Distributed Feedback Laser: Working and Its Importance

In recent years, we've been introduced to various advanced lasers that have been developed to address the growing demand for communication. The DFB laser is one such name on the list.

DFB Lasers produce a single-mode output and are much more stable than Fabry-Perot Lasers and Distributed Bragg Reflector Lasers. A diffraction grating placed along the active region of the chip can accomplish this. Distributed feedback lasers are commonly used as a light source for metro, long-distance, and underwater applications due to their narrow spectral width and wavelength stability.

In this blog, we'll look at how distributed feedback lasers work and how important they are. But first, let us define the DFB laser and its various types.

What Is DFB Laser and What Are Its Different Types?

A DFB laser is a narrow linewidth laser diode or optical fiber laser in which the grating occurs throughout the cavity rather than just at the two ends. The diode's structure creates a one-dimensional interference grating, also called Bragg scattering. Besides, distributed feedback lasers have a narrow linewidth and good side mode suppression because they are single-frequency laser diodes.

Fiber DFB lasers and semiconductor DFB lasers are the two main types of distributed feedback lasers. Semiconductor lasers are devices that cause laser oscillation by passing an electric current through a semiconductor, whereas fiber lasers are devices that channel and amplify light through fiber optic cable.

Working of DFB Laser

The operation of a distributed feedback laser differs significantly from that of traditional lasers. Unlike traditional laser diodes, it does not use two separate mirrors to form the optical cavity. Instead, a diffraction grating creates the upper waveguide layer on top of the active region. The active region comprises several quantum wells, which are then buried by the current blocking layers.

Also, DFB lasers are coated on one side of the cavity with anti-reflection material and the other side with high reflectivity material. As a result, the grating and dispersed mirrors are formed by the anti-reflection coated side, while the reflective side forms the other mirror. Besides that, the optical feedback of the DFB laser is provided by uniform Bragg diffractive gratings.

The grating acts as one of the mirrors and forms the resonator by reflecting light back into the cavity. It is constructed in such a way that only a narrow wavelength band is reflected, resulting in a single longitudinal lasing mode.

However, it is important to note that as technology advances, the architecture of DFB lasers has become increasingly sophisticated and complex. Let us now move on to the final section of the blog: the importance of distributed feedback lasers.

Importance of DFB Laser

DFB lasers have a smooth and tunable wavelength control, low noise, and narrow spectral width, making them an ideal narrow linewidth laser for fiber optic communication and sensing applications. Some of the most common uses for DFB lasers are listed below.

A. Optic Communication: The telecommunications industry makes extensive use of DFBs. Moreover, in optical communication applications such as DWDM, where a tunable laser signal is desired, integrated DFB lasers are highly preferred.

B. Sensing Applications: distributed feedback lasers, as narrow linewidth lasers, are also used in sensing applications where an extremely narrow linewidth is required, such as gas sensing.

C. Medical Uses: DFB lasers are widely used in the medical field, from dentistry to spectroscopy to photodynamic therapy. Its small size, low cost, and ease of use make it an excellent instrument for minor soft tissue procedures.

Inphenix, based in the United States, is a leading laser and light source manufacturer and supplier. The firm deals with multiple lasers, including DFB lasers, SLDs, Swept-source lasers, and broadband light sources, among others. The company also develops customized lasers based on specific requirements.