How is laser vision correction done? Pros and cons of the operation. Making a laser from a DVD drive with your own hands How to make a laser from a remote control

I wanted to collect in one topic the answers to all the questions that newbies have, since many people ask the same questions and flatly refuse to use the search. I will try to explain everything superficially, without going into details, in understandable language. Over time I will add other materials.

Introduction

The full name of modern semiconductor lasers is “semiconductor injection heterolasers.” This includes:

Laser diodes and arrays based on them, including those with feedback photodiodes, pulsed or continuous operation with radiation output directly, or through a fiber, or through an integrator;

Pulse laser emitters, which are a pulse current transformer with a laser diode in the secondary winding;

Actually lasers, which are an integrated driver whose load is a laser diode.

For pulsed operating mode, this is a pump current pulse generator. For continuous operation it is a DC generator. The laser diode has a diode-type current-voltage characteristic, but is “built” not on a conventional p-n junction, like the first homo-lasers, but on heterojunctions, which act as emitters for charge carriers, simultaneously localizing them in the active region and an optical waveguide for radiation. How it works: The pump current creates an inversion of the population of charge carriers in the energy bands of the semiconductor material of the active region: electrons - in the conduction band; holes - in the valence band. The process of their recombination begins spontaneously, perhaps with one single pair. But the photon born in this case repeatedly passes through the optical resonator formed by the mirrors of the active region, literally collapsing electrons into the valence band, where recombination occurs, which is of an avalanche nature, when all recombining pairs simultaneously, i.e. with one phase, produce photons. These photons also pass through the optical resonator many times, thus creating positive feedback, which is an indispensable condition for generation. In fact, it is more correct to call lasers optical quantum generators, because they do not amplify light (light amplification...), but generate it. Superluminescent LEDs provide light amplification. Laser structures, from which laser crystals are subsequently made, are grown using various epitaxy methods, usually on n-type substrates. The profile of future crystals is formed by various methods: - photolithography; — pyrolysis; - proton bombardment. Ohmic contacts and solders are applied to the epitaxial wafer before it is separated into crystals. Optical resonator mirrors are not ground or polished, but are produced by cleaving along natural cleavage planes, which are present in any single crystal. To ensure that the mirrors are strictly perpendicular to the layers of the laser structure, the single crystal is oriented before cutting onto the substrate along crystallographic directions using X-rays. If the radiation from the rear mirror is used, it is for a feedback photodiode. In other cases, reflective coatings are sprayed on it. To facilitate the emission of radiation from the front mirror, anti-reflective films are sprayed onto it. Types of laser diode housings can be viewed Red (wavelength about 650 nm) and infrared (IR) (780 nm) diodes can be obtained from DVD burners. You can also use CD burners or DVD Combo drives (they only have powerful IR). A list of drives containing those suitable for laser design can be found in the table. Not all drives that are suitable are included in the table. Pay attention to column No. 4 in the table, it shows the write speed and the current that needs to be fed to the diodes; the higher these indicators are, the brighter the diode will shine (higher power). Again, if you took an LD from a drive that is not on the list, be guided something like this: for a diode from a drive with a write speed of 16x, it is advisable not to supply more than 250-260mA, for 18x - 300-350mA, 20-22x - 400-500mA, and please publish this drive in the appropriate topic. Find out how to properly remove the diode from the drive. You will find a violet (405nm) diode in Blue-Ray drives. You can buy infrared 808nm diodes in the store (they are usually used in green lasers for pumping crystal gluing). Lasers with other wavelengths are built using DPSS technology. What stands for Diode Pumped Solid State Laser, i.e. the required wavelength is emitted by the active element, which in turn is pumped by the LD. Yellow laser diodes have not yet been encountered; green ones exist in nature, but their prices are still very high. Example. How does a green (532nm) DPSS laser work: The installation contains components such as 808nm IR LD, yttrium vanadate crystal, KTP crystal, and “special” mirrors. The crystals are located in a “single” resonator, that is, between mirrors with different transmittance and reflectivity for different wavelengths. IR radiation with a wavelength of 808 nm from a powerful LD, passing through the resonator mirror, causes the generation of radiation with a wavelength of 1064 nm in a yttrium vanadate crystal doped with neodymium ions. In turn, this radiation, passing through the KTP crystal, doubles, passes through the output mirror and we see a green laser beam. Yellow, blue, cyan radiation is obtained in approximately the same way, but with other crystals and mirrors. The efficiency of optical power conversion of this method is up to 20%. That is, in order to get a green laser of 100 milliwatts, you need 500 mW of IR diode. The conclusion is that greens of more than 100-120 mW simply cannot function in a laser pen. Don’t be fooled when buying! Until recently, high-power blue lasers were built in the same way, until CASIO intervened with the new A140 projectors and the like, which contain 445nm 1000mW diodes.

