This article describes a study of an 8 W optical output power single emitter laser diode. The used device is the WSLX808008-H-T-PD, manufactured by Wavespectrum, with 808 nm emitted wavelength, and with build in NTC (thermistor), photodiode and Peltier cell. First part of the study explains how the Pspice model of the optical output power is proposed and how parameters are obtained, especially considering temperature variations. A short review of related laser diode theory is done including necessary parameters for the model proposal. It is explained the used method to measure the diode's optical output power avoiding temperature drifts (cold measure) and how the method has been implemented in an automatic characterization system using a data acquisition card controlled with LabVIEW, to be applied at different temperatures using a climatic chamber, and to obtain the necessary model parameters values as required by theory. It is also confirmed that the measured parameters are effectively following the expected theoretical behaviour with the temperature variation. With obtained results, model is proposed and programmed in Pspice, and simulation results are compared with measured real results for model validation. In a second part, it has been studied the usage of laser's wavelength drift as a temperature measurement method, and also as a validation of the cold measurement method as it allows the temperature drift supervision during it. Advantages and disadvantages of this method compared with NTC usage are commented. Results using two different spectrometers, comparison with laser diode manufacturer's information and necessary temperature references for the method are commented. In a third part a proposal of an optical output power measurement setup and it use with diode's characterisation system is proposed. System measurements comparison in DC mode with a thermal power meter and related calibration are performed and applied to the automatic characterization system.
Optical profiling techniques, mainly confocal and white light interferometry, have demonstrated to be suitable
techniques for characterization of transparent thick films. Measurements are carried out by vertically scanning the
upper and lower film interfaces. Thickness of the layer is determined from the two peaks in the confocal axial response
or from the two sets of interference fringes developed during the vertical scan. The 3D topographies of the upper and
lower interfaces of the film can also be obtained. Measurements of photoresists or oxide coatings are typical examples
of thick film characterization. On the other hand, measurement of thin films is considered to be a very difficult
application to carry out with most optical imaging profilers. A film should be considered as thin when the two peaks
obtained along the vertical scan become unresolved. We introduce new methods based on confocal techniques, which
make it possible to measure sub-micrometric layers on structured samples. These techniques are based on the
comparison between the axial responses obtained in areas where the film is present and those in other areas where only
the substrate is present. This method has been successfully used for thickness assessment of several samples, such as a
set of calibrated Si-SiO2 layers.