Applications
NF specializes in diode laser testing applications. Our expertise covers a wide range of analyses from electro-optical characterization and visual inspection to burn-in/lifetime testing.
LIV – Light current voltage measurement
A fundamental measuremant for diode lasers is the light-current-voltage sweep test or in short LIV measurement. Current applied to the laser diode is swept and the intensity of the resulting emitted light is measured in the LIV test.
For example following characteristics can be determined based on the LIV measurement:
Spectral Analysis
Spectral analysis is executed measuring an input of light signal magnitude vs wavelength. The results are presented on chart which has the spectrum wavelength on the horizontal axis and the amplitude displayed on the vertical axis.
For example following characteristics can be determined based on the spectral measurement:
Burn-in
Diode laser failure mechanisms can be divided into two main categories: infant mortality failures and wear out failures (see lifetime testing). Infant mortality failures can be caused by defects introduced during the manufacturing process of the diode lasers. These kind of defects can originate in semiconductor material during epitaxial growth for example.
Burn-in process is used to screen out infant mortality failures. In this process testing device is run for certain time (typically less than 100h) under controlled operating conditions. Typical operating parameters are tested before and after the burn-in. A notable change in parameters, when comparing before and after results, typically indicates high possibility for infant mortality failure.
Lifetime testing
Diode laser failure mechanisms can be divided into two main categories: infant mortality failures (see burn-in) and wear out failures. Wear out failures in diode lasers are typically found to be caused by the growth of non-radiative, optically absorbing defects within the active region of the diode laser.
Lifetime testing is used to identity wear out failures. This is done by collecting diode laser lifetime data under carefully controlled operating conditions. Typical operating parameters are tested during the process. Analyzing changes in the results will help to develop statistical models for predicting diode laser lifetime.
Facet Visual Inspection
The facet visual inspection can be used to detect particles, cracks and coating defects on the diode laser facets. Automatic microscope takes an image of the front facet and the image is then analyzed either by the user or by machine vision software.
Far Field measurement
In far field measurement light intensity vs output angle of light is measured and analyzed. For diode lasers this is usually specified as fast and slow axis divergences and for fibers it is expressed as numerical aperture.
Near Field measurement
Near field analysis is based using computer vision to inspect emission uniformity from diode laser facet. Automatic algorithms can detect failures such as filamentation and non-uniformity.
Overhang measurement
Overhang measurement allows to determine overhang of laser bar on the submount. Overhang is measured from both edges of bar and for single emitters measurement is done at the center. The measurement can be used as verification and quality control mechanism for bar mounting process.
Smile measurement
Smile measurement determines the diode laser bar smile. It is detected as a slight bend of the horizontal line connecting the emitters.
