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Laser diode efficiency

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ejeffrey:

--- Quote from: james_s on February 11, 2019, 08:11:03 pm ---
--- Quote from: grouchobyte on February 11, 2019, 06:31:08 pm ---Laser diodes are notoriously inefficient. It really depends on the laser and it’s structure. Blue lasers are probably of the less efficient kind and I expect you may get less than 10% efficiency. Typically lots of power is wasted in heat in a laser so if your input power consumption is 23 watts and you are expecting 15 watts of optical power, you might  be sorely dissapointed. The best way to measure optical power is with a properly calibrated power meter. Trust me on this. I have spent more than half of my 45 year engineering career in fiber optics and test and measurement with a stint at Coherent.

@grouchobyte

--- End quote ---

Huh? Laser diodes are incredibly efficient, especially compared to other types of lasers, for example a typical Ar-ion laser is doing well to reach 0.01% efficiency, the common HeNe lasers are not as bad but still quite low while 50% is not uncommon for a diode laser. Even LEDs made for lighting are only around 50%.

The commonly available 445nm blue diodes can deliver 1W output after the collimator for around 5W input so ~20% efficiency.

--- End quote ---

Yes, compared to an argon ion laser -- I used to use a large frame Ar+ laser operating at 351 nm.  Something like 30 kW in, 1-2 watt out.  Flashlamp pumped Nd:YAG lasers are similarly bad.  However blue laser diodes are considerably less efficient than red lasers and considerably less efficient than blue LEDs.  They are definitely not in the 80-90% that would be required for the OPs laser to have 15 watt output with 23 watts to the controller.

LaserSteve:
Scroll down to the I/V/P pictures at the bottom of this page.Crude but effective.

https://sites.google.com/site/dtrslasershop/home/diodes/445-m140-didoes

Steve

james_s:
I'm sure the 15W claim is bogus, the highest power single blue laser diodes I'm aware of can produce about 7W which is an absolutely crazy amount of power from a visible laser diode but it's not 15W. It's possible something new has come out since then but I haven't really kept up. I have one of the old 1W 445 diodes and it's scary enough, it has a tendency to set things on fire across the room. I played with gas lasers for years and previously the most powerful I had was a 50mW multiline air cooled argon that draws over 1kW. 1W or more meant a large frame ion laser needing 3 phase power and water cooling and then suddenly you could carry a 1W laser in your pocket that runs off a battery. I'm actually surprised that in ~6 years of these things being available we haven't been hearing about large numbers of eye injuries.

Wolfram:
I checked a few datasheets for high power multimode laser diodes in the 450 nm range, and it seems like the typical efficiency of the raw diode is around 30 %, give or take. Here's an example: http://download.insaneware.de/0019.pdf

Zero999:

--- Quote from: blueskull on February 12, 2019, 05:38:21 am ---Lasers, unlike LEDs, rate optical output power instead of electrical input power.
--- End quote ---
Normally both are given for LEDs. Visible LEDs are normally specified in lumen output and invisible/far ends of the visible spectrum are typically specified in radiometric power output. Yes 50% efficiency is typical for royal blue and far red LEDs. It wouldn't surprise me if laser diodes can approach this efficiency.

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