Development in photonics for communications and interconnects pose increasing requirements on reduction of footprint,
power dissipation and cost, as well as increased bandwidth. Nanophotonics integrated photonics has been viewed as a
solution to this, capitalizing on development in nanotechnology and an increased understanding of light matter
interaction on the nanoscale. The latter can be exemplified by plasmonics and low dimensional semiconductors such as
quantum dots (QDs). In this scenario the development of improved electrooptic materials is of great importance, the
electrooptic polymers being an example, since they potentially offer superior properties for optical phase modulators in
terms of power and integratability. Phase modulators are essential for e.g. the rapidly developing advanced modulation
formats, since phase modulation basically can generate any type of modulation. The electrooptic polymers, in
combination with plasmonics nanoparticle array waveguides or nanostructured hybrid plasmonic media can give
extremely compact and low power dissipation modulators. Low-dimensional semiconductors, e.g. in the shape of QDs,
can be employed for modulation or switching functions, offering possibilities for scaling to 2 or 3 dimensions for
advanced switching functions. In both the high field confinement plasmonics and QDs, the nanosizing is due to nearfield
interactions, albeit being of different physical origin in the two cases. Epitaxial integration of III-V structures on Si
plays an important role in developing high-performance light sources on silicon, eventually integrated with silicon
electronics. A brief remark on all-optical vs. electronically controlled optical switching systems is also given.
The current development in photonics for communications and interconnects pose increasing requirements on reduction of footprint, power dissipation and cost, as well as increased bandwidth. Integrated nanophotonics has been viewed as one solution to this, capitalizing on development in nanotechnology as such as well as on increased insights into light matter interaction on the nanoscale. The latter can be exemplified by plasmonics and low-dimensional semiconductors such as quantum dots (QDs). In this scenario the development of better electrooptic materials is also of great importance, the electrooptic polymers being an example, since they potentially offer improved properties for optical phase modulators in terms of power and probably cost and general flexibility. Phase modulators are essential for e.g. the rapidly developing advanced modulation formats for telecom, since phase modulation basically can generate any type of modulation. The electrooptic polymers, e.g. in combination with plasmonics nanoparticle array waveguides or nanostructured hybrid plasmonic media can theoretically give extremely compact and low power dissipation modulators, still to be demonstrated. The low-dimensional semiconductors, e.g. in the shape of QDs, can be employed for modulation or switching functions, offering possibilities in the future for scaling to 2 or 3 dimensions for advanced switching functions. In both the plasmonics and QD cases, nanosizing and low power dissipation are generally due to near-field interactions, albeit being of different physical origin in the two cases. A comparison of all-optical and electronically controlled switching is given.
Metal nanoparticle arrays offer the possibility to considerably surpass the optical field confinement of silicon
waveguides. The properties of directional couplers composed of such plasmonic nanoarrays are analyzed theoretically,
while neglecting material losses. It is found that it is possible to generate very compact, submicron length, high fieldconfinement
and functionality devices with very low switch energies. We further perform a study of spatial losses in Ag
nanoparticle arrays by obtaining the group velocity and the lifetime of the surface plasmon polaritons. The losses are
determined for different host permittivities, polarizations, and for spherical and spheroidal particles, with a minimum
loss of 12 dB/μm. The possibilities to compensate the losses using gain materials, and the added noise associated with
that, is briefly discussed.
The characteristics of intersubband transitions in III-nitride quantum wells are promising for detectors and all-optical
switches through a high intrinsic speed (~1 THz), and can also provide a high optical saturation power and a desired
small negative chirp parameter in electroabsorption modulators. The high LO-phonon energy allows to improve the
operating temperature of THz emitters. Recent achievements and prospects for intersubband III-nitride photonic devices,
mainly for λ=1.55 μm, are briefly reviewed. Further, means to enhance material quality by achieving crack-free growth
of GaN/AlN multiple-quantum-well (MQW) structures, and by employing intersubband transitions in multiple-quantum-disk
(MQD) structures incorporated into dislocation free GaN nanocolumns are discussed. We investigate the occurrence
of cracks in MBE-grown GaN/AlN MQWs on GaN MOVPE templates with respect to the buffer layer, the number of
QWs and the temperature reduction rate after growth. Intersubband absorption in GaN/AlN MQDs in the wavelength
range 1.38-1.72 μm is demonstrated in three samples grown on Si(111).
We have used MBE to grow MQW structures on MOVPE GaN/sapphire templates. The MQW devices are intended for high speed intersubband electroabsorption modulator devices operating at 1.55-&mgr;m. The GaN/AlN multiple quantum well material was systematically studied regarding the surface morphology, structural characterization and optical property by atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The intersubband resonance energy was also calculated considering many-body effects in n-type doped structures. The multiple quantum well structure showed superior performance in terms of linewidth when grown on GaN templates as compared on sapphire. GaN quantum well and AlN barriers with a thickness of 3.3 and 4.2 nm respectively resulted in FWHM of the intersubband absorption peak as low as 93 meV at an absorption energy of 700 meV. This is promising for intersubband modulator applications.
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