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Everything You Need to Know About DFB Laser

Several types of lasers have been invented in the last few decades to tackle the rising need for communication. One such laser is called the DFB laser. It is a type of narrow linewidth laser diode or an optical fibre laser where the grating generally happens along the cavity, and not just at the two ends.

The structure of the diode builds a one-dimensional interference grating, also known as Bragg scattering. Being single-frequency laser diodes, distributed feedback laser provides a narrow linewidth with good side mode suppression.

Unlike other conventional laser diodes, distributed feedback lasers do not use two mirrors to develop the optical cavity. Instead, in this narrow linewidth laser diode, grating acts as the wavelength-selective element for at least one of the mirrors. It provides feedback, which ultimately reflects light into the cavity to form the resonator.

Primarily, there are two types of DFB lasers– Fiber lasers and Semiconductor lasers. Semiconductor lasers can be defined as a device that causes laser oscillation by passing an electric current to the semiconductor. While fibre lasers are devices in which the light is channelled and amplified through fibre optic cable.

Below are some of the principal characteristics of the DFB laser.

Principal Characteristics of DFB Laser:

• DFB lasers are used to generate a signal with a single frequency.
• It provides a higher modulation speed of up to 15Gbps.
• Distributed feedback lasers offer distraction grating above the active region.
• It is less susceptible to temperature variations.
• In DFB lasers, the periodic variation of the refractive index is obtained using a diffraction grating.
• Except for the single-mode, all other modes are suppressed by oscillators near the Bragg wavelength.

Application of Distributed Feedback Laser:

DFB lasers offer smooth and tunable control of the wavelength, low noise, and narrow spectral width, making it a cost-effective, ideal narrow linewidth laser for fibre optic communication and sensing applications. Below are some of the key applications of these lasers.

A. Optic Communication:

Distributed feedback lasers are widely used in the telecommunication industry. Besides, integrated DFB lasers are highly preferred in optical communication applications, such as DWDM, where a tunable laser signal is desired.

B. Sensing:

Being a narrow linewidth laser, distributed feedback lasers are also used in sensing where the extremely narrow linewidth is required or in gas sensing applications where the absorbing gas signal is detected while wavelength tuning the DFB laser.

C. Medical Uses:

DFB lasers are widely accepted in the medical field too. Its shrinking size, cost, and user-friendliness make it an ideal instrument for minor soft tissue procedures. From dentistry to spectroscopy to photodynamic therapy, It is now adopted by almost every medical branch.

A few other DFB laser diodes applications are barcode readers, CD players, image scanning, laser absorption, and spectrometry. Besides, these high power, narrow linewidth laser diodes have a wide-scale use in the industry too. It is used for seam welding, cladding, and heat treating.

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