Design and fabrication of freestanding pitch-variable blazed gratings on a silicon-on-insulator wafer

This paper presents the design, fabrication and characterization of tunable blazed gratings by combining microactuators. A two-mask process is used to define a four-level blazed grating on silicon-on-insulator wafers, and high lateral resolution is achieved by fast atom beam etching. Electrostatic comb drive actuators with double-folded springs are proposed to translate the freestanding grating beams. In association with reactive ion etching and vapor HF release, the freestanding grating beams and the actuator structures are obtained on a 10 νm thick silicon device layer; the vapor HF release is used to remove the buried oxide layer, successfully relieving the residual stress and preventing sticking problems. The changes in the grating period are tested by applying the voltage to the microactuators and the optical experiments are carried out to characterize the diffraction properties of the fabricated grating. These experimental results show good agreement with theoretical prediction.