Worksheet: The Components and Operation of Lasers

In this worksheet, we will practice describing the functions of the different components of a laser.

Q1:

Which of the following diagrams most correctly represents the structure of the electron energy levels in the atoms of the active medium of a laser?

  • A
  • B
  • C
  • D

Q2:

Which of the following most correctly describes the quality of the active medium of a laser that is relevant to its ability to produce lasing?

  • AAn active medium contains atoms with unstable nuclei.
  • BAn active medium contains atoms in which electrons tend to transition to relaxed states at a greater rate than they tend to transition to excited states.
  • CAn active medium contains completely ionized atoms.
  • DAn active medium contains atoms in which electrons tend to transition to excited states at the same rate that they tend to transition to relaxed states.
  • EAn active medium contains atoms in which electrons tend to transition to excited states at a greater rate than they tend to transition to relaxed states.

Q3:

The diagrams shown represent three successive stages of the production of photons in a laser.

In which diagram is energy being supplied to the active medium of the laser?

  • AII
  • BIII
  • CI

The energy supplied to the active medium of the laser consists of photons with a range of wavelengths. Which of the following fractions of the photons shown in the diagram results in stimulated emission in the laser?

  • A33
  • B23
  • C13

How many photons are produced by the lasing process in the diagrams?

Q4:

Which of the following most correctly describes a metastable state for the energy of an electron in an atom?

  • AA metastable electron state is the state of an electron that is at an energy level higher than the ground state energy of that electron, which the electron can only transition to by simultaneously absorbing and emitting photons.
  • BA metastable electron state is the state in which the electron is not completely ionized but moves more like a free electron than a bound electron.
  • CA metastable electron state is the state of an electron that is at an energy level higher than the ground state energy of that electron, in which the electron will tend to remain for significantly less time than the typical lifetime of an electron in an excited state.
  • DA metastable electron state is the state of an electron that is at an energy level higher than the ground state energy of that electron, in which the electron will tend to remain for significantly longer than the typical lifetime of an electron in an excited state.
  • EA metastable electron state is the state of an electron that is at an energy level higher than the ground state energy of that electron, in which an electron is more likely to absorb photons than in other excited states.

Q5:

The diagram represents photons interacting with excited atoms in the active medium of a laser. How many photons will pass through the dashed region shown in the diagram? Assume that all atoms remain in excited states until they emit a photon.

Q6:

Which of the diagrams shown most correctly represents how the active medium and resonant cavity of a laser are connected to each other?

  • A
  • B
  • C
  • D

Q7:

The active medium of a laser contains atoms that have energy levels corresponding to the ground state, metastable state, and excited state of electrons. When the medium is at equilibrium, with no energy being supplied to it from an external source, which of these states will have the highest relative density of electron occupation?

  • AExcited state
  • BMetastable state
  • CGround state

Q8:

One of the reflecting faces of the resonant cavity of a laser must be less than completely reflective for the laser to be effective. Which of the following explains why this is the case?

  • AIf all faces of the resonant cavity are equally reflective, light waves traveling in opposite directions through the cavity destructively interfere.
  • BEnergy cannot be emitted from the resonant cavity if all its faces are perfectly reflective.
  • CExternal energy cannot be supplied to the resonant cavity if all its faces are perfectly reflective.
  • DCoherent light cannot be emitted from the resonant cavity if all its faces are perfectly reflective.
  • EAll the reasons given are true.

Q9:

The diagram represents the relative densities of the electron occupation of relaxed, excited, and metastable states in the atoms of the active medium of a laser that is supplied with external energy to establish a population inversion. A very short time interval Δ𝑡 passes, corresponding to the shortest time within which any of the electrons could change in energy. Which of the following diagrams most correctly represents the energy states of the electrons after the time interval? No external energy is supplied to the active medium during the time interval.

  • A
  • B
  • C
  • D
  • E

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