This type of hologram is known as a white light or rainbow hologram as it can be viewed under white light, where as other traditional forms of hologram need to be imaged using illumination of the same wavelength with which they were made. 

A white light hologram is effectively a double hologram of both a slit and the object to be imaged. The slit diffracts light of different wavelengths through different angles, meaning that as the hologram is turned, the colour changes. 

https://en.wikipedia.org/wiki/Rainbow_hologram

Holograms are formed by Bragg planes within the recording medium which capture phase information of the light when the hologram is being recorded, however the same effect can be achieved using a thin film or ridge effect. 

Holography can be used to produce a wide range of optical elements, including gratings and wavelength specific mirrors and lenses. 

https://en.wikipedia.org/wiki/Holographic_optical_element

As well as wavelength dependence, HOE's can also be used to produce gratings that might otherwise be difficult to produce, such as a sinusoidal grating, and can also be made smaller and more cheaply than traditional optics. 

In terms of changing the spacing of the ridges/groves/diffraction planes, in practice a small change might be seen if the hologram is heated or deformed.

Thank you sir for such an excellent explanation.

I can't wait to use these as diffraction grating for my home-made spectrometer. Could you please guide what modifications would be required to make gratings from existing hologram stickers setup? Would slit width determine the 'groove spacing'?

As I understand, we won't need any 'object' while exposing the nickel master? 

For your application, is there a reason why you can't modify a CD to use as a diffraction grating? I noticed you have asked other similar questions relating to this?

@Alexander : I guess straight grooves works better than curved ones? I don't have an explanation why, though I'm searching for the satisfactory reasons for this 'general' notion.

Main problem with DVD is that to use them as front reflection element, its becomes quite tricky to split it along the width. I am looking for a more permanent yet affordable solution. 

@ Shubham:

Straight grooves (resp. lines) give straight lines in the spectrum - making the optical setup less sensible to misalignments and making observation easier. Curved lines/grooves (as from DVD diffraction) result in a 'curved spectrum'. It depends: if you e.g. use a CCD line sensor as the optical receiver, it does not matter whether the spectrum consists of lines or curves. On the other hand, if you use a 2D camera chip, it can become difficult to compensate for the non-straight lines.

DVDs are easily divided: first separate the layers. Then either use 'brute force' (and wear safety goggles!) - or use a cutter to first scratch the lines along which you want the disc to break (no need to completely cut the DVD - just scratch deep enough). Then apply the force to make the DVD break along the lines.

Regards

Thanks U. Dreher again! 

This simplifies a lot of my worries.

Some say DVD simultaneously behaves like a (Fresnel?) lens too, leading to some complications. What do you think?

DVD segments behaving line a (Fresnel?) lens ? As far as I know: no.

At least regarding the use as a reflective grating. Don't know about trying to use them as transmissive gratings: this would require to remove the reflective layer chemically. As there is always some attenuation coming with transmission, you better use them in the reflective way where lens effects are not to be expected (if you do not bend the DVD segment).

DVDs are certainly not ideal: you have only these grooves - not continuous lines. But at least for hobbyist purposes, DVDs are really useful as reflective gratings. And for these applications it normally does not matter that you get these curves instead of straight spectral lines.

Regards

I am working on a milk analyzer device for developing countries and need to make a spectrometer for the same. Cost is the main constraint here. I want to manufacture the whole unit within 40$. Therefore I turned to DVDs and test them for initial experiments.

I'm sure there are alternative ways to manufacture concave gratings just like CD-DVDs within 4$.

Sadly I couldn't find any data on efficiency of DVDs as gratings.