Pinout of laser diodes. How to connect a laser diode: connection diagram. Focusing the light flux into a beam

Today, many household and other devices use laser diodes (semiconductors) to create a targeted beam. And the most important point in assembling a laser system yourself is connecting the diode.

Laser diode

From this article you will learn about everything you need for a high-quality connection of a laser diode.

Features of the semiconductor and its connection

The laser model differs from the LED diode in its very small crystal area. In this connection, a significant concentration of power is observed, which leads to a short-term excess of the current value in the junction. Because of this, such a diode can easily burn out. Therefore, in order laser diode served as long as possible, a special circuit is required - a driver.

Note! Any laser type diode must be powered with a stabilized current. Although some varieties that give red light behave quite stably, even if they have unstable nutrition.

Red laser diode

But, even if a driver is used, a diode cannot be connected to it. A “current sensor” is also needed here. Its role is often played by the common wire of a low-resistance resistor, which is connected to the gap between these parts. As a result, the circuit has one significant drawback - the power minus is “severed” from the minus present in the circuit’s power supply. Besides this scheme has one more disadvantage - power loss occurs at the current-measuring resistor.
When planning to connect a laser diode, you need to understand which driver it should be connected to.

Driver classification

On this moment There are two main types of drivers that can be connected to our semiconductor:

pulse driver. It is a special case of a pulse voltage converter. It can be either downward or upward. Their input power is approximately equal to the output power. In this case, there is a slight conversion of energy into heat. A simplified pulse driver circuit looks like this;

Simplified switching driver circuit

linear driver. The circuit typically supplies more voltage to such a driver than the semiconductor requires. To extinguish it, a transistor is needed, which will release excess energy with heat. Such a driver has low efficiency, and therefore is used extremely rarely.

Note! When using linear integrated circuit stabilizer chips, the current will decrease as the input voltage across the diode drops.

Line Driver Circuit

Due to the fact that any laser diode can be powered through two different types drivers, the connection diagram will vary.

Connection Features

The circuit that will be used to power the laser diode may contain not only a driver and a “current sensor”, but also a power source - a battery or battery.

Connection diagram option

Typically, the battery/battery in this case must have a voltage of 9 V. In addition to them, the circuit must include a laser module and a current-limiting resistor.

Note! In order not to spend money on a diode, it can be removed from DVD drive. Moreover, this should be exactly computer device, not a standard player.

Computer DVD drive

The laser semiconductor has three terminals (legs), two of which are located on the sides and one in the middle. The middle output should be connected to the negative terminal of the selected power source. The positive terminal must be connected to the left or right “leg”. The choice of left or right side depends on the semiconductor manufacturer. Therefore, you need to determine which output will be: “+” and “-”. To do this, power must be applied to the semiconductor. Two batteries, each 1.5 volts, as well as a 5 ohm resistor will do the job perfectly here.
The negative terminal at the power supply should be connected to the central negative terminal defined at the diode. In this case, the positive side must be connected to each of the two remaining terminals of the semiconductor in turn. Thus, it can also be connected to a microcontroller.
Power for the laser diode can be provided using 2-3 AA batteries. But if you wish, you can also include a battery from mobile phone. In this case, you must remember that you will need an additional 20 Ohm limiting resistor.

Connection to 220 V network

The semiconductor can be powered from 220 V. But here it is necessary to create additional protection against high-frequency voltage surges.

Option for powering a diode from a 220 V network

Such a scheme should include the following elements:

Voltage regulator;
current limiting resistor
capacitor;
laser diode.

The resistance and stabilizer will form a block that can prevent current surges. To prevent voltage surges, a zener diode is needed. The capacitor will prevent the appearance of high-frequency bursts. If such a circuit was assembled correctly, then stable operation of the semiconductor will be guaranteed.

Step-by-step connection instructions

The most convenient way to create a laser installation with your own hands will be a red semiconductor, which has an output power of approximately 200 milliwatts.

Note! This is the semiconductor that any computer DVD player is equipped with. This greatly simplifies the search for a light source.

