Is laser really so amazing?

Friends who have seen science fiction movies must not forget the laser weapons in star wars! The Jedi lightsaber held a great sweep of any hard metal will fell off, in the movie resident evil, the laser beam mesh to special forces coming to see a person instantly cut into pieces of "people", sounds a bit disgusting, what is the laser? Is laser really so amazing?

The formation of "laser", the first to complete two important steps

"Laser (Laser)" is a "Light Amplification by Stimulated Emission of Radiation" acronym, meaning "the use of incentives to increase the intensity of light radiation, the so-called" incentive "is actually radiation complete two important steps, the first is the" energy of excitation (Pumping) ", second is" resonance amplifier (Resonance) ":

The excitation energy (Pumping).

Solid state laser (mostly using photoluminescence) belongs to the "atomic emission", the front have been introduced principle of emitting atoms, plus the energy (or electric energy) electronic excited atoms doped by the inner layer to the outer level jump level, when the electronic level back from the outer inner level, the energy released as light type figure two (a), as shown in. Semiconductor laser (mostly using electroluminescence) is a "semiconductor lighting", we have introduced the principle of semiconductor light emitting for external energy (or electric energy) electronic excitation of semiconductors by the valence band to the conduction band when electrons jump, jump back into the conduction band valence band, will be able to light the type of release, such as figure two shows (B).

A laser stimulated radiation is the most basic conditions, such as shown in Figure two (c), the excitation energy "photoluminescence (PL) and electroluminescence (EL)" in two ways, regardless of the use of a way that can produce laser, photoluminescence (PL) is the external light electronic jump; electroluminescence (EL) is a power electronic jump and will be described in detail later.

Fig. two principle of energy excitation.

Resonant amplification (Resonance).

A pair of "cavity is applied to the light emitting region (Cavity), resonant cavity can actually use a mirror, as shown in Figure three, the beam is reflected back and forth between about two mirrors, constantly through the light emitting region absorb light energy and finally have a resonance effect, the light energy on.

Photoluminescence (PL:Photoluminescence)? Our "titanium sapphire laser (Ti Sapphire laser)" as an example, first in sapphire doped titanium atoms are titanium sapphire crystal, placed many high brightness light source in the crystal (around the issue of a certain wavelength of light) to crystal irradiation, when the crystals absorb the light generated energy excited (Pumping) ", will be issued in a light wavelength (color). Light emitted by the two mirror reflected back and forth "resonant amplification (Resonance)", because the mirror design right can penetrate into the 5% light, so will the right by the high energy laser transmitting, as shown in Figure three (a) shows.

Electroluminescence (EL:Electroluminescence) to our "GaAs laser diode (GaAs laser diode)" as an example, first in GaAs laser diode chip (only about the size of a grain of sand) on the deposited metal electrode, on chip voltage, when the excitation energy could generate "electric chip absorption (Pumping)" will be issued in a certain wavelength (color) light. Light emitted by the two crystal reflecting mirror reflected back and forth "resonant amplification (Resonance)", because the mirror design right can penetrate into the 5% light, so the laser beam will be high energy by right through injection, as shown in Figure three (b) shows.

Figure three principles of laser generation.

What kind of laser the most profound influence on our lives?

The laser can be classified into three types: gas laser, liquid laser, solid laser and semiconductor laser, strictly speaking, a semiconductor laser is a solid laser, but due to the amount of semiconductor laser using commercially, for example: the current optical head, optical communication, laser light source indicator, so laser has a profound impact our life, while the laser diode can be divided into edge emitting laser and surface emitting laser, this time to participate in the 2017 VCSELs (surface emitting laser) technology innovation and application seminar is the subject of surface emitting laser. Before entering the subject, I would like to restore my style and speak in the language of science!

Laser diode (LD:Laser Diode).

1. Definition of laser diode

Of the four lasers introduced above, only the semiconductor laser has the smallest size, the lowest cost, and only a small battery to use, so it can be widely used in a variety of electronic products.

2 kinds of laser diodes

Laser diode (LD) structure is shown in Figure four (a) shows the appearance of a cylindrical, usually in accordance with the package has a different shape, but the true light is only part of the "chip" (Die), the size of a grain of sand and sea chip almost, a chip is so small you can send a strong light, the laser diode chip is very small, so a two inch GaAs wafer can produce thousands of chips, then formed after cutting package, as shown in Figure four (b) appearance, process process and silicon wafer laser diodes are similar, making use of growth. And doping techniques, etching technology, thin film through yellow.

The appearance and construction of a four beam laser diode LD.

There are many laser diodes