A diffraction grating acts like a prism to separate light into parts based on wavelength. It has small, usually periodic features that distort the angle of the incident light.

The polychromatic (multi wavelength) light source is composed of monochromatic (single wavelength) constituents. Upon interacting with the diffraction grating, light of various wavelengths spread at varying degrees. For more information on the effect of wavelength on diffraction see: How do shorter wavelengths of light provide higher spatial resolution images at smaller scales?

Diffraction gratings are used in systems needing high resolution separation of wavelengths. One of the most common uses is in a laser - like the green laser below - in which a monochromatic light source is an important feature to induce lasing.

Other common uses include various forms of spectroscopy, which use diffraction gratings to separate an unknown source of radiation into its spectra. An exciting application of spectroscopy is the analysis of gas spectra of cosmological bodies. By breaking up the electromagnetic radiation from distant stars into their spectra, we are able to know more about their chemical composition.

Images:Optical Spectrometers, Diffraction grating - Wikipedia

A diffraction grating produces spectra, separating light by wavelength. In other words it splits polychromatic light into its constituent colours. A diffraction grating is sometimes called a “super prism” because it can produce better spectra than a glass prism.

Diffraction gratings are useful whenever light needs to be separted into its separate frequencies (or wavelengths), for example in spectroscopy. They are an essential item in spectroscopy in astronomy, where so much information is gained by analysing spectra from stars, etc.

Diffraction gratings can be used to produce monochromatic light of a required wavelength.

Another use is “wavelength tuning” in lasers. The laser output can be varied using a diffraction grating.

Unfortunately, apart from the use of a gratings to produce specrta, many of the applications are difficult to describe in simple, non-technical, terms.

A diffraction grating acts like a prism to separate light into parts based on wavelength. It has small, usually periodic features that distort the angle of the incident light.

The polychromatic (multi wavelength) light source is composed of monochromatic (single wavelength) constituents. Upon interacting with the diffraction grating, light of various wavelengths spread at varying degrees. For more information on the effect of wavelength on diffraction see: How do shorter wavelengths of light provide higher spatial resolution images at smaller scales?

Diffraction gratings are used in systems needing high resolution separation of wavelengths. One of the most common uses is in a laser - like the green laser below - in which a monochromatic light source is an important feature to induce lasing.

Other common uses include various forms of spectroscopy, which use diffraction gratings to separate an unknown source of radiation into its spectra. An exciting application of spectroscopy is the analysis of gas spectra of cosmological bodies. By breaking up the electromagnetic radiation from distant stars into their spectra, we are able to know more about their chemical composition.

Images:Optical Spectrometers, Diffraction grating - Wikipedia

A diffraction grating is an optical component whose effect is similar to a prism: it splits white light into its component colors.

Grating (top), prism (bottom), from Diffraction grating

Some differences between gratings and prisms

• Gratings are usually (but not always) operated in reflection geometry, so they are not subject to the limitation that transmissive optical materials have--becoming opaque at UV and far IR wavelengths
• Prisms make one rainbow, gratings can make several
• Prisms operate by refraction while gratings operate by diffraction

How gratings work
A diffraction grating consists of a series of parallel slits, notches, lines, or steps (some kind of quasi-1D structure). When a plane wave is incident on this structure, each divot will act like a point source, emitting a spherical wavefront (or more accurately, a cylindrical one). For certain angles, there will be destructive interference, and for others, there will be constructive interference, and this will have a wavelength dependence. The preceding two sentences are a rough definition of 'diffraction.' A grating is a double-slit experiment generalized to infinite slits and with many colors.

image source: Waves

diffraction grating, from Physical Chemistry Laboratory

The grating equation is:
[math]d(\sin \theta_i \pm \sin \theta_m )= m \lambda[/math]
where d is the distance between lines on the grating, [math]\theta_i[/math] is the angle of incidence, [math]\lambda[/math] is the wavelength of light in question, and [math]\theta_m[/math] is the angle where the intensity maximum of that wavelength is found. The m parameter refers to the order of the diffracted beam (first rainbow, second rainbow, etc). People usually use m=1 when they can because it is brightest.

