Far-field analysis of infrared sources

Due to their unique properties, surface-emitting lasers with a vertical cavity (VCSELs) are indispensable components for price-sensitive, laser-based applications. Sustainable development necessitates the transfer of lab-proven VCSEL tests to production lines. In particular with safety relevant components such as LiDAR systems or face-ID, manufacturers must ensure that each VCSEL reacts correctly in the terminal. For this purpose, each single emitter must be tested in the near field, as well as the complete VCSEL array in the far field. In the production environment this calls for mass-market, fast and highly reliable quality control of the relevant measurands, e.g. absolute performance, wavelength, single emitter defects, numerical aperture and beam homogeneity.

The VTC 2400 from Instrument Systems is a high-resolution infrared camera that was developed specifically for the 2D far-field analysis of the radiant intensity distribution of VCSELs and IR emitters. The cost-efficient measuring system consists of a light-permeable, diffusely scattering screen and a monochrome camera specially designed for measurements in the near infrared range. Thanks to the light-shielding camera housing, the system is suitable for both lab and production applications. In the measurement setup the screen stands between the radiation source (DUT) and the infrared camera, so that the typical spatial radiation properties of the DUT are displayed on the screen. The infrared camera VTC 2400 captures this 2-dimensional image in a single measurement and converts by calibration the irradiance [W/m2] to the radiant intensity distribution [W/sr] of the DUT.

Mapping of the radiation source on an additional screen makes for a highly flexible measurement setup. Basic measurement parameters, e.g. distance to the DUT, angular field of view or angle resolution can be optimally adjusted for the application in hand. This permits precise reconstruction of the radiant intensity distribution and identification of the maximum intensity (hot-spot) as required e.g. for laser safety evaluation.

The VTC 2400 has a radiometric calibration traceable to PTB standard. Together with the unique measurement concept, this guarantees a minimum error budget and a high level of measurement precision. Manufacturers are thus able to exploit the full performance potential of VCSELs while ensuring reliable operation.