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# What exactly is meany by a DPSS efficiency process?

#### Hap

##### Super Moderator
Staff member
Hey guys,

I searched online but couldn't find much to my question, all I found was mostly explaining how DPSS is less efficient then diodes(which I already knew )

My question is as follows: What exactly is meant by 9% efficiency/1% efficiency etc... when talking about "exotic wavelengths". For example, 473nm has a 9% efficiency rate, what exactly does that mean? In my mind, that means that only 9% of the total starting output ends up coming out of the aperture. Im sure im horribly wrong and any help would be most apprecited :thanks:

Extra question: Dosen't 594nm/593.5nm have the worst efficiency out of all?

Thank you again,
Alex

PS: Just realized I spelt "meant" wrong on the thread title, oh well

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#### Blackwolf

##### New member
that is how much pump power is converted into the wavelength of light that is being desired. 9% seems high for 473. that could possibly be the case in a lab unit but not a hand held. For example say you have a 2000mw 808nm diode pumping the crystals at 9% efficiency (2000*.09) you would get 180mw output power. that is a "perfect conditions" example though as you would need correct alignment and a few other variables too. 473 is hard to produce because 946nm is a weak line for Nd:YAG. the main line is 1064nm. Then it gets worse as you get to the doubling crystal: LBO. the problem with LBO is that it is only quasi-transparent to 946nm light meaning some light is lost in the crystal. to top it off the crystal is temperature sensitive too. If they would find a pump crystal whose principal wavelength is 946nm and a better doubling crystal 473nm light could be generated with super efficiency and cheaper too. here is how the people of the forums calculated 473nm efficiency
I think its because 473nm DPSS is the most inefficient DPSS system we hobbyists got Calculated its around 0.007W/(0.9 driver efficiency * 0.45 808nm diode efficiency * 0.1 473nm DPSS efficiency)=0.172W total in best case its maybe only 0.05 DPSS efficiency

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#### Hap

##### Super Moderator
Staff member
that is how much pump power is converted into the wavelength of light that is being desired. 9% seems high for 473. that could possibly be the case in a lab unit but not a hand held. For example say you have a 2000mw 808nm diode pumping the crystals at 9% efficiency (2000*.09) you would get 180mw output power. that is a "perfect conditions" example though as you would need correct alignment and a few other variables too. 473 is hard to produce because 946nm is a weak line for Nd:YAG. the main line is 1064nm. Then it gets worse as you get to the doubling crystal: LBO. the problem with LBO is that it is only quasi-transparent to 946nm light meaning some light is lost in the crystal. TO top it off the crystal is temperature sensitive too. If they would find a pump crystal who's principal wavelength is 946nm and a better doubling crystal 473nm light could be generated with super efficiency and cheaper too. here is how the people of the forums calculated 473nm efficiency

Wow, thank you Blackwolf! :wave:
I finally got it now.

Nevertheless, I think the idea of which process really is less efficient is debatable, but hey....As long as I get my 473nm light im good

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#### Zeebit

##### New member
Simply put, efficiency=(power in/power out)

#### hakzaw1

##### Well-known member
^^^ what he said..
my DPSS lasers really hate this cold weather we are having- just tried my 473 JL ProPl-E and I bet I saw less than 1mW with the laser being around 45 F- same with a green pointer- very dim at first- I allowed it to warm a little and then it came on bright for a second then went very dim as I repeated this each time it stayed bright longer until it finally stayed on brightly..

BTW.. doing lots of On and Off repeatedly in NOT a good thing to do. but as this 4\$usd green at 90 mW was uber cheap I don't have much to lose..

conclusion----- most DPSS work poorly when too cold. I tried a red(104mW) and BR (89mw) pointer (also from the same 4\$ Greedbay china seller) and they work as well cold as warmed up...

amazing you can get close to a combined RGV 300mW for just 12\$\$\$\$usd

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#### ultimatekaiser

##### Well-known member
that is how much pump power is converted into the wavelength of light that is being desired. 9% seems high for 473. that could possibly be the case in a lab unit but not a hand held. For example say you have a 2000mw 808nm diode pumping the crystals at 9% efficiency (2000*.09) you would get 180mw output power. that is a "perfect conditions" example though as you would need correct alignment and a few other variables too. 473 is hard to produce because 946nm is a weak line for Nd:YAG. the main line is 1064nm. Then it gets worse as you get to the doubling crystal: LBO. the problem with LBO is that it is only quasi-transparent to 946nm light meaning some light is lost in the crystal. TO top it off the crystal is temperature sensitive too. If they would find a pump crystal who's principal wavelength is 946nm and a better doubling crystal 473nm light could be generated with super efficiency and cheaper too. here is how the people of the forums calculated 473nm efficiency
Well.....the high power 473nm lasers tend to use a potassium niobate. it is transparant for the whole visible range we can see (though it struggles with purple (400-2000nm if i remember right)) but they're far more expensive than LBO crystals. I have a few, that are about half the size of an LBO but cost far far more. they also have a much higher Nonlinear coefficient than both LBO and KTP crystals. It's simply a matter of cost vs benefit. :beer:

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#### BShanahan14rulz

##### Well-known member
Should be noted that it is different from what is commonly referred to as "Wall plug efficiency." In lighting, this is not a unitless ratio, but instead a ratio of lumens per watt. Lumens is a dumb unit to use for monochromatic light, so I'm not sure what the real name for electrical power in per optical power out ratio is, but the process efficiency is most definitely talking about the optical power in per power out ratio.

#### trencheel303

##### Well-known member
^^^ what he said..