The word "laser" is in fact the acronym for light amplification by stimulated emission of radiation, in French "amplification of light by stimulated emission of radiation". The first laser was developed in 1960 at Hughes Research Laboratories in California using a silver-coated ruby cylinder that acted as a resonator. Today, lasers are used for many purposes, such as taking measurements or reading encoded data, and there are many ways to make your own laser, depending on your skills and budget.
Part 1 of 2: How a laser works
Step 1. Obtain a source of energy
The laser is the result of stimulation of electrons which emit light on a certain wave. This process was first described by Albert Einstein in 1917. In order for electrons to emit light, they must first absorb enough energy to put them into a higher orbit, where they will discharge that energy to return to their original orbit. These energy sources are called "pumps".
- Small format lasers, such as those used to read CDs and DVDs, as well as laser pointers, use electronic circuitry to supply electricity to diodes that you use as pumps.
- Carbon dioxide lasers use electrical discharges to excite electrons.
- Excimer lasers get their energy from chemical reactions.
- Lasers built around crystals or glass use powerful light sources, such as an arc or an electric torch.
Step 2. Pass the energy through an amplifying medium
An amplifying medium serves to amplify the power of the light supplied by the stimulated electrons. The amplifying medium can be made from the following.
- Semiconductors made with gallium arsenide, gallium aluminum arsenide or indium aluminum arsenide.
- Crystals like the ruby cylinder used for the laser at Hughes Research Laboratories. It is also possible to use sapphire and garnet or optical glass fibers. These glasses and crystals are first treated with ions from rare metals.
- Ceramics, which have also been treated with rare metal ions.
- Liquids, most often dyes, a laser has even been made using gin-tonic as an amplifying medium. Food gelatin could even be used as an amplifying medium.
- Gases, such as carbon dioxide, nitrogen, mercury vapors, or a mixture of neon and helium.
- Chemical reactions.
- Electron beams.
- Nuclear materials. A uranium-based laser was first produced in November 1960, just six months after the first laser made with a cylinder of ruby.
Step 3. Set up mirrors to contain the light
These mirrors, called resonators, keep light inside the laser chamber until it reaches the desired power before being released, whether through a small opening in the laser chamber. one of these mirrors or through a lens.
- The simplest arrangement of resonators, the linear resonator, is set up using two mirrors each arranged on the opposite side of the laser chamber. This type of laser produces only one output.
- The ring resonator, a more complicated type of resonator arrangement, requires three or more mirrors. It will be able to create a single beam, using an optical isolator or several beams.
Step 4. Use a converging lens to direct light through the amplifying medium
In addition to mirrors, the lens will help focus and direct light so that the amplifying medium receives as much of it as possible.
Part 2 of 2: make a laser
Buy a kit to mount a laser
Step 1. Educate yourself so you can find a seller
You can go to an electronics store or search online by typing in "laser kit", "laser module" or "laser diode". You should find the following items in a laser kit box.
- A control card (it can sometimes be sold separately). Obtain a control board that allows you to adjust the electric current.
- A laser diode.
- An adjustable lens made of plastic or glass. Usually, the diode and the lens are packed together in a small tube (sometimes these components can be sold separately without the control board).
Step 2. Mount the control board
You will need to assemble the control board for most kit lasers. These kits contain a card and its components that you will have to solder on it by following the diagram that will be provided. You will find the ready-made control card in other kits.
- You can also make your own control board if you have the electronics skills to do the job. For example, you can take a model from the LM317 control board to make your own board. Be sure to use an RC circuit to protect the light source from possible electrical spikes.
- Once you have assembled the control board, you can test it by plugging it into a light emitting diode (LED). If the LED does not light immediately, adjust the potentiometer. If this still does not resolve the problem, recheck the board to make sure you have properly connected the components.
Step 3. Connect the control board to the diode
If you have a digital multimeter, you can connect it to the board to check the amperage that the diode receives. Most diodes work well with currents between 30 and 250 milliamps (mA), knowing that 100 to 150 mA will be enough to power the beam.
