A laser will go through the lense of the eye without having any effect, and the lense is what determines vision loss, so laser pointers are not likely to affect your vision. It takes a powerful laser, much more powerful than a pointer, to affect tissue so I don't think your immature friends have done you any harm.

It looks like current green and probably blue, laser diodes are made primarily by frequency doubling. Frequency doubling means that an infrared beam is pointed through a crystal which causes the frequency to double. If the IR beam is 1064 nm, the output beam will be 532 nm green or blue. The extra crystal is the cause of the extra price.

I don't know why normal green led technology isn't used for green pointers. Perhaps no one has perfected it in a small package yet. Anyway, laser diodes are made of materials that have an intrinsic "energy bandgap," which determines the wavelength of light emitted from the laser. Some materials may have a broader bandgap, but not enough to tune the laser over multiple colors.

Those laser pointers used in business presentations and school lectures--is there any danger to the eyes if they are pointed directly? And does the answer change depending upon whether one is talking about humans or dogs or cats, for example? No, those lasers are not dangerous to people or any large animals. Their power is firly low, and the beam is not very precise. The beam shape is a primary factor which makes similar-powered scientific lasers more dangerous. Well-shaped beams can focus to a much smaller spot than irregular beams.

All the same, you will see stars if you look at the beam directly. The brightness level is not too different from looking directly at the sun ,which is dangerous for other reasons, mainly unseen UV and IR light. There is a device called an optical parametric oscillator that can increase the wavelength, i.e. reduce the frequency of a laser. If you want to increase the frequency, i.e. reduce the wavelength of a laser, this can be achieved by using the laser to pump another laser, a dye laser for instance.

Would this device work with a laser pointer? I would like to add something to the end of it rather than mess around with the internal parts. You would use the laser pointer as a pump for the laser you would have to construct outside the laser pointer. No need to take the laser pointer apart, but you would need to build some sophisticated optics for this. Actually the green laser pointers that are commercially available use a red laser to pump another laser, this time green. So they are actually two lasers in one device.

I've been wanting to buy a blue laser pointer but found that the only ones with the technology to create them and who hold the patent are a select few so any such laser pointer would cost someone about $1,000. Green laser pointers cost about $100, and the common red ones cost maybe $20 at most. Why the extreme difference in price? What are these diodes and why are they so difficult to make?

You will have to wait a little while to buy a cheap blue laser pointer. The reason is quite simple. Red laser diodes were invented 15 years ago. Green laser diodes were invented 5 years ago, and blue laser diodes were invented last year. Similar to DVD writers, flat-screen TVs, and other new products, the price drops dramatically as time passes. Mainly, this is because one company owns a patent at first and can chjaarge whatever they want. When the patent expires, or alternate technology is invented, the price comes down.

There is nothing particularly difficult about making the diodes. Figuring out how to make them, which semiconductor materials, deposition, heat-sinking, is the hard part. But like I said some of the laser pointers can cause a little harm to your eyes, so if you want to get one or make one, make sure that you don't point it at anyones eyes. Even though you have friends that point there lasers in your eyes thinking that it is funny, which it isn't, to wrongs don't make a right. Just show them how more muture you are.