Distributed Feedback Lasers

Dr. Rüdiger Paschotta

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Distributed Feedback Lasers

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Acronym: DFB lasers

Definition: lasers where the whole laser resonator consists of a periodic structure, in which Bragg reflection occurs

More general term: lasers

Categories: article belongs to category optical resonators optical resonators, optoelectronics, article belongs to category laser devices and laser physics laser devices and laser physics

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DOI: 10.61835/gdn Cite the article: BibTex plain text HTML Link to this page! LinkedIn

A distributed-feedback laser (DFB laser) is a laser where the whole resonator consists of a periodic structure in the laser gain medium, which acts as a distributed Bragg reflector in the wavelength range of laser action. Typically, the periodic structure is made with a phase shift in its middle. Essentially, one has a direct concatenation of two Bragg gratings with optical gain within the gratings. The device has multiple axial resonator modes, but there is typically one mode which is favored in terms of losses. (This property is related to the above-mentioned phase shift.) Therefore, single-frequency operation is often easily achieved, despite spatial hole burning due to the standing-wave pattern in the gain medium. Due to the large free spectral range, wavelength tuning without mode hops may be possible over a range of several nanometers. However, the tuning range may not be as large as for a distributed Bragg reflector laser.

Figure 1: DFB fiber laser, containing a fiber Bragg grating with a phase change in the middle, directly written into a rare-earth-doped fiber.

DFB lasers should not be confused with DBR lasers = distributed Bragg reflector lasers.

Types of DFB Lasers

Most distributed-feedback lasers are either fiber lasers or semiconductor lasers, operating on a single resonator mode (→ single-frequency operation).

Fiber Lasers

In the case of a fiber laser, the distributed reflection occurs in a fiber Bragg grating, typically with a length of a few millimeters or centimeters. Efficient pump absorption can be achieved only with a high doping concentration of the fiber, and unfortunately it is often not easy to write high contrast Bragg gratings into fibers with a composition (e.g. phosphate glass) which allows for a high doping concentration. Therefore, the output power is usually fairly limited (e.g. to a few tens of milliwatts), and the power conversion efficiency is small. However, this kind of single-frequency fiber laser is very simple and compact. Its compactness and robustness also leads to a low intensity and phase noise level, i.e., also a low linewidth, although the fundamental linewidth limit (the Schawlow–Townes linewidth) is higher than for longer fiber lasers.

Diode Lasers

Semiconductor DFB lasers can be built with an integrated grating structure, e.g. a corrugated waveguide. The grating structure may be produced on top of the active region, which however requires time-consuming regrowth techniques. An alternative is to make laterally coupled structures, where the gratings are on both sides of the active region. Semiconductor DFB lasers are available for emission in different spectral regions at least in the range from 0.8 μm to 2.8 μm.

Typical output powers are some tens of milliwatts. The linewidth is typically a few hundred MHz, and wavelength tuning is often possible over several nanometers. Temperature-stabilized devices, as used e.g. in DWDM systems, can exhibit a high wavelength stability.

More to Learn

Single-frequency operation

Single-frequency lasers

Distributed Bragg reflector lasers

Fiber Bragg gratings

Fiber lasers

Semiconductor lasers

Suppliers

The RP Photonics Buyer's Guide contains 43 suppliers for distributed feedback lasers. Among them:

Quantifi Photonics

Quantifi Photonics' Laser 1200 Series is a compact and versatile fixed-wavelength laser source that can be customized to meet specific wavelength and power requirements, and is available in benchtop or PXI form factor.

TOPTICA Photonics

TOPTICA’s DLC DFB pro lasers integrate both distributed-feedback (DFB) and distributed Bragg reflector (DBR) lasers. Available wavelengths include 633 nm and the entire range from 760 nm to 3500 nm. Three laser heads accommodate different diode packages. Due to the absence of alignment-sensitive components, the DLC DFB pro lasers exhibit an exceptional stability and reliability.

Alpes Lasers

Alpes Lasers offers single-mode, tunable DFB lasers with wavelengths from 4 to 14 μm and powers up to hundreds of milliwatts. These lasers are able to emit a single wavelength at a time. They can be tuned within a range that can reach up to 10 cm⁻¹; there exists a variety of modulation schemes which can be used for different purposes.

RPMC Lasers

Serving North America, RPMC Lasers offers a broad selection of distributed feedback lasers in NIR, SWIR, and LWIR wavelengths from approximately 750 nm to 16 µm, eliminating wavelength drift and providing exceptionally high spectral purity with multiple output powers available for most wavelengths.

Our innovative DFB technology delivers narrow linewidth output with stable operation over a broad temperature range, low sensitivity to optical feedback, and high-quality, low-noise performance, enhanced by integrated TEC cooling for efficient thermal management and robust thermal and optical stability.

Customizable, compact designs come in HHL, OEM, or turnkey packages, with lightweight, robust, hermetically sealed options and optional fiber coupling for long-term reliability and easy integration in sensing and telecom applications.

Let RPMC help you find the right laser today!

Exail

Exail’s single-frequency fiber lasers are based on UV Bragg grating technology applied to active rare-earth photosensitive fibers. The ultra-short cavity and the phase-shifted design permit ultra-narrow linewidth and robust mode-hop-free laser operation, ideal for various sensor applications (1.5 and 2 µm available upon request).

Benefits and features:

wavelength range 1530 – 1565 nm and 2 µm
output power: >10 mW (> 10 µW for low noise version)
single longitudinal mode
narrow linewidth, low phase noise, mode-hop-free
linear polarization, PM available
low optical feedback sensitivity

ALPHALAS

Narrow-band distributed feedback diode lasers with free-space beam or fiber coupling at numerous wavelengths: 1030 nm, 1047 nm, 1053 nm and 1064 nm are available from stock. In order to match the gain maximum of popular amplifying media as seed lasers, temperature tuning and wavelength selection are offered for the above standard laser wavelengths.

