A laser medium is confined to a cavity that ensures that only certain photons of a particular frequency, direction of travel, and state of polarization are generated abundantly. The cavity is essentially a region between two mirrors, which reflect the light back and forth. This arrangement can be regarded as a version of the particle in a box, with the particle now being a photon. As in the treatment of a particle in a box (Topic 7D), the only wavelengths that can be sustained satisfy n × 1/2λ = L, where n is an integer and L is the length of the cavity. That is, only an integral number of half-wavelengths fit into the cavity; all other waves undergo destructive interference with themselves. These wavelengths characterize the resonant modes of the laser. For a laser cavity of length 1.00 m, calculate (a) the allowed frequencies and (b) the frequency difference between successive resonant modes.
A laser medium is confined to a cavity that ensures that only certain photons of a particular frequency, direction of travel, and state of polarization are generated abundantly. The cavity is essentially a region between two mirrors, which reflect the light back and forth. This arrangement can be regarded as a version of the particle in a box, with the particle now being a photon. As in the treatment of a particle in a box (Topic 7D), the only wavelengths that can be sustained satisfy n × 1/2λ = L, where n is an integer and L is the length of the cavity. That is, only an integral number of half-wavelengths fit into the cavity; all other waves undergo destructive interference with themselves. These wavelengths characterize the resonant modes of the laser. For a laser cavity of length 1.00 m, calculate (a) the allowed frequencies and (b) the frequency difference between successive resonant modes.
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