A major challenge of in-situ metrology on single-port reactors with small viewport geometries is the combination of curvature measurements by a blue laser with reflectance measurement at 405 nm. The blue laser is a must for patterned sapphire substrates (PSS) and double-side polished substrates.  The 405 nm reflectance is indispensable for monitoring of InGaN MQW growth. Until now, it was impossible to have both features for reactors with only one small optical access because of the cross-talk effect. The new optical and electronic design of EpiCurve® TT eliminates this problem.