Patent ID: 7586611

Claim:
A photoacoustic spectrometer apparatus adapted to enable an observation and characterisation of non-radiative sub bandgap defects in narrow and large bandgap materials using photoacoustic spectroscopy techniques, the apparatus providing for an irradiation of a sample material provided within a photoacoustic cell and the subsequent detection and processing of an acoustic signal emitted by the sample, the apparatus comprising: a) a light source having a polychromatic output substantially in the photonic energy range 0.5 eV to 6.2 eV, b) focusing apparatus adapted to couple the output from the light source onto the sample material, the focusing apparatus providing for an alignment and focusing of the light emitted from the light source so as to provide a substantially parallel incident light onto the sample material, wherein the focusing apparatus comprises: a 1st optical focusing system having a two lens arrangement, adapted to provide for a maximisation of the photonic throughput thereby maximising the intensity of light incident on the sample, and wherein the first and second lenses are provided by a biconcave and biconvex lens respectively; and a 2nd optical focusing system being adapted to provide for an increment in the spatial resolution of the light from the light source; and c) a detector for detecting and acquiring said acoustic signal emitted by the sample in response to said irradiation.