Pump energy ! Something unclear for me

Usage, assemblance and modifications of solid-state and diode-lasers (not: laserpointers)
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smartcut
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Registriert: Mi 22 Aug, 2007 4:30 pm
Wohnort: France

Pump energy ! Something unclear for me

Beitrag von smartcut » So 09 Sep, 2007 6:59 pm

I am working on a Ho:YAG laser. I have the laser, I must calculate the power supply.

And for that, I ask me a stupid question as the result must me obvious ! Unfortunately not for me !

Considering the rate equations (that I have built up considering this laser equivalent to a 3 levels laser), I need to know the pumping rate per volume unit, Wp ( in s-1*m-3).

I intend to draw the curve of the 5I7 Ho3+ population (Upper Lasing Level) versus the time. As I know the total pump efficiency, the Upper Lasing Level energy, the rod volume, the rate equations, the total number of Ho3+ ions, I just have to consider the pump energy curve (in J) versus the time.

The problem is : what kind energy to consider in the rate equation : the mean energy or the instant energy (dE/dT) ?

It could be logical to consider the instant energy. But the result seems to be amazing. If for example one considers the pump pulse as a square signal of constant energy Emax during T seconds, dE/dT = 0 so the pumping rate would be equal to zero ! That physicaly not works !

If one considers the mean power, Emax/T , that works.

Now, I suppose E(t) is not a constant, but a gaussian (that is quite the response curve of a xenon flash tube). If I just consider the mean energy, I cannot see the population evolution versus the time ! (but just the final result).

If I consider the instant energy ... it does not works !

So what to consider ?

Many thanks for some «*coherent light*» about that question !

That must be very obvious and I am ashamed to ask such a question ... sorry ...

:oops:
Philippe

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smartcut
Beiträge: 17
Registriert: Mi 22 Aug, 2007 4:30 pm
Wohnort: France

Pb solved !

Beitrag von smartcut » Di 11 Sep, 2007 10:49 pm

I solved the pb.

To draw the pump curve in J versus the time is a nonsense. That would suppose the instant power to be infinite at each second !

The pump curve must be drawn in W (so in J/s) versus the time !

That is correct !

The mistake was enormous, so I did not see it ! Sorry !

Back to basic !

:D
Philippe

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