I have a green laser pointer, labelled "Orion Skyline". It's rated = 5 mW
output power. I don't have a way to measure actual output, but I'll
assume that it's operating at approximately rated power when it's nice
and bright and the brightness is steady. Unfortunately, the brightness
is constant only when it has "warmed up".

If it sits in a cool room (say 15 degrees C) for a while before I use
it, the inital brightness of the beam appears quite low - perhaps 10%
or less of maximum output. If I keep it turned on, it will flicker -
becoming brighter then dimmer again multiple times, remaining at one
brightness for a fraction of a second to a couple of seconds before
abruptly changing brightness again. After about a minute of operation,
it seems to come to full brighness and remain there, without flickering.

It's not due to bad batteries or poor electrical contact on the
batteries - I've swapped in new alkalines, tested with a battery tester,
with just-cleaned terminals. But it *does* seem to be related to
temperatu if I hold the laser-containing end of the pointer in my
hand for a minute before use, warming it through skin contact while it's
still turned off, it comes on at full brightness (or close to it)
immediately.

So what is likely causing the brightness changes? I can think of 3
plausible explanations (there may be more).

1. A bad electrical contact somewhere in the circuit. When cold, it has
high resistance that prevents sufficient current from getting to the
power supply.

2. The constant-current supply for the IR laser diode is flakey and IR
output is changing, which results in changes in the amount of green
light generated.

3. The IR laser output is constant, but there's some sort of problem in
the 1064 nm laser or the frequency doubler crystal that makes its
efficiency very temperature-sensitive.

Anyone who has seen this problem care to guess what's happening in mine?

Also, how is it likely to be held together? The main body of the
pointer is a brass tube. Batteries are inserted by unscrewing an end
cap from one end. The laser assembly *looks* like it's screwed into
the other end of the tube, but it's not willing to budge with just hand
force attempting to unscrew it.

Dave