Spectrum of Industrial and Scientific Lasers

The first laser ever made used a synthetic ruby crystal- a solid-state laser with an emission wavelength of 694 nanometers. 

Now, over 50 years later, lasers can be from solids, liquids, or gases. They span the electromagnetic spectrum from far-infrared to the edge of ultraviolet, and emit wavelengths from 3 micron to 157 nanometers.

The full diagram of commercial lasers here at Wikimedia Commons.

We made a new and revised chart from the data showing more specifically the industrial and scientific lasers used in micro-drilling applications.

click here to enlarge

From the description:

"Laser types with distinct laser lines are shown above 

the wavelength bar, while below are shown lasers 

that can emit in a wavelength range... the height of 

the line gives an indication of the maximal power/pulse 

energy commercially available. For the Ar+-Kr+ laser 

only the most important lines are labeled...

Currently most of the data is taken from Weber's book 

"Handbook of laser wavelengths", with newer data in 

particular for semiconductor lasers."

From the original, we switched the bar around to go from longer to shorter wavelengths, instead of the other way around. Otherwise, it's the same data. It gives a nice visual overview of the laser spectrum and their myriad types.

Next week I'll be writing about an exciting research paper from NOAA for which we made 3 key parts. It connects atmospheric research, WWII planes, Hurricane Katrina, UV-LEDs, and Lenox Laser orifices all together! So be sure to check back.

And as always, check out past posts and our company website for even more information.

www.lenoxlaser.com

Young's Double Slit

The experiment named for Thomas Young's classic proof of the wave theory of light in 1803. While Young's original experiment used sunlight and calculated the average wavelength to be 550nm, today using monochromatic and coherent light one can calculate wavelength with the following formula:

nλ = xd/L

λ
is the wavelength of the light
d is the separation of the slits
n is the order of maximum observed ( for first order n=1)
x is the distance between the bands of light and the central maximum
L is the distance from the slits to the screen center point.

Young's Double Slits are manufactured by the Lenox Laser Corporation's proprietary technology that gives a very sharp edge to every slit that makes the geometries and areas of each slit equal (within specifications). This guarantees a very high contrast of diffraction patterns and low flux variations through each of the slits providing good metrology.

In application, these slits may be used to demonstrate Young's Interference Fringes, Michelson's Stellar Interferometer (for measuring the separation between double stars) or other applications requiring measurement of the separation between point sources. Go to the Young's Double Slit Page to activate an interactive applet that will show Young interferences resulting from the interaction of a certain number of waves.

For more information call 1-800-49HOLES or 410-592-3106 or email quotes@lenoxlaser.com

Small Hole Features

Every physical object is three-dimensional. A hole is a void in a three-dimensional object and may be of any size or shape. A perfect round hole is a cylindrical surface that extends between and is normal to the front and back surface of a substrate sheet. Further, a round hole generates a circular void in the front surface and a circular void in the back surface of the substrate sheet. There are many parameters to consider when specifying or describing a hole.

For the sake of discussion, let us reflect upon the characteristics of a round hole, as described above. In the micro-dimensional real world, the absolutely perfect round hole is difficult to achieve. Thus, we must consider how the round hole may deviate from perfection. The ends of a cylinder describe flat surfaces that are a circular, parallel to each other and normal to the axis. The hole entrance and exit apertures may not be circular, they might be oval or irregular in shape.

• If the front and back surfaces of the substrate sheet are not parallel to each other, the cross section of the hole cylinder is trapezoidal in shape.
• If the hole is not drilled at the normal to the surface of a parallel surface substrate sheet, the cross-section of the hole cylinder describes a parallelogram.
• If the hole entrance circle diameter is different than the hole exit circle diameter, the surface extending between them (the hole wall) is a section of a cone.

Also, the surface extending between the entrance and exit aperture may be totally irregular and may contain particles. The edges of the circular entrance and exit aperture may be beveled or rounded and may contain particles or burrs known as ablation. The descriptive geometrics of dimensioning and tolerances of a round hole include roundness or circularity, cylindrically or deviation from a perfect cylinder, perpendicularity or how much the cylindrical axis deviates from the normal to the substrate sheet surface.

Meet Thomas Young

THOMAS YOUNG

Thomas Young was an English polymath (a person with encyclopedic or varied knowledge or learning) who contributed to the scientific understanding of vision, light, solid mechanics, energy, physiology and Egyptology.. So great was his knowledge that he was called “Phenomena Young” by his fellow students at Cambridge.

Young was born in 1773, the eldest of 10 children. By the age of fourteen, he had learned Greek and Latin and was acquainted with French, Italian, Hebrew, Chaldean, Syriac, Samaritan, Arabic, Persian, Turkish and Amharic, a Semitic language spoken in North Central Ethiopia.

In 1792, Young began to study medicine in London. He later moved to Gottingen, where he obtained his doctorate in physics in 1796. A year later, in 1797, Young entered Emmanuel College at Cambridge. By 1799, Young had established himself as a physician in London where he published many of his first academic articles anonymously to protect his reputation at a physician. It is to be noted that while studying medicine in London, he explained the mode by which the eye accommodates itself to vision at different distances as depending on change of the curvature of the crystalline lens. This was to prove valuable to him being the first to describe astigmatism.

