In
optics
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultra ...
, a tophat (or top-hat) beam 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 ...
or electron beam has a near-uniform
fluence
In radiometry, radiant exposure or fluence is the radiant energy ''received'' by a ''surface'' per unit area, or equivalently the irradiance of a ''surface,'' integrated over time of irradiation, and spectral exposure is the radiant exposure per un ...
(energy density) within a circular disk. It is typically formed by
diffractive optical element
Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a ...
s from a
Gaussian beam
In optics, a Gaussian beam is a beam of electromagnetic radiation with high monochromaticity whose amplitude envelope in the transverse plane is given by a Gaussian function; this also implies a Gaussian intensity (irradiance) profile. Thi ...
. Tophat beams are often used in industry, for example for
laser drilling
Laser drilling is the process of creating thru-holes, referred to as “popped” holes or “percussion drilled” holes, by repeatedly pulsing focused laser energy on a material. The diameter of these holes can be as small as 0.002” (~50 μm). ...
of holes in
printed circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...
s. They are also used in very high power laser systems, which use chains of
optical amplifier
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback fr ...
s to produce an intense beam. Tophat beams are named for their resemblance to the shape of a
top hat
A top hat (also called a high hat, a cylinder hat, or, informally, a topper) is a tall, flat-crowned hat for men traditionally associated with formal wear in Western dress codes, meaning white tie, morning dress, or frock coat. Traditionally m ...
.
External links
Video of propagation simulation of TopHat Diffractive Optical Element around focal planeby
Holo/Or
Holo/Or is an international high-tech company, dedicated to the design, manufacturing and commercialization of new products based on diffractive optical elements (DOEs).
Company profile
Holo/Or is a leading company in the field of diffractive o ...
Flat top / Beam shaping application notes - Diffractive opticsby HoloOr
MATLAB function for simulating TopHat beamby HoloOr
See also
*
Laser beam profiler
A laser beam profiler captures, displays, and records the spatial intensity profile of a laser beam at a particular plane transverse to the beam propagation path. Since there are many types of lasers — ultraviolet, visible, infrared, continuo ...
*
Bessel beam
A Bessel beam is a wave whose amplitude is described by a Bessel function of the first kind. Electromagnetic, acoustic, gravitational, and matter waves can all be in the form of Bessel beams. A true Bessel beam is non-diffractive. This mean ...
Laser science