An acousto-optical spectrometer (AOS) is based on the diffraction of light by ultrasonic waves. A

piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word ' ...

transducer A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and cont ...

, driven by the RF signal (from the receiver), generates an acoustic wave in a

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macr ...

(the so-called Bragg-cell). This acoustic wave modulates the

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, o ...

and induces a phase grating. The Bragg-cell is illuminated by a collimated

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...

beam. The angular dispersion of the diffracted light represents a true image of the IF-

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of color ...

according to the

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of a ...

and wavelengths of the acoustic waves in the crystal. The spectrum is detected by using a single linear diode array ( CCD), which is placed in the focal plane of an imaging optics. Depending on the crystal and the focal length of the imaging optics, the resolution of this type of spectrometer can be varied.

See also