Opto-mechanical design of tuneable InP-based Fabry-Perot filter for gas analysis

This paper presents the opto-mechanical design of tuneable InP-based Fabry-Perot filters for hydrocarbon gas metrological applications. These filters are composed by a top and a bottom InP/air Bragg mirrors with a central air micro-cavity. The tunability is achieved by changing electrostatically the cavity thickness. For this type of applications, the required performances are a large tunability (similar to 200 run), a high selectivity (similar to 10 nm), a weak temperature dependence and a nearly constant transmission level over the tuning range. Firstly, we have obtained the device composition which permits to attain the optical specifications simulating its optical response (transmission and reflectivity). Secondly, we have developed a mechanical model using finite elements analysis (FEA) calculation method: this one permits to obtain the optimal mechanical design of the device in order to achieve a 200 run tuning range with a bias voltage of around 15 V (usual value for this kind of device). Finally, preliminary experimental results on a first generation of filters are presented. (C) 2001 Elsevier Science B.V. All rights reserved.