The effect of the surface roughness of ice crystals is not routinely accounted for in current cloud retrieval algorithms that are based on pre-computed lookup libraries. In this study, we investigate the effect of ice crystal surface roughness on the retrieval of ice cloud effective particle size, optical thickness and cloud-top temperature. Three particle surface conditions, smooth, moderately rough and deeply rough, are considered in the visible and near-infrared channels (0.65 and 3.75 µm). The discrete ordinates radiative transfer (DISORT) model is used to compute the radiances for a set of optical thicknesses, particle effective sizes, viewing and illumination angles, and cloud temperatures. A parameterization of cloud bi-directional reflectances and effective emittances is then developed from a variety of particle surface conditions. This parameterization is applied in a 3-channel retrieval method for Moderate Resolution Imaging Spectroradiometer (MODIS) data at 0.65, 3.75, and 10.8 µm. Cloud optical properties are derived iteratively for each pixel that contains ice clouds. The impact of ice crystal surface roughness on the cloud parameter retrievals is examined by comparing the results for particles with smooth surfaces and rough surfaces. Retrieval results from two granules of MODIS data indicate that the retrieved cloud optical thickness is significantly reduced if the parameterization for roughened particles is used, as compared with the case of smooth particles. For the retrieval of cloud effective particle size, the inclusion of the effect of surface roughness tends to decrease the retrieved effective particle size if ice crystals are small. The reversed result is noticed for large ice crystals. It is also found that surface roughness has a very minor effect on the retrieval of cloud-top temperatures.

In the present study we investigate the use of polymer liquid crystal for holographic recording. Holographic patterns were produced by means of two-beam interference using an Ar+ laser. The polymer liquid crystal thin layers were prepared by injecting RM257 into cells through capillary action at 140¢XC where the RM257 mesogen was in isotropic state. By exposing the mesogenic layer to the laser interference patterns, we have successfully imprint holographic patterns into RM257 thin layers. In order to reach the best alignment, the intensity of laser beam, sample temperature, the spacial period and exposure time must be properly set.

In this thesis, we use E-Beam lithography to finish the process of positioning system and 2D photonic crystal. We use the new E-Beam system to define some array patterns. By this test, we obtain the minimum linewidth is 55nm, and the maximum writable range is 250£gm*250£gm. First, we fabricated the 2D photonic crystal microcavity and positioning system on the InGaAs/InAlAs which grown by molecular beam epitaxy (MBE) on InP substrate at 1564nm emission wavelength by E-beam lithography. For the positioning system, we set up a origin point first. And then we design many rectangles whose length is 1£gm, width is 10£gm and gap is 1£gm along X axis and Y axis from the origin point. All of the patterns are regarded as the ruler. Finally, we design a big rectangle whose length is 250£gm and width is 10£gm to adjust the positioning angle above the ruler. The maximum error of the positioning system is 20nm. For the 2D photonic crystal (2D PhC) microcavity, a triangular array of air columns is adopted. The lattice constant and air columns radius are 1150nm and 460nm, respectively. The TE modes photonic band gap of this structure are corresponding to wavelength range in 1535nm~1635nm. We remove signal defect and seven defects in the 2D PhC to form 2D PhC microcavities and the PhC microcavities have many defect modes. The Micro-PL measurement shows when the etching depth was deep enough, the PhC microcavities which have 1-defect and 7-defect appeared defect mode at 1622nm (a/£f=0.74) both. The intensity of 7-defect PhC is 7 times than 1-defect PhC. Both of them cooperate with our simulation and design. And the maximum Q value is about 324 at the defect mode.

RM257 consists of photoactive mesogenic end groups. By in situ polymerization of the mesogen, the optical information can be recorded into RM257 thin film. In this study, the RM257 thin films were exposed to a holography irradiation created using an Ar+ laser. The holography patterns have been found to be imprinted into the polymer thin films. The refractive efficiency can be increased when the sample temperature is properly controlled during holography irradiation. The work was started from the use of two beam interferometry, and further to use three beam interference. The molecular arrangement in the resultant polymer film and their function in optical modulation have been studied.

