrode discharge of a fusion splicer [18], but the microspheres had a serious crystallization and became devitrification due to the exorbitant discharge temperature. Fig.…”

“…Our group has done several researches on laser emission of RE ions doped silica microsphere pumped by 976 nm laser [16][17][18][19]. The light coupled into the microsphere can propagate around the inner orbit surface in the way of total internal reflection with extremely low loss because of the atomic-scale smooth surface, which is called whispering gallery mode (WGM).…”