Examples
A real-life example of a diffraction grating is a CD. You might notice that the reflection is a rainbow when you hold it up to the light, and this is because the microstructure includes a series of parallel lines from which light can diffract. But the youngest Quorans might have never held a CD...
An example I like better is the wings of butterflies. Their color and iridescence does not come from pignment, but from a series of parallel ridges which diffract light.

image source: Nikon MicroscopyU | Polarized Light Microscopy | Introduction to Interference

now you're speaking my language, as I am the son of RA. ){R@*)(#D*IH #DIOHQIO@Hpooifhe4[f893y029hj3ipodehjd2u039dh2o
loosely translated in English, diffraction grating can be used to break the usable forms of light into its basic parts which actually have more subsections to the violoet, ultra violet, blue, and infrared, etc wavelengths that we have broken down so far. These forms of light can be used to transport data in the form of light as it is used in fiber optics, but through the air. The different wavelengths will help lay the foundation for storage of data on, not only human cells, but our close cousins the plant cells as they are the embodiment of these diffracted wavelengths of light bouncing of particles of various gases in the atmosphere. As well as give us a introduction into Trans-wavelength quantum ABC particles or (Trans WHQA BC Particles) across wavelengths of diffracted light. Also HALLOW-grams. Angels send them on Valentino Day.
Live long and prosper.

In high school we’re taught to think of light as moving in straight line rays. This is what we call “geometric optics.” However, the way light actually propagates is that whenever light reaches a point (any point at all), it then spreads out from that point in a spherical wave. So you have new spherical waves beginning and spreading out all the time, in an enormously complicated process.

Consider the simplest situation possible - a “plane wave.” Let’s say it’s moving in the positive x direction. So under geometric optics, we don’t think of any light as moving in the y and z directions. But I just said that light spreads out from every point in spherical waves - that would necessarily involve some y and z propagation. So, what’s going on?

The key is that this “spherical spread out” process is going on everywhere. To figure out what you will actually see at some point in space and at some time, you have to first calculate through all of the interference effects. It turns out that if you actually have an infinite plane wave, all of that y and z propagating energy cancels out via destructive interference. In the end, you are left with net energy propagating only in the x direction.

But now place some object into the situation. It will block some of the light, and the points in its shadow will no longer be sourcing new spherical waves. So that part of the whole situation described above is no loner present and cannot engage in destructive interference with any of the remaining light. You will no longer get a full “canceling out.” Now you will find energy moving in the y and z directions in certain ways. It’s once again the result of a hugely complex calculation, but the y and z components will no longer completely cancel out everywhere.

That is how diffraction works. Your grating element blocks portions of the light, and this allows other parts of the light that would have been cancelled out to no longer be cancelled out.

Hope this helps.

Stay safe and well!

Kip

____________________

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Diffraction gratings (often just grating) are used in a wide variety of applications. The most common use of gratings is spectroscopy. In spectroscopy you measures the intensity of light at different colors. A good example that you may be familiar with is the compact disc. CDs are basically diffraction gratings. As you know, CDs produce rainbows. Imagine recording the intensity of the rainbow from a CD -- that's spectroscopy. (Why bother with spectroscopy? Because you can do things like identify what something is made of.) Gratings have many other uses including pulse compression, image quality verification, and even color correction of optics.

The phenomenon of diffraction is seen everywhere in optics. If you step back and think big picture, your first step on the path of learning about gratings is to learn about the physics of diffraction. Your next step is to worry about gratings.

It is the combination of diffraction and interference that gives gratings the ability to separate light into its component wavelengths (dispersion). Diffraction by itself does nothing special, but with a grating, at any given angle you will get only reflected (or transmitted) light at a particular wavelength, since other wavelengths will destructively interfere. Good diffraction gratings are extremely difficult to make, since the grooves must be straight, parallel, evenly spaced and close together. The tolerances are extremely tight. Diffraction grating ruling “engines” that I have used have been mounted on vibration-isolated blocks in basements away from passing traffic, and they are amazing pieces of precision engineering. They might run continuously for many days to produce a good grating. Gratings would be prohibitively expensive were it not for the fact that processes have been developed to “replicate” good gratings.

The light does not need to be incident normal to the grating, but it often is. In fact, that keeps the mathematics simpler. The equation for normally incident light must be modified if the light is not normal to the grating. I describe the mathematics below.

Let theta be the angle required for constructive interference, “d” be the distance between two adjacent slits and lambda be the wavelength of the light. The path difference between light from two adjacent slits is d multiplied by sine theta. Or path difference = d (sin theta).

