Laser Raman Spectroscopy

Atomic spectroscopy and quantum optics in hollow‐core waveguides

“…17c. By fitting the experimental spectra to standard SAS theory [110], values for the saturation parameter (S = 2X2) and the homogeneous linewidth ( = 46 ¦ 5 MHz) were extracted [90]. This value of is consistent with an estimated homogeneous transit-time broadening of 48 MHz that is caused by the finite interaction time of a rubidium atom with the ARROW mode.…”

“…The only exception occurs if the beams are tuned to an atomic resonance in which both beams will be absorbed by atoms with zero velocity relative to the beams. In this case, the pump beam depletes the ground state and reduces the probe absorption which results in narrow spectral features (Lamb dips) that effectively eliminate the Doppler broadening [8]. The width of these Lamb dips is determined by the much smaller homogeneous linewidth of the transition.…”

“…In the centuries to follow, atomic spectroscopy has found numerous applications, including astronomy [2,3] chemical analysis, gas phase sensing, precision spectroscopy [4], time-keeping (atomic clocks) [5,6], nonlinear frequency generation [7], gas lasers, frequency stabilization [8], quantum optics and quantum communications. Breakthrough developments in optical spectroscopy, most notably the laser and magneto-optical trapping, even made possible the controlled spectroscopy of single atoms [9][10][11][12].…”

Basic Electromagnetic Theory of SERS

“…A (Stokes) vibrational Raman scattering event in a molecule is an instantaneous optical scattering process in which an incoming photon from the laser at ω L excites a molecular vibration (with frequency ω ν ) while emitting a scattered photon at ω S = (ω L − ω ν ) [52,53]. The incident photon does not need to be absorbed and induce electronic transitions in the molecule, since Raman processes are usually excited in the transparency region of the optical properties of a molecule (otherwise the process is called resonance Raman scattering).…”

“…Fluorescence, on the other hand, is a stepwise process (not instantaneous) that evolves over time through a series of intermediate steps briefly summarized in Figure 1.11 [52,53]. The initial step involves the absorption of a photon from the ground singlet state S 0 to a state in the vibrational substructure of the first singlet state S 1 .…”