1. Can two-level atomic system generate laser? Yes, if it is pumped sufficiently No, because it can not create population inversion.
2. Laser of a certain wavelength: can machine any material even if it is very hard. can only machine materials which absorb laser radiation at this wavelength beyond certain level.
3. Laser polarization direction can influence the absortion coefficient, for p-ray and s-ray: p-ray can be better absorbed than s-ray. s-ray can be better absorbed than p-ray.
4. Which of the following about excimer laser is not true? Excimer lasers can always generate higher energy photons than Nd:YAG laser Excimer lasers are capable of laser cold cutting of metals Excimer lasers can be focused to smaller spot size than normal light because its wavelength is very short, in UV range
5. The basic mechanism of semiconductor laser is: Recombination radiation Stimulated emission dominates over stimulated absorption when population inversion between two energy levels of the semiconductor material exists
6. Laser resonator can be basically divided into two kinds, they are: plane parallel resonator and spherical resonator confocal resonator and ring resonator stable and unstable resonator
7. Unstable resonator is used when: better focus of the beam is required laser energy is too high inside the cavity
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