As the photonic crystal fibers (PCFs) are fabricated, it is hard to modulate their optical characteristics to function as tunable optical devices. To introduce tunable optical characteristics into the PCF structures, one can infiltrate liquids into the air holes of the PCFs to form the liquid-filled PCFs. However, the propagation losses become larger due to the finite liquid-hole layers and the lossy liquids infused in all the air holes of the cladding. In this thesis, an efficient full-vector finite-difference frequency-domain (FDFD) mode solver cooperated with the PMLs is utilized to investigate the propagation characteristics of the selectively liquid-filled PCFs. The propagation constants and the propagation losses of the guided modes on the selectively liquid-filled PCFs can be successfully obtained. From our numerical results, the propagation losses of both the internally liquid-filled PCFs and externally liquid-filled PCFs can be efficiently reduced by the outer or inner air-hole layers, and the useful tunablility characteristics for optical device applications can be maintained. Besides, the dispersion-related devices based on the selectively liquid-filled PCFs are also investigated. It is demonstrated that a DFPCF with the flatten dispersion value D within 0 ¡Ó 1 ps/nm/km over £f = 1.45 £gm to 1.65 £gm or a DCPCF with a high negative dispersion value D = -3100 ps/nm/km at £f = 1.55 £gm can be achieved by infiltrating the liquid into all air holes or specified air-hole layers. In the experiment, a simple selectively blocking technique using the microscopy, the tool fiber and the alignment technique is employed to fabricate the internally and externally liquid-filled PCFs. The measurement of the optical characteristics of these selectively liquid-filled PCFs is carried out and compared with the simulation results.

Polarization-maintaining fibers (PMFs) have been widely studied and discussed. Nowadays, a novel polarization-maintaining photonic crystal fiber (PMPCF) is proposed with many advantages, such as the large mode area and the single-mode transmission in a wide frequency range. In this thesis, we propose the birefringent liquid-filled PCF with the liquid asymmetrically infiltrated in the cladding region. The Yee-mesh-based finite-difference frequency-domain (FDFD) method is utilized to analyze the birefringent properties of the liquid-filled PCFs. Compared with traditional PMFs, our proposed PCF possesses larger birefringence about 7.1 ¡Ñ 10-3 at 1.55 £gm with useful tunable properties. In the experiment, we have successfully fabricated the birefringent liquid-filled PCF by using the selective blocking technique. The elliptical far field can be observed for our birefringent PCF. We also demonstrate the experiment setup for estimating the birefringence of our birefringent liquid- filled PCF.

Discotic liquid crystal (LC) molecules have a structure that is comprised of a rigid aromatic core with side-chain molecules. Intermolecular £k-£k interactions force the tube to orient and form one-dimensional columnar structures which can act as molecular wires. In recent years, discotic LC molecules have been deposited on surfaces from solution to create the solid-state electronic elements used widely in solar cells, organic light-emitting diodes (OLED), organic photovoltaic, field-effect transistors (FET), and molecular wires. Different stacking morphologies can change the behavior of the material and thus will have potential for different applications. Hence, effective control over the stacking of the LC molecules on surfaces is important for optimizing the performance and effectiveness of LC-based electronic components and devices. This study has focused on LC molecules with acid and ester containing functional groups, and how these groups influence the stacking behavior on surfaces. Here, the self-aggregation behavior of the discotic LC ester in solution was investigated quantitatively by determining the concentration dependence of the 1H NMR chemical shifts. Our results showed that discotic LC ester has different self-aggregation behavior in CH2Cl2, THF and Benzene organic solvents. THF solvent showed the highest degree of aggregation, followed by CH2Cl2, and then benzene. We also studied the effects of (i) different solvents (THF, CH2Cl2, and Benzene), (ii) different surface functional groups (OH, CH3, NH2, SH, and diphenyl), and (iii) temperature, on the stacking phenomenon of discotic LCs on silicon surfaces. In part (i) our results showed that discotic LC ester had different morphologies on silicon surfaces due to differences in solvent polarity and evaporation rate. In part (ii), we observed that different surface functional groups did not affect the intermolecular interaction between either the ester- or acid-type LC molecules. For the acid-type LC, strong hydrogen bonding interactions with the surface caused the crystals to form rod-like fiber structures. However, the ester-type LC molecules formed ribbon-like stacks on the surfaces. For functional groups containing CH3 (more hydrophobic surfaces), we observed no LC molecules on the surface, which was likely due to the poor wettability of the solvents on OTS. In part (iii), we observed that both acid and ester discotic LCs formed large aggregates on the surfaces due to a ¡§ripening effect¡¨. With increased temperature, the molecules were able to overcome the wetting interaction with the surface and self-aggregate into three-dimensional clusters.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes vita. Includes bibliographical references (leaves 226-234).

Thesis--M. Phil., University of Hong Kong, 1985.

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 118-123).