high-brightness laser diodes (original) (raw)
Author: the photonics expert (RP)
Definition: laser diodes with particularly high radiance (brightness)
Category: 
laser devices and laser physics
- semiconductor lasers
- laser diodes
* broad area laser diodes
* high-brightness laser diodes
* diode bars
* diode stacks
* tapered laser diodes
* Fabry–Pérot laser diodes
* photonic crystal surface-emitting lasers
- laser diodes
Related: broad area laser diodestapered laser diodesdiode barsdirect diode lasers
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DOI: 10.61835/yb1 Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn
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Contents
What are High-brightness Laser Diodes
While low-power laser diodes can exhibit a very high beam quality, the beam quality of high-power laser diodes is normally substantially lower. Therefore, the obtained radiance (brightness) is often much less improved than the output power, or even lower than that of a low-power laser. However, there are high-brightness laser diodes which are optimized for a particularly favorable combination of high output power and good beam quality, resulting in a particularly high brightness (more precisely: high radiance).
Types of High-brightness Laser Diodes
The term does not indicate with what technology the high radiance is achieved. In fact, the term is used for quite different types of laser diodes, and particularly for the following categories:
- Most frequently, the term is used for optimized broad area laser diodes, particularly in the form of tapered laser diodes.
- The same principles can be applied to diode bars. However, their radiance is in most cases substantially lower, even if the contained emitters have a very high radiance, since their emission is usually mutually incoherent, and there is some dead space between the emitters.
- Further, there are fiber-coupled diode lasers which are optimized in terms of radiance. That optimization does not necessarily apply to the laser diodes themselves, but can also be done with particularly efficient fiber launch systems.
The radiance of diode laser systems can also be substantially increased with methods of beam combining — in the form of coherent beam combining or spectral beam combining. In such cases, one should actually use the term high-brightness diode lasers instead of high-brightness laser diodes.
Applications of High-brightness Laser Diodes
A typical application of high-brightness laser diodes is the optical pumping of solid-state bulk lasers. A particularly high radiance is required in cases where the pump radiation needs to be strongly focused — for example, in diode-pumped titanium–sapphire lasers. Also, there are cases where a relatively long laser crystal is needed, and the beam quality of the pump radiation then needs to be high enough to avoid substantial divergence within the length of the crystal.
Fiber lasers can also benefit from high-brightness pump sources. For example, these allow one to launch a higher pump power into a double-clad fiber. In other cases, one can use a double-clad fiber with smaller pump cladding, exhibiting stronger pump absorption, so that one can use a shorter length of fiber — as can be beneficial e.g. for minimizing nonlinear optical effects.
The development of pump sources with higher brightness is one of the most important reasons why the performance levels of solid-state bulk and fiber lasers have been substantially raised in recent years. Note that this kind of performance increases should not be considered as resulting from power scaling; they result from component optimization rather than from the application of a scaling procedure.
A high level of radiance is also often required for laser material processing. The substantial technical advances of recent years increasingly enable the use of high-power diode lasers in this area. They are called direct diode lasers, in contrast to lower-brightness lasers which can only be used in conjunction with a diode-pumped laser, functioning as a brightness converter.
Frequently Asked Questions
What is a high-brightness laser diode?
A high-brightness laser diode is a device which has been optimized for a favorable combination of high optical output power and good beam quality, resulting in a particularly high radiance (brightness).
Why is the beam quality of high-power laser diodes often poor?
While low-power laser diodes can have excellent beam quality, design changes made to achieve high output power often lead to a substantial degradation of beam quality, which limits the achievable brightness.
What are common types of high-brightness laser diodes?
What is the difference between a high-brightness laser diode and a high-brightness diode laser?
A 'high-brightness laser diode' typically refers to the semiconductor component. A 'high-brightness diode laser' is a complete system which might use techniques like coherent beam combining or spectral beam combining to boost the radiance of multiple diodes.
Where are high-brightness laser diodes used?
How do high-brightness pump sources improve solid-state lasers?
They allow launching more pump power into small laser crystals or double-clad fibers, or using shorter gain media to minimize unwanted effects like nonlinear optical effects. This has been a key driver for performance increases in solid-state and fiber lasers.
Bibliography
| [1] | J. J. Lim et al., “Design and simulation of next-generation high-power, high-brightness laser diodes”, IEEE J. Sel. Top. Quantum Electron. 15 (3), 993 (2009); doi:10.1109/HPD.2013.6706597 |
|---|---|
| [2] | D. Vijayakumar et al., “Spectral beam combining of a 980 nm tapered diode laser bar”, Opt. Express 18 (2), 893 (2010); doi:10.1364/OE.18.000893 |
| [3] | S. Rauch et al., “Catastrophic optical damage in 950-nm broad-areas laser diodes due to misaligned optical feedback and injection”, IEEE J. Quantum Electron. 54 (4), 2000707 (2018); doi:10.1109/JQE.2018.2856499 |
| [4] | E. Beyatli, “Efficient Tm:YAG and Tm:LuAG lasers pumped by 681 nm tapered diodes”, Appl. Opt. 58 (11), 2973 (2019); doi:10.1364/AO.58.002973 |
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