Comparison To Diode Lasers
DPSS and diode lasers are two of the most common types of solid-state lasers. However, both types have their advantages and disadvantages.
DPSS lasers generally have a higher beam quality and can reach very high powers while maintaining a relatively good beam quality. Because the crystal pumped by the diode acts as its own laser, the quality of the output beam is independent of that of the input beam. In comparison, diode lasers can only reach a few hundred milliwatts unless they operate in multiple transverse mode. Such multi-mode lasers have a larger beam diameter and a greater divergence, which makes them less desirable. In fact, single-mode operation is essential in some applications, such as optical drives.
On the other hand, diode lasers are cheaper and more energy efficient. As DPSS crystals are not 100% efficient, some power is lost when the frequency is converted. DPSS lasers are also more sensitive to temperature and can only operate optimally within a small range. Otherwise, the laser would suffer from stability issues, such as hopping between modes and large fluctuations in the output power. DPSS lasers also require a more complex construction.
Diode lasers can also be precisely modulated with a greater frequency than DPSS lasers.
Neodymium-doped solid state lasers continue to be the laser source of choice for industrial applications. Direct pumping of the upper Nd laser level at 885-nm (rather than at the more traditional broad 808-nm band) offers the potential of improved performance through a reduction in the lasing quantum defect, thereby improving system efficiency, reducing cooling requirements, and enabling further TEM00 power scaling. Because of the narrow 885-nm absorption feature in Nd:YAG, certain systems may benefit from the use of wavelength-locked diode pump sources, which serve to narrow and stabilize the pump emission spectrum to keep it closely aligned to this absorption feature. To date, high power diode laser locking schemes such as internal distributed feedback Bragg gratings and externally-aligned volume holographic grating optics, VHG’s, have not been widely implemented due to the increased cost and assumed performance penalty of the technology. However, recent advancements in the manufacture of stabilized diode pump sources which utilize external wavelength locking now offer improved spectral properties with little-to-no impact on power and efficiency. Benefits of this approach include improvements in laser efficiency, spectral linewidth, and pumping efficiency.
Read more about this topic: Diode-pumped Solid-state Laser
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