From: cd@notformail.com   
      
   On Sat, 13 Dec 2025 14:10:55 -0000 (UTC), Phil Hobbs   
    wrote:   
      
   >Cursitor Doom  wrote:   
   >> On Sat, 13 Dec 2025 11:09:08 -0000 (UTC), Phil Hobbs   
   >>  wrote:   
   >>   
   >>> Gerhard Hoffmann  wrote:   
   >>>> Am 13.12.25 um 05:47 schrieb Bill Sloman:   
   >>>>   
   >>>>> One thing to keep in mid with your constant current source is that the   
   >>>>> lasing region is very compact, and even a very brief over-current can   
   >>>>> burn it out.   
   >>>>>   
   >>>>   
   >>>> Yes, it is usually the frequency-selective optical reflector grid   
   >>>> that dies in ms. Faster than we are used from semiconductors.   
   >>>>   
   >>>> Gerhard   
   >>>>   
   >>>>   
   >>>   
   >>> A nice juicy carpet shock can blow the front facet off much faster than   
   >>> that (although the fragments will still be moving for awhile afterwards.   
   >>>   
   >>> Cheers   
   >>>   
   >>> Phil Hobbs   
   >>   
   >> No one seems to have come up with a viable solution, so I've been   
   >> giving it some extra thought. I considered the use of a semi-silvered   
   >> mirror at 45 degrees to the plane of the beam and sampling the light   
   >> level off that reflection, but then realized the loss through the   
   >> mirror would be unacceptable. The only other idea I can think of is to   
   >> use a mirror just off the plane of the beam which can swivel around   
   >> for a split second every few seconds to deflect the beam into the path   
   >> of the diode. That seems cumbersome and clunky but it's the only thing   
   >> I can come up with, not being a designer of any description.   
   >>   
   >   
   >You’re very likely to blow up more lasers trying to do constant power.   
   >Start with constant current, then wrap a constant power loop around it.   
   >   
      
   Fair enough, but it still doesn't get around the issue of interrupting   
   the beam to sample its output strength. Optical power and electrical   
   power consumed are not reliably correlated due to temperature changes   
   in the laser diode.   
      
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