Laser fundamentals 4 Flashcards
What is the purpose of mode selection in a laser?
Mode selection ensures that a laser runs in only one mode by suppressing undesired modes.
How is a specific laser line typically selected?
A specific laser line is selected by introducing an intracavity element, like a prism, that rejects unwanted lines.
What effect does a prism have when placed inside a laser resonator?
A prism deflects certain wavelengths, making the resonator stable only for a small range of wavelengths.
How can a particular transverse mode be selected?
A particular transverse mode can be selected by introducing a mask or aperture inside the cavity to increase the loss for all modes except the desired one.
Why are Gaussian beams easier to lase in spherical mirror resonators?
Gaussian beams are easier to lase because losses from finite mirror sizes are usually smallest for low-order beams.
How can polarization selection be achieved in a laser?
Polarization selection can be achieved by introducing a polarizer inside the cavity, often using Brewster’s angle.
What is the main advantage of Q-switching compared to gain switching?
Q-switching is more efficient as it allows population inversion to be nearly always present, leading to higher peak powers.
How does mode locking lead to the shortest laser pulses?
Mode locking forces many adjacent longitudinal modes to lase with a fixed phase relationship, producing a train of short pulses.
What is the Purcell effect?
The Purcell effect refers to the enhancement or inhibition of spontaneous emission in a resonant cavity, as determined by the cavity’s lineshape function.
How is the Purcell factor derived?
The Purcell factor is derived from the ratio of modal density of photon states in a cavity to that in free space, considering the cavity’s quality factor and volume.
What is the equation for the Purcell factor?
FP = (3 / 4π²) * (λ/n)³ * (Q/V), where λ is the wavelength, n is the refractive index, Q is the quality factor, and V is the cavity volume.
Why are pulsed lasers important?
Pulsed lasers are important for achieving high peak powers, crucial for nonlinear optics and ultrafast laser science.
What is gain switching in pulsed lasers?
Gain switching involves repeatedly turning the pumping on and off, causing the laser to emit pulses as the population inversion builds and depletes.
How does Q-switching work?
Q-switching works by modulating the losses in the cavity, preventing lasing until the losses are reduced, which then triggers a high-intensity pulse.
What is the basic principle of mode locking in lasers?
Mode locking involves locking the phases of multiple longitudinal modes to produce a train of short pulses with fixed intervals.
