distributed Bragg reflector lasers (original) (raw)

Acronym: DBR laser

Definition: lasers containing semiconductor-based distributed Bragg reflectors as end mirrors

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Related: single-frequency laserswavelength tuningtunable laserslaser diodesdistributed feedback lasersexternal-cavity diode lasersfiber lasersfiber Bragg gratingsBragg mirrors

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Contents

What are Distributed Bragg Reflector Lasers?

A distributed Bragg reflector laser is a laser, where the laser resonator is made with at least one semiconductor-based distributed Bragg reflector (DBR) outside the gain medium (the active region). A DBR is a Bragg mirror, i.e., a light-reflecting device (a mirror) based on Bragg reflection at a periodic structure. In most cases, the Bragg mirror is more specifically a quarter-wave mirror, providing the maximum amount of reflection for the given number of layers.

Lasers of DBR type are usually laser diodes, but the term is also sometimes used for fiber lasers containing fiber Bragg gratings. Both laser types are described below. Most solid-state bulk lasers actually also use laser mirrors which are Bragg mirrors; nevertheless such lasers are not called DBR lasers.

A DBR laser is different from a distributed feedback laser, where the whole active medium is embedded in a single distributed reflector structure. It also differs from Fabry–Pérot laser diodes; those also usually have a Bragg reflector on one side, but a dielectric one, typically having a much broader reflection bandwidth.

DBR Laser Diodes

A DBR laser diode contains some corrugated waveguide structure (a grating section) providing wavelength-dependent feedback to define the emission wavelength. Another section of the laser waveguide acts as the amplifying medium (active region), and the other end of the resonator may have another DBR.

DBR laser diodes are usually single-frequency lasers with diffraction-limited output, and often they are wavelength-tunable (→ tunable lasers). Wavelength tuning within the free spectral range of the laser resonator may be accomplished with a separate phase section, which can e.g. be electrically heated, or simply by varying the temperature of the gain region via the drive current. If the temperature of the whole device is varied, the wavelength response is significantly smaller than for an ordinary single-mode laser diode, since the reflection band of the grating is shifted less than the gain maximum. Electro-optic tuning can also be accomplished. Mode-hop free tuning over a larger wavelength region is possible by coordinated tuning of the Bragg grating and the gain structure.

There are more sophisticated device designs, exploiting a kind of Vernier effect with sampled gratings (SG-DBR laser), that offer a tuning range as wide as e.g. 40 nm, although not without mode hops.

The linewidth of a DBR diode is typically a few megahertz. Due to the relatively short laser resonator, it is substantially larger than that e.g. of an external-cavity diode laser.

There are MOPA structures where an additional amplifier section (a semiconductor optical amplifier) is placed on the same semiconductor chip. The actual DBR laser is then the seed laser. Output powers well above 100 mW can be achieved with such devices. It is also possible to directly generate high powers (> 10 W) with a broad-area laser diode having a surface Bragg grating within its resonator [10]. The emission may then no longer be in a single mode, but still with a relatively small bandwidth.

Vertical cavity surface-emitting lasers (VCSELs) are actually also distributed Bragg reflector lasers, even though the term “DBR laser diodes” is normally used for edge-emitting semiconductor lasers.

Applications of DBR laser diodes include optical fiber communications, free-space optical communications, laser cooling, optical metrology and sensors, and high-resolution laser spectroscopy. DBR lasers actually compete with external-cavity diode lasers (ECDLs), which also offer wavelength-tunable single-frequency output, with potentially better performance e.g. in terms of noise, but also requiring a significantly more complex setup. Chips containing DBR laser arrays can serve as very compact sources for use in wavelength division multiplexing systems.

DBR Fiber Lasers

DBR fiber laser

Figure 1: Short DBR fiber laser for narrow-linewidth emission.

A fiber laser of DBR type usually has a linear laser resonator formed by an active (rare-earth-doped) fiber between two fiber Bragg gratings. Compared with a fiber DFB laser, which consists of a single grating in a fiber with laser gain, a DBR fiber laser has a longer laser resonator and thus the potential for higher output power, higher power efficiency, and narrower linewidth. On the other hand, this can also lead to less robust single-frequency operation, or to multimode operation with a correspondingly much larger emission bandwidth. Single-frequency DBR fiber lasers offer similar output powers as DBR laser diodes: tens of milliwatts or sometimes > 100 mW.

Sampled grating designs, as described in the section on DBR laser diodes, can also be used in DBR fiber lasers. The tuning range achievable can again have a width of tens of nanometers.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is a distributed Bragg reflector (DBR) laser?

A DBR laser is a laser where the optical resonator incorporates at least one distributed Bragg reflector (DBR) that is located outside the active gain medium. The DBR acts as a wavelength-selective mirror.

What is the difference between a DBR laser and a DFB laser?

In a DBR laser, the Bragg reflector is separate from the gain medium. In a distributed feedback (DFB) laser, the gain medium itself is embedded within the distributed reflector structure.

