Tag: DFB laser

Distributed Feedback Laser

Distributed feedback laser (DFB) is a type of laser device that utilizes a diffraction grating to create an active region in a device, enabling it to emit light with a narrow line width. DFB lasers have become increasingly popular in industries and research laboratories due to their wide range of applications, such as optical communications, sensing, and medical technology.

Compared to other types of lasers, such as quantum-cascade or optical-fiber lasers, DFB lasers have unique advantages. For example, they offer stable output over time and temperature, low power consumption, and greater tolerance for misalignment in the optical system. Additionally, DFB lasers can produce light with reduced spectral line widths compared to alternative laser sources.

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The main applications for DFB lasers:

Distributed feedback laser devices use a diffraction grating for their active region, making them ideal for different scientific and industrial tasks. Their unique properties and design features enhance accuracy and performance compared to standard laser technologies.

One primary application of DFB lasers is in optical communications, which can be used in high-speed systems such as fiber-optic cables. The narrow spectral line widths enabled by the diffraction grating allow greater flexibility, allowing multiple signals to be coded onto one carrier or wavelength. As a result, these DFB fiber laser systems are increasingly reliable and robust, with less power consumption than traditional lasers.

DFB laser diodes can also be found at the heart of sensing systems, such as those used in astronomy, optical imaging, or chemical detection. The ability to produce light with high-resolution line widths enables accurate monitoring and tracking of various aspects of the environment around us, increasing safety and efficiency in many sectors.

The most significant advantages of DFB laser diode systems include the following:

• They have excellent stability over time and temperature when operated at higher power levels due to their reduced sensitivity to thermal stresses.
• Lower power consumption requirements.
• Improved tolerance for misalignment within optical systems.
• Enable higher speed in optical communications through narrow spectral linewidths that allow multiple signals to be coded onto one carrier or wavelength.
• They can produce light with high resolution, making them ideal for use in sensing systems such as those used in astronomy, optical imaging, or chemical detection.
• Complex active components and periodic structures enable better performance than alternative laser technologies.

Top Manufacturers of DFB lasers:

Eblana Photonics LTD: Dublin, Ireland. They specialize in MIR and NIR laser diodes. They have been in business since 2001 and have years of experience with DFB laser diodes.

CSRAyzer Optical Technology: Wuhan, China, They are an optical device supplier to a worldwide audience. They have been in business since 2013 and have one of the world’s most extensive production facilities for DFB lasers.

Frankfurt Laser Company: Friedrichsdorf, Germany. The team here has experience with DFB DBR and FP laser diodes. They offer a massive selection of power ranges and have been in business since 1994.

Conclusions:

Overall, distributed feedback laser diodes are powerful tools for scientists in many fields due to their unique properties, enabling better accuracy and performance than some standard laser technologies. As research continues into developing DFB devices, further advancements will likely lead to even broader capabilities for this type of laser diode.

Everyone’s heard about lasers, with most of us aware of the important role they play in communications. With fiber optic cabling now the best way to transmit information, lasers are more essential than ever.

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A pivotal technology here is distributed feedback lasers. These are now essential to telecommunications, as well as a host of other research and commercial applications.

But what are DFB lasers?

Below, we’ll answer this question by taking at how distributed feedback diodes work, what they’re used for, and who supplies them. Whether you’re visiting out of curiosity or looking to use DFB lasers, keep reading to find out more.

What are DFB lasers?

DFB stands for “Distributed FeedBack laser” and refers to a type of laser used in fiber optics, telecoms, spectroscopy, atomic analysis, and precise measurement tools.

They are a type of semiconductor, quantum cascade, or optical laser that spreads light in a specific way to form a single-frequency signal.

They are valued for having low noise, a tunable wavelength, and for producing an extremely stable signal that works on a single longitudinal mode. Distributed feedback lasers are also considered extremely cost-effective despite costing more than traditional lasers.

DFB lasers use Bragg grating

The structure of distributed feedback laser diodes consists of an active layer with a periodic grating on top.

Unlike other types of laser structures (such as Fabry-Perot), DFB fiber laser diodes don’t have mirrors sitting on either end of an optical cavity.

Instead, DFB lasers use periodic grating to create a Bragg diffraction effect capable of producing wavelength forms from 640nm all the way up to 14,000nm.

