Page 159 - Principles and Applications of NanoMEMS Physics

3. NANOMEMS PHYSICS: Quantum Wave Phenomena 147

emission can be forbidden, thus potentially eliminating non-radiative
transitions. This is so because, in the band gap of a PBC, the density of
photons states, ρ = 0 . The first experimental demonstration of the use of
PBC
-
three dimensional PBCs to control the dynamics of spontaneous emission
from quantum dots has been recently published [173]. In this case, Fig. 3-31,

Figure 3-31. (a) Scanning electron microscope image of the (111) face of a titania inverse
opal with lattice parameter a=460 nm. Reprinted with permission from[170] Copyright 2004
Nature. (b) Luminescence decay curves of quantum dots inside three different photonic
-1
-1
crystals. The data are recorded at frequencies 15,670 cm (a= 370 nm) and 15,100 cm (a
=420 nm, and a=500 nm). The curves have been overlapped after 5 ns. The first part of the
-1
decay curve is influenced by emission of titania (recorded at 15,400 cm ). After 5 ns this
contribution is negligible. [173].
the spectral distribution and time-dependent decay of light emitted from
excitons confined in the CdSe quantum dots are shown to be controlled by
the host PBC. In particular, the fact that lifetimes of .9 ± 1 . 0 ns and
6
19 3 . ± 2 . 0 ns for quantum dots embedded in PBCs of lattice constants
a=420 nm and a=500 nm, respectively, are obtained, demonstrate a factor of