# All about cheap Reflection Diffraction Gratings-Self manufacturing!

by shubham | | 981 views | 4 comments | 04 Apr 16:13

I am working towards the prototype of a spectrometer with a light source to work in a range of 400-1100nm. Left part is an incandescent bulb which is fitted in a reflector and lens assembly to focus the light into the slit. Source assembly is equipped with height adjustment unit. Right part shows the optical components - two concave mirrors and a DVD used in reflection mode. Will also make microcuvette: pathlength 1mm for very turbid liquids like milk.

## Help

I'm facing problems with interfacing TCD1304DG. Any leads appreciated.

### Doubt: 2

I want to use 4.7GB DVD-R as reflection grating. Is there any tricky way to split it up to get the reflection part out neat. I always end up splitting it untidy. I want to use it as front surface reflection grating.

### Doubt: 3

While using DVD/CD as grating, we have two spectra (plus and minus) on either side of the zero order. Is there any preferred portion? Spectrum towards the outer radius appears more straight but less intense whereas spectrum towards inner radius is more intense but also more curvy. Would the curve bother us, since we only capture a line?

### Doubt: 4

Can holograms (security stickers), with no design, be used as diffraction gratings?

### Case:1

I called a DVD-ROM manufacturer in Delhi, and asked if he could make a straight groove 'DVD' rather than conventional. Apparently I came out as a fool. But I, still, am very hopeful that this could be done in some good part of the world. It consumes a one time cost of making a Nickel master (die-mould) which could be easily copied from a professional diffraction grating, but the running cost would be rather cheap.

### Request: 1

If there's someone with big money (and bigger heart) who'd like to try this method, please consider. It could be a great business opportunity given the increasing craze of DIY spectrometers. Grating manufacturing could be done in a way very similar to CD/DVD or hard-substrate holograms.

### Request: 2

Can someone please make a surface property for DVD in Tracepro. I can get straight grooves, but have no idea how to get curved grooves.

### Gyaan

Diffraction gratings are one of most critical and expensive part of any good spectrometer. Aspheric mirrors can be manufactured as low as 0.2$/piece, but gratings are blocking the way to high quality cheap spectrometers. CCD cost is okayish (3.7$). There's a huge potential to manufacture aspheric concave diffraction gratings as low as 2\$/piece, which could bring a spectrometer in each household.

## Team up!

If there's someone who like to collaborate in this project, you're most welcome. Any suggestion will be appreciated.

## Thanks Publiclab

Thanks to Publiclab founders (Warren et al) who have made this outstanding platform.

I wonder if you could make a diffraction grating by using the negatives of a film photo of narrowly spaced lines?

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Thanks Warren for the advice. I searched a bit on internet and I think its important that the silver salt crystal to be of sub micron size to get satisfactory results. This is possible with good quality film. Shooting such fine lines would require Laser interference pattern right? I wonder if a DVD writer could be hacked to shine straight grooves into the film?

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Okay, you and I want the same thing, for different reasons. I am looking for pure aluminium holographic foil, which is definitely being produced, but I am not sure of the quality. On the other hand, you can get away with Pet, holographic film, which is almost as cheap as wrapping paper, and the quality is remarkably good. How good it is, compared to a commercial grating, is unkown, but certainly better than using a DVD...