Welcome to Laser Pointer Forums! If you are looking for a laser you may want to check out the database of laser pointer companies. The link will open in a new window for your convenience.

 Laser Pointer Forums - Discuss Laser Pointers Calculating Green Output on Commercially Available Pointers Laser Pointer Company Database     Laser Top Sites List     Lasers by Type     Green Lasers

05-26-2011, 08:12 AM #1
 Class 3B Laser Join Date: Jan 2011 Location: Davis, CA Posts: 3,828 Rep Power: 226
Wolfman29
Class 3B Laser

Join Date: Jan 2011
Location: Davis, CA
Posts: 3,828
Rep Power: 226
Calculating Green Output on Commercially Available Pointers

Hey all. I am curious as to what the average efficiency is of a green DPSS system.

The reason I ask is because I measured the tailcap current to my driver to be roughly 550mA, and I am looking for a way to figure out, within reason, what kind of output this thing will be putting out of green. It's been stated to be >200mW by Rayfoss, but I don't totally trust that, especially because I am pretty sure it's not IR filtered. See this link: www.rayfoss.com.

The thing takes 3V, and it is drawing .55A, meaning the driver should be outputting anywhere around 1.4W, assuming a decent efficiency on that thing (should be pretty good because I am pretty sure it's a buck driver).

Next, assuming 1.4W of input to the 808nm LD, what kind of output can we be expecting? 700mW of power?

Based off of some research, I gather that an 808nm LD may have Vf of roughly 2V, and has a W/A ratio of about one, meaning about 50% efficiency on this diode (not that surprising, I hear 808nm LDs are the most efficient out there). So, it's reasonable to say that 1.4W of input to the 808nm LD is roughly equal to 700mW of output power on the LD.

So, then what is the efficiency of the Nd:YAG or Nd:YVO4? I read on Wikipedia (see here: Diode-pumped solid-state laser - Wikipedia, the free encyclopedia) that a normal DPSS system has an efficiency of 20%, meaning that I am *probably* getting something like 130-140mW of power (chose a lower range so it's more realistic).

Is this a rough method for measuring the GREEN output power?

The method I used here is described simply:

1) Find "Working voltage" of your laser, may be on spec sheet of the laser.
2) Measure amperage at tailcap with a fully charged battery.
3) Find total wattage input to driver by multiplying these two; reduce by 20% for a lower average of driver efficiency to get output wattage of driver.
4) Divide driver output wattage in half, roughly the efficiency of a 808nm LD.
5) Divide that number by five (rough efficiency of DPSS system).

Math terms:

Vw*At*.08 = Po_532nm
(Vw = working voltage of laser, At = tailcap measured current)

What do you guys think?

05-26-2011, 09:26 AM #2
 Class 3R Laser Join Date: Nov 2010 Location: Portugal Posts: 2,472 Rep Power: 62
anselm
Class 3R Laser

Join Date: Nov 2010
Location: Portugal
Posts: 2,472
Rep Power: 62
Re: Calculating Green Output on Commercially Available Pointers

IF the crystals are perfectly aligned.
IF duty cycle is respected in passively cooled units.
__________________
I'm away from home and lasers until late July!
Kryton Groove switch workaround
Get your warning label stickers 0.90\$ or less, depending on qty
The INDEX to the LPF
Beware! Scams a-plenty, don't be a sucker!
___________________________
ATTENTION
This forum is fullfilled mit special electronische equippment. Fingergrabbing and pressing the cnoeppkes from the lasers is
allowed for die experts only! So all the “lefthanders” stay away and do not disturben the brainstorming von here working
intelligencies. Otherwise you will be out thrown and kicked anderswhere! Also: please keep still and only watchen astaunished the blinkenlights.

05-26-2011, 02:13 PM #3
 Class 3B Laser Join Date: Jan 2011 Location: Davis, CA Posts: 3,828 Rep Power: 226
Wolfman29
Class 3B Laser

Join Date: Jan 2011
Location: Davis, CA
Posts: 3,828
Rep Power: 226
Re: Calculating Green Output on Commercially Available Pointers

Well, hopefully my crystals are aligned because my duty cycle is respected :P

05-27-2011, 12:41 PM #4
 Class 1M Laser Join Date: Dec 2008 Posts: 107 Rep Power: 8
Low-Q
Class 1M Laser

Join Date: Dec 2008
Posts: 107
Rep Power: 8
Re: Calculating Green Output on Commercially Available Pointers

Quote:
 Originally Posted by Wolfman29 Well, hopefully my crystals are aligned because my duty cycle is respected :P
If the uncollimated green dot is quite circular, the focus of the 808nm diode are good. I have tested different distances, and the green dot becomes oval and dimmed when the 808nm focus isn't right.

The size of the chrystal and the cooling capacity of the surrounding brass is also a factor to take into account. Bad cooling on a undersized chrystal will give a bright beam for a short while before it dimms to a weaker beam.

Vidar

05-27-2011, 05:12 PM #5
 Class 3B Laser Join Date: Jan 2011 Location: Davis, CA Posts: 3,828 Rep Power: 226
Wolfman29
Class 3B Laser

Join Date: Jan 2011
Location: Davis, CA
Posts: 3,828
Rep Power: 226
Re: Calculating Green Output on Commercially Available Pointers

Yeah. Although, interestingly, about a second after I turn it on, it switches to a higher mode and then back to TEM00.

06-05-2011, 06:53 AM #6
 Class 3B Laser Join Date: Jan 2011 Location: Davis, CA Posts: 3,828 Rep Power: 226
Wolfman29
Class 3B Laser

Join Date: Jan 2011
Location: Davis, CA
Posts: 3,828
Rep Power: 226
Re: Calculating Green Output on Commercially Available Pointers

So if my new DIY LPM is calibrated correctly (which I hope to God it isn't, otherwise both my blu-ray and my 445nm are sucky diodes), I am getting 133mW or so on my green laser (must be IR filtered). So that's a pretty accurate prediction I made, and it turned out pretty close if my LPM is right.

It started out pretty low though (at around 75mW), but after about 30s-1min of on-time, it started rising much more rapidly.

06-05-2011, 12:09 PM #7
 Class 4 Laser Join Date: Sep 2008 Location: Quebec, Canada Posts: 14,823 Rep Power: 477
lasersbee
Class 4 Laser

Join Date: Sep 2008
Posts: 14,823
Rep Power: 477
Re: Calculating Green Output on Commercially Available Pointers

The only way you will be sure of the accuracy of your DIY LPM
is to check your LPM against a known calibrated LPM...

Jerry
__________________

LaserBee Laser Power Meter Products meet your needs
at affordable Prices:
See then all here on LPF

LaserBee Power Meter products ALWAYS in Stock

Available on eBay:Check availability here..

Search

This banner is available to and can be copied/used FREE by any LaserBee owner

06-05-2011, 08:29 PM #8
 Class 3B Laser Join Date: Jan 2011 Location: Davis, CA Posts: 3,828 Rep Power: 226
Wolfman29
Class 3B Laser

Join Date: Jan 2011
Location: Davis, CA
Posts: 3,828
Rep Power: 226
Re: Calculating Green Output on Commercially Available Pointers

Of course. However I can get rough estimations by assuming values for multiple lasers and calibrating so all three are close.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

All times are GMT. The time now is 01:13 PM.

 -- DarkShadows V5 -- Responsive LPF -2562016 -- Default Style Contact Us - Laser Pointer Forums - Archive - Top