laser diode is a kind of laser generator. The working material is a semiconductor, which belongs to a solid-state laser. Most of the laser diodes are similar in structure to general diodes. A laser diode is essentially a semiconductor diode. According to whether the PN junction materials are the same, laser diodes can be divided into homojunction, single heterojunction (SH), double heterojunction (DH) and quantum well (QW) laser diodes. Quantum well laser diodes have the advantages of low threshold current and high output power, and are currently the mainstream products in the market.

Compared with lasers, laser diodes have the advantages of high efficiency, small size and long life. However, its output power is small (generally less than 2mW), its linearity is poor, and its monochromaticity is not very good, which greatly limits its application in cable TV systems, and cannot transmit multi-channel, high-performance analog signals. In the backhaul module of the bidirectional optical receiver, the quantum well laser diode is generally used as the light source for uplink emission.

The light-emitting principle of laser diodes

The crystal diode is a p-n junction formed by a p-type semiconductor and an n-type semiconductor, and a space charge layer is formed on both sides of the interface, and a self-built electric field is built. When there is no applied voltage, the diffusion current caused by the difference in carrier concentration on both sides of the p-n junction is equal to the drift current caused by the self-built electric field and is in an electrical equilibrium state.

When there is a forward voltage bias in the outside world, the mutual suppression of the external electric field and the self-built electric field increases the diffusion current of the carriers and causes the forward current.

When there is a reverse voltage bias outside, the external electric field and the self-built electric field are further strengthened, forming a reverse saturation current that is independent of the reverse bias voltage value within a certain reverse voltage range.

The light-emitting principle of a laser diode: The P-N junction in a laser diode is formed by two layers of doped gallium arsenide. It has two flat-ended structures, mirrored parallel to one end (highly reflective surface) and one partially reflective. The wavelength of the light to be emitted is exactly related to the length of the connection. When a P-N junction is forward biased by an external voltage source, electrons move through the junction and recombine like a normal diode. When electrons recombine with holes, photons are released. These photons hit the atoms, causing more photons to be released. As the forward bias current increases, more electrons enter the depletion region and cause more photons to be emitted.

Eventually, some photons drifting randomly in the depletion region hit the reflective surface vertically, reflecting back along their original path. The reflected photons bounce off the other end of the junction again. This movement of the photon from one end to the other occurs several times in a row. During the motion of photons, more atoms release more photons due to the avalanche effect.

This process of reflecting and generating more and more photons produces a very intense laser beam. Each photon produced during the emission process explained above is identical to other photons in energy level, phase relationship and frequency. Therefore, the emission process gives a laser beam of a single wavelength. In order to generate a laser beam, the current of the laser diode must exceed a certain threshold level. Current below the threshold level forces the diode to behave as an LED, emitting incoherent light.

Laser Diode Module Laser Dot

Laser diodes module manufacturer

Changshu Desheng Optoelectronics Co., Ltd. is an excellent laser module manufacturer, producing laser diodes using advanced 520nm and 780-980nm laser diode manufacturing technology. Laser diodes emit the brightest, most visible light. This great revolutionary product opens up a new field of laser modules with reasonable price and stable performance.