Triggered by the need for arrays of individually resolvable excitation foci or trapping potentials in photonics applications, coherent lattice theory describes a unique approach to design structured interference patterns. Typically, large periodicity lattices remain unexplored due to limitations in the theoretical description. Here, we present a method for efficient computation of coherent lattices, successfully covering all periodic and quasi-periodic lattices. The previously unrelated moiré theory and prime number factorization are the foundation of the proposed method. Additionally, we experimentally verify key optical coherent lattices and propose broadening their applicability towards structured light microscopy and optical trapping using photonic integrated circuits.
Fluorescence microscopy is an indispensable tool in biology and medicine, fuelling many breakthrough discoveries in a wide set of sub-domains. Yet, the resolution is intrinsically restricted by the diffraction limit. The last two decades have witnessed the emergence of several super-resolution fluorescence microscopy techniques that are breaking this limit (cfr. Nobel Prize in Chemistry 2014). Structured illumination microscopy (SIM) is one of such techniques that has gained much popularity and is available in commercial systems. In SIM, a biological sample is illuminated by a spatially structured light field — a sinusoidal interference pattern — which causes normally inaccessible high-resolution information to be encoded into the observed image due to the Moiré effect. Typically, the illumination patterns are generated by a grating or SLM and focused onto the sample through an objective lens to excite the fluorophores. Next, the fluorescence is transmitted to the imager through the same lens. Multiple images are taken under certain illumination patterns and used to reconstruct a single super-resolved image. However, making use of free space optics, state-of-the-art SIM systems require multiple bulky and precision optical components that give these systems the drawbacks of high cost and cumbersome size.
In this talk, a structured illumination microscopy system based on a photonic integrated circuit (PIC) is presented. The unique properties of photonic integrated circuits allow us to create truly innovative microscopy systems that have the potential to go well beyond the current state-of-the-art: higher resolution due to the use of high refractive index materials, easier alignment with on-chip illumination light path, large field of view, a compact form factor resulting from on-chip integration, and lower cost due to compatibility with CMOS chip fabrication.
Low energy operation is a must for using silicon photonic system to replace the conventional electrical interconnection systems. Three energy-saving approaches in silicon photonics are highlighted in this paper: low driving voltage for Mach-Zehnder modulator (MZM), negative chirp compensation for MZM-based long-haul transmission, and athermal filter for wavelength division multiplexing (WDM). These methods serve to reduce energy consumption of modulation and WDM, and are thus valuable to the development of future communication systems.
A thermally tunable half-disk resonator (HDR) with directly-integrated metallic heater is presented. The proposed resonator is based on the structure of HDR, which allows direct electrical contacts in HDR region without causing extra loss. The metallic heater is designed to be directly integrated on the silicon devices, and single-mode operation can be retained simultaneously. Metallic heater deposited on inner side of the ring, which cannot realize before because of weakened light confinement resulting in substantial leakage and loss, guides most heat power to the waveguide. This thermal localization enhances tuning efficiency. The simulation result shows a wavelength shift of 0.855 nm under ultralow driving voltage of 0.02V, corresponding to high thermal tuning efficiency of 2.831 nm/mW. The structure possesses both the advantages of high thermal tuning efficiency and low resistance, hence requiring smaller voltage and energy to drive, desirable for optical interconnects applications. Moreover, the proposed structure also eliminates the need to use doped silicon slab for electrical contacts, as widely used in conventional directly integrated heaters. Undoped strip waveguide in HDR enables higher Q-factor and improves optical performance.
After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterned on a metal film have generated wide interest as they offer high optical transmission and strong localized electric near-field intensities. However, the large ohmic losses exhibited by SPs in the optical regime represent a fundamental limitation that reduces drastically the practical applicability of EOT properties. Furthermore, not compatible with silicon platform make it difficult for application purposes. As a possible solution to this fundamental problem, gain medium have been introduced to compensate the loss created by metallic film. But the most important yet challenging requirements for gain material are to be silicon compatible and working at telecommunication regime. The aim of this paper is to theoretically study optical amplification of EOT properties in periodic hole arrays incorporating optically pumped gain media. The gain media was selected Erbium/Ytterbium(Er/Yb) silicate that is silicon compatible with photoluminescence peak at telecommunication regime. Use of Er3+ ions has the advantages of proven, stable, and low-noise operation at the technologically important 1.54 m region. To excite the active material a laser with a maximum power of 372 mW at the wavelength of 1480 nm is applied. Geometrical parameters was obtained by solving the surface plasmon dispersion relation on periodic hole arrays. The condition for lossless propagation was obtained analytically. Simulation results shows that for lossless propagation we will need higher gain value. By considering higher gain values the absorption was approached to zero 30% transmission enhancements was observed at telecommunication wavelength.