Varifocal Scanner Using Wafer Bonding

We present a varifocal mirror integrated with a comb-drive scanner (varifocal scanner) fabricated by using a wafer bonding technology. An Au-Au thermocompression bonding technology is utilized for the integration. The bonding technology enables fabricating the multiple single crystalline Si layers on a wafer. The varifocal scanner consists of the three Si layers: 1) the fixed comb layer; 2) the scanner frame layer; and 3) the varifocal mirror layer. The 2-mm-diameter and 10-μm thick varifocal mirror is fabricated on the 60 μm thick combdrive scanner. The focal length modulation range of the varifocal mirror is from -523 to 139 mm at the frequency of 18.3 kHz. The optical angle is 7° at the resonant frequency of 3.59 kHz. The motion couplings between the varifocal mirror and the scanner are also investigated.