Sacher Lasertechnik

Sacher Lasertechnik offers single-mode narrow-linewidth distributed feedback lasers emitting between 760 nm and 2800 nm. Free space and fiber pigtailed versions available.

CSRayzer Optical Technology

CSRayzer DFB butterfly package laser modules are widely used for fiber-optic sensing, laser radar, optical communication, and scientific research.

eagleyard Photonics

TOPTICA EAGLEYARD offers different kinds of laser types as single frequency laser diodes. The portfolio comprises a variety of laser and package designs from TO-package to hermetically sealed butterfly packages suitable for industrial applications. Benefit from space-qualifable laser diodes and those that are space-qualified or have space heritage. We offer Distributed Feedback lasers (DFB lasers), Distributed Bragg Reflector lasers (DBR lasers), Rich Waveguide Stabilized lasers (RWS), miniECLs and uMOPA.

AeroDIODE

SHIPS TODAY: Fiber-coupled DFB laser diodes (1030 nm DFB, 1064 nm, 1310 nm, 1550 nm or any wavelength between 1250 nm and 1650 nm) are offered as stock items or associated with a CW or pulsed laser diode driver. They are compatible with our high speed nanosecond pulsed drivers or low noise laser diode driver for ultra-narrow linewidth single frequency emission. The single-mode laser diode can reach high powers up to 500 mW in the nanosecond pulse regime. Most turn-key diode & driver solutions are optimized for single-shot to CW performances with pulse durations down to 1 ns. The laser diode precision pulses are generated internally by an on-board pulse generator, or on demand from an external TTL signal.

See also our tutorial on fiber-coupled laser diodes.

NKT Photonics

Koheras single-frequency fiber lasers are longitudinally single-mode and feature extremely low phase and intensity noise levels. These lasers are available in erbium or ytterbium wavelength ranges and can be frequency-converted to various other bands. The all-fiber DFB design ensures robust and reliable operation for thousands of hours, prioritizing reliability. Koheras lasers are highly stable and mode-hop-free, even under changing environmental conditions. We also offer shot-noise-limited lasers for applications requiring exceptionally low-intensity noise.

Thorlabs

Thorlabs’ single-frequency laser portfolio includes a wide variety of distributed feedback (DFB) lasers. We design and manufacture low-noise DFB laser systems in a turnkey platform with a center wavelength of 1310 nm or 1550 nm. Individual DFB laser diodes in butterfly packing are available from stock with center wavelengths of 1320 nm, 1550 nm, 1642 nm, 1646 nm, 1650 nm, or 1654 nm. We also manufacture DFB quantum cascade lasers (QCLs) in either D-Mount, Two-Tab C-Mount, or thermally cooled Horizontal Heat Load packages; with output at key wavelengths in the mid-infrared, these lasers are a popular choice for gas and chemical sensing applications.

Eblana Photonics

Eblana Photonics core product offerings are based on our patented Discrete-Mode manufacturing technology, which delivers industry leading performance with fully scalable, consistent production and integration capability. Eblana’s Discrete-Mode laser diodes are used extensively for trace gas sensing, fibre sensing and LIDAR applications and environmental monitoring in the near- and mid-IR (650 nm – 12 μm).

Bibliography

[1]	H. Kogelnik and C. V. Shank, “Stimulated emission in a periodic structure”, Appl. Phys. Lett. 18, 152 (1971); https://doi.org/10.1063/1.1653605
[2]	H. Kogelnik and C. V. Shank, “Coupled-wave theory of distributed feedback lasers”, J. Appl. Phys.43 (5), 2327 (1972); https://doi.org/10.1063/1.1661499
[3]	A. Yariv, “Coupled-mode theory for guided-wave optics”, IEEE J. Quantum Electron. 9 (9), 919 (1973); https://doi.org/10.1109/JQE.1973.1077767
[4]	H. W. Yen et al., “Optically pumped GaAs waveguide lasers with a fundamental 0.11 μ corrugated feedback”, Opt. Commun. 9, 35 (1973); https://doi.org/10.1016/0030-4018(73)90330-1
[5]	K. H. Ylä-Jarkko and A. B. Grudinin, “Performance limitations of high-power DFB fiber lasers”, IEEE Photon. Technol. Lett. 15 (2), 191 (2003); https://doi.org/10.1109/LPT.2002.806827
[6]	B. K. Das et al., “Distributed feedback-distributed Bragg reflector (DFB-DBR) coupled cavity laser with Ti:(Fe:)Er:LiNbO₃ waveguide”, Opt. Lett. 29 (2), 165 (2004); https://doi.org/10.1364/OL.29.000165
[7]	K. Sato, “Chirp characteristics of 40-Gb/s directly modulated distributed-feedback laser diodes”, IEEE J. Lightwave Technol. 23 (11), 3790 (2005); https://doi.org/10.1109/JLT.2005.857753
[8]	A. Schülzgen et al., “Distributed feedback fiber laser pumped by multimode laser diodes”, Opt. Lett. 33 (6), 614 (2008); https://doi.org/10.1364/OL.33.000614
[9]	M. Pollnau and J. D. B. Bradley, “Optically pumped rare-earth-doped Al₂O₃ distributed-feedback lasers on silicon”, Opt. Express 26 (18), 24164 (2018); https://doi.org/10.1364/OE.26.024164

(Suggest additional literature!)

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