The connection looks like this:

One semiconductor must be used for connection. They must be checked for functionality (just connect to a battery);
choose a brighter model. When testing the IR LED (taking it from the computer player), it will glow a faint red glow. Remember that it

DO NOT aim at the eyes, otherwise you may completely lose your vision;

Diode check

Next, we install the laser on a homemade radiator. To do this, you need to drill a hole in an aluminum plate (about 4 mm thick) with such a diameter that the diode fits into it quite tightly;
It is necessary to apply a small layer of thermoplastic between the laser and the radiator;
Next, we take a wire-wound ceramic resistor with a resistance of 20 Ohms with a power of 5 W and, observing the polarity, connect it to the circuit. Through it you need to connect the laser and power source ( mobile battery or battery);
the laser itself should be bypassed using a ceramic capacitor having any capacitance;
Then, turning the device away from you, you should connect it to the power supply. As a result, the red beam should turn on.

Red beam from a homemade device

It can then be focused using a biconvex lens. Focus it for a few seconds on one point on the paper that absorbs the red spectrum. The laser will leave a red light on it.
As you can see, we have a working device that is connected to a 220 V network. Using various circuits and connection options, you can create different devices, even a pocket laser pointer.

Conclusion

When connecting a laser diode, you need to remember about safe handling and also know the nuances that are present in its operation. After this, all that remains is to choose the circuit you like and connect the semiconductor. The main thing to remember is that all contacts must be well sealed, otherwise the part may burn out during operation.

Calculation of lumens per square meter for different rooms

This scheme is quite accurate and does not require large number components, is designed to control a laser diode and is designed in accordance with the requirements for medical equipment. The device is currently undergoing clinical trials. The performance of laser diodes is subject to short- and long-term drift due to temperature and aging. They are usually driven by direct current, so their optical output power is monitored and the current is adjusted according to changes in power.

The body of the structure is grounded, so the source configuration direct current designed to include a power transistor in the upper arm of the laser, and not the simpler opposite option. In addition, to avoid “tattooing” the patient, the current must be initially limited.

In a single-supply +5V circuit, current-sensing and current-limiting resistor R1 and p-channel MOSFET Q1 form the source follower (Figure 1). The MOSFET's gate voltage is slightly higher than the source voltage, so the transistor is partially on and the laser diode current creates a voltage drop across resistor R1. In the worst case, when Q1 is fully open, the maximum laser current is given by

R DS(SAT) = 25 mOhm - open channel resistance of the MOS transistor,
V LASER = 2.0 V - voltage on the laser diode.

The R DS(SAT) and V LASER values were taken from the transistor and laser diode data sheets, respectively. The choice of resistor R1 is determined by the requirements for the laser current (in this case, 250 mA) taking into account the correction introduced by the forward voltage of the laser diode, a typical value of which is 2.0 V. Solving the equation for R1, we obtain:

where I LASER = 250 mA.

The resistance R DS(SAT) is so small that it can be ignored. At known values R1 and the maximum current of the laser diode, the power dissipated by R1 can be calculated by the formula

which means that a resistor with a permissible power dissipation of 800 mW will provide a small additional margin.

The laser current is set using a DAC, the output voltage of which is set ratiometrically. The +5 V source voltage is used as a reference here, so the DAC output tracks all power fluctuations. During operation, the required value of the control voltage is set at the ADC output. Divider R2, R3 scales this setting relative to the nominal +5 V supply.

For example, if the DAC output voltage is set to half scale, that is, +2.5 V, the voltage between R2 and R3, (or at the non-inverting input of op-amp IC1), will be +3.5 V. Included in the loop feedback IC1 regulates the gate voltage of Q1 and therefore the current flowing through R1, Q1 and the laser diode. The circuit mode is stabilized when the feedback voltage becomes equal to +3.5 V. In this steady state, 5 V - 3.5 V = 1.5 V drops across resistor R1, and the current is 125 mA, that is, in the middle of the scale. Similarly, if the DAC output is set to a minimum value of 0 V, the voltage at the non-inverting input of IC1 will be +2 V. IC1 will increase the voltage at the gate of Q1 until the voltage drop across R1 rises to 3 V, and the current accordingly up to 250 mA. This is the saturation point where Q1 is fully on and the forward voltage across the laser diode is +5V minus the voltage drop across R1.

The complete circuit must include elements R4 and C1, ensuring the stability of the control loop and having a cutoff frequency f equal to

Special attention should be paid to the process that occurs in the circuit during an abrupt change in the control voltage, during which the op-amp, which previously worked as an adder of the setpoint and feedback voltages, becomes a voltage follower, and a step tends to appear at its output. In this regard, in our example, capacitor C2 is added, forming a low-frequency filter for the setpoint voltage with a cutoff frequency

where R2||R3 = 12 kOhm.

