Design of MEMS-based SiO2 Waveguides on Quartz Substrate for Evanescent Field-based Saturable Absorbers

A saturable absorber is a key device for Q-switching, mode-locking, or Q-switched mode-locking pulsed laser. D-shaped fiber is commonly used to interact evanescent field for saturable absorption. However, reproducibility of D-shaped fiber is restricted due to its manual fabrication process. Microelectromechanical system (MEMS) fabrication can be a solution in terms of reproducibility and precise fabrication. This paper presents a MEMS-based silicon dioxide (SiO₂) waveguide on quartz substrate for applying to evanescent field-based saturable absorbers. An SiO₂ waveguide on quartz substrate is designed with consideration of MEMS fabrication limitations. The refractive indexes of fabricated device are measured. Under the measured refractive indexes, dimensions of the SiO₂ waveguide are determined to satisfy the waveguide condition at the wavelength of 1550 nm. Simulation results show that the designed waveguide has desirable beam propagation properties.