@misc{zhang_chen_chang_2019, title={Recent progress in near-field nanolithography using light interactions with colloidal particles: from nanospheres to three-dimensional nanostructures}, volume={30}, ISSN={["1361-6528"]}, DOI={10.1088/1361-6528/ab2282}, abstractNote={The advance of nanotechnology is firmly rooted in the development of cost-effective, versatile, and easily accessible nanofabrication techniques. The ability to pattern complex two-dimensional and three-dimensional nanostructured materials are particularly desirable, since they can have novel physical properties that are not found in bulk materials. This review article will report recent progress in utilizing self-assembly of colloidal particles for nanolithography. In these techniques, the near-field interactions of light and colloids are the sole mechanisms employed to generate the intensity distributions for patterning. Based on both ‘bottom-up’ self-assembly and ‘top-down’ lithography approaches, these processes are highly versatile and can take advantage of a number of optical effects, allowing the complex 3D nanostructures to be patterned using single exposures. There are several key advantages including low equipment cost, facile structure design, and patterning scalability, which will be discussed in detail. We will outline the underlying optical effects, review the geometries that can be fabricated, discuss key limitations, and highlight potential applications in nanophotonics, optoelectronic devices, and nanoarchitectured materials.}, number={35}, journal={NANOTECHNOLOGY}, author={Zhang, Xu A. and Chen, I-Te and Chang, Chih-Hao}, year={2019}, month={Aug} }
 @article{poteet_zhang_nagai_chang_2018, title={Twin photonic nanojets generated from coherent illumination of microscale sphere and cylinder}, volume={29}, ISSN={0957-4484 1361-6528}, url={http://dx.doi.org/10.1088/1361-6528/aaa35d}, DOI={10.1088/1361-6528/aaa35d}, abstractNote={Photonic nanojets, highly focused beams of light created by planar illumination of a microsphere, have been shown to produce narrow subwavelength beams over distances of several wavelengths in the near field. In this work, we investigate the generation of twin photonic nanojets through the illumination of a microsphere or cylinder from two coherent sources with relative phase shift. Under these conditions, symmetric twin nanojets separated by an intensity null can be generated. Compared to a photonic nanojet, the twin nanojets can achieve an even smaller subwavelength beam, and have the added advantage of having more complex intensity profiles that can be controlled by multiple parameters. Using both finite-difference time-domain and Mie theory models, the width, length, and intensity enhancement factor of the nanojet geometry are found to be functions of the phase, angle offsets, and particle geometry. Such twin photonic nanojets can find applications in optical trapping, manipulation, nanolithography, and enhancement of nonlinear optical properties.}, number={7}, journal={Nanotechnology}, publisher={IOP Publishing}, author={Poteet, Austen and Zhang, Xu A and Nagai, Hironori and Chang, Chih-Hao}, year={2018}, month={Jan}, pages={075204} }
 @article{zhang_chen_bagal_chang_2017, title={Enhanced total internal reflection using low-index nanolattice materials}, volume={42}, ISSN={["1539-4794"]}, DOI={10.1364/ol.42.004123}, abstractNote={Low-index materials are key components in integrated photonics and can enhance index contrast and improve performance. Such materials can be constructed from porous materials, which generally lack mechanical strength and are difficult to integrate. Here we demonstrate enhanced total internal reflection (TIR) induced by integrating robust nanolattice materials with periodic architectures between high-index media. The transmission measurement from the multilayer stack illustrates a cutoff at about a 60° incidence angle, indicating an enhanced light trapping effect through TIR. Light propagation in the nanolattice material is simulated using rigorous coupled-wave analysis and transfer matrix methods, which agrees well with experimental data. The demonstration of the TIR effect in this Letter serves as a first step towards the realization of multilayer devices with nanolattice materials as robust low-index components. These nanolattice materials can find applications in integrated photonics, antireflection coatings, photonic crystals, and low-k dielectric.}, number={20}, journal={OPTICS LETTERS}, author={Zhang, Xu A. and Chen, Yi-An and Bagal, Abhijeet and Chang, Chih-Hao}, year={2017}, month={Oct}, pages={4123–4126} }
 @article{bagal_zhang_shahrin_dandley_zhao_poblete_oldham_zhu_parsons_bobko_et al._2017, title={Large-area nanolattice film with enhanced modulus, hardness, and energy dissipation}, volume={7}, journal={Scientific Reports}, author={Bagal, A. and Zhang, X. A. and Shahrin, R. and Dandley, E. C. and Zhao, J. J. and Poblete, F. R. and Oldham, C. J. and Zhu, Y. and Parsons, G. N. and Bobko, C. and et al.}, year={2017} }
 @article{tippens_bagal_zhang_chang_2017, title={Nanostructured antireflective in-plane solar harvester}, volume={25}, ISSN={["1094-4087"]}, DOI={10.1364/oe.25.00a840}, abstractNote={In this work, we demonstrate a two-dimensional nano-hole array that can reduce reflection losses while passively trapping and harvesting incident light. The surface structure is designed to scavenge a small portion of incident light that would typically be lost due to Fresnel reflection, while the majority of light transmits unobstructed like a regular window. The trapping mechanism is dependent on angle and wavelength, and can be designed to selectively trap narrow wavelength bands using the constructed theoretical models. We demonstrate that structures with periods of 275 nm and 325 nm can trap different wavelength range within the visible spectrum, while simultaneously suppressing reflection losses. The trapping effect can be observed visually, and can be converted to a current output using a photovoltaic (PV) cell on the glass edge. The fabrication of such materials employs a simple replication process, and can be readily scaled up for large-scale manufacturing. The demonstrated solar harvester can be potentially be widely deployed in residential and commercial buildings as multifunctional windows for solar energy harvesting, scavenging, spectra splitting, and anti-glare properties.}, number={16}, journal={OPTICS EXPRESS}, author={Tippens, Jared and Bagal, Abhijeet and Zhang, Xu A. and Chang, Chih-Hao}, year={2017}, month={Aug}, pages={A840–A850} }
 @article{nagai_poteet_zhang_chang_2017, title={Three-dimensional colloidal interference lithography}, volume={28}, ISSN={0957-4484 1361-6528}, url={http://dx.doi.org/10.1088/1361-6528/aa5e3f}, DOI={10.1088/1361-6528/aa5e3f}, abstractNote={Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle–light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd’s mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics.}, number={12}, journal={Nanotechnology}, publisher={IOP Publishing}, author={Nagai, Hironori and Poteet, Austen and Zhang, Xu A and Chang, Chih-Hao}, year={2017}, month={Feb}, pages={125302} }