If the cutoff frequency of this filter is much less than the feedback loop bandwidth, the op amp will be able to track setpoint step changes with minimal overshoot during DAC switching.

R5 provides some bias to the op amp by ensuring that a small amount of current is always guaranteed to flow through resistor R1. When the DAC output is set to +5V full scale, the laser current driven by the op amp will always be slightly higher than the setting. Therefore, the op-amp output, trying to turn off Q1, will go into saturation. Without R5, the op amp's input offset voltage could be perceived as a false setpoint and cause Q1 to be turned on to restore balance.

This is one of the main reasons why ratiometric DAC switching is used. If the DAC's reference voltage were fixed, programming low currents would be virtually impossible. If the voltage at the DAC output is set slightly below the exact value of +5 V, then even with small fluctuations in the +5 V supply voltage, the control voltage will change quite significantly. However, in a ratiometric circuit, the DAC tracks changes in the +5 V supply voltage, and the relative control voltage at its output remains stable.

The price for the ability to accurately set low currents is a poor power supply ripple suppression ratio. However, in the medical application for which the laser was intended, the current regulation loop is itself part of the power regulation loop, and the power supply ripple in it is minimal. If necessary, you can add to the board small stabilizer voltage, and at the cost of slightly increasing the number of components, you will receive stable, low-noise laser power.

Laser diodes - Previously, manufacturing lasers was associated with great difficulties, since it requires a small crystal and the development of a circuit for its operation. For a simple radio amateur, such a task was impossible.

With the development of new technologies, the possibility of obtaining a laser beam in everyday conditions has become a reality. The electronics industry today produces miniature semiconductors that can generate a laser beam. Laser diodes became these semiconductors.

The increased optical power and excellent functional parameters of the semiconductor make it possible to use it in high-precision measuring devices both in production, in medicine, and in everyday life. They are the basis for writing and reading computer disks, school laser pointers, level gauges, distance meters and many other useful devices for humans.

The emergence of such a new electronic component is a revolution in the creation electronic devices of varying complexity. High-power diodes form a beam, which is used in medicine to perform various surgical operations, in particular to restore vision. The laser beam is able to quickly correct the lens of the eye.

Laser diodes are used in measuring instruments in everyday life and industry. The devices are manufactured with different power levels. A power of 8 W is enough to assemble a portable level gauge at home. This device is reliable in operation and is capable of creating a laser beam of very long length. Getting a laser beam into the eyes is very dangerous, since at a short distance the beam is capable of damaging soft tissues.

Design and principle of operation

In a simple diode, a positive voltage is applied to the anode, then we are talking about biasing the diode in the forward direction. Holes from the “p” region are injected into the “n” region of the p-n junction, and from the “n” region into the “p” region of the semiconductor. When a hole and an electron are located next to each other, they recombine and release photon energy with a certain wavelength and phonon. This process is called spontaneous emission. In LEDs it is the main source.

But under certain conditions, a hole and an electron are capable of remaining in one place for a long time (several microseconds) before recombination. If a photon with a resonance frequency passes through this area at this time, it will cause forced recombination, and a second photon will be released. Its direction, phase and polarization vector will absolutely coincide with the first photon.

The semiconductor crystal is made in the form of a thin rectangular plate. In fact, this plate plays the role of an optical waveguide in which radiation acts in a limited volume. The surface layer of the crystal is modified to form the “n” region. The bottom layer serves to create the “p” area.

The end result is a flat p-n junction of significant area. The two side ends of the crystal are polished to create parallel smooth planes that form an optical resonator. A random photon perpendicular to the planes of spontaneous emission will travel along the entire optical waveguide. In this case, before leaving outside, the photon will be reflected several times from the ends and, passing along the resonators, will create forced recombination, forming new photons with the same parameters, which will cause an increase in radiation. When the gain exceeds the loss, the creation of a laser beam will begin.

There are different types of laser diodes. The main ones are made on particularly thin layers. Their structure is capable of creating radiation only in parallel. But if the waveguide is made wide in comparison with the wavelength, then it will function in various transverse modes. Such laser diodes are called multi-house laser diodes.