What are the main types of DBR lasers?

The most common types are DBR laser diodes, which are semiconductor lasers, and DBR fiber lasers, which use an active optical fiber and fiber Bragg gratings as reflectors.

How can the wavelength of a DBR laser diode be tuned?

Tuning can be achieved by changing the temperature of the gain region via the drive current or by using a separate phase section in the waveguide. Coordinated tuning of the grating and gain sections allows for wider tuning ranges.

What are common applications for DBR laser diodes?

They are used in optical fiber and free-space communications, laser cooling, optical metrology, sensor technology, and high-resolution laser spectroscopy.

Can DBR lasers produce high output power?

Yes. Devices with an integrated semiconductor optical amplifier can exceed 100 mW. Broad-area DBR laser diodes can even generate powers greater than 10 W, though often with a larger emission bandwidth.

Suppliers

Sponsored content: The RP Photonics Buyer's Guide contains nine suppliers for distributed Bragg reflector lasers. Among them:

Sacher Lasertechnik, supplier of distributed Bragg reflector lasers

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distributed Bragg reflector lasers

Sacher Lasertechnik offers distributed Bragg reflector lasers with emission wavelengths from 760 nm to 1083 nm. Free-space and fiber-coupled versions are available.

Vescent, supplier of distributed Bragg reflector lasers

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distributed Bragg reflector lasers

The D2-200 laser module features an advanced Virtual Point Source (VPS) Distributed Bragg Reflector (DBR) diode laser. This new design uses a proprietary lensing system to reduce astigmatism, matching the divergence in the fast axis to that of the slow axis. The D2-200 employs two stages of temperature control and incorporates optical isolation for dependable long-term, mode hop-free operation.

Innolume, supplier of distributed Bragg reflector lasers

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distributed Bragg reflector lasers

Innolume offers a wide range of Distributed Feedback (DFB) laser diodes with emission from 780 nm to 1330 nm. DFB lasers can be selected from the portfolio with a tolerance of ±1 nm and following assembly options:

Peak wavelength fine-tuning is possible within 0.1 nm precision through continuous adjustment of chip temperature and current.

TOPTICA Photonics, supplier of distributed Bragg reflector lasers

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distributed Bragg reflector lasers

TOPTICA's distributed feedback (DFB) laser diodes feature a grating structure within the semiconductor and thus operate in both longitudinal and transverse single mode. Mode-hop free tuning is maintained over several hundred GHz. Tuning is achieved by modulating either the laser current or the chip temperature. Applications include alkaline spectroscopy, laser cooling, gas detection and the generation of tunable cw terahertz radiation.

Bibliography

[1] R. D. Dupuis and E. P. Dapkus, “Room-temperature operation of distributed-Bragg-confinement Ga1-xAlxAs-GaAs lasers grown by metalorganic chemical vapor deposition”, Appl. Phys. Lett. 33 (1), 68 (1978); doi:10.1063/1.90147
[2] M.-C. Amann et al., “Tunable twin-guide laser: a novel laser diode with improved tuning performance”, Appl. Phys. Lett. 54, 2532 (1989); doi:10.1063/1.101065
[3] G. A. Ball et al., “Modeling of short, single-frequency, fiber lasers in high-gain fiber”, IEEE Photon. Technol. Lett. 5 (6), 649 (1993); doi:10.1109/68.219698
[4] W. H. Loh et al., “High performance single frequency fiber grating-based erbium:ytterbium-codoped fiber lasers”, J. Lightwave Technol. 16 (1), 114 (1998); doi:10.1109/50.654992
[5] G. Morthier et al., “A λ/4-shifted sampled or superstructure grating widely tunable twin-guide laser”, IEEE Photon. Technol. Lett. 13 (10), 1052 (2001); doi:10.1109/68.950732
[6] L. A. Coldren et al., “Tunable semiconductor lasers: a tutorial”, J. Lightwave Technol. 22 (1), 193 (2004)
[7] R. Todt et al., “Wide wavelength tuning of sampled grating tunable twin-guide laser diodes”, Electron. Lett. 40, 1491 (2004); doi:10.1049/el:20046997
[8] R. Todt et al., “Sampled grating tunable twin-guide laser diodes with over 40-nm electronic tuning range”, IEEE Photon. Technol. Lett. 17 (12), 2514 (2005); doi:10.1109/LPT.2005.859155
[9] X. Xu et al., “Chirped and phase-sampled fiber Bragg grating for tunable DBR fiber laser”, Opt. Express 13 (10), 3877 (2005); doi:10.1364/OPEX.13.003877
[10] J. Fricke et al, “High-power 980-nm broad-area lasers spectrally stabilized by surface Bragg gratings”, IEEE Photon. Technol. Lett. 22 (5), 284 (2010); doi:10.1109/LPT.2009.2038792

(Suggest additional literature!)

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