Home Laser Experiments LE-0400 Diodelaser Characterisation

Keywords:

  • Binding of Molecules
  • Fermi Distribution
  • Inversion in Semiconductors
  • Types of Laser Diodes
  • Spatial Intensity Distribution
  • Spectral Properties
  • Beam Shaping
  • Polarisation Properties

Basic experiment

Intended institutions and users:

Physics Laboratory

Engineering department

Electronic department

Biophotonics department

Physics education in Medicine

 

Introduction

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LE-0400 Diodelaser Characterisation

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.

The experiments investigate the variation of the emitted laser wavelength versus temperature and current. The divergence and polarisation of the laser emission are examined. The set-up comprises a 30 mW laser diode, with integrated Peltier cooler, mount and driver. Collimating optics, lenses and a polarisation analyser are provided, along with a photodiode detector. A Nd:YAG rod is supplied, whose absorption provides defined wavelengths (a monochromator 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 polarisation for different values of the injection current is analysed by means of a polariser.

The wavelength will be calibrated by employing the well known absorption transitions of the Nd:YAG. In addition, an optional monochromator can be used to measure the change of wavelength by varying the temperature. The shift is app. 0.25 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 12.5 nm.

Temperature and injection current are stabilised 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.

LE-0400 Diodelaser Characterisation

 

 

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LE-0400 Diodelaser Characterisation

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