19.1 Photonic Band Gap Materials
499
(a)
(b)
(c)
Fig. 19.17 2D photonic band gap waveguide structure. a Fabrication principle, b SEM image of the structure, c light
guiding at a 90 ◦ bend. Reprinted with permission from [1612], ©2000 AIP
due to limitation of the number of cavity modes with efficient confinement; also the mode closer to
the band edge has a higher quality factor.
19.1.9 Coupling to an Electronic Resonance
In a vertical-cavity surface-emitting laser (cf. Sect. 23.4.14), an optical defect mode in a 1D dielectric
structure is coupled to an electronic excitation, such as an exciton in a quantum well or dot. In the
simplest picture, the oscillator must emit its radiation into the cavity mode since other modes do not
exist in the Bragg band. Thus, the emission energy is given and fixed by the cavity mode. However,
the photon mode (field oscillator) and the electronic oscillator form a coupled system that generally
must be described using quantum electrodynamics. Energy is periodically exchanged between the two
oscillators with the Rabi frequency. An analogous phenomenon is investigated in the field of atom–
cavity interactions. A necessary condition for the observation of such an oscillation is that the radiation
energy remains long enough in the cavity that can be expressed as [1621, 1622] (cf. (19.42))
α d 1 − R ≈ π/Q ,
(19.37)
where α is the absorption coefficient of the electronic transition, d is the length of the absorbing
medium, R is the reflectance of the cavity mirror and Q is the finesse of the cavity given in (19.36).
499
(a)
(b)
(c)
Fig. 19.17 2D photonic band gap waveguide structure. a Fabrication principle, b SEM image of the structure, c light
guiding at a 90 ◦ bend. Reprinted with permission from [1612], ©2000 AIP
due to limitation of the number of cavity modes with efficient confinement; also the mode closer to
the band edge has a higher quality factor.
19.1.9 Coupling to an Electronic Resonance
In a vertical-cavity surface-emitting laser (cf. Sect. 23.4.14), an optical defect mode in a 1D dielectric
structure is coupled to an electronic excitation, such as an exciton in a quantum well or dot. In the
simplest picture, the oscillator must emit its radiation into the cavity mode since other modes do not
exist in the Bragg band. Thus, the emission energy is given and fixed by the cavity mode. However,
the photon mode (field oscillator) and the electronic oscillator form a coupled system that generally
must be described using quantum electrodynamics. Energy is periodically exchanged between the two
oscillators with the Rabi frequency. An analogous phenomenon is investigated in the field of atom–
cavity interactions. A necessary condition for the observation of such an oscillation is that the radiation
energy remains long enough in the cavity that can be expressed as [1621, 1622] (cf. (19.42))
α d 1 − R ≈ π/Q ,
(19.37)
where α is the absorption coefficient of the electronic transition, d is the length of the absorbing
medium, R is the reflectance of the cavity mirror and Q is the finesse of the cavity given in (19.36).