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paul1598419

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I'm curious where you got the optical powers of the laser's beam shot you have shown here. I'm guessing you don't yet have a laser power meter, but you have claimed the green 303 is between 100 mW and 120 mW while the M140 diode laser is 1 watt. I'm guessing the 303 laser is a 532nm one, but I suppose it could be a 505nm one, though I have never seen one of these in a 303 host.

I see you have a 2.2 watt 445nm in your signature. That would likely be an M140 diode driven at 1.8 amps as I have one doing a little better than that as well. Most of the M140 diodes I've seen don't make it to 2.2 watts. Only a few make it there or a little over that high of optical power. I'm curious why you have an M140 diode only doing 1 watt as they usually do better than 2 watts when driven at 1.8 amps.

Just trying to wrap my head around these numbers. Thanks. :)
 

Gianakakis

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Hi Paul. Sorry for the late reply I was in Eng class ( I go to a secondary private school for Eng) These values are from my good estimates based on a few factors: The m140 is being driven with a 1.25A SL driver ill have to update the profile to add the other stuff. Sorry about that ill update it in a bit and accounting for losses since this was a good diode lpmed by the seller (2.2w at about 1.86A) I get an output of roughly 900mw-1w(I am using 3 element glass lenses). As for the 303 its my second one and the 100-120mw guess is based on its measured input current of about 400mA and the relative brightness of it to my previous sanwu metered 80mw. It even produces a somewhat visible beam at day( not direct sunlight ofc) Which leads me to believe together with that more that average input current that its hovering in the 100mw+ range. If you have any other questions about that feel free to ask me. I might have been not as active on lpf and I hope that will change but I've been active on the daily over at styros discord laser channel and I think I know a lot about diode lasers. Still I have to read up on gas and solid state lasers but yea don't think I'm marking myself as an expert in lasers. Cause I've only been on this hobby for 6 months while some of the guys here have been at it for more than 10 yrs.I still have a lot to learn but I think I have learned enough to provide help to ppl with questions about lasers/their projects.
 

paul1598419

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Unfortunately, the input current to the 808nm pump diode's driver won't translate at all to the optical power of the SHG 532nm green laser light. There are far too many variables that will effect that to a much greater extent. While seeing a greater brightness of lasers of the same wavelength can be indicative of greater output power, it is much more difficult to quantify that effect. If you had been matching many lasers at the same wavelength knowing the output power you might get to a point where you can predict the power to maybe +/- 30% at best just using visual cues, but in the end an LPM measurement is the gold standard for stating output power.
 

Gianakakis

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Unfortunately, the input current to the 808nm pump diode's driver won't translate at all to the optical power of the SHG 532nm green laser light. There are far too many variables that will effect that to a much greater extent. While seeing a greater brightness of lasers of the same wavelength can be indicative of greater output power, it is much more difficult to quantify that effect. If you had been matching many lasers at the same wavelength knowing the output power you might get to a point where you can predict the power to maybe +/- 30% at best just using visual cues, but in the end an LPM measurement is the gold standard for stating output power.
Yea it kinda helps that the efficiency of the crystals is known but yea cant argue with that an LPM will be the best way to measure it. Sadly I don't own one and the shipping cost to send it to a member for lpming would be too much. If I recall correctly the efficiency of the Nd:YaG is 62% and the KTP 48%*the diode should be a common 500mw one with 2.2vin x0.422(measured it exactly with a better non eBay) meter = about 928mw of power going into the diode
*take that with a grain of salt https://www.osapublishing.org/josab/abstract.cfm?uri=josab-3-5-683 it says here efficiency is in excess of 50% but its cheap crystals mass produced so 48 sounds more reasonable
1573680296378.png
Ill do 2 calculations depending on the possibility that the diode has focusing lens before the Nd:YaG and KTP stage cause I've seen dpps modules without that.
The maximum power conversion efficiency is 57.38% for 808nm diodes but ill use 52% seems more reasonable (source for efficiency here: https://www.researchgate.net/publication/237715614_808nm_high-power_high-efficiency_GaAsPGaInP_laser_bars )
With lens) Ok so we have 0.9284mw in to the diode -48% 482mw out and lets give that lens about an 92% efficiency not too crazy so 482mw -8% = 443mw- 38% = 274mw - 52% = 131mw out at lets say that the expanding lens is too 92% efficient so 121 mw and that the acrylic lens is too 94% efficient so 113.738496‬mw out lets get that to 110mw to give it a margin of error. Boom maths XD
Without lens) Ok so we have 0.9284mw in to the diode -48% 482mw out -38% = 298mw - 48% = 143mw -8% = 131mw -6% = 123mw = 120 to give it a small margin of error and here you go is that estimate better?
Ps(took waaay too long to type this almost midnight now so sorry for any small mistakes with grammar I legit cant keep my eyes open also ill do the cyan builds tmr see signature post office tolled me that the package {drivers} will arrive tmr)
 
