Photoacoustic chemical detector

A chemical species detector, comprising:

• a light source configured to produce beams of monochromatic light including:
• a first beam, having a wavelength corresponding to an absorption feature of the chemical species to be detected;
• a second beam;
• and
• a third beam;
• a pressure-sensing diaphragm which when impacted by the pressure waves resulting from the first beam interacting with a chemical species that is located away from the third beam responsively vibrates;
• a photo-electromotive force (photo-EMF) sensor, configured and arranged to detect displacements of the pressure sensing diaphragm as little as 10 femtometers;
• a housing defining an interior space, and
• wherein the light source the pressure-sensing diaphragm, the photo-EMF sensor, the second beam and the third beam are contained within the interior space;
• wherein the chemical species is located outside of the interior space and the first beam is directed outside of the interior space;
• wherein the third beam is directed against the second side of the pressure sensing diaphragm;
• and
• wherein the third beam is directed to the photo-EMF sensor from the pressure-sensing diaphragm which photo-EMF sensor outputs a signal corresponding to the displacement of the diaphragm caused by the incident pressure wave;
• and
• wherein the second beam is frequency shifted from that of the third beam and the sensor is configured to perform phase measurements by heterodyning a frequency shifted second beam and the third beam.