Assembling the laser

A driver is an electronic circuit that controls the power supply to the diode; without it it will burn out; its absence is not even discussed! Article about drivers

A laser diode does not shine with a direct beam, it shines with a cone and needs to be focused, and it needs to be focused with a collimator. For me, the AIXIZ modules are an ideal choice, you immediately get both a collimator and primitive cooling in one bottle. But you can also use DVD lenses to focus at short distances. For the first time, you can make a stationary module yourself. If you are going to make a monster of 1W or more, you need to think about cooling. Let's calculate: Voltage 4.2 V, Current about 1.1 A: 4.2 x 1.1 = 4.6 W, and the beam is ~1 W. Where did the other 3.6 W go? And they went to heat up. Temperature is detrimental to the diode; in addition, the higher the temperature, the lower the power, so the heat must be removed. We go to the radio market and buy a used heatsink for the processor, drill a hole in it for AIXIZ, press the module in there, having previously lubricated it with thermal paste. And in general, I advise you to re-read it here. And also do not operate the laser in the cold if it is working at its limit! At low temperatures, the laser power increases and an optical breakdown of the resonator may occur, then the laser diode will burn out. At the end I want to add: If you are making a laser for sale, first re-read the topic, a real story that happened to me. The current situation cost me a lot of nerves and the health of an innocent person. I was very lucky that I got off like that, in reality it could have all ended with a checkered sky, friends with stripes, a criminal record being entered into a personal file, and as a result, the inability to find a normal job and a ruined life. Think twice. And then everything depends on your imagination, so go for it! Attention! Laser is dangerous to your eyesight! Protect your eyesight, BUY SAFETY GLASSES taken with minor edits. Original:

The word “laser” or “laser” is an abbreviation for “light amplification by stimulated emission of radiation.” In Russian: - “light amplification by stimulated emission”, or optical quantum generator. The first laser, which used a silver-coated ruby ​​cylinder as a resonator, was developed in 1960 by Hughes Research Laboratories, California. .Today, lasers are used for a variety of purposes, ranging from measuring various quantities to reading encoded data. There are several ways to make a laser, depending on your budget and skills.

Steps

Part 1

A laser requires an energy source to operate. Lasers work by exciting electrons in the laser's active medium with an external energy source and stimulating them to emit light of a specific wavelength. This process was first proposed in 1917 by Albert Einstein. In order for electrons (in the atoms of the active medium of the laser) to emit light, they must first absorb energy by moving to a higher orbit, and then release this energy in the form of a particle of light when returning to their original orbit. This method of introducing energy into the active medium of a laser is called “pumping.”

Channel passage of energy through an active (amplifying) medium. An amplifying medium or active laser medium increases the intensity of light due to induced (stimulated) radiation emitted by electrons. The enhancing medium can be any of the following structures or substances:

Installing mirrors to contain the light inside the laser. Mirrors, or resonators, hold light within the working chamber of the laser until the desired level of energy is accumulated to be emitted through a small hole in one of the mirrors or through a lens.

• The simplest resonator or “linear resonator” uses two mirrors placed on opposite sides of the laser working chamber to generate a single output beam.
• A more complex "ring resonator" uses three or more mirrors. It can generate multiple beams or a single beam using an optical isolator.

1. The use of a focusing lens to direct light through an intensifying medium. Along with mirrors, the lens helps concentrate and direct the light so that the intensifying medium receives as much light as possible.

   Part 2

   Building a Laser

   Method One: Making a Laser from a Kit

   1. Purchase. You can buy at an electronics store or buy online a "laser kit", "laser kit", "laser module" or "laser diode". The laser kit should include the following:

      • Driver circuit. Sometimes sold separately from other components. Select a driver circuit that will allow you to regulate the current.
      • Laser diode.
      • The regulating lens can be made of glass or plastic. Typically, the diode and lens are assembled together in a small tube. These components are sometimes sold separately without a driver.

   2. Assembling the driver circuit. Many laser kits are sold with the driver unassembled. These kits include the PCB and related parts, and you have to solder them according to the included diagram. Some kits may have an assembled driver.

      Connect the control unit to the laser diode. If you have a digital multimeter, you can add it to the diode circuit to monitor the current. Most laser diodes have a current ranging from 30 to 250 milliamps (mA). A current range of 100 to 150 mA will produce a fairly powerful beam.

      • You can apply more current to the laser diode to produce a more powerful beam, but the additional current will shorten the lifespan or even burn out the diode.

   3. Connect the power supply or battery to the driver circuit. The laser diode should glow brightly.

   4. Rotate the lens to focus the laser beam. Point it at the wall and focus until a nice, bright point appears.

      • Once you have adjusted the lens this way, place a match on the beam line and rotate the lens until you see the match head begin to smoke. You can also try popping balloons or burning holes in paper.

