Beam expander
Encyclopedia
Beam expanders are used in laser physics
either as intracavity or extracavity elements. They can be telescopic in nature or prismatic. Generally prismatic beam expanders use several prisms and are known as multiple-prism beam expanders.
Telescopic beam expanders include refracting
and reflective telescopes. A refracting telescope commonly used is the Galilean telescope which can function as a simple beam expander for collimated light. When used as intracavity beam expanders, in laser resonators, these telescopes provide two-dimensional beam expansion in the 20–50 range.
In tunable laser
resonators intracavity beam expansion usually illuminates the whole width of a diffraction grating
. Thus beam expansion reduces the beam divergence and enables the emission of very narrow linewidths which is a desired feature for many analytical applications including laser spectroscopy.
, is known as the multiple-prism dispersion theory
.
Multiple-prism beam expanders and arrays can also be described using ray transfer matrices
. The multiple-prism dispersion theory is also available in 4 X 4 matrix form. These matrix equations are applicable either to prism pulse compressors
or multiple-prism beam expanders.
, microdensitometry, and microscopy
.
Laser Physics
Laser Physics is an international scientific journal published by Nauka/Interperiodica. It is distributed through the Springer.-Topics covered:The journal specializes in laser physics, but also publishes papers about:...
either as intracavity or extracavity elements. They can be telescopic in nature or prismatic. Generally prismatic beam expanders use several prisms and are known as multiple-prism beam expanders.
Telescopic beam expanders include refracting
Refracting telescope
A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an image . The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long focus camera lenses...
and reflective telescopes. A refracting telescope commonly used is the Galilean telescope which can function as a simple beam expander for collimated light. When used as intracavity beam expanders, in laser resonators, these telescopes provide two-dimensional beam expansion in the 20–50 range.
In tunable laser
Tunable laser
A tunable laser is a laser whose wavelength of operation can be altered in a controlled manner. While all laser gain media allow small shifts in output wavelength, only a few types of lasers allow continuous tuning over a significant wavelength range....
resonators intracavity beam expansion usually illuminates the whole width of a diffraction grating
Diffraction grating
In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as...
. Thus beam expansion reduces the beam divergence and enables the emission of very narrow linewidths which is a desired feature for many analytical applications including laser spectroscopy.
Multiple-prism beam expanders
Multiple-prism beam expanders usually deploy two to five prism to yield large one-dimensional beam expansion factors. Designs applicable to tunable lasers with beam expansion factors of up to 200 have been disclosed in the literature. Initially multiple-prism grating configurations were introduced in narrow-linewidth liquid dye lasers but eventually were also adopted in gas, solid-state, and diode laser designs. The generalized mathematical description of multiple-prism beam expanders, introduced by DuarteF. J. Duarte
F. J. Duarte is a laser physicist and author/editor of several well-known books on tunable lasers. He introduced the generalized multiple-prism dispersion theory and has discovered various multiple-prism grating oscillator laser configurations...
, is known as the multiple-prism dispersion theory
Multiple-prism dispersion theory
The first description of multiple-prism arrays, and multiple-prism dispersion, was given by Newton in his book Opticks. Prism pair expanders were introduced by Brewster in 1813. A modern mathematical description of the single-prism dispersion was given by Born and Wolf in 1959...
.
Multiple-prism beam expanders and arrays can also be described using ray transfer matrices
Ray transfer matrix analysis
Ray transfer matrix analysis is a type of ray tracing technique used in the design of some optical systems, particularly lasers...
. The multiple-prism dispersion theory is also available in 4 X 4 matrix form. These matrix equations are applicable either to prism pulse compressors
Prism compressor
A prism compressor is an optical device used to shorten the duration of a positively chirped ultrashort laser pulse by giving different wavelength components a different time delay. It typically consists of two prisms and a mirror. Figure 1 shows the construction of such a compressor...
or multiple-prism beam expanders.
Extra-cavity beam shaping
Extra cavity hybrid beam transformers: using a telescopic beam expander, followed by a convex lens, followed by a multiple-prism beam expander, a laser beam (with a circular cross section) can be transformed into an extremely elongated beam, in the plane of propagation, while extremely thin in the orthogonal plane. The resulting plane illumination, with a near one-dimensional (or line) cross section, eliminates the need of point-by-point scanning and has become important for applications such as N-slit interferometryN-Slit interferometer
The N-slit interferometer is an extension of the double-slit interferometer also known as Young's double-slit interferometer. One of the first known uses of N-slit arrays in optics was illustrated by Newton...
, microdensitometry, and microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
.
See also
- Multiple-prism dispersion theoryMultiple-prism dispersion theoryThe first description of multiple-prism arrays, and multiple-prism dispersion, was given by Newton in his book Opticks. Prism pair expanders were introduced by Brewster in 1813. A modern mathematical description of the single-prism dispersion was given by Born and Wolf in 1959...
- Multiple-prism grating laser oscillators
- N-Slit interferometerN-Slit interferometerThe N-slit interferometer is an extension of the double-slit interferometer also known as Young's double-slit interferometer. One of the first known uses of N-slit arrays in optics was illustrated by Newton...
- Ray transfer matrix analysisRay transfer matrix analysisRay transfer matrix analysis is a type of ray tracing technique used in the design of some optical systems, particularly lasers...