What is the best efficiency on visible wavelengths?

Hello

Not sure if this should be in general, science or measurements section.

After getting familiar with the fact that 532 nm lasers have a lousy efficency and that they waste 300 mA for nothing before starting to operate, and that my "5 mW" green pen uses 1.14W (for a nominal efficiency of 0.44 %) I began to wonder if all the other wavelenghts differ greatly in this regard.

According to a datasheet of a 520 nm blueish green diode, it will have 4.6 V across when outputting 1 W worth of light at a current of 1.5 A. That is 1 / (1.5 * 4.6) = 14.5 % efficient. Are all direct diodes (is that what "single mode" means) about equal to that or is one end of the visible spectrum easier than the other?

All 532nm are DPSS, not direct diode and therefore very inefficient. They convert IR to 532nm with a complex design, see examples: http://www.repairfaq.org/sam/dpss1.gif All direct diode lasers are much more efficient but vary a great deal from one diode to the next.

Alan

Single mode and multi-mode refer to how the diode die are made. For our concerns, single mode creates an actual dot, and mutimode a line. Single mode have better beam, multi-mode more power.

As for efficiency, I believe all diodes beat dpss. With diodes, the new greens are the worst on efficiency. Diodes also shift WL when overdriven.

Your "5mw" pen is typically closer to 30mW, firstly.

The second problem is you're considering the inefficiencies of the DPSS driver, but not those of a diode's driver. A DPSS green has a IR pump, remember, which operates at ~1.9V. Apples to apples, your ebay pen is roughly 10% efficient. Higher DPSS powers and better designs yield up to 25% or more. IR diodes themselves can be upwards of 60% efficient in high powers.