Ultra-low-threshold Er:Yb sol-gel microlaser on silicon

Hsiu-Sheng Hsu,Andrea M Armani,Can Cai

doi:10.1364/oe.17.023265

Abstract

Ultra-low threshold lasers which operate in the telecommunications band and which can be integrated with other CMOS compatible elements have numerous applications in satellite communications, biochemical detection and optical computing. To achieve sub-mW lasing thresholds, it is necessary to optimize both the gain medium and the pump method. One of the most promising methods is to use rare-earth ions in a co- or tri-dopant configuration, where the lasing of the primary dopant is enhanced by the secondary one, thus improving the efficiency of the overall system. Here, we demonstrate an Erbium:Ytterbium co-doped microcavity-based laser which is lithographically fabricated on a silicon substrate. The quality factor and pump threshold are experimentally determined for a series of erbium and ytterbium doping concentrations, verifying the inter-dependent relationship between the two dopants. The lasing threshold of the optimized device is 4.2 microW.

Highlights

Ultra-low threshold lasers which operate in the telecommunications band and which can be integrated with other CMOS compatible elements have numerous applications in biochemical detection [1,2], satellite communications [3,4] and optical computing [5,6,7,8,9,10,11]
A series of Er3+:Yb3+ co-doped sol-gel films are made with different doping concentrations of erbium and ytterbium ions and the Q factors of the
The lasing threshold is as low as 4.2μW, which is more than seven times lower than the previously reported lowest threshold to date for a Er3+:Yb3+ co-doped laser, which was based on a microsphere resonant cavity [39]

Summary

Introduction

Ultra-low threshold lasers which operate in the telecommunications band and which can be integrated with other CMOS compatible elements have numerous applications in biochemical detection [1,2], satellite communications [3,4] and optical computing [5,6,7,8,9,10,11]. Initial research on ultra-low threshold lasers revolved around rare-earth doped, ie Ho, Yb, Er, Nd, optical fiber based-lasers [19] While these lasers achieved sub-mW thresholds, their performance is limited by the short interaction time of the pump laser and the efficiency of the gain medium [20]. Previous research has investigated fabricating erbium and ytterbium doped microtoroid resonant cavity-based lasers using either ion implantation or sol-gel techniques [26,27,28] While these detailed studies did successfully demonstrate single ion doped toroid microlasers, it is well-known that co-doped lasers have significantly improved performance over single doped devices, because the absorption efficiency of the primary dopant is increased by the secondary dopant (sensitizer) [29,30]. The lasing threshold is 4.2 μW, and we believe this is the lowest threshold yet achieved with a Er3+:Yb3+ co-doped laser

Sol-gel preparation

Fabrication of devices

Experimental set-up

Experimental results and discussion

Conclusion