Single Element Raman Thermometry

Despite a larger sensitivity to temperature as compared to other microscale thermometry methods, Raman based measurements typically have greater uncertainty. In response, a new implementation of Raman thermometry is presented having lower uncertainty while also reducing the time and hardware needed to perform the experiment. Using a modulated laser to excite the Raman response, the intensity of only a portion of the total Raman signal is leveraged as the thermometer by using a single element detector monitored with a lock-in amplifier. Implementation of the lock-in amplifier removes many sources of noise that are present in traditional Raman thermometry where the use of cameras preclude a modulated approach. To demonstrate, the portion of the Raman spectrum that is most advantageous for thermometry is first identified by highlighting, via both numerical prediction and experiment, those spectral windows having the largest linear dependence on temperature. Using such windows, the new technique, termed single element Raman thermometry (SERT), is utilized to measure the thermal profile of an operating microelectromechanical systems (MEMS) device and compared to results obtained with a traditional Raman approach. The SERT method is shown to reduce temperature measurement uncertainty by greater than a factor of 2 while enabling 3 times as many data points to be taken in an equal amount of time as compared to traditional Raman thermometry.