Nonlinear Nanophotonics

Future optical systems require compact, ultra-fast devices capable of switching and logic across a wide range of wavelengths. To realize this goal, ultrafast nonlinearities must be exploited while maintaining manageable linear losses and nonlinear absorption. We present TiO2 as a nonlinear material to meet these needs. TiO2 is highly transparent for wavelengths > 400 nm and possesses both high linear and nonlinear refractive indices. We measurements the nonlinear index and multiphoton absorption in bulk TiO2 (rutile) using the z-scan technique near the half bandgap (800 nm). Using... Read more about Simultaneous multiphoton absorption in rutile (TiO2) across the half-bandgap

We fabricate and characterize integrated polycrystalline anatase TiO2 micro-ring resonators at around λ = 1550 nm. We obtain quality factors of 1.5×10^4 and calculate a propagation loss of 8.0 ± 1.3 dB/cm.

We fabricate submicrometer-width TiO2 strip waveguides and measure optical losses at 633, 780, and 1550 nm. Losses of 30, 13, and 4 dB/cm (respectively) demonstrate that TiO2 is suitable for visible-to-infrared on-chip microphotonic devices.

In these interactive lectures we explore how light can be manipulated at the nanoscale. We begin by describing optical propagation in ordinary materials and then show how materials can be engineered to achieve a refractive index of zero. These zero-index materials have remarkable properties and can be integrated in photonic circuits. We also give an introduction to nonlinear optics and discuss how zero-index materials can be used to accomplish phase matching in nonlinear optics.

Outline

 

• Optical properties of materials
• Dispersion of...

Read more about Manipulating light at the nanoscale (Lectures 3–5)

We have identified titanium dioxide (TiO2) as a promising material for on-chip nonlinear optical devices. Its high refractive index and large intrinsic nonlinearity can strongly enhance confinement and non-linear interactions. In this study we optimize our deposition process to lower the linear losses in planar waveguides. We deposit titanium oxide thin films by RF reactive sputtering titanium onto oxidized silicon wafers in an argon/oxygen environment. The oxygen partial pressure in the chamber has a large impact on the deposition rate and the film composition. We investigate the composition... Read more about Impact of sputtering parameters on titanium dioxide thin films for nonlinear nanophotonics

We discuss the propagation of laser pulses in materials, the basics of nonlinear optical interactions, wave guiding and propagation of modes, fabrication of nanophotonic devices and the use of nonlinear optics at the nanoscale to fabricate optical logic gates.

We will present measurements of the complex nonlinear response of sputtered amorphous and polycrystalline titanium dioxide (TiO2) thin films using the thermally managed z-scan technique. Using a Ti:Sapphire laser with 100-fs pulses at 800 nm, we observe ultrafast electronic effects near TiO2's half band-gap. We explore the relation between material processing parameters and observed nonlinearity. In addition, we will discuss the consequences for applications such as all-optical switching.

Titanium dioxide (TiO2) represents an attractive candidate for nonlinear optical devices due its high transparency, large refractive index, and large Kerr nonlinearity. Using electron beam lithography and a liftoff procedure, we can structure both amorphous TiO2 as well as polycrystalline anatase thin films to create photonic devices that exploit the material’s properties in order to do nonlinear optics. Nonlinear optics benefit from long interactions, necessitating large intensities along long waveguide lengths. For this reason, waveguide losses need to be minimized. We study the effects... Read more about Maximizing intensity in TiO2 waveguides for nonlinear optics

Titanium dioxide (TiO2) is a promising material for nonlinear photonic applications. Its large bandgap (> 3 eV) means it is highly transparent and has minimal two photon absorption over a wide wavelength range. TiO2’s high linear and nonlinear refractive indices (> 2 and 25 × that of silica at 800 nm, respectively) allow for high optical confinement in nanophotonic structures, such as waveguides, photonic crystals and resonators, and efficient nonlinear interactions. Thus, TiO2 is a potential platform for on-chip nonlinear optical devices operating across the three traditional... Read more about TiO2 nanophotonic waveguides for on-chip nonlinear optical devices

Titanium dioxide (TiO2) has attractive optical properties for nonlinear optical applications ranging from telecommunication to interconnect wavelengths (800–1600 nm). TiO2 demonstrates large linear and nonlinear refractive indices, wide transparency from the infrared to as low as 400 nm wavelengths, and low two-photon absorption for wavelengths longer than 800 nm. We use the Z-scan technique to investigate the nonlinear refraction and multiphoton absorption of bulk rutile TiO2 for wavelengths ranging from 800–1600 nm. Using our results, we calculate nonlinear figures of merit and discuss... Read more about Nonlinear refraction in rutile TiO2

We deposit TiO2 planar waveguides on oxidized silicon substrates by reactive sputtering. The films exhibit Raman spectra consistent with an amorphous or anatase phase and have losses as low as 0.4 dB/cm at 826 nm.