NALUX NANO OPTICAL, INC.
65 E.State Street, Suit2000
Columbus, Ohio 43215
c/o Schneider Downs
"Lighting a path to the future with nano-optics."
Diffraction gratings are another type of optic that is found in all kinds of optical applications and Nalux has special expertise in creating them. The main use of a diffraction grating is to split up light into it's component wavelengths or to make copies of a beam of a single wavelength. It is this ability to split up light that makes these optics valuable. When the spectra of a beam can be split up it can be analyzed. Knowing the wavelengths that comprise the beam and their intensities can tell us valuable information (such as the composition) about the object that emitted the light in the first place. This leads to applications in astronomy, medical applications, spectroscopy, food safety, and a host of other areas where diffraction gratings improve our lives.
In their simplest form, diffraction gratings are simply a sequence of grooves with a constant spacing. Look at the two pictures shown at the top center of this page. Those are two kinds of diffraction gratings. You can also see the dimensions of these diffraction gratings and you can see how small the dimensions must be in order to get the light to split up properly. The angle of the light as it splits from one beam to several and the efficiency (the percentage of the light that gets split up and doesn't travel straight through) of diffraction gratings is controlled by three things:
1. The fidelity of the shape created. If the shape is supposed to be a perfect square wave but the fabrication technology only enables rounded corners instead of sharp 90 degree corners then more light gets scattered as opposed to being diffracted into a tight beam.
2. The spacing of the grooves in diffraction gratings will dictate the angles of the diffracted beams. One spacing may result in a spread angle of 10 degrees while another spacing will result in an angle of 30 degrees.
3. The depth of diffraction gratings is also important. If you are trying to simply divide up a beam that is composed of a single wavelength then the depth of the diffraction gratings needs to be the same depth as the wavelength of light being diffracted. If it is the perfect depth, down to the nanometer, then theoretically diffraction gratings have a chance to be 100% efficient. However, if the depth isn't perfect then some of the beam doesn't get diffracted and travels straight on through the diffraction gratings as though the optic didn't exist. This undiffracted beam is termed the "zero order" and sometimes too much zero order is very harmful and at other times (like with pick up heads in DVD players) you want most of your light going into the zero order and just a small percentage to be diverted off to a tracking head or similar device.
Diffraction gratings can be made by a variety of methods. These methods include mask lithography, electron beam lithography, diamond milling, focused ion beam ablation, plastic injection molding, and glass molding. Diffraction gratings can also be made out of a wide variety of materials. Just about any type of clear plastic can be used for mass production purposes. Glasses also are often used in optics for spectrometers and astronomical instruments because they have the strength and the dimensional stability to still do the job despite mechanical stresses and varying temperatures. Diffraction gratings can even be superimposed over mirrors in order to split light up into multiple beams at the same time as it is being reflected.
The design of diffraction gratings is an intricate and detailed process using some very sophisticated software programs, probably the most well known of these being G-Solver. Other programs are used to calculate the correct shape and depth required in diffraction gratings for the performance desired.
Diffraction gratings are everywhere and Nalux is ready to supply them when you need them. Give us a call.