Examples of Investigations and Measurments

The energy scheme of the Nd ions within the YAG host-crystal is the most essential detail of this experiment. Since this material is one of the most important lasing media, the discussion of this scheme is already a preparation for later applications. The absorption transitions (A) are used within this experiment. By optical pumping of these transitions, further levels are populated. The generated radiation of these levels is measured static and time resolved. Special attention will be given to the line of 1064 nm. By means of the well known spectral data of the absorption transitions, the emission wavelength of the diodelaser can be calibrated. By modulation of the diodelaser the timely decay of the fluorescent radiation is observed. Since the life-time of the initial level is about 250 ms, the decay curve can easily be recorded with a simple oscilloscope and the lifetime determined.

Absorption spectrum
The dependence of the emission wavelength of the diodelaser on its temperature and to a certain extent also on the injection current can be used to study the spectral absorption behaviour of the Nd:YAG. By the measurement of the diodelaser radiation transmitted by the Nd:YAG rod, one gets the figure shown in (B).

Spectral characteristics of the diodelaser
The maximum absorption is characterised by a significant reduction of the diodelaser radiation at the exit of the Nd:YAG crystal. In this case the wavelength of the radiation of the diodelaser has the same value as the well known absorption peak of the Nd:YAG material. From this, the dependence of the laser diode€™s radiation wavelength on temperature and injection current can be determined (C).

Output power of the diodelaser
The characteristic data of the diodelaser can be measured in relative units. If a laser power meter is available this can also be done in absolute units. Output power as a function of injection current, slope efficiency and threshold current are determined (D).