It is desired to have artificial optical materials with controllable optical properties. One approach is to create composite materials with nanomachining and nanostructures. In this research, two-dimensional (2D) nanostructures were created on the surface of optical glass using nanosphere lithography. The effective refractive index of the artificial layer is smaller than the refractive index of the substrate and can be varied by changing the size of the nanoparticles and depth of etching. In comparison with conventional techniques, this approach is more efficient and cost-effective for the creation of large areas of thin surface layers as an artificial material. A uniform monolayer of 200 nm polystyrene nanospheres was deposited on soda-lime glass slides. Deposition was performed via a slide-coating technique to take advantage of capillary forces. The slides were etched with vapor-phase hydrofluoric acid (HF) to create 2D structures. Vapor-phase etching was selected in order to etch the substrate without disturbing the monolayer nanoparticle mask. The etching rate of nanostructures was studied. An atomic force microscope (AFM) was used to monitor the nanosphere monolayers and etching analysis. It was shown that the nanoparticle pattern was successfully transferred to the surface of the substrate. The resultant thin-layer of modified substrate serves as an artificial material with a desired refractive index which modifies the surface reflection and transmission properties. The substrate with the created artificial material layer demonstrated reduced reflectivity in optical wavelengths.
Two-dimensional periodic structures with nanometer feature sizes have been widely used in many photonic devices. The profile and size of the nanostructure elements can greatly affect optical performances. Various practical subwavelength structures working in the visible and near infrared region have been fabricated using electron-beam writing or laser interference techniques. In this paper, we present a new technique which use nanosphere lithography (NSL) and reactive-ion etching to fabricate two-dimensional nanostructures with tunable nanoelement size and profile.
Linear and nonlinear optical phenomena in quantum dot (QD) systems caused by interlevel transitions are investigated theoretically. The electron-electron (e-e) interaction is taken into account by employing the self-consistent field approach in the quasistatic limit. It is shown that presence of metal surface, and especially another resonant system, can dramatically enhance the effect of the e-e interaction on the optical phenomena. The conditions for the intrinsic optical bistability in QD systems caused by the e-e interaction are discussed. The obtained results can find applications for designing, manufacturing, and exploiting nanooptoelectronics devices, in part, all-optical components like QD-based optical switches and optical transistors.
Infrared interlevel electromagnetic response of different quantum
dot (QD) systems is investigated theoretically within the
self-consistent field approach. Individual QDs as well as lattices
of QDs electromagnetically interacting are considered. The Coulomb
interaction in the QD systems is shown to essentially affect the
optical spectra of the systems. Systems of QDs with uniaxial
rotation symmetry are considered. It is shown that the shape of QD
can dramatically affect the spectra, in particular, depending on
the polarization of incident radiation and number of electrons in
the dot. It is shown that the Coulomb interaction in the QD
systems causes the depolarization shift of the peak(s) in the
spectra, can affect the peak(s) height, and cause the peak split.
It is numerically established that the approximation of the point
dipole-dipole interaction can be used for adequate representation
of the effect of the dynamic interdot electron-electron
interaction on the spectra of the considered QD lattices. It
is found that the effects of the intradot and interdot Coulomb
interactions on the response can be analyzed separately. Effect of
the intradot electron-electron interaction on the spectra is
considered for different QD sizes and shapes. Illustrative maps of
the interlevel transitions are utilized to facilitate application
of the approach of the modified oscillator strength for
reproducing the absorption spectra of the considered QD
systems with interacting modes of the collective excitation. The
results obtained can be useful for designing nanooptoelectronics
devises based on the QDs, and engineering composite materials
including the QDs with predermined optical properties.
We report the first results of self-assembled nanostructures using colloids for antireflection optical coatings. Two-dimensional (2D) periodic nano-structures were made by using self-assembled 2D colloidal crystals on top of a transparent substrate. An atomic force microscope was used to evaluate the quality of the nanostructure. The feature size of the structures was around 105 nm. This sub-wavelength structure is equivalent to an artificial film on top of the substrate. The effective refractive index of the film is found to be around 1.3. Such a low-index materials is desired for anti-reflection coating to reduce Fresnal reflection. We have observed the reduced reflection from glass surfaces as well as enhanced transmission. Our calculated results agree well with experimental measurement.
Advanced device structures are proposed for high-performance polymeric light emitting diodes based on the ferroelectric, pyroelectric, and piezoelectric properties of the very thin crystalline Langmuir-Blodgett films of P(VDF-TrFE). This ferroelectric incorporated polymeric light emitting diode structure has a capability to lower the barrier height for efficient carrier injection and modulate the balance of the carriers for enhanced quantum efficiency. The barrier height can be reduced up to 1 eV while the tunneling barrier width can be modulated up to 8&percent;. This can be achievable only using the crystalline thin films of P(VDF-TrFE).
Two-dimensional periodic waveguides have been made by depositing colloidal crystals on top of a planar waveguide. We present a fabrication technique and discuss applications of 2D periodic waveguides in optical coupling, filtering, and wavelength demultiplexing.
A few major schemes for all-optical switching/modulation is considered and the comparison of the values of nonlinear index change required for the device operation is presented. Each design is assumed to be optimized to meet the requirement for insertion losses of 1 dB (about 80% transmission or reflectance depending on the geometry of the device) and the switching contrast of 10 dB. A number of numerical results of transmission and reflectance in those devices are proposed in this paper. The advantage of the design of optimized integrated optical switchers/modulators with losses include extremely low switching refractive index change (delta) n. In addition, we suggest one new optimized design based on Bragg grating.
Phase-conjugate external ring cavity modes of semiconductor lasers and phase-conjugate feedback effects were investigated. The phase-conjugate ring cavity is formed with a double phase-conjugate mirror. The effects of bi- and uni- directional phase-conjugate feedback on the operating state of a laser diode were studied. When the bidirectional phase- conjugate feedback is above -40 dB, the output spectrum of the laser is broadened and the operating state of the laser changes to multimode state. It was experimentally observed that in the ring cavity two opposite traveling waves, which are phase conjugates of each other, propagate.
This paper reports the results of our study on structure configurations and material compositions for the construction of smart photonic bandgap structures. The study focuses on the deposition of various Langmuir-Blodgett films for realizing these structures. Multilayer polymeric L-B films using different materials have been deposited and their physical properties studied using atomic force microscopy. Possible causes of film non-uniformity are investigated.
A design useful for small spatial range distributed fiber optic sensor is presented. This sensor array has advantages of zero dead zone, high spatial resolution, and fast response time, which can be used in the areas of smart skin as well as distributed pressure, force, displacement, and temperature sensors.
Large signal two-wave mixing in photorefractive materials was studied. A theory based on the Kukhtarev-Vinetskii's model was developed. The coupled-mode equations for large modulation was obtained and their numerical solutions were found. It is shown that large modulation reduces the coupling coefficient of the two-wave mixing interaction, and, therefore, the effective gain. Theoretical results of large modulation agree well with experimental measurements.
An experiment to study the characteristics of the cladding-length-dependent sensor has been performed using an optical fiber with silica core and lossy liquid cladding (mercury). The results show that the output light power is linear and sensitive to the change of lossy cladding length and acceptance angle.
This paper presents two methods for improving and evaluating the imaging quality of the multi-core image fiber. A square shape preform technique is employed to decrease the deformation of element fiber and a lateral view method is proposed to measure the number, diameter of element fibers and to test the twist of image fiber. The results of experiments showed that these methods are effective to fabricated high quality multi-core image fiber.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.