   Method two: Building a diode laser from an old DVD or Blu-Ray drive

   1. Take an old DVD or Blu-Ray recorder or drive. Choose devices with write speeds of 16x or faster. These devices have laser diodes with an output power of 150mW or more.

      • The DVD drive has a red laser diode with a wavelength of 650 nm.
      • The Blu-Ray drive has a blue laser diode with a wavelength of 405nm.
      • The DVD drive must be in good enough condition to burn discs, although not necessarily successfully. In other words, its diode must be good.
      • Don't try to use a DVD reader or CD reader and writer instead of a DVD writer. The DVD reader has a red diode, but it is not as powerful as the DVD writer. The laser diode in the CD writer is quite powerful, but emits light in the infrared range, and you will get a beam that is invisible to the eye

   2. Removing the laser diode from the drive. Turn the drive upside down. You will see screws that will have to be removed before you can separate the drive mechanism and pull out the diode.

      • Once you disassemble the drive, you will see a pair of metal guides held in place with screws. They support the laser kit. Unscrew the guides to remove them. Remove the laser kit.
      • A laser diode is smaller in size than a penny. It has three metal contacts in the form of legs. It may be placed in a metal shell with a protective transparent window or without a window, or it may not be covered with anything.
      • You have to pull the diode out of the laser head. It may be easier to remove the heatsink from the assembly first before attempting to remove the diode. If you have an antistatic wrist strap, use it while removing the diode.
      • Handle the laser diode with care, especially if it is an unprotected diode. If you have an anti-static container, place the diode in it until you begin to assemble the laser.

   3. Prepare the focusing lens. You will have to pass the beam from the diode through a focusing lens to use it as a laser. You can do this in one of two ways:

      • Using a magnifying glass as a focusing lens. Rotate the lens to find the desired location to receive the focused laser beam. If necessary, this will have to be done each time before using the laser.
      • Buy a low-power laser diode, such as a 5mW laser diode complete with lens and tube. Then replace it with a laser diode from a DVD writer.

For many people, regardless of gender, excess hair on the body is a subject of terrible complexes. Today, smooth, clean skin is a dream come true.

Laser hair removal is one of the methods that can rid a patient of excess hair without much effort and for a long time. This article will tell you how laser hair removal works and how it works.

Laser hair removal is perhaps the most common and popular cosmetic procedure today. The popularity of the procedure is due to the safety of the process. By following all recommendations before and after the procedure, the patient will not have any side effects. The effect of laser hair removal is smooth skin for many years, and this is not an advertising slogan, but reality.

How laser hair removal works: the method is based on the destruction of the hair follicle, after which it simply stops growing in the treated area. The laser device is capable of removing hair from small and large areas of the skin; the cooling device with which the device is equipped protects the skin from overheating and the appearance of age spots.

The duration and result of the procedure depends on the structure of the skin of the treated area: on thinner skin (armpit and bikini area) hair is removed faster, on the back - a little longer. For example, the mustache above the upper lip will disappear in approximately 25 minutes, a deep bikini takes up to 45 minutes, a classic one – 20 minutes.

Since hair does not grow evenly, laser hair removal will need to be repeated. After the first procedure (again, depending on the skin area), from 15 to 40% of the hair is removed.

Types, capabilities and brief characteristics of lasers for hair removal

Laser hair removal devices operate on short and long waves. Depending on this, some devices may be more effective, others less. There are devices that cause less discomfort to the patient compared to others. Also, each device is designed for a specific skin type.

Alexandrite

The Alexandrite laser is considered an effective device; it is used in many salons, and its effectiveness is quite high.

Advantages:

• the device is capable of removing light hairs;
• there is no pain during the procedure;
• the risk of burns is minimal;
• quick result.

Disadvantages of the device:

• hair that is too light or gray may not respond to the device;
• the price of the procedure is high.

Ruby

The operating principle of the ruby ​​laser epilator is based on short waves. This device is the oldest of all currently used, but is still used in beauty salons.

Advantages:

• low price of the procedure;
• works on any part of the body.

Minuses:

• duration of the process;
• reduced efficiency;
• feeling of discomfort during the procedure;
• possibility of an irritable reaction;
• The device is not suitable for red and blond hair, or for dark skin.

Diode

This device is equipped with a skin cooling function, which eliminates discomfort during laser hair removal.

Advantages:

• unlike ruby, it completely destroys the follicle;
• suitable for removing tougher male hair;
• the procedure does not cause pain.

Minuses:

• not suitable for light hair.

Neodymium

This laser operates at longer wavelengths. Laser hair removal with this device has a special feature: the device acts directly on the hair follicle and the vessel that nourishes it, so the effect is even on light hair.

Advantages:

• removes red and blond hair;
• removal is possible at a deeper level.

Minuses:

• the procedure is painful;
• frequent repetition of procedures compared to other lasers.