“VCSELs are components with an intrinsic single longitudinal mode and normally exhibit complex polarization properties,” says Stephanie Grabher, Head of Key Accounting at Instrument Systems. “The light they emit is typically linearly polarized along one of two orthogonal directions. If there is a change in temperature or bias current, abrupt polarization switching can be observed. VCSELs thus emit in more than one polarization state, so that their polarization angle cannot be controlled. In order to exploit the full performance potential of VCSELs while guaranteeing safe operation, this polarization dependency should also be taken into account in the measurement of magnitudes and absolute power.”
Thanks to an innovative one-shot process, the VTC 4000 simultaneously measures the spatial polarization of the single emitters of a VCSEL array in the near-field and supplies the information necessary to reduce the polarization dependency of the measurement setup. This procedure minimizes the error budget of the VCSEL test system and delivers highly accurate readings, e.g. for the eye safety of the laser source. In addition to defects, the infrared camera also characterizes position, power and radiation information of single emitters. In combination with a CAS spectroradiometer, the single emitter wavelengths can also be determined. An extended system with transmission screen measures the radiation behavior of emitters in the far-field.
In its portfolio, Instrument Systems has tailor-made solutions suitable for the characterization and quality control of the electrooptic properties of VCSELs in the lab and in production environments. The high-resolution array spectroradiometers of the CAS series are the central components of the VCSEL measuring systems. They offer a spectral solution up to 0.12 nm, and due to short integration times they are also suitable for high throughput rates in production. The PVT Pulsed VCSEL Tester is specially tailored to the time-resolved measurement of nanosecond pulses in the lab.
Instrument Systems GmbH