What is the best efficiency on visible wavelengths?

[Thinkcat]

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?

 

[Pi R Squared]

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

 

[ChaosLord]

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.

 

[Cyparagon]

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.