For light emitting devices we have optical power measurement capabilities through an integrating sphere, and optical power meter. Spectrometery capababilities are also readily available to gauge the peak emission and FWHM:

A micro-PL system is also available for material characterization down to wavelengths of 365nm. Micro-PL is a useful technique to see material quality before the effort is undertaken to fabricate devices. Micro-PL is also useful for determining the nature and location of wavelengths of interest.

For some transparent materials optical interfence is leveraged for information such as film thickness. This can be a useful metric when developing a new process:

At our state-of-the-art facility, we specialize in comprehensive semiconductor reliability testing services. Our advanced capabilities encompass various aspects of device evaluation, including dielectric film testing and thermal analysis of integrated circuits. Additionally, we are experts in assessing numerous other degradation mechanisms that may impact semiconductor performance. With our extensive experience and cutting-edge technologies, we deliver reliable results to ensure optimal functionality and longevity of your semiconductor devices.