Although a higher amperage will produce a more powerful beam, the additional amperage of current flowing through the diode will shorten its life
Step 4. Connect the power source (battery) to the control board
The diode should start to glow brightly.
Step 5. Adjust the lens to create the laser beam of light
If you are pointing the laser at a wall, adjust the lens until you see a nice, sharp dot forming.
Once you have set the beam, put a match through the beam and adjust the lens until the match smokes. You can also try popping balloons or piercing a sheet of paper
Build a laser with a recovery diode
Step 1. Get an old DVD or Blu-Ray recorder
Try to find one with a write speed of 16X or more. This type of equipment has diodes that provide a power of 150 milliwatts (mW) or more.
- A DVD recorder has a red diode with a wavelength of 650 nanometers (nm).
- A Blu-Ray recorder has a blue diode with a wavelength of 405 nm.
- The DVD recorder you are going to recover should still be able to copy DVDs, even if it does not always work (in other words, the LED must be working).
- Do not use a DVD player, CD player or CD recorder with the DVD recorder. A DVD player also has a red LED, which, however, is not as powerful as that of the DVD recorder. The diode of the CD recorder is strong enough, but it emits infrared light, which will produce a beam that you cannot see.
Step 2. Disassemble the diode
Flip the card over. There you will see four or more screws that you will need to remove to be able to separate the card and recover the diode.
- Once you've disassembled the board, you'll see a pair of metal rails on it that are held in place by screws. They bind the elements together. When you disassemble the rails, you can take them out, then take out the laser.
- The diode will be smaller in size than a penny. It has three metal pins and it could be that it is embedded in a metal support, covered or not with a transparent glass which protects it or else it will be mounted without any form of protection.
- You need to remove the diode from the rest of the components. You may find it easier to remove the heat sink before removing the diode. If you have an antistatic wrist strap, wear it while you remove the diode.
- Handle the diode with care and even more carefully if the diode was not protected. You should keep the diode in an anti-static container until you want to use it for your laser.
Step 3. Obtain a converging lens
You will need to focus the diode beam through a converging lens to get your laser. There are several ways to do this.
- Use a magnifying glass. You will have to move the magnifying glass in front of the beam to find its ideal position to produce a laser and you will have to start over each time.
- Obtain an assembly kit with a lens in a tube and a low power diode (eg 5 mW) and replace the diode on your DVD recorder with this one.
Step 4. Obtain or assemble a control board
Step 5. Connect the diode to the control board
Connect the positive pin to the positive edge of the control board and the negative pin to the negative edge. You will notice that the pins are in different places on the diode depending on whether you have chosen a red diode DVD recorder or a blue diode Blu-ray recorder.
- Hold the diode with the pins facing you, then turn them so that the pins form a triangle that points to the right. On both types of diodes, the positive pin will be on top.
- If you have a red DVD recorder diode, the center-most pin, which forms the top of the triangle, is the negative pin.
- The bottom pin is the negative pin on a Blu-Ray recorder diode.
Step 6. Connect the power source to the control board
Step 7. Adjust the lens to adjust the laser beam
- The finer and more focused the beam, the more powerful the laser will be, but it will only be effective over the distance you focus it. If you focus the beam for a distance of one meter, it will only be effective for one meter. When you are not using your laser, adjust the lens to get a beam the size of a pingpong ball.
- You could keep the laser you just mounted in some kind of case to protect it, for example in an electric torch or a battery box, depending on the size of your control board.
- Always wear protective eyewear specified for the wavelength you are going to produce (in this case, the wavelength of the laser diode). Protective glasses for laser have a color complementary to the color of the beam, they are green for red lasers of 650 nm, orange-red for a blue laser of 405 nm. Do not replace them with a solder mask, goggles, or sunglasses.
- Do not aim the laser beam at your eyes or the eyes of another person. Class IIIb lasers, those described in this article, can damage the eyes, even when wearing specially designed glasses. It is also forbidden to point this kind of laser at someone else.
- Do not point the laser at a reflective surface. A laser is a beam of light that can be reflected like any other type of light, with far greater consequences.