High-sensitivity optopneumatic convertor

A novel direct optopneumatic convertor has been developed which can provide a pressure pulse signal of about 150 Pa (before amplification) within 0.5 s of receipt of 5 mW mean power light from an infrared pulsed laser diode. After two seconds, the signal level is about 300 Pa. The optofluidic gain of the convertor can be expressed as 60 Pa/mW or 60 Pa/mJ of optical input. A theoretical model has been developed which has enabled the efficiency of the convertor to be maximised by optimisation of the variables. Experimental results followed the general trends of theoretical predictions. The unit employs a miniature optoacoustic cell (~5 mm3 in volume) with a flexible membrane which acts as the flapper in a simple pneumatic flapper/nozzle arrangement. The use of the new convertor should enable the position of a pneumatic cylinder to be controlled by light down either of two optical fibres, using standard fluidic amplifiers, without the need for an electrical interface. The convertor will have applications for use with fluidic control equipment working in inflammable, corrosive or aqueous environemnts where electrical control is impractical or difficult.