I have to simulate this laser model if it requires an amplifier or resonator structure in a simulation software, please suggest some simulation software to design diode pumped pulsed 350mJ Nd:YAG 30MW output without fluid cooling whether Thermoelectric or conduction cooling if it's possible with amplifier with multipass or single pass or else if it's possible with a resonator.
Dear Bhanu,
Based on the information you provided, it seems you intend to build a Q-switched Nd:YAG for up to 350 mJ per pulse. At this energy level, you would probably need a humongous diode laser source with some implication on thermal management. You will likely need liquid cooling. It would be interesting to see what you end up with, but I doubt TEC or passive cooling is adequate. Please keep us posted.
Kin
Dear Bhanu,
in order to decide what cooling you need you have to look for the average thermal power the laser is generating. In order to find this efficiency and repetition rate of your laser is required. For thermal effects the peak power is irrelevant.
So lets assume you chose a diode pumped Nd:YAG system to increase operational reliability and efficiency. Pulsed pumping of the crystal could provide you with an efficiency of up to 10%.
In this case the 350 mJ pulse is associated with a thermal pulse of ~3,2J and requires a pump pulse of 3,5J.
Generating this pump pulse is possible using a laser diode stack with an efficiency of ~50%. As a result it generates a thermal pulse of 3.5J and requires an electrical pulse of 7J.
As heat flow is slow and the generation of the Pulse is fast this heat load of ~7J will be stored in the active laser components in any way. The chiller will need to reduce the temperature of these components to the value previous to the laser shot before the next laser pulse is extracted.
For a repetition rate of 1Hz the thermal load of the laser will be as low as 7W which seems ideal for passive or Peltier cooling.
However this is an idealized example.
- You will need an active cooling (at least a Peltier element) to stabilize the laser diode temperature.
- Your efficiencies may turn out to be significantly lower.
- Your repetition rate may be higher increasing thermal load.
- Your beam quality may require thermal stabilization of the setup and the use of many Peltier elements may generate more heat than the laser itself. Especially when used in outer space, as the heat radiating surfaces may be rather hot rendering Peltier elements low in efficiency.
- In case you need to run at a single frequency or you want to generate ultra short pulses, you will need an additional seed lasers that will generate additional heat load.
I think it is worth to consider MOPA scheme with fiber laser as master oscillator and disk laser as power amplifier. Both fiber and disk configurations meet cooling and beam quality requirements correspondingly under medium and high power levels. Fiber laser operation at high power is limited by nonlinear processes in fiber material.
The usage of Yb doping instead of a Nd doping could be useful for you. This increases laser efficiency and therefore reduces heat load. In addition, it has a ten times longer upper state lifetime allowing longer pump pulses and therefore ~30 times lower peak power of the diodes.
For low repetition rates and thermal loads, the demands of the laser are best fulfilled in a rod laser as the high gain provides a very compact laser system still providing the required energy.
For higher repetition rates the cooling demands will strongly increase. Here a slab laser may be optimal.
At repetition rates of up to 2kHz a thin disk laser is the best solution.
All the best,
Karsten
Sorry it has a 4 (Nd:YAG ~250µs Yb:YAG ~1ms) times longer upper state lifetime. I should have crosschecked it.
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