We at Dangerous Laboratories enjoy experimenting with two different lasers: a diode pumped solid state laser and a sealed tube carbon dioxide laser.
What you see here is the Dangerous Laboratories "Laser Light Show" utilizing a 60 Milliwatt, 532 Nanometer (Green), Diode Pumped Solid State (DPSS) Laser . It is easy to build your own laser light show using a laser source, a speaker, motor, mirror, plastic film, and mirrored "Disco Ball"
First, the speaker is oriented so the speaker cone is facing up. The plastic film is then placed over the speaker cone and taped into place on the sides of the speaker. Any thin plastic film will do. A sheet of thin latex rubber would probably work, too. A small mirror is affixed to the film directly above the center of the speaker cone with double sided tape. A small mirrored "Disco Ball" (available at some novelty shops) is attached with a piece of thin wire to a slow speed motor. We used a motor that we found in an old microwave oven. When sound is played through the speakers, it causes the plastic film and mirror to vibrate. The laser beam is reflected off the mirror, which creates a unique and ever-changing pattern on the rotating ball. A fog machine is used to enhance the effect. Notice: extreme caution must be used with this type of device! Even a small laser pointer can cause eye damage! You must wear protective eyewear when testing or operating this device. Laser protective goggles are available sometimes from Ebay or always from Edmund Industrial Optics.

And Now on to the 35 Watt Sealed Tube Carbon Dioxide Laser!

We decided not to use the carbon dioxide laser with the Laser Light show because:

1) The beam is invisible and 2) It can burn holes in things from ten feet away!

The laser was purchased on Ebay. It was removed from a "Domino" Laser Marking Unit. We found the perfect enclosure for the laser head and added the "Ghostbuster" logo. This is a Radio Frequency excited unit. It won't operate unless the tube is mounted directly on a metal surface. In this case, the laser tube was mounted directly on a stainless plate and then installed in the black metal box. The large box in the rear is the 28 volt DC power supply, the small box on top of it is the RF exciter. Here the laser is energized. The spot of light is not the beam itself, but the plywood starting to incandesce and burn from the heat of the beam. CO2 lasers eminate an invisible beam in the 10.6 micron infrared region.
An Excellent resource for anyone wanting to build a laser is "Build Your Own Laer, Phaser, Ion Ray Gun & Other Working Space Age Projects" by Robert Iannini. This book has a chapter on building a "Flowing Gas" CO2 laser. This type of laser is relatively simple to build and can generate tremendous amounts of heat! The book is available from online retailers like Amazon.com.
Click Here to see Osama Bin Laden feel the wrath of the Ghostbuster from 10 feet away!
The following "Brief Description of General Laser Theory" is from the aforementioned book:

LASER is the acronym for "Light Amplification by Stimulated Emission of Radiation." Laser light differs from conventional light in several aspects. Even though both are electromagmetic in nature, laser light has certain properties that make it highly desirable in a multitude of fields and applications. Unlike conventional light, laser light is highly monochromatic, that is, pure light of almost a single wavelength or small line width (bandwidth). It is also temporally and spatially coherent. One may think of temporal coherence as a source of light where if the observer were to snap a picture of the wave, he would observe a group of peaks and valleys occurring with equal separations or wavelengths. This quality of the light contributes to the sharp line width approaching spectral purity. Temporal coherence is the time relation of the field intensity at a particular point in space. Spatial coherence of the wave now is tbe valley and peaks remaining stationary relative to space and position. It is this characteristic that gives the laser beam directionability due to the minimal constructional and destructional interferences. We shall refer to laser light as being both temporal and spatially coherent and spontaneous light as being random and unsynchronized.

Atoms absorb or emit energy in thc form of electromagnetic waves as a result of electrons changing from one energy level to another. These energy levels are numerous and well defined being characteristic of the particular atom in question. They also have an equivalent frequency response defined as resonance that is functional of the difference in energy of these levels as stated by the familiar relation E = hfc.

Absorption is the result of electrons jumping from a lower state to a higher state (excitation) taking energy at the resonant frequency from the system. Typical are the spectral lines of absorption in spectrographic analysis. An excited atom may now contribute this energy to a system in the form of spontaneous or stimulated emission. Spontaneous emission is the random natural decay of these higher energy levels dropping to their normal lower
rest levels and emitting energy equivalent in wavelength to that particular transition. This energy equivalent bandwidth is broad and incoherent. Energy must obviously be externally supplied to the atom for it to achieve a higher energy state.

Stimulated emission is the reciprocal process of resonant absorption and it only occurs when a population inversion is produced. A population inversion is when a higher energy level contains more population than its lower counterpart. When this occurs stimulated emission is easily obtained by photons of energy near to that of the inverted transition now triggering other identical electrons to drop to a lower level producing the in-phase coherent emission energy characteristic of the laser beam.

The trick is to create this necessary population inversion between these levels in question, by forcing, or pumping externally. Achieving this unnatural phenomena is accomplished by several different means, usually depending on the particular laser in question. The usual means is to excite a medium containing three or more involved energy levels. These levels are usually pumped either electrically or optically to their respective excited states. If part of this decay from the highest level drops down to the intermediate level and adds to the population, temporarily causing it to have more population than the ground level, this creates the population inversion necessary for stimulated emission between the intermediate and ground levels. This emission when directed between two mirrors such as a Fabry-Perot resonator is reflected back through the laser medium many times stimulating more photons and exiting the device as a powerful beam of energy.

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