Laser beam shaping Hi I like to build a laser pointer that reflects different shapes for a project I am working on. I know this can be done with Diffractive Optical Elements. Are there other options? DOEs are expensive. 
I see all these laser pointers with different shapes (arrow, hand etc), I am suspecting there is a lower cost but lower performance way. Any pointers?
 A: It is possible to do diffractive optics really cheap - either with photography (with a non-digital camera) or a widely available DTP polygraphic technique. What you need is to:


*

*Make a Fourier transform of an image you want to have (it should be relatively simple).

*Make an image which is white when the real part of the FT is positive, and black - when it is negative. 

*Either print it, make a photo with a classical camera, develop the film and use it as you diffractive device OR prepare a pdf/ps file and go to a DTP point (resolution up to 5000dpi should be possible; a few $ per A4 sheet on which you can make a lot of patterns).


As it uses absorption, not refraction, so some loss of intensity is unavoidable.
Some patterns can be found here (mainly: Fresnel zone plates and diffractive gratings)
http://migdal.wikidot.com/en:spz-moire-ps
A: One option would be to expose a hologram into photographic film (or ideally a photographic plate).
I also heard of people who wrote holograms into (or onto) plastic but I'm not sure if you need pulsed lasers to write those holograms.
A cool solution is to use a phase-only spatial light modulator, e.g. by Hamamatsu. The Hamamatsu device costs probably 5000 EUR but possibly you can use a normal LCD screen after you removed the polarizer foils.
The coolest solution (in my opinion) is to build an acousto optic deflector. There you use an ultrasound transducer to create a thick grating within some transparent crystal  (but I think glass works as well). The laser light will be deflected. You can vary the angle of deflection by changing the frequency of the ultrasound. You can put two of these things behind each other. Then you can scan the beam in XY (like an oscilloscope). Note that this isn't really shaping the beam. But you can scan the beam very fast.
I always wondered if one could write a hologram on a DVD or Blue-Ray medium. If one understands the burners firmware good enough to put the data into specific places this might actually work. And 50Gb of information would make for some pretty detailed pictures.
A: Some time ago I thought of the possibility of engraving microstructures with a disc burner on a CD/DVD/Blue-Ray to use them as diffracting plates, as @whoplisp mentioned in his answer. But it is now that I find this SE question. I'd like to share some sites I saved, where some ideas/software may be found useful to build low-res, low-efficiency DOEs or holograms at home: Controlling the burner, forum, another forum, article, patent. To finish, another maybe related article.
