The development of nanotechnology industry is one of the high

Chapter 1

Introduction

The development of nanotechnology industry is one of the high

technology trends of 21-th century. Nanotechnology is a cross-cutting and

Multi-functional technology, and it makes all industries to advance and to

innovate. It is estimated that the annual production value will be one

trillion dollars from the year 2010 to 2015 [1]. Obviously, there are vast

market-potential and business opportunities in nanotechnology. In the

past several years, it is a great interest in research on nanotechnology,

which focuses on several issues that include the developing new skills for

fabricating nanometer size devices and the designing of new nanometer

structures for novel applications [2]. With the rushing progress in

integrated circuits (IC) fabrication technology, to fabricate nanometer

scale devices were easier than past time. However, to fabricate

nanometer scale structures are demanded for control the size in several

nanometers, accurately, that to acquire the suitable equipments is

necessary. Nanotechnology is a multi-field development field mixed

science and technology comprehensively, including physics, chemistry,

material science, optics, electronics, biology, etc... The application of

nanomaterials in the field of optical sensors and biosensors has become a

new, growing area of interest in recent years [3].

Biosensors are devices that convert biological interactions to

measurable quantities such as an electrical or optical signal. This signal

contains information about a biological event, for example presence of a

specific biomolecule in a medium of interest. Important requirements that

a biosensor should meet are high sensitivity, high detection speed,

repeatability, specificity to the biomolecule of interest, and capability of

real time detection [4]. Over the past ten years, biosensor has made great

strides, and a large number of sensor platforms, biomolecular recognition

elements, and measurement formats have been developed. Applications

of biological and optical sensors hold long-standing interests due to their

close relationship with human life. There has been growing interest in

commercialization of biosensor technology leading to a number of

systems available on today's market. Biosensors have played a significant

role in research into biomolecules and their interactions and have been

increasingly used for detection and identification of optical and biological

substances [5]. Detection limits for large analytes such as bacteria and

viruses still need to be improved to meet today's needs. These aspects

stimulate the demand and development of ultrasensitive devices to detect

biomolecules with very low concentrations. Undoubtedly, future

development of Biosensors will be driven by the needs of the consumer.

Conventional methods are actually reaching the highest accuracy with

low detection limits, but are expensive, time-consuming, and require the

use of highly trained personnel [6]. The current tendency to carry out

field monitoring has driven the development of biosensors as new

analytical tools able to provide fast, reliable, and sensitive measurements

with lower cost; many of them aimed at on-site analysis. Biosensors can

be also a defense tool through the early detection of hazardous materials

such as germs. Biosensor device has the potential to benefit numerous

important fields including pharmaceutical research, medical diagnostics,

environmental monitoring, food safety, and security. Applications in

these areas present unique challenges and impose special requirement on

analytical technologies. In addition, there is a growing interest in tools for

home medical diagnostics. Mobile analytical systems enabling rapid

detection of food-borne pathogens in food would be important for food

producers, processors, distributors and regulatory agencies and thus

benefit the food safety. Environmental monitoring would benefit from

detection systems which could be deployed in the field for continuous

monitoring and from mobile systems enabling fast identification of

environmental threat. Biosensors could also play an important role in

defense, where fast, portable and rugged units are needed for early

detection and identification of biological warfare agents in the field.

Among the existing biosensors, planar optical sensors are promising

because of their robustness, easy patterning of reagents, and simple

incorporation of various materials such as polymers, metals, and

dielectrics [7]. Biosensors have been used in the applications of

biomolecule detection, environment monitoring, medical diagnostics,

food safety, and industrial process control. Within these decades, planar

optical sensors are emerging due to several advantages, such as good

robustness, easy handling, and easy patterning of reagents, simple

incorporation of different materials, and high integration capability with

photonic and electronic devices. Some examples of planar optical sensors

include channel waveguide sensors [8], surface plasmon resonance

sensors [9], photonic crystals (PCs) sensors [10], interferometric sensors,

grating-coupled planar waveguide sensors [11], and micro-resonator

sensors [12]. Among different types of planar optical sensors, photonic

crystals (PCs) sensors possess several unique advantages, including

compactness, easy fabrication, high sensitivity, cost low, small size

device and photonic crystals (PCs) are easy to compact with integrated

circuit owing to well technique of semiconductor fabrication [13]. In this

kind of photonic crystals (PCs) sensor, the characteristic of the

electromagnetic wave including amplitude, phase place, leaning towards

polarized direction and wavelength can get enormously different results

by controlling the light frequency spectrum, group velocity chromatic

dispersion, phase matching.

We judge the bio-molecules from the slight different changes of

effective-index, which caused photonic crystals (PCs) strongly

polarization sensitivity. In the effective-index sensing general, there are

two sensing mechanisms, the homogeneous sensing and the surface

sensing. In this thesis, the groundwork of our silicon nano-pillars array

sensor is homogeneous sensing. Homogeneous sensing scheme is used to

detect the concentration of analytes in a solution, e.g., Plasmid, Herpes

Simplex Virus Type-1 (HSV-1), glucose in blood. The presence of

analytes modifies the refractive index of the solution. Higher

concentration leads to lower refractive index. When the solution is

introduced onto a device and serves as the upper-cladding layer of the

device structure, different solution index due to different concentrations

changes the effective refractive index of the guided mode.

The outline of the thesis is as follows: In Chapter 2, according to the

various analysis of 2-D silicon nano-pillars array with cubic and

hexagonal lattice of several shapes are compared. From the compare of

the results, we choose the best arrange of sensor design. In Chapter 3, we

will fabricate which we choose the best arrange of sensor design in

chapter 2. In Chapter 4, we will utilize the sensor to soak in the solution

of samples and come to do the experiment and analysis with Polarization

Shift Keying (PolSK) fiber-optic system. Polarization Shift Keying

(PolSK) fiber-optic system has higher sensitivity with sensor measured

DNA and germ. This is a very promising value from this preliminary

experiment in comparison with other planar optical sensors [14-15]. We

hope that our sensor can diagnosis virus and the innovation technique will

be contributed for the medical field. The basic performance comparisons

of several optical sensors are shown in Table 1-1.

Table 1-1 The basic performance comparisons of several optical sensors list

Performance

Structures

Material Sensitivity Year Ref.

Surface plasmon

resonance Polymer 1×10

2003 [16]

ARROWs Silicon 6× 10

2003 [17]

Dual-Window Waveguide Silicon 2×10

2004 [18]

Photonic Wire SOI 1×10

2005 [19]

Photonic crystal ^{PS-PMMA 1×10}

^{2005 [20]}