Tunable monolithic Fabry-Perot filter manufactured by selective etching of InGaAs/InP epitaxial films

Abstract
With this paper we report the successful manufacturing of a monolithic Fabry-Perot tunable filter. The filter consists of an air-gap cavity defined between two high reflectance Bragg mirrors. The top mirror is placed on an InP bridge which can be actuated electrostatically. When biased, the bridge moves towards the substrate, reducing the length of the cavity and tuning the resonance wavelength. The air-gap cavity was manufactured by wet etching of InGaAs epitaxial layers with excellent selectivity to InP and InGaAsP. The bottom mirror is a high reflectance 50 periods InGaAsP/InP Bragg reflector. The resonance dip of the cavity is less than 3 /spl Aring/ wide. A tuning range of 30 nm was demonstrated for a bias voltage of up to 25 V.