We have successfully utilized the temperature dependence of the refractive indices of various substrates (GaAs and InP) in detecting their temperature variations. The detectionwas accomplished by injecting a beam of HeNe laser (1.15 μm) toward a double-sidepolished substrate. An interference pattern developed among the reflected laser beams, and the actual temperature increment/decrement could be deduced from the interference maxima and minima. The method was first calibrated inside a diffusion furnace from room temperature up to 200ºC, and the detection resolution was found to reach as high as ±0.7ºC. The same measurement setup was later used on the temperature calibration of a substrate heater in a molecular beam epitaxy (MBE) growth chamber, and was finally used to detect surface temperature change during Ar+ laser assisted metalorganic MBE (MOMBE) growth. Because a direct contact is unnecessary and only the relative signal intensity is needed, this low-cost method can be applied to any otherexperiments in a fairly straightforward manner.