From: pcdhSpamMeSenseless@electrooptical.net   
      
   Cursitor Doom  wrote:   
   > 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.   
   >   
      
   Bounce it off a bit of window glass like the rest of us. ;)   
      
   Five percent of the light is better than good enough for the job.   
      
   Cheers   
      
   Phil Hobbs   
      
   --   
   Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /   
   Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics   
      
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