Patent ID: 8040516

Claim:
An oscillator element for use in a photo acoustic detector for detecting a concentration of a sample in a sample mixture, the photo acoustic detector using a light beam for excitation of molecules of the sample in proximity of an excitation area of the oscillator element, the excitation resulting in resonance of the oscillator element, the oscillator element comprising: piezoelectric material for generating a voltage when mechanically distorted; and electrodes at least partially covering a surface of the oscillator element for detecting the generated voltage, wherein the excitation area is arranged in such a way that, when the light beam hits the oscillator element, heating of the electrodes in the excitation area by the light beam is avoided by interrupting at least one electrode in the proximity of the excitation area, the at least one electrode having a first portion and a second portion, wherein first portion is heated by absorption of the light beam, and wherein the second portion is substantially transparent to the light beam.