The use of such lasers is justified for creating increased power radiation without high-quality beam convergence. Some dispersion is allowed. This effect is used to pump other lasers, in chemical production, laser printers. However, if a certain focusing of the beam is necessary, the waveguide must be made with a width comparable to the wavelength.

In this case, the beam width depends on the boundaries that are imposed by diffraction. Such devices are used in optical storage devices, fiber optic technology, and laser pointers. It should be noted that these lasers are not capable of supporting multiple longitudinal modes and emitting a laser beam at different wavelengths at the same time. The band gap between the energy levels of the “p” and “n” regions of the diode affects the wavelength of the beam.

The laser beam diverges immediately at the output, since the emitting component is very thin. To compensate for this phenomenon and create a thin beam, converging lenses are used. For wide multi-house lasers, cylindrical lenses are used. In the case of single-house lasers, when symmetrical lenses are used, the laser beam will have an elliptical cross-section, since the vertical divergence exceeds the beam size in the horizontal plane. A good example of this is the laser pointer.

In the considered elementary device it is impossible to distinguish certain length waves, except for the wave of the optical resonator. In devices that have a material capable of amplifying the beam over a wide range of frequencies, and with several modes, action at different waves is possible.

Typically, laser diodes operate at a single wavelength, which, however, has significant instability and depends on various factors.

Varieties

The design of the diodes discussed above has n-p structure. Such diodes have low efficiency, require significant input power, and operate only in pulse mode. They cannot work any other way, as they will quickly overheat, so they are not widely used in practice.

Double heterostructure lasers have a layer of substance with a narrow band gap. This layer is located between layers of material that has a wide bandgap. Typically, aluminum gallium arsenide and gallium arsenide are used to make a double heterostructure laser. Each of these connections with two different semiconductors is called a heterostructure.

The advantage of lasers with this special structure is that the region of holes and electrons, called the active region, is located in the middle thin layer. Consequently, many more pairs of holes and electrons will create amplification. In the region with low gain there will be few such pairs left. In addition, light will be reflected from the heterojunctions. In other words, the radiation will be completely located in the region of greatest effective gain.

Quantum well diode

By making the middle layer of the diode thinner, it begins to function as a quantum well. Therefore, electronic energy will be quantized vertically. The difference between the energy levels of quantum wells is used to produce radiation instead of a future barrier.

This is effective in controlling the beam waveform depending on the thickness of the middle layer. This type of laser is much more efficient, unlike a single-layer laser, since the density of holes and electrons is distributed more evenly.

Heterostructure laser diodes

The main feature of thin-layer lasers is that they are not able to effectively contain a beam of light. To solve this problem, two additional layers are applied on both sides of the crystal, which have a lower refractive index, unlike the central layers. This structure is similar to a light guide. It holds the beam much better. These are heterostructures with separate confinement. Most lasers were produced using this technology in the 90s.

Lasers with feedback Mainly used for fiber optic communications. To stabilize the wave on р-n junction a transverse notch is performed to create a diffraction grating. Because of this, only one wavelength is returned to the resonator and amplified. Such lasers have a constant wavelength. It is determined by the grating notch pitch. The notch changes under the influence of temperature. This laser model is the basis of telecommunication optical systems.

There are also laser diodes VСSEL and VECSEL, which are surface-emitting models with a vertical resonator. Their difference is that the model VESSEL The resonator is external, and its design is available with optical and current pumping.

Connection features

Laser diodes are used in many applications where a directed light beam is needed. The main process in assembling a device using a laser with your own hands is the correct connection.

Laser diodes differ from LED diodes in that they have a miniature crystal. Therefore, a large amount of power is concentrated in it, and therefore the amount of current, which can lead to its failure. To facilitate the operation of the laser, there are special device circuits called drivers.

Lasers require a stable power supply. However, there are models of them that have a red glow of the beam and operate normally even with an unstable network. If there is a driver, then the diode still cannot be connected directly. To do this, you additionally need a current sensor, the role of which is often played by a resistor connected between these elements.

This connection has the disadvantage that the negative pole of the power supply is not connected to the minus of the circuit. Another disadvantage is the power drop across the resistor. Therefore, before connecting the laser, you must carefully select the driver.

Types of drivers

There are two main types of drivers that can ensure normal operation of laser diodes.

