High-sensitivity optopneumatic converter

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 recept 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 converter to be maximised by optimisation of the variables. Experimental results followed the general trends of theoretical predictions. The unit employs a miniature optoacoustic cell ( approximately 5 mm³ in volume) with a flexible membrane which acts as the flapper in a simple pneumatic flapper/nozzle arrangement. The convertor will have applications for use with fluidic control equipment working in inflammable, corrosive or aqueous environments where electrical control is impractical or difficult.