Indumathi Raghu Srimathi

Method of Fabrication for Encapsulated Polarizing Resonant Gratings

In this letter, we present a novel method of fabricating encapsulated resonant gratings. The fabrication method uses selective etching, conformal deposition, conventional lithography, and direct bonding techniques. Our letter includes simulation and experimental results, confirming a strong resonance unique to the TE polarization at 1550 nm with a 5 nm full-width at half-maximum.

Guided-Mode Resonance Filters for Wavelength Selection in Mid-Infrared Fiber Lasers

A narrowband mid-infrared (mid-IR) guided-mode resonance filter (GMRF) is designed and fabricated using a Hafnium Dioxide film/quartz wafer material system. The fabricated GMRF is then integrated into an erbium (Er)-doped Zr-Ba-La-Al-Na (ZBLAN) fluoride glass fiber laser as a wavelength selective feedback element. The laser operated at 2782 nm with a line-width less than 2 nm demonstrates the viability of GMRFs for wavelength selection in the mid-IR.

Subwavelength grating based metal-oxide nano-hair structures for optical vortex generation.

An all-dielectric, subwavelength grated based metal-oxide nano-hair structure for optical vortex beam generation has been presented in the paper. The nano-hair structure fabricated with alternating layers of alumina/hafnia on a fused silica substrate has a high diffraction efficiency of ~90% around the design wavelength, λ(o) = 1.55 μm and is insensitive to the polarization of the incident optical beam. The phase in transmission of these devices are controlled by azimuthally varying the fill fraction of the subwavelength grating. Realization of phase optical elements in an all-dielectric platform, based on subwavelength gratings offering full 0-2π phase modulation, is important for miniaturization and integration of conventional refractive optical elements.

Creation and exploitation of orbital angular momentum for maritime environments (Conference Presentation)

The abstract is not available

Resonant optical devices for IR lasers

This paper highlights recent developments in resonant optical devices for infrared (IR) and mid-infrared (mid- IR) lasers. Sub-wavelength grating based resonant optical filters are introduced and their application in 2 μm thulium fiber laser and amplifier systems has been discussed. The paper focuses on applying such filtering techniques to 2.8 μm mid-IR fiber laser systems. A narrowband mid-IR Guided-Mode Resonance Filter (GMRF) was designed and fabricated using Hafnium(IV) Oxide film/quartz wafer material system. The fabricated GMRF was then integrated into an Erbium (Er)-doped Zr-Ba-La-Al-Na (ZBLAN) fluoride glass fiber laser as a wavelength selective feedback element. The laser operated at 2782 nm with a linewidth less than 2 nm demonstrating the viability of GMRF’s for wavelength selection in the mid-IR. Furthermore, a GMRF of narrower linewidth based on Aluminum Oxide/quartz wafer material system is fabricated and tested in the same setup. The potentials and challenges with GMRFs will be discussed and summarized.

Monolithic fabrication and performance control of multilayered, polarization sensitive, guided-mode resonance filters

An efficient monolithic fabrication technique of multiple Guided-Mode Resonance Filter (GMRF) devices on a single substrate is presented. The devices consist of two crossed linear sub-wavelength grating (SWG) dielectric layers, formed by etching deposited silicon oxide films, separated by a silicon nitride waveguide. The buried SWG duty cycle is lithographically modulated to control the device resonance wavelengths, independent of the top SWG. This is because the buried SWG acts as a tunable effective index layer, controlling the waveguide mode coupling wavelength into the silicon nitride waveguide layer. The two SWG have different spatial periods, to further reduce resonance coupling between them. The fabrication is accomplished using existing photolithographic technology, and conventional PECVD coating techniques.