[AR] Re: Liquid Lasers? was Re: Re: Hypersonics have finally arrived
- From: Peter Fairbrother <peter@xxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 26 Oct 2020 00:23:01 +0000
On 25/10/2020 18:41, ken mason wrote:
Side pumping is no different than the original method like the ruby
laser with its helical flash lamp and other side pumped lasers do flood
the pump chamber with clear DI water or even glycol solution.
Yes, but side pumping fiber would be new afaik. And if you want power it
is useful to have length, which is easy with fiber but which can be
inconvenient with straight solid rods.
There is a technique called fiber disk lasing which pumps at about 30
degrees to the fiber, but it still uses a double clad fiber - double
clad for high power - the pump beam goes in the middle layer, the outer
layer only keeps the pump beam in the middle layer.
But if you have a fiber bundle in a optically suitable liquid with side
illumination you do not have to contain the pump to the individual
fibers, so you do not need the outer layer of cladding.
I wondered whether you might even be able to use completely unclad
lasing fiber in a flowing liquid coolant, with the liquid/fiber
interface performing the beam containment function otherwise done by the
cladding; but on reflection thought it better to have a single layer of
cladding with the liquid optically matched to the cladding.
However this cladding could be thin giving better heat transfer from the
lasing medium to the coolant than a thicker and/or double layer cladding
would allow.
Also, for a high power military laser, I expect that the main medium is
just an amplifying medium - a small driver laser inserts a low power but
high quality beam into the main power medium, which amplifies it, so
there is only one pass and power densities in the medium are not
increased by multiple reflections - also there is no need for a
partially reflective mirror or Bragg grating at the output.
We need an 'expert' to chime in.
Agreed. The above is just speculation on my part.
Peter Fairbrother
K
On Sat, Oct 24, 2020 at 9:49 PM Peter Fairbrother <peter@xxxxxxxxxx
<mailto:peter@xxxxxxxxxx>> wrote:
On 25/10/2020 02:26, ken mason wrote:
> I just don't see where the
> refractive index matching comes into the picture.
Supposing it is a fiber bundle, the coolant may be given the same RI as
the cladding to allow better coupling between drivers and lasing medium
- instead of shooting the drive beam down the fiber cladding (as in
conventional fiber lasers) you could just irradiate the whole bundle
from the sides.
But I know very little about >1kW or military lasers.
Peter Fairbrother
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