The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions and that their optical transitions can be substantially modified through electrical gating, much like electrical transport in field-effect transistors. This gate dependence of interband transitions adds a valuable dimension for optically probing graphene band structure. For a graphene monolayer, it yields directly the linear band dispersion of Dirac fermions, whereas in a bilayer, it reveals a dominating van Hove singularity arising from interlayer coupling. The strong and layer-dependent optical transitions of graphene and the tunability by simple electrical gating hold promise for new applications in infrared optics and optoelectronics.

/pdf/gate-variable-optical-transitions-in-graphene-3q6kb2wuwu.pdf

Gate-Variable Optical Transitions in Graphene

On productivity of laser additive manufacturing

Additive manufacturing (AM), which is also known as three-dimensional (3D) printing, uses computer-aided design to build objects layer by layer. Here, we focus on the recent progress in the development of techniques for 3D printing of glass, an important optoelectronic material, including fused deposition modeling, selective laser sintering/melting, stereolithography (SLA) and direct ink writing. We compare these 3D printing methods and analyze their benefits and problems for the manufacturing of functional glass objects. In addition, we discuss the technological principles of 3D glass printing and applications of 3D printed glass objects. This review is finalized by a summary of the current achievements and perspectives for the future development of the 3D glass printing technique.

3D printing of glass by additive manufacturing techniques: a review

Optical metasurfaces with subwavelength thickness hold considerable promise for future advances in fundamental optics and novel optical applications due to their unprecedented ability to control the phase, amplitude, and polarization of transmitted, reflected, and diffracted light. Introducing active functionalities to optical metasurfaces is an essential step to the development of next-generation flat optical components and devices. During the last few years, many attempts have been made to develop tunable optical metasurfaces with dynamic control of optical properties (e.g., amplitude, phase, polarization, spatial/spectral/temporal responses) and early-stage device functions (e.g., beam steering, tunable focusing, tunable color filters/absorber, dynamic hologram, etc) based on a variety of novel active materials and tunable mechanisms. These recently-developed active metasurfaces show significant promise for practical applications, but significant challenges still remain. In this review, a comprehensive overview of recently-reported tunable metasurfaces is provided which focuses on the ten major tunable metasurface mechanisms. For each type of mechanism, the performance metrics on the reported tunable metasurface are outlined, and the capabilities/limitations of each mechanism and its potential for various photonic applications are compared and summarized. This review concludes with discussion of several prospective applications, emerging technologies, and research directions based on the use of tunable optical metasurfaces. We anticipate significant new advances when the tunable mechanisms are further developed in the coming years.

Active optical metasurfaces: comprehensive review on physics, mechanisms, and prospective applications

Direct pixel-by-pixel phase engineering in a SLM is an effective method for the holographic fabrication of graded photonic super-quasi-crystals with desired disorder and graded photonic super-crystals with rectangular unit-cells. Multiple levels of filling fractions of dielectric in the crystal have been created in the graded regions. Fabrication of these graded photonic super-crystals and super-quasi-crystals with small feature size is possible, using a laser projection system consisting of integrated spatial light modulator and reflective optical element.

Fabrication of multi-level graded photonic super-crystals

Transparent conducting oxides are part of a robust material class that is capable of supporting near-IR surface plasmon resonances (SPRs) which are strongly dependent on size, structure, and doping of the material. This study presents the implementation of holographic lithography to structure large area square lattice cylindrical hole arrays on the transparent conducting oxide thin film, aluminum doped zinc oxide (AZO). For fabricated structures on a glass substrate, SPR are indirectly measured by FTIR transmission and verified with electromagnetic simulations using a finite difference time domain method. Furthermore, it is shown that the SPR excited are standing wave resonances in the (1,1) direction of the lattice array located at the interface of the patterned AZO and glass substrate. This research extends the robust CMOS compatible fabrication techniques of holographic lithography into tunable conductive materials,and contributes to the core technology of future integrated photonics.

Holographic fabrication of hole arrays in AZO for study of surface plasmon resonances

Using the pixel-by-pixel phase engineering in a spatial light modulator together with reflective optical element, we have studied holographic fabrication of graded photonic super-crystals with a square lattice in square and hexagonal symmetries.

David Lowell

Papers

Fabrication of multi-level graded photonic super-crystals

Holographic fabrication of hole arrays in AZO for study of surface plasmon resonances

Holographic fabrication of graded photonic super-crystals using spatial light modulator