For a constructive interference maximum, d (sin theta) = m lambda (where “m” is a whole number).

However, if the light is incident at an angle “i” to the normal then the equation becomes: d (sin i + sin theta) = m lambda. The path difference for constructive interference must be the same, of course. So, the value of theta must be different for different angles of incidence. In other words, the angle at which a maximum occurs is affected if the incident ray is not normal to the grating.

This link has diagrams that should help with the formula derivations:

phy217 - instruments - spectrographs - the grating equation

Note: The formula involving "sin i" assumes the light is coherent before it reaches the double-slits. That's not always the case, depending on the experimental set-up.

An optical component called a diffraction grating splits (disperses) polychromatic light into its individual wavelengths (colors). Each wavelength of the polychromatic light that strikes the grating is scattered, reflecting from it at a slightly different angle. The periodic grating structure's periodic wavefront division and interference with the incident radiation cause the dispersion.

The desired wavelength range is then routed to a detection device after the spectrograph re-images the scattered light. Gratings are reflective coatings with parallel grooves developed on them that are evenly spaced and placed on a substrate.

What wavelength range the grating is best optimized for is influenced by the design of the grooves (blaze angle).

The spacing between neighboring grooves and the groove angle affect a grating's dispersion and efficiency. Gratings are typically preferable to prisms because they are more effective, offer a linear dispersion of wavelengths, and are free from the absorption effects that prisms experience, which reduce the range of usable wavelengths.

Diffraction gratings are very good at dispersing light due to interference. They are generally more useful than prisms, and so are used to show the underlying spectrum of wavelengths in a source. Thus they are the basis for most spectroscopic measurements. Diffraction gratings have the benefit that the degree of dispersion can be designed into the grating by varying the density of lines in the grating. Furthermore, the diffraction efficiency can be boosted in certain orders, especially the first order, using a “blaze". This makes them extremely versatile. Most spectroscopic measurements are made with spectrometers using diffraction gratings. Apart from an undergraduate lab, I have never encountered a spectrometer based on a prism. However, dispersive prisms are often used in lasers to selectively amplify certain spectral lines.

The usual, I measure the wavelength of a laser whose wavelength is well known.

If my numbers agree, the grating is working.

It spreads light into a spectrum according to a precise mathematical relation. This means that, knowing the spacing of the grating, you can determine the wavelength of light to extremely high precision. In contrast, a glass prism spreads the light out non-linearly.

This had been known for quite a while, but nobody could make precise gratings. Henry A. Rowland of Johns Hopkins University took on the challenge. He realized it was impossible to make a machine rigid enough, and described it as picturing the entire machine as being made of rubber. He invented complex feedback mechanisms to keep everything aligned. It took several weeks to make a three-inch grating, ruling three miles of grooves on a glass plate, 20,000 to the inch. During his career, he and his team made several hundred gratings.

Every measurement that contributed to the development of quantum mechanics traces back to one of Rowland’s gratings.

No quantum mechanics, no lasers, CD players, computers, LED’s, or solid state electronics.

Nowadays we have better techniques but they all depend on physics developed as a result of Rowland’s work. You can buy replica grating for pennies a square foot, and shopping bags made of it. And not one person in ten thousand knows the story.

https://www.scientificamerican.com/article/henry-a-rowland/ (Paywall but easily found in libraries)

EDIT:

Here’s a “cheap n’ cheerful” CD/DVD diffraction grating:

It’s an easy grade school project, and you can get some interesting spectra. This is the spectrum of compact fluorescent lamp.

I can’t figure out how to post the PDF file of instructions, but here’s a PNG version.

Enjoy!

Original Answer: the “split the DVD-ROM” method.

If you’re looking for a cheap diffraction grating, you can make a workable one from a recordable DVD-ROM. Carefully split the DVD into two layers; you’ll have two circular slices. One should have a vaguely purplish film if you look at it with a glinting light angle.

Here’s a screen shot showing what I mean. Notice that I’ve just “peeled” the left-hand disk from the right-hand disk. I started the process by gently pressing the tip of a sharp knife into the edge. I’m using the disk on the left.

Dissolve that film by swishing it gently in a tray of ordinary rubbing alcohol. (You’ll know you’ve got the right slice if the alcohol turns purple.) Rinse the slice in distilled water and blot it dry with a very clean lint-free cloth.

