The diffractive beam splitterDiffraction Gratings and Applications, Loewen, Erwin C. and Popov, Evgeny. Marcel Dekker, Inc. 1997.
/ref>Digital diffractive optics: an introduction to planar diffractive optics and related technology, Bernard C. Kress, Patrick Meyrueis , 2005.
/ref> (also known as multispot beam generator or array beam generator) is a single optical element that divides an input

beam Beam may refer to: Streams of particles or energy * Light beam, or beam of light, a directional projection of light energy ** Laser beam * Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized g ...

into N output beams.Diffractive Optics – Design, Fabrication and Test, O'Shea, Suleski, Kathman and Prather, 2004. p.83
/ref> Each output

retains the same optical characteristics as the input beam, such as size,

polarization Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by ...

and

phase Phase or phases may refer to: Science *State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter), a region of space throughout which all physical properties are essentially uniform *Phase space, a mathematica ...

. A diffractive

beam splitter A beam splitter or ''beamsplitter'' is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding wid ...

can generate either a 1-dimensional beam array (1xN) or a 2-dimensional beam

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

(MxN), depending on the diffractive pattern on the

element Element or elements may refer to: Science * Chemical element, a pure substance of one type of atom * Heating element, a device that generates heat by electrical resistance * Orbital elements, parameters required to identify a specific orbit of o ...

. The diffractive beam splitter is used with

monochromatic light {{Short description, Electromagnetic radiation with a single constant frequency In physics, monochromatic radiation is electromagnetic radiation with a single constant frequency. When that frequency is part of the visible spectrum (or near it) the ...

such as a

laser beam 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 ...

, and is designed for a specific

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

and angle of separation between output beams.

Applications

Normally, a diffractive beam splitter is used in

tandem Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction. The original use of the term in English was in ''tandem harness'', which is used for two ...

with a focusing lens so that the output beam array becomes an array of focused spots on a plane at a given distance from the lens, called the "working distance". The

focal length The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative foca ...

of the lens, together with the separation angle between the beams, determines the separation distance between the focused spots. This simple optical set-up is used in a variety of high-power

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 ...

research and industrial applications that typically include: :* Laser scribing (

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.Glass dicing (

LCD displays A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but i ...

) :*

Perforation A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized fashion, where all of the holes collectively are called a ''perforation''. The process of creating perforations is called perfor ...

(

cigarette filter A cigarette filter, also known as a filter tip, is a component of a cigarette, along with cigarette paper, capsules and adhesives. Filters were introduced in the early 1950s. Filters may be made from plastic cellulose acetate fiber, paper or ...

s) :* Beam samplingBeam sampler
/ref> (Power monitoring and control) :* 3-D

motion sensing Motion detection is the process of detecting a change in the position of an object relative to its surroundings or a change in the surroundings relative to an object. It can be achieved by either mechanical or electronic methods. When it is done by ...

OPTICAL DESIGNS FOR ZERO ORDER REDUCTION(patent)
/ref> (

Example Example may refer to: * '' exempli gratia'' (e.g.), usually read out in English as "for example" * .example, reserved as a domain name that may not be installed as a top-level domain of the Internet ** example.com, example.net, example.org, e ...

) :* Medical/aesthetic applications (skin treatment)Fractional Laser Skin Treatment Using Diffractive Optics
/ref> Phase image

Design principle

The theory of operation is based on the

wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (r ...

nature of

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

and Huygens' Principle (See also Diffraction). Designing the diffractive pattern for a beam splitter follows the same principle as a

diffraction grating In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structural ...

, with a repetitive pattern etched on the surface of a substrate. The depth of the

etching Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio (incised) in the metal. In modern manufacturing, other chemicals may be used on other type ...

pattern is roughly on the order of the wavelength of light in the application, with an adjustment factor related to the substrate's index of refraction. The

pattern is composed of "periods" – identical sub-pattern units that repeat cyclically. The width d of the

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

is related to the separation angle θ between output beams according to the

grating equation In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structural ...

: :

d \sin \theta_m = m  \lambda

''m'' represents the order of the diffracted beam, with the zero order output simply being the undiffracted continuation of the input beam. While the

determines the direction of the output beams, it does not determine the distribution of light intensity among those beams. The

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may ...

distribution is defined by the etching profile within the unit period, which can involve many (not less than two) etching transitions of varying duty cycles. In a 1-dimensional diffractive beam splitter, the diffractive pattern is linear, while a 2-dimensional element will have a complex pattern. For information on manufacturing process, see

lithography Lithography () is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone ( lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by the German ...

References

{{reflist

External links

HOLOOR Diffractive beam-splitter

Video presenting diffractive beam splitter developing. IFTA

Video.Light propagation simulation through diffractive splitter
Optical components Diffraction