Wavelength Upconversion Research Articles

Dy3+‐ and Er3+‐codoped YBr3 upconversion phosphor for detection of 1.3‐μm band infrared light

AbstractThe efficient upconversion of 1.3‐μm infrared light to visual light was investigated using YBr3: Dy3, Er3+ fluorescent material. When the fluorescent material with an optimum composition (2DyBr3: 20ErBr3: 78YBr3) was illuminated with 1.3‐μm laser beam from a semiconductor laser (LD 5 mW), the intensities of the colors red (Er3+: 4F9/2 → 4I15/2 radiation transition) and green (Er3+: 4S3/2 → 4I15/2 radiation transition) emitted from the fluorescent material were about 170 and 60 times stronger, respectively, than those from chloride‐based fluorescent material.When this fluorescent material is illuminated by collimated LD beam with power higher than 1 mW, it continuously emits visual light (yellow) without preexcitation. Therefore, 1.3‐μm infrared light can be detected visually under room light. This bromide‐based fluorescent material is stable when it is packaged in a sealed dry atmosphere and its high efficiency wavelength upconversion characteristic is maintained over a year.In this material, Dy3‐ acts as an absorption center of 1.3μm light (6H15/2 → 6H9/2 transition) and fluorescence is caused by energy transmission to the Er3+ light‐emission center due to suppression of multiphonon relaxation from the Dy3+ excitation level. The high efficiency also results because a large number of Dy3+ absorption centers can be added due to the low energy‐transfer efficiency in the bromide‐based material. This paper also describes the wavelength conversion process and the reverse transfer process from Er3+ to Dy3+.