LE-0400 Diode laser Characterization

Laser diodes differ from most “classical” lasers in two distinct ways:
Firstly, they do not posses an inherently defined wavelength. Instead of two defined energy levels, the lasing transition occurs between two energy bands.
Secondly, the pn junction of the diode defines the lasing volume, instead of the resonator in a classical laser.
These experiments investigate the variation of the emitted laser wavelength versus temperature and current. The divergence and polarization of the laser emission are examined. These experiments investigate the variation of the emitted laser wavelength versus temperature and current. The divergence and polarization of the laser emission are examined. The set-up comprises a modern 30 mW green (525 nm) emitting laser diode, with integrated Peltier cooler, mount and driver. Collimating optics, lenses and a polarization analyser are provided, along with a photodiode detector. A spectrum analyser is available as an option. All optical mounts and positioners are included. The laser diode is mounted in a rotational stage which allows the independent rotation around the beam propagation axis as well as perpendicular to this axis to measure the spatial distribution of the emitted laser light. The polarization for different values of the injection current is analyzed by means of a polarizer. The spectrum analyser will be used to measure the change of wavelength by varying the temperature and injection current. The shift is app. 0.05 nm per °C. The temperature range of the diode laser controller can be varied from 10 to 60° C which results in a shift of 2.5 nm. Temperature and injection current are stabilized and displayed by the controller. The use of an oscilloscope is recommended to suppress disturbing environmental light. In this case some of the measurements are carried out with modulated diode laser light.