**8. References**


plasma column. Transmitted power of 18 GHz with electrodes (without plasma between electrodes) and with plasma in electrodes are measured. Results reveal that transmitted power of – 38 dBm is received at + 450 for electrodes at a separation of 20 mm which becomes -48 dBm when plasma is formed between electrodes. In another experiment, a plasma column is formed between MPC and transmitter and transmitted power is measured for every angle. Findings of the study suggest that when plasma column of length 15 mm is formed in electrodes, which are fixed 70 mm to 100 mm away from the MPC, flat band of power level -35 dBm is received at + 450 while forbidden band of power level – 50 dBm is noticed when plasma column is formed at a diastase of 10 mm to 40 mm from the MPC.

Fig. 10. Variations in the transmitted microwave power at different angles in the presence of plasma column at different places in between transmitter and metallic photonic crystal.

Angle (Degree)

**0 20 40 60 80 100**

 70 mm to 100 mm 40 mm to 10 mm

Therefore, by switching ON and OFF the plasma column, propagation of microwave in metallic photonic crystal can be controlled in such a way that positive and negative refraction can be achieved. This chapter can be concluded from the fact that plasma can be

Author acknowledges the RTRA STAE, Toulouse, France for financial support to this work

Botton M. and Ron A. (1991), Efficiency enhancement of a plasma-filled backward-wave

Chen H. T. et al (2006) Active terahertz metamaterial devices. *Nature,* vol. 444, pp.597-600. Cubukcu E. (2003), Negative refraction by photonic crystals. *Nature (Lomdon)*, vol.423, pp

Fan Weili et al (2009), A potential tunable plasma photonic crystal : Applications of Atmospheric patterned gas discharge. *IEEE Trans. On Plas. Sci.*, vol. 37, no.6, pp. 1016-1020. Ginzberg V. L., *The propagation of electromagnetic waves in plasmas*, Pergammon press, New

oscillator by self-induced distributed feedback. *Phys. Rev. Lett*, vol. 66, no.19, pp.

used to form tunable / controllable photonic crystals.

**-52 -50 -48 -46 -44 -42 -40 -38 -36 -34**

Transmitted wave power (dBm)

**7. Acknowledgment** 

**8. References** 

under the PLASMAX project.

2468-2472.

604-605.

York (1970).


**15** 

*USA* 

Bayat and Baroughi

*South Dakota State University* 

**Photonic Crystal for Polarization Rotation** 

Due to the unique guiding properties of photonic crystal (PC) structure, such as sharp low loss bends, it is considered one of the main contenders of a compact optical integrated circuit (OIC). PC is foreseen as the next generation of hybrid photonic-electronic integrated circuit. However, one of the main issues in implementation of a PC based OIC is its strong

The components of optical integrated circuit exhibit strong polarization dependence behavior which translates into their random response to random polarizations. One approach to render the polarization sensitivity of an optical integrated circuit is to eliminate the randomness of the input polarization by splitting it into two orthogonal polarizations (TE, TM) and rotating one of the polarizations; thus, single polarization is realized on the chip (Barwicz et al., 2007). The focus of this chapter is to implement PC based polarization rotator which is capable of rotating the polarization of light to an arbitrary angle. The large birefringence in PC structure leads to a small optical path difference between the two polarizations which can result in realization of ultra-compact polarization rotators. Ease of fabrication and its compatibility with integrated PC technology is considered another main advantage of the PC based polarization rotator. This chapter is organized as follows. In Sec.2, an overview on the passive polarization rotators is given. In Sec. 3, a novel polarization rotator structure is introduced and designed. Fabrication and characterization

of the PC based polarization rotator are discussed in Sec. 4 and Sec. 5, respectively.

Passive polarization rotator structures are mostly composed of geometrically asymmetric structures where the symmetry of the structure is disturbed so that two orthogonal polarizations could be coupled to each other. Imposing asymmetry into a symmetric waveguide structure leads to a perturbation in the primary waveguide axes, depicted in Fig.1, where Ef and Es are projected fields on fast and slow axes called fast and slow normal modes, respectively. They travel with different speeds resulting in phase delay between the two components. For the phase delay of 180o, the power conversion between the two components has reached to its maximum and the propagating distance is called the half-beat

<sup>0</sup> ( ) 2( ) *<sup>s</sup> <sup>f</sup> <sup>s</sup> <sup>f</sup> <sup>s</sup> <sup>f</sup>*

*n nk n n*

 

(1)

**2. An overview on passive polarization rotators** 

*L*

 

length Lπ, defined as (Mrozowski, 1997):

**1. Introduction** 

polarization dependence guiding behavior.

