Currently, they are just suggestions. (If you can't wait, there are also some links to Web sites with educational laser projects below.) Eventually, additional details of the setup and required supplies will be added. However, even then, in most cases, most of the details will be left as an exercise for the student. What fun or challenge would it be if we told you everything? After all, besides its educational value, hands-on experience should indeed be both fun and challenging! However, where more information is available in this document, links are provided.
A 1 to 5 mW internal mirror helium-neon laser will be suitable for most of the experiments (though a somewhat higher power one would be better for those like holography). It should be possible to procure such a laser for under $50, possibly under $25 depending on your resourcefulness and scrounging abilities. See the chapter: Laser and Parts Sources.
Some experiments may require a polarized laser but for most, any type will do, even a better quality (one with an adjustable focusing lens) laser pointer - and those are practically given away in cereal boxes these days. :) Where access to the laser cavity is required, an external mirror HeNe or Ar/Kr ion laser will be needed. A one-Brewster HeNe laser setup can be put together quite inexpensively (probably under $100) using a surplus one-Brewster HeNe tube and power supply, the OC mirror from a deceased HeNe laser, and some scrap materials available in any well equipped junk box. Of course, if you have access to a nice lab laser, that would be fine as well but probably not nearly as much fun or as rewarding compared building one (at least partially) yourself. :)
Alternatives like bare laser diodes and appropriate drive circuitry may be more desirable for projects like laser communications where modulation is required. And, other color lasers (than the boring red HeNe or laser pointer) will be desirable for laser display.
In addition, those experiments requiring access to the interior of the resonator of an external mirror laser may expose the user to potentially lethal voltages in the vicinity. If possible, any exposed high voltage terminals should be well insulated or blocked from accidental access. And, where all you have is an exposed HeNe laser tube and separate power supply, building all this into a safe enclosure is highly recommended.
Read the chapter: Laser Safety in its entirety and follow its guidelines - particularly in regards to the safety of others who may not be as aware as you in dealing with your equipment.
Basic principles:
Now, what happens if multiple dichroic mirrors are placed in series? Under certain condition, more light will get through than might be expected. For example, using the same example as above, if T = .1 for both mirrors, the resulting output may actually be as high as for an equivalent mirror with T = .05 (rather than T = .01). Why? Under what conditions will this happen? How does the T factor of each mirror affect this behavior? What other factors are important?
Here are some suggested experiments and questions to ponder using this rig:
o--- NC (Light) COM ---o/ o--- NO (No light) +6 V o-------+---------+---------------+----+ (4 AA Cells) | | | | | \ _|_ )|| K1 / / R3 1N4148 /_\ )|| 6V coil \ R1 \ 1.5K | )|| 500 ohms / 3.3K / | | \ | +----+ | | | __|__ | 5.6K B |/ C LIGHT ----> _/_\_ PD1 +------/\/\--------| Q2 2N3904 Sensor | | |\ E Photodiode | B |/ C | PDB-V107 +-------| Q1 2N3904 | | |\ E | \ | | +->/ R2 | | | \ 100K | | | / Sens. | | | | | | Return o-----+--+---------+--------------------+