Use tin snips to cut small rectangles near the outer rim of the prepared slice.

Be very careful to handle the useful DVD slice and cut pieces by the edges only. You’ll notice I’m wearing gloves as well. These are light cotton gloves used by art conservators, and you can buy them in bulk. You can also use vinyl gloves that haven’t been powdered.

I made a video showing the process, but it’s too long to post here.

These are examples of a home made diffraction grating. It is not high technology and very simple yet lo and behold it did give results. Viewing piece is via black cardboard.

This cereal-box type diffraction with attached C.D can be positioned near DSLR camera. Recommended to use a stand to avoid hand movements.

First attempt looks awful! The CD clearly has a spectrum but the image is hazy.

This following image is much clearer.

With a home made device (using even a cereal box and C.D) the spectra of other light sources can be captured. This method is applied by professional astronomers for distant stars.

After many cereal boxes and tape, the final product does indeed work.

A very narrow slit in reinforced paper to avoid any threads. Finer this slit causes greater the resolution.

The following were using an inexpensive commercial lens. These are available here. Rainbow Glasses | Diffraction Glasses | Custom Options

Worth joining a local astronomy club to get ideas and practice.

A diffraction grating creates a very distinct interference pattern. When monochromatic light (say, a laser) shines on a diffraction grating, “constructive interference” creates widely spaced maxima.

But the spacing between each maximum depends on the wavelength of the light used. So when a beam of white light shines on a diffraction grating, the maxima for each component wavelength occur in different directions - hence instead of white light maxima, one would see color spectra - little rainbows at location of each of the maxima.

The simple answer is YES.

But the the question has a rich historical background which I attempt to discuss below.

This was the question that Prof. Max von Laue had asked more than a hundred years ago. And the positive answer to the question fetched him the Nobel prize for physics in 1914.

The whole story was this. Wilhelm Roentgen had discovered x-rays in 1895. He got the the first Nobel prize for physics in 1901. However, the nature of these rays were not known. That’s why Roentgen called them x-rays, x standing for the unknown, just like in our algebraic expressions. The real questions was whether the rays are a stream of particles or some sort of wave. In fact, Roentgen, in his pioneering article, entitled ‘A new kind of Rays’ postulated that they are “longitudinal” waves!

An older problem in science was that of crystal. Man found that some natural objects have nice geometric shapes, like salt crystal forming from its saturated solution. Whereas, others, like glass, have no such natural shape. So they classified the matter into two classes: crystalline (having natural shape) and amorphous (lacking any natural shape).

Naturally, of course, this curiosity arose in human mind: “Why are crystalline materials naturally shaped”? This question bothered greatest of scientist and they attempted to answer it.

One of them was Johannes Kepler, (yes, the astronomer). He was trying to explain the beautiful shape of snowflakes. He wrote his article entitled ‘De Nice sexangula’ (On Six Cornered Snowflake) as a new year (1611) gift to his patron: a nice new year card to have-an original research paper by one of the greatest scientists.

Much later, another great scientist, Robert Hooke came to similar conclusion. Yes, the same Hooke, after whom we have the the law of elasticity: Hooke’s law. He wondered what could be the reason for such nice external shapes of naturally grown crystals. In his 1667 book entitled ‘Micrographia’ he postulated that crystals are made up of some internal building blocks (Hooke was in pre atomic age), and the nice external shape of crystals are due to regular internal arrangement of these blocks.

Thus a postulate emerged that nice external shapes of natural crystals are due to regular arrangement of building blocks. And this postulate remained as postulate for more than two hundred years. There was no clear idea of what these building blocks were, neither there were any tools to see or study them.

When von Laue came to the scene the building blocks had already taken a form and a name: atoms. Thus von Laue had two questions:

Question 1: Are regular external shapes crystals due to regular arrangement of atoms inside the crystal as postulated by Hooke and Kepler.

Question 2: Are x-rays waves?

He combined these two questions into a bold postulate:

If crystals are regular arrangement of atoms
and
if x-rays are waves
then Crystals should act as a 3D grating and DIFFRACT x-rays.

Experiments were planned and conducted to look for this diffraction. And nature was kind. Diffraction happened. So in one go, Laue could answer both the questions positively:

Crystals are regular arrangement of atoms and x-rays are waves.

