L17

Question 1

LASER Acronym

Answer 1

LASER = Light Amplification by Stimulated Emission of Radiation

Question 2

Stimulated Emission

Answer 2

• Emission of a duplicate photon
• with the same characteristics as the original
• crucial for laser operation.

Question 3

Absorption Probability of a Photon

What is it proportional to and when does it occur?

Answer 3

• Proportional to the number of photons
• Occurs only if the mode contains a photon.

Question 4

Spontaneous Emission Rate

Name typical value / range

Answer 4

• Typical value: 1 / 10^-8 s for atomic transitions (e.g., Hydrogen).
• Can vary from subpicoseconds to minutes.

1 / per subpicosecond or what is meant?

Question 5

Rate Equation

what are the terms?

Answer 5

Terms:

• absorption (positive)
• spontaneous emission (negative)
• stimulated emission (negative)

Question 6

Einstein Relation

Answer 6

• Stimulated emission is essential to align thermal equilibrium condition with Planck’s distribution.
• stimulated emission & absorption coefficient (B) are the same (expressed as function of lifetime)
• spontaneuos emission rate = 1/t_sp