Only 1.8W from 3W Laser

[Photonz]

So I put together my "3W" build
For this I used:

9mm 445nm Diode 3 element - DTR
2.2A Driver and Pill Combo - Survivallaser
2x 18350 AW 700mAh Batteries - Lighthound
Host: DIY Stainless Steel + Extended Heatsink - Survivallaser

After putting it together... it only reads 1.8W on my LPM with the batts fully charged.
I was expecting something in the range of 2.5W with the 3 element lens.

Any suggestions, or info as to what may be going on? I can add photos if needed. Thanks:beer:

 

[ARG]

Try it with a G2 lens.

What LPM do you have? If you have a TEC based LPM the peak power may have already passed. IIRC the stainless steel host has a rather small heatsink so the power will drop fast.

 

[upaa27]

The heatsink is very small for a 3w laser. What happens is a process known as depolarization of the diode due the thermal influences. Basically the heat causes the diode to surpass its maximum basic charge and therefore causing an energy drop. I have only studied this a bit so I could be wrong but in the process of making lasers the hardest thing for me was having a good heatsink. Hope this helps

 

[DTR]

Average range with 2.4A and a G-2 lens is 2.7W-3.2W. You loose about 25% with a three element lens.:beer:

 

[Photonz]

I have the Radiant X4 and I don't have a G-2 lens (I can always order one if that's the issue) and I could look to upgrade to a host with a larger heatsink but I've seen another build with this same host and heatsink hit its desired output.

Edit: Looks like it's the lens that needs to be swapped.
Thanks for the help!:thanks:

 

[Pi R Squared]

You wont be able to meter it accurately with the Radiant X4, if you can meter it at all the power will begin dropping too soon as it gets hot. I have this problem with a less powerful laser in a C6 that's about 1.5W. I am not convinced the Radiant X4 can even measure a 3W+ laser without burning the coating on the sensor. If anyone has done so please say so. I have the exact same laser as you Photonz (link in my sig) except I have a G2 lens, the twice I tried to measure it, it smoked the coating on the sensor in about 2 seconds. I guess I could be lucky and got a record powerful diode I don't know. The 1.5W doesn't even begin to compare to it.

Your lens is surely the issue, even if its not that efficient a diode, in the worst case you will surely get at least 2.5W with the G2.

Alan

 

[ARG]

You wont be able to meter it accurately with the Radiant X4, if you can meter it at all the power will begin dropping too soon as it gets hot. I have this problem with a less powerful laser in a C6 that's about 1.5W.

Slow response time in TEC based LPM's will always lead to error with lasers that have changing powers. Trevor did the math, check out this thread.
http://laserpointerforums.com/f70/lpm-response-time-who-needs-84428.html#post1221446
Edit: and this post http://laserpointerforums.com/f70/lpm-response-time-who-needs-84428-3.html#post1222237
That is the disadvantage of all TEC based LPM's, but they are the best thing we have without buying a professional radial thermopile like an Ophir head.

I am not convinced the Radiant X4 can even measure a 3W+ laser without burning the coating on the sensor. If anyone has done so please say so.

I have, sensor is fine. You just have to unfocus the laser. Remember damaging the coating is not about the power applied, it depends on the power density. Greater area means lower power density.

 

[Photonz]

I hadn't seen those threads. I hadn't known TEC LPM's can be so slow and inaccurate at times.

 

[ARG]

Would actually make an interesting problem. The time rate change of the laser vs. the inaccuracy.

 

[Pi R Squared]

Thanks ARG for that info. That's very interesting about LPM response time. After a recent build I have become a fan of large finned heat sinks. My future builds will be mostly in larger hosts unless they are very low power.

Alan

 

[ARG]

Okay, here's what I came up with.

This is a rough logarithmic approximation using real data. On the y axis you have discrepancy between true power and LPM power. On the x axis you have the absolute value of the time rate change of the laser, how much the power changes in a second (mW/s)

At 250mW/s and greater you near 100% discrepancy, and at 100mW/s it's around 50% discrepancy.

So, in conclusion if your laser power is changing fast (small heatsink, or DPSS lasers) don't use a TEC based LPM. For measuring most lasers TEC based LPM's will perform within reason as this only becomes a problem in a few circumstances (such as this one) where the rate of change in the power is large.