Can I fry a Schnitzel using a terawatt laser?
and how long does it take?

Multiterawatt lasers can indeed supply radiation with a power that equals a dozen nuclear power plants – combined! But can we abuse this technology to quickly warm up food? Can I heat up some eggs without instantly pulverizing them? Could I use such a laser to achieve a nice crust on my crème brûlée? And how long does it take?

Okay, give me some numbers! I am hungry!

Let’s assume we have a 175 g Schnitzel with a specific heat capacity of 1,7 kJ/(kgK) and we need to heat it from fridge temperature (8°) to a cooking temperature of 100 °C. The total energy needed is then 27.37 kJ. Well, this is not too complicated. We approximate a power source with let’s say 50 terawatts. A laser continuously providing that power would heat up our Schnitzel in only 547 ps. That is far out of the human reaction time, and surely the Schnitzel would burn before we are able to take it out from the laser. In fact, we can turn that around and consider the energy that deposited within the reaction spawn of a human, about 300 ms. Multiplying this time with the continuous power of 50 terawatt leads to a deposited energy equal to 15 terajoule. Our initial 8°C cold Schnitzel would heat up to a temperature of about 50.4 *109 °C, 8 730 000 times the temperature of the sun at its surface. Arguing if it is still eatable at this point is unnecessary.

So, how can it be that there are physicists working with terawatt laser systems without taking out all the power from the public grid, and not completely destroying their labs? How does one deal with something that has the power of a dozen nuclear power plants?

The image shows a Schnitzel decorated on a plate, surrounded by potatoe salad and decorated with a slice of lemon.
A wonderful looking, freshly fried Schnitzel, but would it look the same if we use a terawatt laser instead of the pan? Credit: RitaE/ Pixabay

A terawatt laser might be not what you think.

The clue is that multi-terawatt lasers can only provide that power in a very short time spawn. It is pulsed. Indeed, the laser pulses reaching that power is released within pulses of few femtoseconds duration. That’s 10-15 seconds. Additionally, these pulses come with rather low repetition rates between 0.1 and 100 Hz. The Terawatt laser system at the Lund Laser Center has a pulse energy of 100 mJ (uncompressed), but due to pulse compression loses another 40 %. What’s left is 60 mJ per shot with a repetition rate of 10 Hz (pulses per second). To warm up our Schnitzel, we need to target it 456 166 times, or for 45 616 seconds. This equals 760 minutes or 12.67 hours. This is certainly longer than I ever waited for my food at a restaurant, and since we neglected the cooling down by heat dissipation to its surroundings, we would be probably not able to reach this temperature at all.

Conclusion: The answer is NO! DO NOT DO IT!

When you are working at a terawatt laser facility, there is still a kitchen with lots of microwaves standing around that are frequently used by most of employees to warm up their food. This is not only because it is way faster to use a microwave, but you also don´t want to have any food rests (or the debris from warming it up) even close to your optics.

Marius Plach

Hi, I am Marius and currently do my PhD at the Atomic Physics Division at Lund University. My research field is attosecond science, and I write articles about my work, lasers, and what else one can do with them.

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