One of the first lasers used synthetic ruby as its laser medium.   However, a ruby laser is a three-state laser; its lower laser state is its ground state. Why does that arrangement make the ruby laser relatively inefficient? Hint: page 456 A. It is harder to pump electrons from the ground state to an excited state when there are fewer states. B. Atoms that have just emitted a photon at the laser wavelength can easily re- absorb a photon at the same wavelength because the lower laser state remains occupied by electrons for longer times. C. Electrons cannot emit photons if they shift from an excited state directly to the ground state. D. To make an efficient laser, radiation trapping has to be maximized, and this is done by providing at least four levels for the electrons to occupy. Solution D is the answer as in ruby laser the radiation is not continious due to less levels. in four level laser the continiou sbeam is supplied as second level emission is working when first has stooped. .

1. One of the first lasers used synthetic ruby as its laser medium.  However, a ruby
laser is a three-state laser; its lower laser state is its ground state. Why does that
arrangement make the ruby laser relatively inefficient?
Hint: page 456
A.
It is harder to pump electrons from the ground state to an excited state when
there are fewer states.
B.
Atoms that have just emitted a photon at the laser wavelength can easily re-
absorb a photon at the same wavelength because the lower laser state remains
occupied by electrons for longer times.
C.
Electrons cannot emit photons if they shift from an excited state directly to the
ground state.
D.
To make an efficient laser, radiation trapping has to be maximized, and this is
done by providing at least four levels for the electrons to occupy.
Solution

2. D is the answer as in ruby laser the radiation is not continious due to less levels. in four level
laser the continiou sbeam is supplied as second level emission is working when first has stooped.