Laser fundamentals 3 Flashcards
What are the two main types of line broadening mechanisms in atomic transitions?
Homogeneous and inhomogeneous broadening.
What causes lifetime broadening in atomic emission and absorption lines?
Lifetime broadening is caused by the finite lifetime of atomic states.
How is the energy broadening of a transition related to the lifetime of the states?
Energy broadening is inversely proportional to the effective lifetime of the states.
What is the shape of the intensity spectrum when lifetime broadening is the dominant mechanism?
Lorentzian.
What does the lineshape function g(ν) represent in the context of lifetime broadening?
It represents the relative probabilities for emission or absorption processes with lifetime broadening.
What is collision broadening and in which type of systems is it usually important?
Collision broadening occurs due to frequent collisions between atoms, randomizing the phase of the atomic wavefunction, and is important in gases and liquids.
How is the total linewidth affected when both lifetime and collision broadening are considered?
The total linewidth is the sum of the linewidths due to lifetime broadening and collision broadening.
What causes inhomogeneous broadening in a population of emitters?
Inhomogeneous broadening is caused by differences in transition energies among a population of emitters.
What effect does the Doppler effect have on inhomogeneous broadening in gas lasers?
The Doppler effect causes atoms moving at different velocities to experience different frequencies, broadening the overall transition lines.
What is gain clamping in the context of laser physics?
Gain clamping occurs when the population inversion is clamped at a constant value above the threshold, and any additional pumping only increases photon flux.
Why does gain clamping prevent the generation of more gain above the threshold in a laser?
Because additional excited atoms decay through stimulated emission, keeping the population inversion constant.
What is the relationship between the small-signal gain coefficient γ0(ν) and the loss coefficient αr(ν) in steady-state laser operation?
In steady-state, the small-signal gain coefficient γ0(ν) must equal the loss coefficient αr(ν).
What is spectral hole burning and when does it occur?
Spectral hole burning occurs when a resonator’s free spectral range is larger than the FWHM of the single modes, leading to non-uniform gain depletion.
What is spatial hole burning and how does it affect laser operation?
Spatial hole burning is caused by the standing wave pattern in the cavity, leading to non-uniform gain depletion along the cavity length.
How is the output photon flux related to the output coupler transmittance T?
The output photon flux increases with T up to an optimal point, after which further increase in T reduces the output flux.
