Photonics Dictionary

distributed feedback laser

A distributed feedback laser (DFB laser) is a type of semiconductor laser diode designed to emit coherent, narrow-bandwidth light with precise control over the wavelength. It achieves this through a structure that incorporates a grating within the laser cavity. This grating, often referred to as a distributed feedback grating, provides feedback for specific wavelengths, resulting in the emission of laser light at a well-defined frequency.

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Key features of a DFB laser include:

Grating structure: The laser cavity of a DFB laser includes a grating structure integrated into the semiconductor material. This grating acts as a wavelength-selective reflector.

Single mode operation: DFB lasers are designed to operate in a single longitudinal mode, meaning they emit light at a specific, well-defined wavelength. This characteristic makes them suitable for applications requiring precise and stable optical frequencies.

Narrow linewidth: The feedback provided by the grating results in a narrow linewidth, contributing to the laser's ability to emit light at a specific wavelength with high spectral purity.

Wavelength tunability: Some DFB lasers can be tuned to specific wavelengths by adjusting the grating period or using other tuning mechanisms.

Applications: DFB lasers are commonly used in telecommunications, fiber optics, spectroscopy, and other applications where precise control over the emitted wavelength is crucial.

High coherence: The distributed feedback mechanism contributes to the high coherence of DFB lasers, making them suitable for applications that require stable and coherent light sources.

DFB lasers play a crucial role in optical communication systems, where their narrow linewidth and stable wavelength are essential for transmitting and receiving data over fiber-optic networks. They are also employed in various sensing and measurement applications where precise wavelength control is necessary.
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