A silicon micro-lens is proposed and analyzed when it is integrated into the photodiode for the application of a backside illuminated (BSI) image sensor (Pixel size is around 1 um). Due to the small dimension of the BSI pixel, each pixel of the image sensor receives from its adjacent pixels cross-talk (x-talk) due to large light incident angle and light diffraction, resulting in reduced sensor MTF and possible color artifacts. A silicon ulens formed between the photodiode and RGB color filter works as an inner lens to improve the focus of the light and guide it into its corresponding pixel, thus decreasing optical x-talk and reducing noise. Since the silicon ulens is integrated into the photodiode and could be doped as part of the photodiode, this design would eliminate any internal reflection caused by traditional inner micro lens solutions (made of Si oxide, Si nitride or polymer). ‘By color' anti-reflection coatings (ARC) on top of the silicon ulens can work as a versatile optical filter to compensate the light spectrum and angular mismatch. Our design and analysis provide a solution to improve the quantum efficiency (QE) and x-talk of the BSI image sensor and the QE enhancement for each pixel are discussed in detail.
Second harmonic generation generated by an obliquely incident fundamental wave in a nonlinear photonic
bandgap structure is analyzed by applying the transfer matrix method, where multiple reflection and interference
effects are taken into account. The radiation of fundamental and second harmonic waves from the exit plane of
the nonlinear photonic bandgap structure, and the distribution of the fields within the structure are discussed.
Under the non-depleted pump wave assumption, the conversion efficiency of the second harmonic wave versus
the incident angle of the fundamental is studied in detail.
Photolithography is widely used to transfer a geometric pattern from a mask to a photoresist film, but the minimum
feature sizes are limited by diffraction through the mask. Focused ion beam and electron beam lithography can be used
when higher resolution is desired, but the write times are long and costly. Deep ultraviolet interference lithography,
which is a maskless technique, can be used as an alternative to produce high resolution patterns with feature sizes as
small as 100 nm. Since double negative metamaterial superlenses can be used for super-resolving and imaging subwavelength
objects, there is a need for fabricating such objects to characterize the performance of these metamaterials.
In this paper, simulations using standard finite element methods are first used to verify super-resolution and near-field
imaging at 405 nm for such objects using a metamaterial superlens previously fabricated from silver and silicon carbide
nanoparticles. Thereafter, results of fabrication and characterization of sub-wavelength objects using molybdenum of
typical thickness 50 nm initially sputtered on a glass substrate is presented. A deep ultraviolet laser source at 266 nm is
used. An anti-reflection layer followed by a high resolution negative tone photoresist is coated on the top of the
molybdenum film. The cross-linked photoresist created after the development and bake processes is used as a mask for
etching. Fabrication of the sub-wavelength object is completed using reactive ion etching in fluorinated plasma. Both
1D and 2D patterns are fabricated. The quality of the sub-wavelength objects during fabrication is checked using
scanning electron microscopy, and the 1D object is characterized using TE and TM polarized illumination.
The transfer matrix method (TMM) has been used to analyze plane wave and beam propagation through linear
photonic bandgap structures. Here, we apply TMM to determine the exact spatial behavior of TE and TM waves
in periodic refractive index structures of arbitrary thickness. First, we extend the TMM approach to analyze
plane wave propagation through Kerr type nonlinear media. Secondly, we analyze second harmonic fields in a
1D nonlinear photonic crystal for arbitrary angle of incidence of the fundamental plane wave. This allows us to
construct the overall transfer matrix of nonlinear waves for the whole nonlinear optical structure from all the
individual layer transfer matrices. We extend this method to analyze the effect of second order nonlinearity to
beam propagation by applying TMM to the angular spectral components of the beam(s).
Metamaterials exhibiting a negative index of refraction in the visible are of recent interest due to many possible
applications including cloaking and perfect lensing. Nanoparticle dispersed metamaterials have been researched due to
their flexibility in operating frequency, electronic tunability, ease of fabrication and low cost. We propose sputtered
binary polaritronic-plasmonic nanoparticles as candidates for metamaterials. Specifically, we show that co-sputtered SiC
and Ag nanoparticles are used to obtain a negative index in the visible. Experimental verification of the negative
refractive index include the z-scan technique for measurement of the linear refractive index, phase and group velocity
measurements using a double Michelson interferometer, and surface plasmon resonance measurements for s and p
polarizations for finding the effective permeability and permittivity. Through numerical simulations, we show that our
nanoparticle mixture can yield near-field super-resolution for both TE and TM polarizations.
The development of electromagnetic (EM) metamaterials for perfect lensing and optical cloaking has given rise to
novel multilayer bandgap structures using stacks of positive and negative index materials. Propagation of a
collection of TE or TM plane waves, comprising the angular plane wave spectrum, through such structures is
analyzed by using the transfer matrix method (TMM) on every plane wave component. Results obtained from this
TMM approach for a Gaussian spectrum are compared with those using standard FEM techniques.
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