I know lasers can cut or create holes on some hard materials such as diamond and metals. Is there any similar concept in tunnel engineering?
If not, what are the difficulties?
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First is power those cutting lasers usually make relatively small cuts and take quite a bit of power and time. Scaling that up means waiting for a few decades to move a few meters if you can't get more power.
Second is conservation of mass. All that rock has to go somewhere. If you use a laser it will evaporate. No-one wants to be breathing metal fumes in an enclosed space. They will also cool off again and deposit themselves everywhere.
Barring other difficulties, it is unclear what advantages laser cutting would have in such an application. Lasers are useful in drilling/cutting of materials because of their high precision and ability to make very small cuts. Digging a tunnel is not a precision activity though.
Even if a tunnel drilling machine were set up to use lasers, the cut between the bore and the tunnel wall would have a very small separation (~1 mm), and a massive amount of equipment would still be needed to remove the rest of the material from the bore.