High power red laser pointers?

[lasercrazy]

We all know about the special high power greenies, but are there any high mw red laser pointers? /ubbthreads/images/graemlins/smile.gif

 

[abeland1]

A red pointer is a relatively simple device compared to a green. Even the best of them consist of a simple two transistor circuit to keep the current steady, a laser diode and a collimating lens. If the objective is to see the actual beam as with a green, you would need two to three hundred mW of output, a level that should never be allowed in a hand-held device.

 

[lasercrazy]

Oh well, thanks for the info. /ubbthreads/images/graemlins/smile.gif

 

[PhotonWrangler]

While we're on the topic of driver circuits, I believe that all of the LD pointers use a 'soft-start' circuit which ramps up the drive current rather than hitting the LD with a sudden inrush of current. I've noticed that on the green pointers the soft-start is actually visible, probably taking around 500 milliseconds according to my roughy calibrated eye. But the soft-start on a red LD pointer is so short that I've never been able to perceive it. I wonder if the greenies (actually the infrared pump diodes) are just that much more sensitive to inrush current, or is it just that the whole assembly is so much more expensive that it warrants the prolonged startup?

 

[Lasernerd]

I believe it is the heating of the KTP crystal you are seeing..

 

[PhotonWrangler]

Hmm, so it comes up to operating temperature that fast? Interesting. I gather this means that if I start out with a really cold pointer, that ramp-up would take considerably longer...? Maybe I'll stick it in the fridge for awhile and then try it out.

 

[Canuke]

Doing that would probably cause it to stay dim for a time... I have an Alpec Team greenie, which is a Leadlight, and I noticed right away that it seemed to have "moods", sometimes bright, sometimes dim.... it fooled me into replacing the batteries early a few times until I realized it was always bright when fresh out of my pocket and operating at near body temps. So it is definitely heat sensitive.

(so now let's see who preheats their greenie in search of even more extra milliwatts! /ubbthreads/images/graemlins/popcorn.gif )

 

[The_LED_Museum]

When I had that green laser pointer the cleaners stole or hid in late 2002, I found it worked best (brightest) when preheated to at least 85°F (29.4°C) before firing it up.
When it was started cold (room temperature, 65°F (18.3°C)), it started out dim and then brightened up some number of seconds later.

 

[PhotonWrangler]

[ QUOTE ]
The_LED_Museum said:
When I had that green laser pointer the cleaners stole or hid in late 2002, I found it worked best (brightest) when preheated to at least 85°F (29.4°C) before firing it up.
When it was started cold (room temperature, 65°F (18.3°C)), it started out dim and then brightened up some number of seconds later.

[/ QUOTE ]

Is there a high end of the operating window also? Would it start to dim again after operating for awhile?

 

[The_LED_Museum]

Not that I remember.
But I never ran it for more than a minute at a time, so maybe I never reached the upper thermal limit.

 

[Lasernerd]

Yes each crystal has a sweet spot..
Peltier cooling with a differential power supply coupled to thermsistor controller than it will stabilize at maximum output same thing with the pump diode isolated of course

 

[hungryforlasers]

What mW does a red laser need to excede for the beam to be visable?

 

[The_LED_Museum]

That will depend very greatly on what particulates are IN the air at the time. 0.5mW will do if there is smoke or a lot of water vapour (fog) in the atmosphere; 500 watts might not show a beam if the air is clean and dry.

 

[hungryforlasers]

Oh, okay. /ubbthreads/images/graemlins/ohgeez.gif