In 1801, Thomas Young was appointed professor of natural philosophy (mainly physics) at the Royal Institution in Cambridge. His initial interest in light and vision carried over to this new academic endeavor. Here, Young presented the hypothesis, later developed by Hermann von Helmholtz, that color perception depends upon the presence in the retina of three kinds of nerve fibers which respond respectively to red, green and violet light. This theory was experimentally proven in 1959, one hundred fifty eight years later!

While at Cambridge, Young performed his now famous double slit experiment where he passed a beam of light through two parallel slits in an opaque screen, forming a pattern of alternating light and dark bands on a white surface beyond which established that light was a transverse wave motion whose wavelength determined color (see wave interference). His findings were strongly opposed by contemporary scientists who believed that Newton, who had proposed that light was corpuscular in nature, would not possibly be wrong. However, Young’s work was soon confirmed by the French scientists, Fresnel and Arago.

In 1804, Young’s essay, “Cohesion of Fluids”, founded the theory of capillary phenomena on the principle of surface tension. He also observed the constancy of the angle of contact of a liquid surface with a solid, and showed how from these two principles to deduce the phenomena of capillary action (see Young-Laplace Equation and the Young-Dupre Equation). He went on to describe the characterization of elasticity that came to be known as Young’s Modulus.

After holding positions at St. George’s Hospital and on various scientific boards and committees, Thomas Young died in 1829 after a relatively short but distinguished career. His contemporary, Sir John Herschel, called him a “truly original genius”. Young being the first to define the term “energy” in the modern sense, was praised by Albert Einstein in his 1931 forward to an edition of Newton’s Opticks. Other admirers include physicist Lord Rayleigh and Nobel laureate Philip Anderson.

For more information on this topic please visit www.lenoxlaser.com

Spatial Filter Basics

A spatial filter is an optical device which uses the principles of Fourier Optics to alter the structure of a beam of coherent light. Spatial filtering is commonly used to remove aberrations in the beam due to imperfect, dirty or damaged optics, or due to variations in the laser gain medium itself. This can be used to produce a laser beam containing only a single transverse mode of the laser’s optical resonator.

In spatial filtering, a lens is used to focus the beam. A beam that is not a perfect plane wave will not focus to a single spot, but rather will produce a pattern of light and dark regions in the focal plane. It can be shown that this two-dimensional pattern is the two-dimensional Fourier transform of the initial beam’s transverse intensity distribution. Light in the very center of the transform pattern corresponds to a perfect, wide plane wave. Other light corresponds to “structure” in the beam, with light further from the central spot corresponding to structure with higher spatial frequency. A pattern with very fine details will produce light very far from the transform plane’s central spot. This pattern is called an Airy pattern.

By altering the distribution of light in the transform plane and using another lens to reform the collimated beam, the structure of the beam can be altered. The most common way of doing this is to place an aperture in the beam that allows the desired light to pass, while blocking light that corresponds to undesired structure in the beam. In particular, a small circular aperture or “pinhole” that passes only the central bright spot can remove nearly all fine structure from the beam, producing a smooth transverse intensity profile. With good optics and precisely measured pinhole, one could even approximate a plane wave.

The diameter of an aperture is chosen based on the focal length of the lens, the diameter and quality of the input beam, and its wavelength. If the hole is too small, the beam quality is greatly improved but the power is greatly reduced. If the hole is too large, the beam quality may not be improved as much as desired.

The size of the aperture that can be used also depends on the size and quality of the optics. To use a very small pinhole, one must use a focusing lens with a low f-number, and ideally the lens should not add significant aberrations to the beam.

A commonly used spatial filter configuration is to use a microscope objective lens for focusing the beam, and an aperture made preferably by laser drilling a small, precise, hole in a piece of metal foil. Such apertures made in a variety of sizes and materials are readily available commercially from companies, such as, Lenox Laser, Inc., the leader in microhole technology.

Introduction to Young's Double-slit Experiment

Lenox Laser Young's Double Slit

The double slit experiment, thought to have been first performed by English scientist Thomas Young circa 1800, generally refers to an experiment in which light is allowed to diffract through slits which produces fringes, or wave-like interference patterns on an opposing screen.

A similar experiment was performed by Claus Jonsson of the University of Tubingen where beams of electrons showed similar interference patterns. The results of this experiment are often taken as evidence of the “wave-particle duality” predicted by quantum physics. (a.k.a. Englert-Greenberger duality)

In the case two pinholes are used instead of slits, as in the original Young’s experiment, hyperbolic fringes are observed. This is because the difference in paths traveled by the light from the two sources is a constant for a fringe which is the property of a hyperbola. If the two sources are placed on a line perpendicular to the screen, the shape of the interference fringes is circular as the individual paths traveled by light from the two sources are always equal for a given fringe.

It is little wonder that the experiment performed by Dr. Jonsson (Young’s Double Slit applied to the interference of single electrons) ranks first in the list of the top ten most beautiful experiments as chosen by the readers of Physics World magazine.

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