Preparation And Spectrum Properties Of Yb³⁺,Er³⁺:YAG Single Crystal Fiber With Upconversion Emission

The upconversion luminescence is a special property of rare-earth ion. Recently, with the improvement of separation and purification technique, great progresses have been made on both research and applications of rare-earth upconversion material.The selection of suitable matrix and activate ion for high luminescence efficiency is a hot spot in this field.Yttrium Aluminum Garnet (YAG) shows stable physical and chemical properties; good ability to withstand high temperature damage for its high melting point.It is also an excellent matrix material for rare-earth dopant. Rare-eath doped YAG single crystal upconversion material has the additional characteristic of optical waveguide. With the usage of high-power LD pump source, it is promising to get high luminescence upconverion light source with good beam direction.Yb3+, Er3+ doped YAG single crystal samples have been made by the laser heated pedestal growth method (LHPG) as upconversion materials. Parameters during the growth process are discussed in detail, found that source rod and the line of seeds for crystal growth is rather important. The power of CO2 laser is critical due to the non-uniform density and the air bubble in it. It must be strictly controlled. Right action should be taken corresponding to the growth status.In this dissertation the absorption spectrum and the upconversion property under 980nm LD excitation were discussed under different rare-earth concentration. The upconversion mechanisms have been discussed in terms of experiment results. The conclusions as below:(1) Yb3+ in the single crystal has strong absorption from 870nm to 1000nm; Er3+ has three absorption peaks lies in 645nm,655nm,789nm. When the Er3+ concentration increases, the position of absorption peaks do not change, but the height of the peaks increases. When the concentration reaches 1%, secondary peak is observed which lies in 525nm. (2) Using 980nm LD as excitation source, green light emission at 540-550nm, 550-560nm corresponding to 2H11/2â†'4I15/2 and 4S3/2â†'4I15/2 transition of Er3+ was observed. Red light emission at 650-690 corresponding to 4F9/2â†'4I15/2 transition of Er3+ was also observed. Yb3+ improves the efficiency of luminescence. When Yb3+ concentration remains at 5%,Er3+ concentrations varies, the emission wavelength does not change, both for green and red light; the intensity increases with the increasing of Er3+ concentration. The intensity ratio of red and green light also increases with the increasing of Er3+ concentration.