Near-field optical power transmission of dipole nano-antennas

Nano-antennas in functional plasmonic applications require high near-field optical power transmission. In this study, a model is developed to compute the near-field optical power transmission in the vicinity of a nano-antenna. To increase the near-field optical power transmission from a nano-antenna, a tightly focused beam of light is utilized to illuminate a metallic nano-antenna. The modeling and simulation of these structures is performed using 3-D finite element method based full-wave solutions of Maxwell’s equations. Using the optical power transmission model, the interaction of a focused beam of light with plasmonic nanoantennas is investigated. In addition, the tightly focused beam of light is passed through a band-pass filter to identify the effect of various regions of the angular spectrum to the near-field radiation of a dipole nano-antenna. An extensive parametric study is performed to quantify the effects of various parameters on the transmission efficiency of dipole nano-antennas, including length, thickness, width, and the composition of the antenna, as well as the wavelength and half-beam angle of incident light. An optimal dipole nanoantenna geometry is identified based on the parameter studies in this work. In addition, the results of this study show the interaction of the optimized dipole nano-antenna with a magnetic recording medium when it is illuminated with a focused beam of light

Large-area epitaxial growth of InAs nanowires and thin films on hexagonal boron nitride by metal organic chemical vapor deposition

Large-area epitaxial growth of III-V nanowires and thin films on van der Waals substrates is key to developing flexible optoelectronic devices. In our study, large-area InAs nanowires and planar structures are grown on hexagonal boron nitride templates using metal organic chemical vapor deposition method without any catalyst or pre-treatments. The effect of basic growth parameters on nanowire yield and thin film morphology is investigated. Under optimised growth conditions, a high nanowire density of 2.1×109cm-2is achieved. A novel growth strategy to achieve uniform InAs thin film on h-BN/SiO2/Si substrate is introduced. The approach involves controlling the growth process to suppress the nucleation and growth of InAs nanowires, while promoting the radial growth of nano-islands formed on the h-BN surface. A uniform polycrystalline InAs thin film is thus obtained over a large area with a dominant zinc-blende phase. The film exhibits near-band-edge emission at room temperature and a relatively high Hall mobility of 399 cm-2/(Vs). This work suggests a promising path for the direct growth of large-area, low-temperature III-V thin films on van der Waals substrates.Aswani Gopakumar Saraswathy Vilasam, Sonachand Adhikari, Bikesh Gupta, Sivacarendran Balendhran, Naoki Higashitarumizu, Julie Tournet, Lily Li, Ali Javey, Kenneth B Crozier, Siva Karuturi, Chennupati Jagadish, and Hark Hoe Ta

Optical trapping and fluorescence collection using a dualwavelength diffractive optic

We demonstrate a silicon diffractive element that serves as an optical tweezer in the near infrared and as a fluorescence collector in the visible. The 1.3 NA lens is achromatic and has high diffraction efficiency

Scanning microscopy using a short-focal-length Fresnel zone plate

We demonstrate a form of scanning microscopy using a short-focal-length Fresnel zone plate and a low-NA relay telescope. Owing to a focal length of only 5 μm, the zone plate produces large wavefront tilt and consequently severe vignetting for off-axis illumination. By scanning an optically trapped fluorescent sphere, we measure the vignetted collection region of the zone-plate imaging system. The fluorescence collection efficiency is sharply peaked and has a lateral width of 550 nm, which agrees with numerical simulations

Optical trapping and fluorescence collection using a dual-wavelength diffractive optic

We demonstrate a silicon diffractive element that serves as an optical tweezer in the near infrared and as a fluorescence collector in the visible. The 1.3 NA lens is achromatic and has high diffraction efficiency

Fabrication of high aspect ratio optical light pipes

We report fabrication techniques for high aspect ratio vertical light pipes in a 10μm thick SiO2 layer. Light pipes with an aspect ratio of 2.8:1 and a sidewall angle of 89.5o were demonstrated

Fabrication of high-aspect-ratio lightpipes

The authors report the development of two fabrication processes for creating high-aspect-ratio lightpipes in a 10 μm thick SiO2 layer, with smooth, uniform, and straight vertical sidewalls. Both processes require only standard optical lithography, without the need for advanced electron beam or deep-UV lithography. One process employs a dielectric etch mask and the other uses a negative photoresist as the etch mask. The experiments show that the CF4 -based reaction gases are best for deep etching with high selectivity and etch rate. Trenches with diameters or width of 1.5 μm are demonstrated, with an aspect ratio of 7.2:1 and a sidewall angle of 87.4°. The authors also achieve cylindrical lightpipes with an aspect ratio of 3.8:1 and a sidewall angle of 89.5°. They anticipate that these high-aspect-ratio lightpipe structures would be useful for complementary metal-oxide semiconductor image sensors, where they would increase the efficiency of light collection, and reduce interpixel cross-talk

Fabrication techniques of high aspect ratio vertical lightpipes using a dielectric photomask

We report the development of new fabrication techniques for creating high aspect ratio optical lightpipes in SiO2 layers of 10μm thickness and above. A dielectric photo mask was used for deep reactive ion etching. Our experiments show that CF4-based reaction gases were best for deep etching with high selectivity and etch rate. Trenches with diameters or width of 1.5μm were demonstrated, with an aspect ratio of 7.2:1 and a sidewall angle of 87.4 degrees. We also present the lift-off process of the etch masks and the via-filling procedures for the lightpipes. These structures are useful for image sensors, vertical interconnect and waveguiding applications

Silicon nitride light pipes for image sensors

We describe a means for improving the performance of CMOS image sensors using vertical waveguides, known as light pipes. We describe experimental results on the etching of silicon nitride pillars, and the fabrication of photodiodes