Patent ID: 7263871

Claim:
A doubly resonant photaoacoustic gas detector comprising: i) a continuous wave external light source for generating a light beam whose wavelength coincides with an absorption wavelength of a gaseous analyte; ii) a closed path optical cavity having at least two reflective surfaces; iii) an acoustic resonator chamber, said acoustic resonator chamber being contained within said optical cavity, and comprising: a) an acoustic sensor for detecting sound waves generated by a gaseous analyte present within said chamber, b) a first entrance port for admitting light from said external light source into said chamber, c) a second port which passes said light out of said chamber after transmission of said light through said first port and said chamber, whereby the light beam generated by said external light source passes sequentially into, through and out of said chamber, said light beam being repeatedly reflected back and forth through said chamber, and being modulated at a frequency which is equal to or equal to one-half of an acoustic resonance frequency of said acoustic resonator chamber.