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paul1598419

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Wow. Where to start? I have measured the output of many 532nm lasers using 500 mW 808nm pump diodes and they never get above 100 mW even with the unfiltered IR component. The setups you referenced aren't the same as these very cheap units with the two crystals bonded together and set on a brass heat sink which is too often glued in place over the pump diode. I also have had my share of ones with 1 watt pump diodes and those don't do more than 200 mW with the unfiltered IR. You run into too many problems when trying to figure out the output power by assuming these efficiencies are all that hold sway on the output. Temperature is very important for your crystal sets and that is not factored into any of your equations. Temperature also has an effect on the pump diode. Also, the polarization of the pump diode will have an effect over the output power. Really, there is no way forward but to measure the output.
 

Gianakakis

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Wow. Where to start? I have measured the output of many 532nm lasers using 500 mW 808nm pump diodes and they never get above 100 mW even with the unfiltered IR component. The setups you referenced aren't the same as these very cheap units with the two crystals bonded together and set on a brass heat sink which is too often glued in place over the pump diode. I also have had my share of ones with 1 watt pump diodes and those don't do more than 200 mW with the unfiltered IR. You run into too many problems when trying to figure out the output power by assuming these efficiencies are all that hold sway on the output. Temperature is very important for your crystal sets and that is not factored into any of your equations. Temperature also has an effect on the pump diode. Also, the polarization of the pump diode will have an effect over the output power. Really, there is no way forward but to measure the output.
Eh a least I tried. Know any decent cheap Lpms to recommend?
 

paul1598419

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Lasersbee, Jerry Baurer, offers many different LPMs for sale. You might want to look over the ones he has on his site. Many members have one or more of his LPMs. I had one for years. They are good and accurate meters.
 

Gianakakis

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Ok a little pricey but I understand I pay for quality So *dear Santa I want a laser bee Ax meter thanks!*
 

paul1598419

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There are more reasonably priced LPMs than that meter. I maybe be wrong, but I believe you can get an accurate LPM that will read up to 3 watts for a little over $100.00. That was my first LPM.
 

BowtieGuy

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Gianakakis, if you don't want to purchase an LPM right now, many members who have one will meter your laser for just the cost of shipping. :)
 

paul1598419

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He live in Greece, so I don't know if that is really an option for him. Might be, though.
 

BowtieGuy

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Ah yeah, that does make things a bit more complicated.
 

cyberdoc

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Ok a little pricey but I understand I pay for quality So *dear Santa I want a laser bee Ax meter thanks!*
Hi Gianakakis:
Ok a little pricey but I understand I pay for quality So *dear Santa I want a laser bee Ax meter thanks!*
Hi Gianakakis:

Investment in a LaserBee LPM should pay off in the long run, as they are accurate and sturdy instruments. Perhaps you can leave some extra milk and cookies out for Santa this year. Take Care.

- cd :)
 




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