Microcavity in Photonic Crystals
insight review articles
Optical microcavities
Kerry J. Vahala
California Institute of Technology, Mail Stop 128-95, Pasadena, California 91125, USA (e-mail: vahala@caltech.edu)
Optical microcavities confine light to small volumes by resonant recirculation. Devices based on optical microcavities are already indispensable for a wide range of applications and studies. For example, microcavities made of active III–V semiconductor materials control laser emission spectra to enable long-distance transmission of data over optical fibres; they also ensure narrow spot-size laser read/write beams in CD and
DVD players. In quantum optical devices, microcavities can coax atoms or quantum dots to emit spontaneous photons in a desired direction or can provide an environment where dissipative mechanisms such as spontaneous emission are overcome so that quantum entanglement of radiation and matter is possible.
Applications of these remarkable devices are as diverse as their geometrical and resonant properties.
L
ike its acoustic analogue the tuning fork, the optical microcavity (or microresonator) has a size-dependent resonant frequency spectrum.
Microscale volume ensures that resonant frequencies are more sparsely distributed throughout this spectrum than they are in a corresponding
‘macroscale’ resonator. An ideal cavity would confine light indefinitely (that is, without loss) and would have resonant frequencies at precise values. Deviation from this ideal condition is described by the cavity Q factor (which is proportional to the confinement time in units of the optical period). Q factor and microcavity volume (V) figure prominently in applications of these devices, and a summary of values typical for the devices discussed in this review is given in Table 1. In addition, representative examples of the three methods of confinement employed in microcavities are provided in Figs 1–3 (refs 1–7).
In this review, I consider four applications of
Optical microcavities
Kerry J. Vahala
California Institute of Technology, Mail Stop 128-95, Pasadena, California 91125, USA (e-mail: vahala@caltech.edu)
Optical microcavities confine light to small volumes by resonant recirculation. Devices based on optical microcavities are already indispensable for a wide range of applications and studies. For example, microcavities made of active III–V semiconductor materials control laser emission spectra to enable long-distance transmission of data over optical fibres; they also ensure narrow spot-size laser read/write beams in CD and
DVD players. In quantum optical devices, microcavities can coax atoms or quantum dots to emit spontaneous photons in a desired direction or can provide an environment where dissipative mechanisms such as spontaneous emission are overcome so that quantum entanglement of radiation and matter is possible.
Applications of these remarkable devices are as diverse as their geometrical and resonant properties.
L
ike its acoustic analogue the tuning fork, the optical microcavity (or microresonator) has a size-dependent resonant frequency spectrum.
Microscale volume ensures that resonant frequencies are more sparsely distributed throughout this spectrum than they are in a corresponding
‘macroscale’ resonator. An ideal cavity would confine light indefinitely (that is, without loss) and would have resonant frequencies at precise values. Deviation from this ideal condition is described by the cavity Q factor (which is proportional to the confinement time in units of the optical period). Q factor and microcavity volume (V) figure prominently in applications of these devices, and a summary of values typical for the devices discussed in this review is given in Table 1. In addition, representative examples of the three methods of confinement employed in microcavities are provided in Figs 1–3 (refs 1–7).
In this review, I consider four applications of