定义：是一种光学泵浦装置，其产生的光学输出比泵浦光源的亮度更高。

激光器装置的输出功率通常比泵浦功率低。但是，光学泵浦激光器的亮度则比起泵浦光源的亮度更高，即如果泵浦光源的光束质量较低（亮度也较低），那么输出光束的光束质量更高。 

下面是一些激光器作为亮度转换器的例子： 

• 固态体激光器可能是由高功率激光二极管进行端泵浦或者边泵浦的，然后发射衍射极限光束，亮度被极大的提高。尤其是在采用弧光灯发出的扩散光的边泵浦激光器这一效应尤其明显，虽然其输出光束质量并不是衍射极限的。 
• 采用双包层光纤制作的高功率光纤激光器也可以实现亮度增强。泵浦包层可以传导几千个模式，因此可以采用具有很大M2因子的二极管线阵。单模光纤纤芯可以实现衍射极限的光束质量，并且功率转换效率大于80%。 
• 光学泵浦的垂直外腔表面发射激光器（VECSEL）是一种半导体激光器，也可以得到衍射极限的输出。它对泵浦光束质量的要求很低，主要是由于泵浦辐射由很薄层吸收，因此其光束发散角影响不大（尽管很大的光束发散角会引起激光器制作过程中的几何尺寸问题）。 
• 原理上来说，高功率光学参量振荡器可以作为亮度转换器。虽然大多数OPOs是由接近于衍射极限光束来泵浦的，也可以用很多模式光束泵浦OPO来产生衍射极限的信号光束。闲散光的光束质量可能比较差，但是没有太大影响。 

大多数情况下，亮度转换器主要用在激光器应用中。例如，很多固态激光器用在材料加工中，因为它们的泵浦光亮度很低，不能直接应用。（另一个常用的功能是脉冲产生，例如通过Q开关。） 

Definition: optically pumped devices where the generated optical output has a higher brightness than the optical pump source

The output power of a laser device is of course always lower than the pump power. Nevertheless, the brightness of an optically pumped laser can be far higher than the brightness of its pump source, if the pump source has a poor beam quality (thus a low brightness) while the beam quality of the output beam is much better.

Some examples of lasers serving as brightness converters are:

• A solid-state bulk laser (e.g. a rod laser or a thin-disk laser) may be end-pumped or side-pumped with high-power laser diodes and emit an essentially diffraction-limited beam, having a significantly increased brightness. This effect is typically more pronounced for a side-pumped laser utilizing the very diffuse light from an arc lamp, even though the output beam quality is then also often not diffraction-limited.
• A large brightness enhancement can also be achieved with a high-power fiber laser based on a double-clad fiber. The pump cladding may guide thousands of modes, so that e.g. a diode bar with very high M² factor can be used. The single-mode fiber core allows for diffraction-limited beam quality, and the power conversion efficiency can be higher than 80%.
• An optically pumped vertical external cavity surface-emitting laser (VECSEL), which is a kind of semiconductor laser, can also generate a diffraction-limited output. Its requirements concerning pump beam quality are very low, since the pump radiation is absorbed in a very thin layer, so that its beam divergence does not matter very much (even though a too high beam divergence can result in problems with geometric constraints in the laser construction).
• High-power optical parametric oscillators can in principle also be operated as brightness converters. Although most OPOs are pumped with close to diffraction-limited beams, it is possible to pump an OPO with a highly multimode beam while still generating a diffraction-limited signal beam. The idler beam quality will then be poor, but this may not matter.

In many cases, the function as a brightness converter is essential for laser applications. For example, many solid-state lasers are used in laser material processing because their pump light, having too low brightness, could not be used directly. (Another frequently required function is pulse generation e.g. via Q switching.)