This paper proposes a method to prevent silicon from a notching in a reactive ion etching (RIE) process by introducing a self-aligned metal interlayer to a silicon/glass bonded fixture. A metal interlayer prevents a charge buildup at the bottom of a silicon trench, therefore silicon structures do not suffer from charge-induced local damage. A self-aligning process of Ti/Au interlayer is accomplished by a lift-off process using a photoresist etch mask as a sacrificial layer. Titanium is a diffusion barrier of gold to silicon and gold is preferred due to its chemical stability in a pre-cleaning step. The effectiveness of the proposed method is verified by applying it to the fabrication of a simple trench and comb electrode. The applicability of the proposed methodology is examined by fabricating an optical knife edge device.

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A reflection-type variable optical attenuator (VOA) using the translation of a 45° tilted vertical mirror is proposed. The translation of the mirror results in an optical axis offset between transmitting and receiving optical signal, which attenuates the transmitted optical power. Single- and dual-mirror-type VOAs are implemented and compared. A conic-cladding fiber and collimating lensed fiber are applied for low insertion loss. Optical attenuation performances are predicted using the CODE V optical simulator. An electrical spring method is studied for mode separation of the mirror actuator. The self-aligned metal interlayer process is applied for achieving a notching-free mirror surface. Performances of the fabricated VOAs are measured and discussed. An attenuation range is achieved from −0.9 dB (0 V) to −35 dB (10 V). The wavelength-dependent loss (WDL) is as small as 0.4 dB even at −20 dB attenuation level. Excellent polarization-dependent loss (PDL) less than 0.24 dB is achieved in the whole attenuation range.