This corrugated grating surface can produce changes in the refractive index of the signal, acting as a wavelength-selecting element alongside a mirror.

This is then reflected back into the diode’s internal cavity, transforming it into a resonator.

Advantages and uses of DFB lasers

• Modulation speeds up to 15Gbps
• Narrow linewidth
• Low-noise
• Temperature resistant
• Excellent side mode suppression
• Strong signal over long distances

This alternative approach to diode structure produces a DFB laser linewidth that is narrow with a waveform that doesn’t mode hop.

Properly implemented, this distributed feedback suppresses non-single modes near the Bragg wavelength. This produces strong and clear signals that can operate over tens of miles before coherence becomes an issue.

This means fast modulation speeds of up to 15Gbps and DFB lasers being less susceptible to temperature interference than other types of laser.

Types of DFB lasers

Distributed feedback lasers typically come in two varieties:

Semiconductor DFBs

Also known as semiconductor DFB lasers, diode DFBs are built with an internal periodic grating structure on top of the active region or laterally coupled on both sides.

These diodes use the internal grating structure as a waveguide and have a linewidth value of 200 MHz and higher.

Fiber lasers

There are also fiber lasers that use Bragg grating to distribute and amplify light reflection through a fiber optic cable. DFB fiber lasers have limited output power but are compact and efficient.

This is considered a more difficult approach than semiconductor DFBs, however, as integrating high-contrast periodic grating into the cable is challenging.

Uses of DFB lasers

Because the wavelength of DFB lasers can be finely tuned, they are highly prized within a variety of industries for a wide range of applications.

As well as barcode readers and image scanning, DFBs find themselves used most commonly for the following:

• Optical communication: used by telecommunications and optical communication to carry strong, stable signals. DFB technology is especially useful for increasing the bandwidth of existing fiber networks through multiplexing.

• Spectroscopy: having a narrow linewidth and the ability to tune the wavelength make DFB lasers essential to sensing applications. DFB gas detectors, for instance, can tune laser light to match the absorption line and oscillation linewidth of a gas to detect its presence.
  
  Click here to learn more about how DFB lasers are being used in gas sensing applications.

• Medical instruments: now that the size and cost of DFB lasers have become more commercially viable, they are increasingly being used within the medical field. Specifically, distributed feedback lasers are used to treat soft tissue issues such as cancerous tumors.

Where can I find DFB laser suppliers?

There are now manufacturers across the globe producing DFB lasers. Some of the main DFB suppliers include:

• AeroDIODE: producing single-mode laser diodes capable of 180mW output power.
• AlphaLas: distributed feedback laser diodes at wavelengths including 1030 to 1064nm.
• Frankfurt Laser Company: offering DFB laser diodes with wavelengths ranging from 760nm to 3640nm.
• iXblue: using Bragg grating to produce fiber lasers with extremely narrow linewidths with zero mode-hopping.
• RPMC Lasers: large selection of DFB and quantum cascade lasers.
• TeraXion: packaging DFB semiconductors, temperature controllers, and low-noise current sources within a single product.
• Toptica Photonics: reliable DFB lasers in wavelengths ranging from 633nm to 3500nm.

FAQs

Why are DFBs more expensive than FP lasers?

Manufacturing DFB lasers is a lot more complex than traditional Fabry-Perot-type lasers.

As it stands, DFB manufacturing has a significantly lower yield rate, with each individual unit requiring more robust testing. However, with a single-mode output that is considerably more stable, DFB lasers are highly prized and in demand despite their higher price.

How are DFB lasers made?

DFB laser fabrication begins with a crystalline silicon structure called an epitaxial wafer. This wafer also contains rare materials that will help modulate the wavelength and power of the laser.

Using cutting-edge machines, gain regions and gratings are buried under cladding layers with special coatings applied to facilitate mode selection.

A single wafer will produce multiple DFBs once cleaved, chipped, and housed.

After fabrication, all DFBs undergo rigorous testing, including temperature resistance and and voltage checks, before being sold.

What’s the difference between DFB lasers vs. DBR lasers?

DBR lasers and DFB lasers are similar in that they both use Bragg gratings.

Structurally DBR lasers are an older technology that uses a high index contrast and high reflectivity. Manufacturing DBR lasers produce a higher yield but only produces a single frequency.

DFB lasers, however, are low index contrast with low reflectivity with a tunable wavelength.