Optical Spectroscopy III
Er3+:YLiF4 Emission Spectrum and Up-conversion

 Objective:

In the following exercises students will excite Er3+ with a diode laser and obtain emission spectra. From the spectra, they will identify energy levels important in the visible emission of trivalent erbium. Among the observed emission lines, several are due to up-conversion. Students identify these emission lines and the excitation pathways, which enable this effect.

Background:

Inexpensive compact semiconductor diode lasers are readily available, which supply high intensities of near infrared light. A common technological problem is that semiconductors seldom emit in the visible region of the spectrum. One solution to this problem is the use of an up-converting material. That is, a material which absorbs photons of a certain energy and emits photons with higher energy. The details of this process will be made apparent in the following exercise.

Procedure:

Diode Laser Operation and Characteristics  

The following procedure will guide you through the measurement of the emission of Erbium in a crystal host, the identification of energy levels, and the analysis of linear and nonlinear absorption processes.

CAUTION: THE DIODE LASER EMITS INTENSE RADIATION AND EXPOSURE TO THE EYES AND SKIN MUST BE AVOIDED. PAY PARTICULAR ATTENTION TO REFLECTIONS OF THE LASER BEAM, AS THESE ARE SOMETIMES DIFFICULT TO PREDICT.

Er3+:YLiF4 Emission Spectrum  

 Suggested reading (a step ahead): A new process, called quantum cutting, which can be considered the opposite of up-conversion is now being studied. Future mercury-free fluorescent lighting will likely be produced using this process.