Laser fundamentals 2 Flashcards
What is the purpose of combining an active medium with a feedback system in laser oscillations?
To achieve coherent light emission.
What does the laser lineshape function g(ν) represent?
The spectral distribution of transition probability.
What is the condition for a mode to dominate in a single-mode laser?
The mode must be closer to the peak of emission lineshape with the greatest emission probability.
What does the FWHM of the emitted spectrum represent?
The full width at half maximum of the emitted spectrum centered around ν0.
What is the significance of the Q-factor in a laser cavity?
It measures the number of roundtrips a photon can undergo before it gets either absorbed or coupled out.
What is the relationship between the Q-factor and resonator lineshape broadening?
Lower Q-factor leads to broader resonator lineshape function.
What are the main contributors to the broadening of the emission spectrum?
Intrinsic losses, imperfect mirrors, and re-absorption or scattering processes.
What is the role of the gain medium in a laser oscillator?
To amplify light by increasing the intensity of photons with each pass.
How is the gain coefficient γ(ν) related to the light intensity in the cavity?
It determines the extent to which light energy density increases inside the cavity.
What is the threshold gain coefficient γth(ν) in a laser cavity?
It is the gain coefficient at which overall light intensity increases after each roundtrip.
How is the threshold population inversion density Nth related to the gain coefficient?
Nth is proportional to the threshold gain coefficient divided by the transition lineshape.
What is the significance of the photon cavity lifetime τp in a resonator?
It represents the average time a photon spends confined in the structure before leaking out.
What are the primary considerations in designing a three-level laser system?
Large R1 and R2, large τ2, small τ1, and small τs.
In a three-level laser system, what is the role of level |3⟩?
It serves as the pumping level, quickly decaying into level |2⟩.