Pulse driver made by analogy with a pulse voltage converter capable of increasing and decreasing this parameter. The output and input powers of such a driver are approximately equal. However, there is some heat generation, which consumes a small amount of energy.

Line driver operates according to a circuit that most often supplies more voltage to the diode than required. To reduce it, a transistor is needed to convert excess energy into heat. The driver has low efficiency, so it is not widely used.

When using linear microcircuits as stabilizers, as the input voltage decreases, the diode current will decrease.

Since lasers are powered by two types of drivers, the connection diagrams are different.

The circuit may also include a power source in the form of a battery or accumulator.

The batteries must produce 9 volts. The circuit must also have a current-limiting resistor and a laser module. Laser diodes can be found in a faulty computer disk drive.

The laser diode has 3 outputs. The middle pin is connected to the minus (plus) of the power supply. The plus connects to the right or left leg, depending on the manufacturer. To determine the correct pin to connect to, power must be applied. To do this, you can take two 1.5 V batteries and a resistance of 5 Ohms. The minus of the source is connected to the middle leg of the diode, and the plus first to the left, then to the right leg. Through such an experiment, you can see which of these legs is the “working” one. Using the same method, the diode is connected to the microcontroller.

Laser diodes can be powered by AA batteries or rechargeable batteries cell phone. However, we must not forget that an additional limiting resistor of 20 ohms is required.

Connecting to a home network

To do this, you need to provide auxiliary protection against voltage surges. high frequency.

The stabilizer and resistor create a block that prevents current surges. A zener diode is used to equalize the voltage. The capacitance prevents high frequency voltage surges. Proper assembly ensures stable operation of the laser.

Connection procedure

The most convenient for operation will be a red diode with a power of about 200 mW. Such laser diodes are installed on computer disk drives.

Before connecting using a battery, check the operation of the laser diode.
You need to choose the brightest semiconductor. If the diode is taken from a computer disk drive, then it emits infrared light. The laser beam must not be pointed at the eyes, as this will cause eye damage.
The diode is mounted on a radiator for cooling, in the form of an aluminum plate. To do this, pre-drill a hole.
Apply thermal paste between the diode and the radiator.
Connect a 20 Ohm and 5 watt resistor according to the circuit with batteries and a laser.
Bypass the diode with a ceramic capacitor of any capacity.
Turn the diode away from you and check its operation by connecting the power. A red beam should appear.

When connecting, be aware of safety. All connections must be of high quality.

I bring to your attention an article describing the creation of a powerful red laser capable of lighting matches and burning through various objects!

To obtain a burning red beam (650nm) you need writing DVD drive, maybe old and broken (most likely the laser diode is working there). Suitable CD-RW drive, also writing Blu-ray drive, only the first will shine with an almost invisible infrared ray (780nm), and the second with violet (405nm).

We disassemble the drive and look for something like this laser diode:

It is inserted into a metal heat-sinking housing. And this body is also inserted into a metal base. It is up to you to decide whether to remove the LD from the base and body or not. It’s definitely not worth pulling out flat, frameless ice cubes. I left it in the case - the radiator, and pulled it out of the base. This all affects heat removal, which necessary!

I have come across the opinion that the heat sink of the carriage is not enough when powered by non-pulse current. This may be true for some drive models, or if maximum power is required.

DVD-RW has 2 laser diodes, one infrared for playing and recording CDs, and the second red for recording and playing DVDs. You can make 2 lasers! And from BD-RE - three! Modern DVD-RW models use dual LEDs on one chip. It is impossible to turn on red and infrared diodes simultaneously at high current in such assemblies! Laser diode is afraid static electricity , so as soon as you see 3 legs LD, wrap their

bare wire!

Do not direct the laser beam into the eyes or at reflective surfaces, as this can lead to partial or complete loss of vision!!! This also applies to the invisible infrared laser because it has the same burning power as red or violet!!!

The laser diode must be powered with a certain current, exceeding which causes the LED to overheat, as a result it will shine like a regular LED or even burn out. To avoid this, you need to assemble a special circuit - a driver.

