Overview of DFB Laser: Types, Characteristics, Working And Applications

Different kinds of lasers have been developed in recent years to meet the growing need for telecommunication. The DFB laser is one such example. Using distributed feedback lasers is one of the greatest approaches to addressing the demands of low-signal lasers. Such lasers not just assisted to satisfy the demands of the telecommunications sector, but also forced DBR lasers to disappear from the markets.

This blog will examine the significance of DFB lasers, and also explore why these have been a good choice for telecommunication systems in recent years.

Characteristics, Working, And Applications of DFB Laser

What Is a DFB Laser?

A DFB laser is a laser diode or optical fiber laser with a low linewidth grating that extends throughout the cavity rather than simply at the opposite edges. Because they are single-frequency laser diodes, distributed feedback lasers have short linewidth and effective side modes.

Distributed Feedback Lasers, unlike standard laser architectures, do not need two mirrors on both sides of the active zone to form optical cavities. Rather, diffraction on the active region serves as a wavelength select component and provides feedback through one mirror. Because of its high output power and stability, this laser is primarily utilized for high data rate long-distance transmission and clean single-mode operation.

What Are Its Different Types?

Distributed Feedback Lasers are divided into two types: fiber lasers and semiconductor lasers. Let’s take a deeper look at these two separate categories to better grasp their functioning and features.

1. Fiber DFB lasers

The distributed reflection in a fiber laser operates in a fiber Bragg grating, which generally has a width of a few millimeters or centimeters. This type of single-frequency fiber laser, on the other hand, is relatively simple and small. Because of its compactness and resilience, it has a low intensity and phase noise level, resulting in a low linewidth, even if the linewidth limit is larger than for longer fiber.

2. Semiconductor DFB lasers

Another form of distributed feedback laser is a semiconductor DFB Laser. It is built with an integrated grating structure that utilizes the Bragg reflection to unify the laser longitudinal mode. A semiconductor DFB Laser connection layer is generally a few micrometers thick, and the crystal’s end sides are somewhat reflected to form an optical resonance.

Working of DFB Laser

A distributed-feedback laser is a laser in which the whole resonator is made up of a pattern in the laser host material that functions as a distributed Bragg reflector throughout the range of wavelengths of laser activity. The device features various axial resonator modes, although one mode is commonly preferred in respect of any loss. 

DFB lasers have an anti-reflection coating on one side of the cavity and a strong reflectivity coating on the other. As a consequence, the anti-reflection coated side creates the grating and scattered mirrors, while the reflecting side makes the other mirror. It is designed to reflect just a restricted wavelength band, resulting in a single spatial lasing phase.

After knowing the DFB laser working principles, let’s see some of its special characteristics.

Characteristics of Distributed Feedback Laser

The following are some of the major qualities of DFB lasers that make them a popular choice for fiber communication networks.

  1. The DBB laser exhibits very narrow linewidths with a very low relative intensity noise.
  1. Fabry Perot (FP) lasers have long been utilized as a light source for fiber communication. These lasers, however, were only successful for short-distance communication. Because FP lasers have serious problems with long-distance transmission. The DFB laser provided a solution to all of these restrictions.
  1. Another element that separates the DFB laser from other lasers is its construction. Unlike conventional laser diodes, It does not construct the optical cavity with two separate mirrors. Instead, a diffraction grating on top of the active zone creates the upper waveguide layer
  1. Furthermore, Distributed Feedback Lasers are commonly constructed with a quantum well structure. Whenever light is confined in a cavity smaller than its wavelength, it acts as a particle rather than a wave.
  1. Because of DFBs Quantum Well (QW) structure, it has a low threshold current, less temperature dependence, and a narrow gain spectrum.

These were some of the features of the DFB laser which make it special and different from other lasers. Next, let’s see some important applications of distributed feedback lasers.

Applications of DFB Laser

Some of the most important uses for DFB lasers are listed below.

1. Optic Communication

Distributed Feedback Laser is frequently utilized in the telecommunications sector because of its smooth and adjustable wavelength control, low noise, and narrow spectral width. Furthermore, integrated DFB lasers are widely sought in optical communication applications such as DWDM optical fiber multiplexing technology, in which a tunable laser signal is needed.

2. Undersea Applications

The mysterious ocean hides many secrets. To detect which signal processing techniques UWC (underwater wireless communication) are used. Distributed feedback lasers are an important component of these techniques. UWC is used in different applications like undersea monitoring, observing marine life, detecting oil and natural gas sources, and early warning of tsunamis.

3. Sensing

Distributed Feedback Laser-like tiny linewidth lasers are also utilized in sensing applications where an extremely thin linewidth is required, such as gas sensing, where the absorbing gas signal is measured while wavelength adjusting the DFB laser.

4. Medical Uses

DFB lasers are also commonly used in the medical industry. Its small size, low cost, and ease of use make it the ideal equipment for modest soft tissue treatments. Distributed feedback lasers are currently used in practically every medical field, from dentistry to spectroscopic to photosensitizer treatment.

5. Telecommunication

DFB lasers are used globally for enhanced telecommunication due to their stable outputs. They propagate narrow bandwidth spectrum lines that benefit the telecommunication industry. It is ideal for fast and reliable data transmission in telecommunication. Therefore, distributed-feedback lasers are extensively used to streamline communication networks in combination with optical fibers. 

6. Sensing and Metrology

DFB lasers emit wavelengths that are stable and coherent, therefore facilitating metrology applications. It increases the precision of metrology to reduce consumer risk and costs by ensuring the highest product quality in various industries including engineering, aerospace, manufacturing, energy, and healthcare.

7. Defence and Security

DFBs are popular in defence for their effective range and accurate target-detecting abilities. Their ability to emit light at specific wavelengths makes them valuable in military and security applications. Moreover, their stability during targeting provides exact imaging and sensing abilities for military activities.

8. Biophotonics

DFB lasers are employed in biophotonics applications, such as fluorescence microscopy, flow cytometry, and DNA sequencing. Their precise wavelength control and high power output enable sensitive and selective detection of biomolecules. By using DFBs researchers are looking forward to finding the roots of some of the fatal diseases whose causes are hidden deep within the DNA.

Final Words

So these are the working principles, characteristics and some applications of the DFB laser that distinguish it from other lasers. We hope that this blog has made you aware of the distributed feedback laser. Visit our other blogs to learn more about this laser.

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