From: bill.sloman@ieee.org
On 14/12/2025 12:51 am, 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:
> 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.
The microscope slide at the Brewster angle strikes me as likely to offer
an acceptable solution.
https://en.wikipedia.org/wiki/Brewster%27s_angle
A couple of percent of the beam will be reflected off the microscope
slide and you should be able to monitor that. It's likely to be much
smaller proportion than you could get off a semi-silvered mirror.
Getting the angle of incidence to precisely the Brewster angle for the
wavelength of your laser and the particular glass in you microscope
slide may take a bit of fiddling. The laser beam will presumably be
polarised anyway, and you will have rotate the microscope slide to get
angle of incidences to line up with the plane of polarisation of the
light coming out of the laser. I don't recall that any of the packages
we played with had a clearly marked plane of polarisation, but it's
while ago, and I didn't have any responsibility for the optics.
--
Bill Sloman, Sydney
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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