Scheme 1: Capacitors any voltage (from 3V) C1 capacity 0.1uF And C1 C2 100uF protect against static electricity and ensure smooth transient processes. After connecting them to the LD, the wire can be removed from the terminals. A minus signal is applied to one of the terminals and to the housing. , to the second pin plus, the third pin is not used. The location of the poles is clearly visible in the second diagram. For some LDs,+ is supplied to the body

. I've seen this with 808nm LEDs. Dual diodes have a common minus G in the middle terminal, plus the outer terminals: C for powering the CD, D for powering the DVD. To power this circuit, it is convenient to use a cell phone battery or 3 AA batteries. Battery voltage may be higher than specified

, especially immediately after charging (up to 4.2 V, with the indicated 3.7 V), so check it with a multimeter!

Approximate correspondence between DVD recording speed, current strength and power of laser diodes:

16x - 250-260mA. Power 200mW.

20x - 400-450mA. Power 270mW.

22x - 450-500mA. Power 300mW.

24x - 450-500mA.

IR LD power in CD-RW is 100-200 mW.

The power of violet LD in BLU-RAY RW is 60-150 mW.

The power of the violet LD in non-writing BLU-RAY is 15 mW.

The above relationships between recording speed and current can be not applicable to all accounts, for example, when checking 2 dual LEDs on one chip, it turned out that at a voltage of 3V, one of them received a current of 260 mA, the second - 280 mA, which corresponds to 16x, although the drives were 24x. Therefore it costs more pay attention to voltage drop than the relationship between speed and current given above. The infrared LEDs in these crystals produced a current of 110 mA at a voltage of 2.2 V. At 250mA they also continued to work, the voltage exceeded the safe drop and reached 2.8V, which can cause shortened life or burnout in some cases.

You can first find out the required resistance of resistor R1 using the formula:

R1=(Uin.-Ufall.)/I, Where:

Uin. - battery voltage,

Upd. - voltage drop across the ld. Approximately safe Upd.for red (650nm) - 3V(for a low-power non-DVD writing device, this voltage may be excessive), for infrared (780nm) - 2.2V, for infrared (808nm) - 1.9V, for violet (405nm) - 5.5V, for blue (445nm) - 4-4.4V.

I is the current strength indicated in the table above.

Example for red ice: R1=(3.6V-3V)/0.25A= 2.4 Ohm

Resistor power: P=(Uin.-Ufall.)^2/R=(3.6V-3V)^2/2.4 Ohm=0.15W or P=(Uin.-Ufall.)*I=(3.6V-3V)* 0.25A=0.15W

It is recommended to initially install a resistor more , measuring the current value with a multimeter. This is necessary to protect non-standard LDs, which at 3V can create excessive current. And then reduce the resistance, monitoring the current.

Scheme 2:

The disadvantage of the first scheme was that the sag in battery voltage during discharge causes a linear decrease in laser brightness.

There is no such problem in this circuit, thanks to the use of an adjustable stabilizer KREN12A or its analogue LM317T.

But this stabilizer is compensatory, the supplied voltage should be 1.4V more than we need, i.e. to get 3V on LD, from 4.4 V to 37 V must be supplied to the circuit, but the output will still be 3V (with the correct selection of resistors). If you connect less than 4.4V, then the laser brightness will drop, as in scheme 1, as the battery continues to discharge. For 780nm ld (2.2 V, 110 mA) is supplied to the circuit from 3.8 V to 37 V.

This scheme may not be suitable for LDs in which volt-ampere characteristics floats strongly due to temperature changes, and cause them to burn out, if you do not notice the excess current in time. There is information that such an effect is observed in blue ice. That's why, it is necessary to measure the current until the LED is completely warmed up to ensure that no overshoot occurs.

R2 is calculated using the formula:

R2=R1*(Uout.-Uref.)/Uref.

Example for red ice:

R2=240 Ohm*(3V-1.25V)/1.25V= 336 Ohm

It is recommended to initially install R2 less resistance, than it turned out according to the formula, while simultaneously measuring the current strength of the LD by connecting a multimeter in series with it. This is necessary to protect non-standard LDs, which at 3V can create excessive current. And then increase the resistance R2, monitoring the current.

The capacitors are the same as in the first circuit.

Resistors must be qualitatively connected to the circuit(variable resistor must be fully operational, without the slightest open circuit). Loss of contact will cause the voltage on the LD to increase, causing it to will burn out instantly!

Scheme 3:

This circuit differs from the second in that it maintains a stable current, while the second maintains a stable voltage. Limits current 250 mA, provided that the variable resistor is set to 0 ohm And fixed resistors(5 Ohm resistor of suitable power), the ratings of which are indicated in the diagram. Power circuit with red LED current250 mA : 5.7 V to 37 V. With infrared(2.2V 110mA) from 5 V to 37 V.

