0.20 Chapter 5. section 5.6. metamaterials.

Chapter 5. Section 5.6. Metamaterials.

Meta material science is a multidiscipline enterprise which includes applied physics, engineering, material science and nano technology. It aims at designing materials with physical properties beyond those available in nature. In metamaterials we want go beyond the natural materials and fabricate metamaterials with undreamt of properties e.g. invisible cloak.

Metamaterial Science challenges and overcomes the currently held limitations offered by the classical physics. Careful engineering and mixing of meta-atoms has led to completely unconventional standards and yardsticks of classifying the materials.

Metamaterials derive their properties from the structure rather than their constituent components hence they are called super lattices.

For example Photonic Crystals derive their anomalous properties from higher order spatial modes whereas meta materials work with dominant propagation mode and with sub-wavelength spacing between neighboring elements. Macroscopic desired and tailor made properties can be obtained by applying several mixing rates and homogenization principles.

Section 5.6.1. Diffraction Limit of Abbe and its conquest by Xu et.al. Metamaterial Superlens 1

[1. Xu, T.; Agarwal.A.; Abashin, M; Chau, K.J.; Lezec, H.J. “All-angle negative refraction and active flat lensing of Ultra-Violet Light”, Nature, 497, #7450, pp. 470-474 (2013)]

Ernest Abbe(1840-1905) a top Physicist and the CEO of Carl Zeiss Lns Company, had set the resolution of a microscope as follows:

According to this Formula, the wavelength of the light and Numerical Aperture = nSinα set the resolution limit.

Finer feature sizes can be resolved if wavelength is shorter and n(refractive index) is higher.

Present generation of ICs with 40nm node are using Deep Ultra Violet Light with wavelength 193nm and pure water immersion system to achieve the node size of 40nm.

Future Generation IC Lithography is going to use Extreme UV of λ= 100nm with immersion technique.

In 2000 J. B. Pendry made a proposal of synthesizing Negative Refraction Index Meta material which could be used as super lens for perfect lensing to any feature size.[“Negative Refractive Makes a Perfect Lens”, Physical Review Letter , 85, #18, 39 ^th October 2000].

They suggested that electron cloud in a dielectric behaves like a plasma and it has the following dielectric theoretical formulation:

When ω<ω _ep the we have ε is negative.

Similarly we can have loops of conducting wire mimicking magnetic plasma. It wll have the following formulation:

When ω<ω _mp the we have μ is negative.

Xu et al using Ag and TiO ₂ layers on glass substrate synthesized negative refraction lens.

Here both ε = -1 and μ= -1.

This results in n= ±√(με) . When ε = -1 and μ= -1 then n = -√(με)

Here the characteristic impedance Z = √(μ/ε) = Z ₀ = free space characteristic impedance.

Therefore at the interface of the lens there is no reflection and transmission is 100%.

Also it is taken flat with a thickness ‘d’.

The negative refraction index restores the phase of the propagating waves and also the amplitude of the evanescent waves. The device focuses light tuned to the surface plasma frequency of silver and is limited only by the resistive losses. Here both propagation wave and evanescent waves contribute to the perfect resolution of any feature size dimension. Therefore there is no physical obstacle to perfect reconstruction of the image beyond practical limitations of aperture and the lens surface.

The field of meta materials which is emerging shows us how to engineer the refraction of light through metallic composites with nano scale structure so that we get perfect lensing with no diffraction limit as given by (5.6.1).

Section 5.6.2. The diverse field of Metamaterials.

In their short history, metamaterials have been applied to the most diverse areas, including invisibility cloaks, artificial optical black holes, cosmology, high-temperature

superconductors, just to name a few particularly fascinating examples.

It has been used to fabricate Super lens described above.

It has been used in Automotive Industry.

It has been used in THz Time Domain applications.

It has been used in Specrometers.

It has been used invisibilty Cloaks.

In 2002, Lucent Technologies has developed Resonant Antennas.

In 2003, MIT urilized photonic crystals for making metamaterials.

Boeing Company has developed the method for fabricating electromagnetic materials.

In 2004, Lucent Technologies has fabricated Miniature antennae based on negative pewrmittivities.

Boeing Company has developed Metamaterial scanning lens antenna system and methods.