Nonresonant cavity

Since a resonant cavity can enhance spontaneous emission, it is not surprising that a nonresonant cavity can depress it. Consider for instance a cavity whose fundamental frequency is at twice the resonant frequency of the atomic transition. In this case, the radiation rate becomes... 

YLiF4 (YLF) 5% 135 165 9 1023 Brewster cut, f c, nonresonant cavity, external mirrors, attached GaAs/GalnP load (2 am thick, 800 am diameter) Seletskiy et al (201 Oc)... 

Fig. 16.3 Simulation of transmission spectrum for a four resonator array. FDTD simulation showing the steady state electric field distributions when the device is excited at the (a) resonant wavelength and (b) nonresonant wavelength. Note that the color levels in this image are scaled to the maximum field intensity in each image not to each other. The field levels in (b) are roughly of 20 times greater magnitude than those shown in (a), (c) Output spectrum for a device consisting of a waveguide with four evanescently coupled side cavities adjacent to it. Here each resonator consists of a cavity with four holes on either side. Reprinted from Ref. 37 with permission. 2008 Optical Society of America...

LIF (Ezekiel and Weiss, 1968 Cruse, et al., 1973 Zare and Dagdigian, 1974 Kinsey, 1977) is an example of an indirect technique for the detection of a one-photon resonant upward transition. There are many other indirect detection techniques (optogalvanic, optothermal, photoacoustic, cavity ringdown), but Multi-Photon Ionization (MPI) is a special type of indirect technique uniquely well suited for combining absorption detection with other useful functionalities (see Section 1.2.1.1). In MPI, photo-ion detection replaces photon detection. The one-color, singly-resonant-enhanced (n + m) REMPI f process consists of an n-photon resonant e, v, J <— e",v",J" excitation, followed by a further nonresonant m-photon excitation into the ionization continuum... 

The mode-locking mechanism for the titanium sapphire laser can be described by the optical Kerr effect (OKE). Owing to the nonresonant bound-electron nonlinearity of the gain medium, the OKE can be exploited in the laser cavity to simulate a saturable absorber with a virtually instantaneous absorber recovery. However, the picture of saturable absorber is not strictly correct since there is no saturation or depletion of a population across the transition. The OKE leads rather to a nonlinear intensity-dependent refractive index in the optical elements of the laser cavity, given by... 

Figure 6 Modelling of the frequency-dependent PA signal. The excited modes are the first (001), third (003) and fifth (005) longitudinal modes of the cavity. The dotted line shows the nonresonant contribution.

---