And humanity not only got answer to these long-standing questions, but also a tool to study and explore the structure of crystals in form of x-ray diffraction. A new field of x-ray crystallography was born. This was exploited by Bragg's (father and son) to solve several crystal structure. They won the Nobel prize just the year after von Laue, in 1915. Only father and son two have shared a Nobel prize.

Light gratings are used to diffract, or bend, light in a specific direction. They are often used in spectroscopy, where they are used to spread out light of different wavelengths so that they can be analyzed separately. They can also be used in imaging and optical communication systems. In these applications, the gratings are used to direct or focus light in a specific direction

Light gratings are also used in a variety of other applications such as laser cavity stabilization, beam steering, and the production of structured light patterns. They can also be used in diffraction-limited optical systems, such as microscopes and telescopes, to improve their resolution.

Light gratings can be made using a variety of materials and techniques, including metal, glass, and plastic. The most common type of grating is the ruled grating, which is made by ruling a surface with fine lines. The distance between the lines, known as the grating constant, determines the amount of diffraction that will occur. Another common type of grating is the holographic grating, which is made by exposing a photographic emulsion to a pattern of laser light.

There are also different types of grating geometries such as transmission gratings, reflection gratings and blazed grating.

Light gratings are widely used optical devices that diffract or bend light in a specific direction, they are used in spectroscopy, imaging, laser cavity stabilization, beam steering, structured light patterns, diffraction-limited optical systems, and many other applications.

CDs and DVDs have groove spacing that is on the proper order for diffraction of visible light, but your question is about a “laser diffraction grating”, not a visible light diffraction grating, and that makes me question if the answers already provided are sufficient for your intent. Were you looking for something like this?

Diffraction gratings are based on diffraction while prisms are based on dispersion, two very different principles.

From the point of view of applications, diffraction gratings offer at least two important advantages:

1. Higher intensity of the diffracted light: as light does not pass through matter (apart air) it is not attenuated so there is more “signal” to measure
2. On diffraction gratings it is possible to change somewhat the relation between the angle of diffraction and the incoming light changing both the distance between the grooves and the form of the groove itself

One important consequence of point 1 is that diffraction gratings are better (or the only choice) in regions of the light spectrum where the glass of prisms become opaque, like ultraviolet or infrared.

It is possible to build diffraction gratings using a process that draws on them very “thin” interference fringes: the so called holographic gratings that can be easily adapted to many applications.

Last but not least, the diffraction grating can be drawn on a concave mirror, thus focusing and separating light with the same device.

The lines of a diffraction grating need to have a spacing about the size of the wavelength of the radiation that you want to diffract. Visible light has wavelengths of several hundred nanometers, depending on the color. We are able to use machines to make scratches on a piece of glass or plastic with an accurate spacing of that size. However, if you want to diffract X-rays with a wavelength of one nanometer, you can’t construct a machine which can make scratches with that small of a spacing.

Natural crystals of pure elements have periodic structures on the scale of the size of atoms, which is around 0.1 to 0.3 nanometers. Thus they are the obvious choice for diffracting X-rays in that range of wavelengths. From the other direction, those X-rays are the obvious choice for studying the structure of crystals made of atoms, because they are the right size to do the job.

Simply put, a diffraction grating and a prism use different properties of light. They both separate the colours of light which is their common property. But the separation of colours is not the same by both.

Any object whose size is comparable to the wavelength of light would change the direction of light if light strikes such object. This happens in the same medium through which light travels. This property of light is called diffraction which is due to wave type behaviour of light and quite elaborate theories are developed to explain diffraction of waves in general; and of light in particular. Diffraction is observed in case of highly energetic electrons, neutrons and other charged particles. Diffraction of charged particles and neutrons find a number of applications in studies of materials.

For a prism on the contrary, you need two different media. Light changes its direction when it passes from one medium to another medium. This is called refraction. Here also, different wavelengths of light change their direction by different amounts. This property of light is called dispersion. It was first demonstrated by Newton. This the reason why we see a colourful rain bow where the minute droplets of water play the role of a prism. .

Its straightforward geometry. The screen needs to be approximately parallel but its easy to revise the math to account for other orientations.