The capacitors are identical to those used in the first two circuits.

The resistances from the image must be recalculated for a specific type of LD!

The resistor is calculated using the formula:

R=1.25/I, where R is the sum of the resistances of the circuit resistors, I is the current strength.

To obtain the current 250 mA, you need to use a resistor 5 ohm.

Select the current strength by adjusting the variable resistor, monitoring the readings of the multimeter. Please note that for proper operation The stabilizer needs to use a voltage greater than in the second circuit.

It is necessary to assemble the circuit, and only then connect the power source. Connecting an LD to a switched-on circuit may cause it burnout!

Below is a photo of my laser. It is attached to the battery compartment for 3 AA batteries, and there is also a button glued there. The main aluminum structure plays the role of a radiator.

The light of a laser diode diverges like from a regular LED, but we need a laser beam! For this purpose it is necessary to use collimator, i.e. a lens that focuses the radiation into a beam. I used the lens from a laser pointer, you can also use the output lens from the drive. In my assembly, the lens is glued with double-sided tape to a plate, which is suspended, as it were, on two springs. By rotating two nuts, the laser is focused - the lens approaches or moves away from the lens.

View from the collimator:

And a couple of photos of the device in action. In the direction from which the beam shines:

In the direction where the laser is shining:

Most convenient setup focusing is possible using a collimator from a cheap pointer glued to the LD with epoxy glue. In my case, I had to grind the collimator down to the size of the cutout where the board was inserted. Photo below.

And a few words about green, yellow, blue and blue semiconductor lasers.

Due to the fact that powerful laser diodes of these colors have not yet been created (only in 2012 information appeared about the creation of a 50 mW green laser diode) or they are very expensive, lasers of these colors use an 808 nm infrared laser diode with radiation conversion using crystals in the desired color - these are diode-pumped solid-state lasers.

Receipt scheme green beam from invisible infrared: In yellow lasers, the 808nm beam is converted into a 1064nm beam, then the 1064nm beam is converted into a 1342nm beam, and only then is doubled into a 593.5nm beam. The efficiency of yellow lasers in this scheme is about 1%.

Blue473nm The laser beam is usually produced by doubling the frequency of 946nm laser light. To obtain 946 nm, a yttrium aluminum garnet crystal with neodymium additives (Nd:YAG) is used.

And here blue laser 445nm And violet 405nm , collected in the same way as red, without additional crystals, using ice of its color.

Video of lighting a match with a 100mW violet laser through an additional lens to obtain a narrower beam.

New articles have been added to the second site, which can be accessed through the "Spectroscopy" button in the site menu!

Making a powerful burning laser with your own hands is not a difficult task, however, in addition to the ability to use a soldering iron, you will need to be attentive and careful in your approach. It’s worth noting right away that deep knowledge from the field of electrical engineering is not needed here, and you can make a device even at home. The main thing when working is to take precautions, since exposure to a laser beam is harmful to the eyes and skin.

A laser is a dangerous toy that can cause harm to health if used carelessly. Do not point the laser at people or animals!

What will you need?

Any laser can be divided into several components:

emitter luminous flux;
optics;
power supply;
current supply stabilizer (driver).

To make a powerful homemade laser, you will need to consider all these components separately. The most practical and easiest to assemble is a laser based on a laser diode, which we will consider in this article.

Where can I get a diode for a laser?

The working element of any laser is a laser diode. You can buy it at almost any radio store, or get it from a non-working CD drive. The fact is that drive inoperability is rarely associated with failure of the laser diode. If you have a broken drive, you can extra costs get it required element. But you need to take into account that its type and properties depend on the modification of the drive.

The weakest laser, operating in the infrared range, is installed in CD-ROM drives. Its power is only enough to read CDs, and the beam is almost invisible and is not capable of burning objects. The CD-RW has a built-in more powerful laser diode, suitable for burning and designed for the same wavelength. It is considered the most dangerous, as it emits a beam in a zone of the spectrum invisible to the eye.

The DVD-ROM drive is equipped with two weak laser diodes, the energy of which is only sufficient for reading CDs and DVD discs. The DVD-RW burner has a red laser high power. Its beam is visible in any light and can easily ignite certain objects.

