Progress in InP-based MOEMS

InP-based micro-opto-electro-mechanical systems (MOEMS) for the long wavelength range (1.3 and 1.55 mm) have been extensively investigated during the last years. The fabrication of ultra-thin and hence ultra-flexible structures that can be actuated electrostatically was limited by residual strain within the structural layers. Highly flexible membranes are necessary if the tuning voltage is to be kept below 10 V and a wide tuning range is required. Adapting the metal-organic vapour phase epitaxial growth conditions. the residual strain was significantly reduced. allowing the fabrication of InP membranes as thin as 30 nm. Tunable micro-cavities (L(cavity)=0.5 l, l=1.55 mm) with a InP membrane thickness of only 123 nm show an optical tunability of up to 30.5 nm/V2 and a maximum tuning range of more than 160 nm. When reducing the thickness to 123 nm (which corresponds to l/4) a significant deformation of the membranes was observed that has to be taken into account for the fabrication of MOEMS since additional losses are created. A highly selective. widely tunable filter for dense wavelength division multiplexing systems (WDM) was fabricated and exhibits a selectivity of < 0.4 nm throughout the entire tuning range of 48 nm.