A Review on the Laser Diode

Abstract

Similar to a light-emitting diode, a laser diode (LD), sometimes injection laser diode, ILD, semiconductor laser, or diode laser is a semiconductor device that can produce lasing conditions at its junction when a diode is directly pumped with electrical current.[22]. The doped p–n-transition, which is powered by voltage, permits the recombination of an electron with a hole. Radiation is produced in the form of an emitted photon when an electron falls from a higher energy level to a lower one. This is an example of spontaneous emission. When the process is repeated, light with the same phase, coherence, and wavelength can be created, which is known as stimulated emission. The wavelength of the emitted beam, which in today\'s laser diodes ranges from the infrared (IR) to the ultraviolet (UV) spectrum, depends on the semiconductor material selection. Fiber-optic communications, barcode readers, laser pointers, CD/DVD/Blu-ray disc reading/recording, laser printing, laser scanning, and light beam illumination are just a few of the many applications for laser diodes, the most widely produced form of laser. Laser diodes can be utilized for general illumination if a phosphor similar to that of white LEDs is used [22].

Introduction

A laser is a device that emits coherent, monochromatic, and highly directional light through optical amplification based on the phenomenon of stimulated emission, first predicted by Albert Einstein (1916). The first working laser was built by Theodore Maiman in 1960, following theoretical contributions from Townes and Schawlow. Lasers differ from ordinary light sources because they exhibit spatial and temporal coherence, enabling applications such as cutting, welding, lithography, communication, surgery, measurement, and entertainment displays.

Historically, the development of lasers evolved from earlier masers (microwave amplification). Important milestones include Townes' maser in the 1950s, the Townes–Schawlow optical maser theory (1958), and Maiman’s ruby laser (1960). Soon after, helium–neon gas lasers and semiconductor lasers were created, paving the way for practical uses in barcode scanners, laser printers, CD players, and medical surgery.

Principle of Operation

Laser action depends on:

• Energy levels in atoms

• Stimulated emission

• Population inversion

• Optical resonator with mirrors

A strong pumping mechanism is needed to achieve population inversion, often using electrical current or intense light. Lasers typically operate as three-level or four-level systems, with four-level systems allowing continuous operation.

Characteristics of Laser Beams

Laser beams are known for:

• High coherence

• Monochromaticity

• Low divergence

• High intensity

The resonant cavity and the gain medium determine beam properties. Lasers may operate in continuous-wave or pulsed modes, with pulsed lasers capable of extremely high peak powers.

Laser Diodes

Laser diodes are semiconductor-based PIN structures where electrons and holes recombine in the active region to produce light. Modern designs use double heterostructures and quantum wells for efficiency. Laser diodes can be driven by electrical injection or optical pumping (OPSLs). They are widely used due to small size, high efficiency, and ease of integration.

Conclusion

With sales of almost 733 million units in 2004 [26] compared to 131,000 of other laser kinds, laser diodes are numerically the most popular form of laser.[27] Because they are simple to modify and couple light sources for fiber-optic communication, laser diodes are frequently utilized in telecommunications. They are found in a variety of measuring devices, including rangefinders. Barcode readers are another typical application. As laser pointers, visible lasersusually red, but subsequently green as wellare widely used. [26][27]. The printing industry makes considerable use of both low- and high-power diodes as light sources for image scanning (input) and for the production of printing plates (output) at extremely high speeds and resolutions. Red and infrared laser diodes are frequently found in DVD technologies, CD players, and CD-ROMs. Blu-ray technology and HD DVD both use violet lasers. Diode lasers are also widely used in laser absorption spectrometry (LAS) for the quick and inexpensive measurement or tracking of different species\' concentrations in the gas phase.

References

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Copyright

Copyright © 2025 Muhammad Arif Bin Jalil. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.