We all know that laser diodes are widely used in daily life, so do you know what the actual working principle of high-power laser diodes is like? Let's take a look at it together

First, the principle is not complicated, but it is much more precise than you think.

In principle, a high-power laser diode is actually a bit like an ordinary light-emitting diode (LED), and its core is a PN junction structure.

P-type semiconductor (with positive holes) on one side, N-type semiconductor (with free electrons) on the other side, and an active layer in a key area in the middle.

When we apply a forward current to the diode, electrons run from the N region to the P region, recombine with holes, and release photons. The special feature of laser diode is that it also designs an optical resonator to make photons reflect back and forth in the cavity, forming a "stimulated radiation" effect.

Simply put, one photon triggers another photon, and the second photon triggers more photons. Finally, all photons have the same direction, the same frequency and concentrated energy, which is what we call "laser".

Second, where is the high-power LD better than the ordinary LD?

The output power of ordinary laser diodes is generally only tens of milliwatts, while the output of high-power LD can reach several watts or even hundreds of watts.

The difference between them, just like the flame of lighter and the flame of welding torch, has the same principle, but the energy density is completely different.

To achieve high power output, technically, efforts must be made in several directions:

1. Multi-quantum well structure

In the traditional laser diode, there is only one layer of electronic recombination zone; The high-power LD adopts multi-quantum well design, which is like stacking several layers of photon "reaction layers", which improves the luminous efficiency and makes the light output stronger.

2. Chip structure optimization

The chip area is larger, the electrode design is more scientific, and the current distribution is more uniform. Otherwise, if a certain area is overheated, the chip will burn easily.

3. Heat dissipation design is the key

The heat generation of high-power LD is very high, so it must rely on professional packaging structure to conduct heat.

Common examples are:

C-mount package: simple and direct, fast heat conduction;

Suk Kim welding package: high reliability and long service life;

FAC(Fast Axis Collimator) collimator lens package: It can make the emitted light beam more concentrated.

High-end equipment will even be equipped with TEC refrigeration or water cooling system to keep the temperature constant in the best working range.

4. Optical shaping system

The light emitted by a laser diode is usually elliptical with a large divergence angle. By means of collimating lens and optical fiber coupling, divergent light can be turned into parallel beams with high energy density.

Third, how does it work?

If understood in the most intuitive way, the working process of high-power laser diode is roughly as follows:

1. After electrifying, electrons and holes recombine in the active region to generate photons;

2. Photons reflect back and forth in the resonant cavity to form stimulated amplification;

3. The intensity of light increases continuously, and finally a high-energy laser is formed from the output end;

4. The cooling system takes away the heat in time to ensure the stable work of the light-emitting area.

The essence of high-power laser diode is to make stimulated light output continuously, stably and efficiently through structural optimization and heat dissipation enhancement.

Fourth, what can it do?

Nowadays, high-power laser diode has become the core light source in the fields of industrial manufacturing, medical treatment, scientific research and communication.

Take the high-power 808nm laser diode introduced by QSI in South Korea as an example, which is widely used in solid-state laser pumping source and medical beauty equipment.

The development speed of laser technology is far beyond imagination, and high-power laser diode is one of the core driving forces of this progress.

From the earliest tens of milliwatts to the output of hundreds of watts on a single chip, its energy density, efficiency and reliability are constantly breaking through.