The BD-ROM contains a violet or blue laser, which is similar in parameters to the analogue from the DVD-ROM. From BD-RE recorders you can get the most powerful laser diode with a beautiful violet or blue beam capable of burning. However, finding such a drive for disassembly is quite difficult, and a working device is expensive.

The most suitable one is a laser diode taken from a DVD-RW drive. The highest quality laser diodes are installed in LG, Sony and Samsung drives.

The higher the DVD drive's writing speed, the more powerful the laser diode installed in it.

Drive disassembly

Having the drive in front of you, first remove the top cover by unscrewing 4 screws. Then remove the movable mechanism, which is located in the center and connected to printed circuit board flexible cable. The next goal is a laser diode, securely pressed into a radiator made of aluminum or duralumin alloy. It is recommended to provide protection against static electricity before dismantling it. To do this, the leads of the laser diode are soldered or wrapped with thin copper wire.

Next, there are two possible options. The first involves operating a finished laser in the form of a stationary installation together with a standard radiator. The second option is to assemble the device in the body of a portable flashlight or laser pointer. In this case, you will have to apply force to cut through or saw the radiator without damaging the radiating element.

Driver

Laser power supply must be handled responsibly. As with LEDs, it must be a stabilized current source. On the Internet there are many circuits powered by a battery or accumulator through a limiting resistor. The sufficiency of this solution is questionable, since the voltage on the battery or battery changes depending on the charge level. Accordingly, the current flowing through the laser emitting diode will deviate greatly from the nominal value. As a result, the device will not work efficiently at low currents, and at high currents it will lead to a rapid decrease in the intensity of its radiation.

The best option is to use a simple current stabilizer built on the basis. This microcircuit belongs to the category of universal integrated stabilizers with the ability to independently set the output current and voltage. The microcircuit operates in a wide range of input voltages: from 3 to 40 volts.

An analogue of LM317 is the domestic chip KR142EN12.

For the first laboratory experiment, the diagram below is suitable. The only resistor in the circuit is calculated using the formula: R=I/1.25, where I is the rated laser current (reference value).

Sometimes a polar capacitor of 2200 μFx16 V and a non-polar capacitor of 0.1 μF are installed at the output of the stabilizer in parallel with the diode. Their participation is justified in the case of supplying voltage to the input from a stationary power supply, which can miss an insignificant alternating component and impulse noise. One of these circuits, powered by a Krona battery or a small battery, is presented below.

The diagram shows the approximate value of resistor R1. To accurately calculate it, you must use the above formula.

Having collected electrical diagram, you can make a preliminary switching on and, as proof of the circuit’s operability, observe the bright red scattered light of the emitting diode. Having measured its actual current and body temperature, it is worth thinking about the need to install a radiator. If the laser will be used in a stationary installation at high currents for a long time, then passive cooling must be provided. Now there is very little left to achieve the goal: focus and get a narrow beam of high power.

Optics

In scientific terms, it's time to build a simple collimator, a device for producing beams of parallel light rays. The ideal option for this purpose would be a standard lens taken from the drive. With its help you can obtain a fairly thin laser beam with a diameter of about 1 mm. The amount of energy of such a beam is enough to burn through paper, fabric and cardboard in a matter of seconds, melt plastic and burn through wood. If you focus a thinner beam, this laser can cut plywood and plexiglass. But setting up and securely attaching the lens to the drive is quite difficult due to its small focal length.

It is much easier to build a collimator based on a laser pointer. In addition, its case can accommodate a driver and a small battery. The output will be a beam with a diameter of about 1.5 mm and a smaller burning effect. In foggy weather or heavy snowfall, you can observe incredible light effects by directing the light stream into the sky.

Through the online store you can purchase a ready-made collimator, specifically designed for mounting and tuning a laser. Its body will serve as a radiator. Knowing the dimensions of all the component parts of the device, you can buy a cheap LED flashlight and use its housing.

In conclusion, I would like to add a few phrases about the dangers of laser radiation. First, never point the laser beam into the eyes of people or animals. This leads to serious visual impairment. Secondly, wear green glasses when experimenting with the red laser. They block most of the red portion of the spectrum from passing through. The amount of light transmitted through the glasses depends on the wavelength of the radiation. Looking from the side at the laser beam without protective equipment is allowed only for a short time. Otherwise, eye pain may occur.