This section provides an overview for dfb lasers as well as their applications and principles. Also, please take a look at the list of 10 dfb laser manufacturers and their company rankings.
Table of Contents
A DFB laser is a type of laser diode with a constant output wavelength. By creating diffraction gratings at the boundaries of the diode layers, only the wavelength of light emitted from the active layer that is twice the distance between the gratings can be amplified and emitted. The output wavelength of a DFB laser is stable at a constant wavelength, whereas the wavelength of a normal laser diode is distorted by the applied current, the operating environment, or modulation.
DFB lasers are mainly used in high-capacity, long-distance optical communications. The reason for their use in optical communications is that they can maintain stable output at a constant wavelength even with high current levels, operating environments, and high-speed modulation. Other applications of DFB lasers include endoscopy of the colon and esophagus, structural analysis using Raman spectroscopy, wavelength conversion, and gas testing, etc. When selecting DFB lasers, it is necessary to consider the allowable current, output wavelength, connection terminals, corresponding operating environment, and size.
This section describes the principle of operation of DFB lasers. Like a normal laser diode, DFB lasers have a p-type cladding layer, an n-type cladding layer, and an active layer between these layers. The p-type cladding layer has a positive electrode connected to it, n-type cladding layer has an n-type base, and n-type base has a negative electrode connected to it . Reflectors are attached to the sides of those layers. the DFB lasers are manufactured so that the interface between the p-type cladding layer and the active layer is a diffraction grating.
During operation, a forward voltage is applied from the electrode. The applied voltage causes electrons and holes to enter the active layer from their respective cladding layers, and when these charges recombine, light is emitted. This light is amplified by the active layer boundaries and reflectors. The light reflected by the diffraction grating reflects only a specific wavelength, resulting in the amplification of only a single wavelength of light. The amplified light is extracted from the DFB lasers.
DFB lasers are characterized by their extremely stable wavelengths with respect to temperature. Another important factor is the temperature controllability of the wavelength.
In general DFB lasers, the wavelength gradient with respect to temperature is said to be about 0.1 nm/℃. The oscillation wavelength is determined and controlled by two parameters: wavelength adjustment by the period of the DFB lasers grating and this temperature gradient.
To reduce cost and current consumption, DFB lasers that do not require external temperature control are also being actively researched, along with packaging methods and the application of new compound semiconductor materials such as Al-based materials. DFB lasers, which do not require external temperature control, are also being actively researched to reduce cost and current consumption.
In the world of long-distance optical communications, wavelengths with the lowest possible optical fiber transmission loss are selected to minimize communication loss. Optical fibers made of quartz actually have significantly different losses depending on the wavelength of light that passes through them, and generally, wavelengths in the 1.3μ band and 1.5μ band are often used. In particular, the wavelength of 1550 nm is a typical wavelength for long-wavelength DFB lasers because it has the lowest loss.
Other types of 1550 nm wavelength lasers include DFB lasers with a λ/4 phase-shifted grating (grating), which can in principle oscillate in a single mode, and DBR lasers with the grating located far from the top and bottom of the active layer.
A semiconductor laser that is often compared to the DFB lasers is the Fabry-Perot (FB) laser.
The major difference between FP lasers and DFB lasers are that FP lasers have difficulty oscillating in a completely single mode.
FP lasers are used in optical pickups for CDs and DVDs, laser printers, etc.
*Including some distributors, etc.
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