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2012 BFY Abstract Detail Page
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||W61 - Thorlabs' Teaching Spectroscopy Kit (SKDAV)
||Thorlabs SKSAS spectroscopy kit is an ideal tool for undergraduate teaching labs. The kit provides a set of proven components for a fiber-coupled Saturated Absorption Spectroscopy setup. It offers a method for producing a highly stable lock for tunable lasers at the peak of atomic hyperfine structure transitions.
How does it work?
Every atom has a unique set of absorption frequencies determined by the hyperfine structure of the electronic states. If the atoms are at rest, as light is propagated through the system, light is only absorbed at these discrete transition frequencies, f0. At a given temperature, however, the atoms may be moving according to the Maxwell-Boltzmann temperature distribution of velocities. Because of this distribution, some atoms will be stationary, while others will be moving with various speeds along the direction of light propagation. For laser light at one of the hyperfine transition peaks, f0, the only atoms that will interact are those that are stationary. Atoms at a speed v can only interact with a laser of frequency f (offset from the transition frequencies) which satisfies a Doppler shift to a transition frequency f0.
Imagine having two counter-propagating laser beams traveling through a vapor cell. The light beam at a frequency less than f0 propagating to the left (right) can only interact with a group of atoms moving to the right (left). For a laser frequency greater than f0, the light can only interact with atoms moving in the same direction as the beam's propagation. For a particular laser frequency, each beam interacts with a different group of atoms with a different velocity.
When the laser has a frequency of f0, however, both counter-propagating beams can only interact with atoms that are at rest. Therefore, there will be a depletion of zero-velocity ground state atoms, which will be evidenced by dips in the Doppler-broadened absorption profile. These dips create very narrow peaks which can be used as a frequency locking point for a tunable laser.
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