A-level Physics (Advancing Physics)/Young's Slits Diffraction Grating[edit]

A diffraction grating consists of a lot of slits with equal values of d. As with 2 slits, when

, peaks or troughs from all the slits coincide and you get a bright fringe. Things get a bit more complicated, as all the slits have different positions at which they add up, but you only need to know that diffraction gratings form light and dark fringes, and that the equations are the same as for 2 slits for these fringes.

According to his diagram it looks like there is a big difference in angles from each of the slits. But, in fact, the screen is a long way from the grating and these lines are virtually (and considered to be) parallel Hope that helps

Diffraction grating | Interference of light waves

A grating is an optical element that uses diffraction to send light of different frequencies in different direction. Note that for historical reasons we talk about “single-slit diffraction”, “double slit interference” and then “diffraction” again for gratings with many parallel slits, but it’s all variations on the same idea of Fourier optics, whereby if you send light through an aperture, the pattern on a screen at a large distance is the square of the 2D Fourier transform of the function describing the aperture. So all diffraction with various numbers of slits is about the FT of various numbers of copies of the Boxcar function. (Some gratings have more sophisticated patterns than simple slits, but the same principle with the 2D FT applies.)

A grating is a physical object. Diffraction is a phenomenon that describes the behavior of light when it encounters a hard edge.

A diffraction grating is basically a reflective or transmissive substrate with some sort of pattern ruled on one of its surfaces. Like a series of finely scribed lines very close together, or finely scribed concentric circles or dots. The geometry is not important. What defines a grating is the fact that when light hits the surface, it diffracts according to the known laws of physics.

Gratings play an important role in spectrometers. These are instruments that allow light to enter an aperture and inside, a grating separates the constituent wavelengths of the source.

That would depend on what you mean by diffraction grating.

If you mean those thin plastic “replica” transmission gratings used in intro physics to demonstrate diffraction of visible light, then probably not. The electrons of the appropriate wavelength would not have the energy to get through the plastic film.

If you mean a ruled metal, reflection grating used in optical spectrometers, then I would say probably not because I don’t think the electrons would reflect in the same way light would. However, I wouldn’t rule it out (if you will pardon the pun). I just don’t know if this experiment has been tried.

But if you are willing to expand your definition of diffraction grating to include the periodic arrangements of atoms on the surface of a material, then, yes, for sure. The technique called LEED (low energy electron diffraction) is a standard technique in surface science for determining the atomic structure of the surfaces of materials. It is just what the name implies. Electrons with an energy such that their wavelengths are of order the interatomic spacings of the material are directed onto the surface where they diffract while reflecting off the surface to a position sensitive electron detector. The resulting diffraction patterns can be analyzed to determine the atomic structure of the surface.

If you mean a physical model rather than a mathematical model, just light a candle under a slide of glass to form soot, then use a razor blade to cut a line through the soot as straight as you can (a ruler will help), then with a paper page behind the slit, shine a laser pointer at the slit and you will see a central spot with smaller light spots on its sides; this is a diffraction pattern on the paper; you can also try just shining the laser on the edge of the razor blade.

For interference, cut another slit parallel and as close to the original slit as you can, shine the laser pointer at the double slit, and you will see constructive and destructive interference in the form alternating light and dark lines on the paper. For easier results, you can buy a double slit from Amazon!

Diffraction gratings are most often implemented on metal, though replica gratings may be implemented in dimensionally stable polymers.

Scratches make very inefficient gratings, but certainly usable. (Shaped grooves, usually triangular in cross-section are usually used and they are called “blazed.” The blaze angle determines which diffraction order will be observed.)

The length of the scratch is determined by how wide the beam of light is falling on the grating. In most instruments, you want to collimate light falling on the grating and use a slit to create a line source. The length of the slit determines the length of the rulings. The width of the slit determines the spectral resolution.

If you are just using the eye and some light source in the environment, about a centimeter will do. I once made a diffraction spectrometer from simply two razor blades spaced parallel to each other and closely spaced. It was not efficient, but it worked well enough.

If your source is a laser beam, and the beam is two mm in diameter, your rulings need not be longer than 2 mm.

Most gratings I have used have been about 2 to 4 cm long and roughly the same width.

If you are going to try to put scratches in at anything close to 1000 per cm, it is going to take a precision machine to make the scratches. As other people point out, you could try making lines at a more convenient spacing and then photographically reduce them using photographic lithography.

For practical information on how to use an optical disk as a grating, see Tim Cole ‘s excellent answer. (You can click on the word answer if you like.)