Temperature Coefficient of High-Q Microsphere Cavity

Abstract

Optical microsphere resonant cavity has been widely researched in the field of high sensitivity sensor and optical communication because of its high Q value and minimal model volume. Optical resonance wavelength shifts are measured with temperature changes for unpackaged and encapsulated microsphere. Linear dependence of red shift against temperature rise with high linearity is observed. The temperature cofficient is 25.6 pm/℃ for unpackaged microsphere, whereas is 4.4 pm/℃ for encapsulated one, which mostly results from ultraviolet (UV) glue′s negative thermo-optic coefficient. The thermo-optic effect is analyzed based on UV glue. The fraction of light in UV glue can be changed by the thickness of glue, and then, temperature coefficient is also changed. The temperature coefficient decreases to zero when the fraction is 0.1135, which means the depression of temperature drift as well as the realization of thermal compensation. Sensitivity of temperature is improved as fraction increases.