This section provides overview, applications, and principles of laser diodes. Also, please take a look at the list of 17 laser diode manufacturers and their company rankings.
A laser diode is a laser that uses recombination emission from a semiconductor.
The color of the laser is determined by the elements that make up the semiconductor. Some lasers operate at room temperature, while others require cooling, depending on the resonator structure and output power.
The difference between laser diode and LEDs is that laser diode meet the requirements for laser oscillation. Variations in wavelength and amplitude of the light are much smaller in laser diode as well.
Laser diodes are widely used in consumer information equipment because of their small size, low power consumption, and low cost.
They are used in optical pickups for optical drives such as CDs, DVDs, and BDs, copiers, laser printers, and optical fiber-based communication devices. High-power laser beams are also used in laser markers and laser processing machines.
The diffusion-resistant and long-distance reach of laser light is also used in surveying instruments and laser pointers for pointing at objects.
In laser diodes, light is emitted by the recombination of holes (holes through which electrons have been released) and electrons when a voltage is applied.
The emitted photon triggers another electron to recombine with the hole one after another, emitting photons, so that the generated light has the same phase and wavelength. Since the wavelength of the light is always constant, it is used in bar code readers, laser pointers, fiber-optic communications, and other applications requiring a constant amount of light.
The L/I curve is used to understand laser diodes specifications. This curve allows us to keep track of the drive current supplied in relation to the light intensity output.
This curve is used to determine the operating point (drive current at rated emission output) and threshold current (starting current of laser oscillation) at the laser, and is also used to determine the current required to obtain high output power at a particular current.
By reading this curve chart, one can see that optical output depends greatly on temperature, and that as temperature increases, laser characteristics also decrease. This makes it possible to visualize and estimate the efficiency of a laser diodes by incorporating the L/I curve.
Light-emitting diodes have disparate phases, so light rays are diffused radially. In contrast, laser diodes are in phase with each other, resulting in a linear beam of light.
Therefore, the light-emitting diode has a characteristic that it is difficult to enter a fiber with a small core system due to the wide surface of the light-emitting layer. On the other hand, laser diodes have a narrow emitting layer, but it is easy for the light to enter a fiber with a small core system.
And since laser diodes emit photons by colliding every emitted photon with another atom, the light produced is coherent and the light beam is monochromatic. In contrast, the light produced by a light-emitting diode is incoherent and the emitted light consists of various colors.
The average life of a laser diodes varies depending on the operating environment (operating temperature, static electricity, power surges) and is generally between 10,000 and 50,000 hours.
The following section discusses operating temperature among the environmental factors that affect the average life of laser diodes.
First, operating temperature is said to reduce life expectancy by half when the operating temperature rises by 10°C. If the operating temperature continues to rise above the maximum operating temperature, the laser diodes are more likely to be damaged and its long-term performance degraded. And the degradation rate at operating temperatures increases exponentially with operating temperature.
Therefore, the use of heat sinks (radiating plates) is recommended to reduce the effects of operating temperature and to increase luminous output.
*Including some distributors, etc.
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