Cleaved Silica Microsphere for Temperature Measurement

A sensing structure based on a cleaved silica microsphere is proposed for temperature sensing. The microsphere was cleaved using focused ion beam milling. The asymmetry in the structure introduced by the cut generates not only new cavities but also random interferometric reflections inside the microsphere. These two spectral components can be separated using low-pass and high-pass filters, respectively. The sensor response to temperature can be extracted from the cavities’ component using a correlation method. The device achieved a temperature sensitivity of −10.8 ± 0.2 pm/°C between 30 °C and 80 °C. The same effect is impossible to be obtained in a normal uncleaved microsphere. The random interferometric component did not provide any information on temperature using the same analysis. However, when changing the temperature, a new and completely distinct reflection spectrum with no apparent correlation with others at different temperatures was achieved.