• Broad area laser diodes typically generate several watts and are suitable for pumping solid-state lasers with output powers up to a few watts. Their beam quality is substantially asymmetric, but normally still sufficient for achieving a diffraction-limited laser output without using complicated optics.
• High-power diode bars emit tens of watts (or even > 100 W), allowing for higher output powers, particularly when several bars are combined. Their beam quality is strongly asymmetric and fairly poor, so that their brightness (radiance) is much lower than that of lower-power diodes. Various types of beam shapers are used to symmetries the beam quality. This makes it easier either to pump a bulk laser or to couple the light into a fiber.
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     Advantages of Diode Pumping

       The main advantages of diode pumping are:

• A high electrical-to-optical efficiency of the pump source (of the order of 50%) leads to a high overall power efficiency (→ wall-plug efficiency) of the laser. As a consequence, small power supplies are needed, and both the electricity consumption and the cooling demands are drastically reduced, compared with those for lamp-pumped lasers.
• The narrow optical bandwidth of diode lasers makes it possible to pump directly certain transitions of laser-active ions without losing power in other spectral regions. It thus also contributes to a high efficiency.
• Although the beam quality of high-power diode lasers is not perfect, it often allows for end pumping of lasers with very good overlap of laser mode and pump region, leading to high beam quality and power efficiency. In the domain of slab lasers, it allows edge pumping instead of face pumping, which brings important advantages.
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