A design of hybrid elliptical air hole ring chalcogenide As₂Se₃glass PCF: application to lower zero dispersion

A design of hybrid elliptical air hole ring chalcogenide As₂Se₃glass PCF: application to lower zero dispersion

Ravindra Kumar Sharma[1], Ashish Mittal[2], Vineet Agrawal[3]

M.Tech. (Scholar), Department of Electronics & Communication.

Abstract

Photonic crystal fibers(PCFs) are a different type of optical fibers. Photonic crystal fibers (PCFs) are made with an internal periodic air holes structure, laid to form of square and hexagonal lattice. In this paper, a hybrid ring hexagonal lattic PCF with circular and elliptical (with different angle) air holes has designed and shifting of zero dispersion wavelengths towards higher wavelength range with change of elliptical air holes angle. Here chalcogenide As2Se3 glass is used as a core material because chalcogenide glass tran smit to a large IR wavelength. In this design we have achieve zero dispersion wavelength. When we design the hybrid elliptical air holes and change the air holes angle (horizontal to vertical), dispersion is decreased. We used transparent boundary condition (TBC) for zero dispersion.

Keywords: Effective refractive index (neff), Finite difference time domain (FDTD), Photonic crystal fiber (PCF), transparent boundary condition (TBC).

1. Introduction

   Photonic crystal fibers (PCFs) [1,2] a re attracting in recent years because of there different and unique properties that are not present in conventional optical fibers. Photonic crystal fibers are made with a periodic air holes structure along its length and single core materia l as silica glass, chalcogenide glass . [3-7]. Here we use the chalcogenide As2Se3 glass as a core materia l because chalcogenide glasses are based on chalcogen ele ments as S, Se and Te and other additional elements, as Ge, As and Sb. Chalcogenide glasses have lower energy less than 350 c m-1 compare to oxide glasses [8,9]. In the PCF central region is called solid core when we re moved the central air hole. First we designed a hexagonal six layer chalcogenide As2Se3 glass PCF and calculate the dispersion. When we change the first, third and fifth ring periodic circular a ir holes to elliptica l air holes the PCF is called hybrid elliptica l air hole PCF. The dispersion of hybrid

   elliptica l air hole ring PCF is calculated using fully vectorial FDTD method and transparent boundary condition (TBC). Proposed hybrid vertical e lliptica l a ir hole ring is also compared with the conventional circula r a ir hole chalcogenide As 2Se3 glass PCF. It is possible to control the PCF dispersion properties by changing the air hole dia meterd and pitch ^ [10-13].

   In the proposed As2Se3 glass PCF we change the ma jor and minor dia meter of a ir holes and change it into elliptica l a ir ho les.

2. Design principle

   Figure 1 shows the conventional As2Se3 glass PCF. In conventional hexagonal As2Se3 glass PCF we find that there is only one missing air ho le, which ma ke solid core of the PCF.

   Figure 1. layout of circular a ir hole rings PCF having six rings and air hole d ia meter d = 1.0 µm.

   Figure 2. 2-D mode field pattern of conventional PCF.

   Now, we change the first, third and fifth ring of conventional As2Se3 glass PCF, circula r air hole to horizontal e lliptica l air holes. The elliptical a ir hole is defined as the ratio of a and b. here a is the ma jor dia meter and b is the minor dia meter of air hole. However, elliptical air holes are very d ifficult to control when the fabrication of PCF [14].

   Figure 3. layout design for a hexagonal chalcogenide As2Se3 glass PCF with first, third and fifth ring horizontally elliptica l air holes, here a = 1.0 µm and

   b = 0.4 µm for e lliptica l a ir holes and d = 1.0 µm for circula r a ir ho les.

   Figure 4. 3-D Mode fie ld pattern of hybrid horizontally elliptica l As2Se3 glass PCF having six rings.

   Chalcogenide As2Se3 glass is used as a core materia l with 2.82 refractive inde x and air holes refractive index is 1.0. The wafer is designed for width 26 micro meter amd thic kness 22.5166 micro meter.

   Figure 5. A hexagonal chalcogenide As 2Se3 glass PCF with first, third and fifth ring vertically e lliptica l a ir holes, here a = 0.4 µm and b = 1.0 µm for e lliptica l air holes.

   Figure 6. Three dia mensional view of refractive inde x of proposed hybrid elliptica l air hole ring.

   The effective refractive inde x is neff = /k0, is propagation constant. The waveguide dispersion parameter Dw is obtained as

   d 2

   Figure 7. Material d ispersion curve of As2Se3 glass PCF.

   The proposed As2Se3 glass PCF (hybrid vertica lly elliptica l a ir hole ring) makes a lmost zero and flat dispersion compare to conventional six layer hexagonal PCF.

   DW c d

   2 neff

   (1)

   and total dispersion D = DW + DM. where is the signal wavelength and c is velocity of light in a vacuum [15,16].

   We can calculated the refractive inde x of chalcogenide As2Se3 glass PCF by selle mie r formula [17,18].

   n2 1

   Ai

   (2)

   2

   i 2 2

   1

3. Simulation Results

   Material dispersion is always unchanged for any lattice structure as hexagonal and square. It is also independent of structural parameter as air hole d ia meter

   d and pitch ^. So for good explanation first we have plotted materia l dispersion of chalcogenide As2Se3 glass.

   Figure 8. Shows the comparision of chro matic dispersion of the proposed As2Se3 glass PCF and conventional As2Se3 glass PCF when pitch ^ = 2.0

   µm.

4. Conclusions

   The above results indicate that the proposed hybrid vertically elliptical a ir hole ring PCF has almost zero and flat dispersion compare to norma l conventional As2Se3 glass PCF. It has been shown the results of flattened dispersion of 0.37317 ps/(km.n m) can be obtained in the range 2.5 µm to 2.9 µm. As shown in figure 3 and figure 5 the a xis of ellipt ical a ir holes has roated by 90 degree.

5. Future work

   The above design can be done by changing the air hole dia meter and also changing the layers of air hole rings. The further analyses can be done by removing inner layer and changing circula r a ir holes to elliptical.

6. Acknowledgment

   The authors thanks Prof. D. K. Parihar, Ms. Kirti Vyas, Dept. of Electronics & Co mmunication Engin eering, Arya college of Engineering & I.T., Jaipur and Mr. Ajay Ku mar Ba irwa, Head of depart ment, Rajdhani institute of technology & management, jaipur for valuable efforts in preparat ion of the manuscript

7. References

1. E. Yab lonovitch, phys. Rev. Lett. 58 (1987) 2059.

2. J. C. Knight, T. A. Birks, P. St. J. Russell, D.M. Atkin Opt. Lett. 21 (1996) 1547.

3. Bjarklev A, Broeng J. Bjarklev As. Photonic crystal fibers Dordrecht: Kluwa r Academic publishers; 2003.

4. Broeng J, Mogilevstev D, Barkou SE, Bja rklev A. photonic crystal fibers: a new class of optical waveguides Opt Fiber Technol 1999; 5: 305-30.

5. Rceves WH, Kn ight JC, Russell psT J. De monstration of ultra flattened dispersion in photonic crystal fibers Opt Exp ress 2002; 10: 609- 13.

6. Birks TA, Knight JC, Russel PSJ. Endlessiy single mode photonic crystal fiber.Opt Lett 1997; 22: 961-3.

7. Sa itoh K, Koshiba M. Leakage loss and group velocity dispersion in air co re photonic bandgap fibers.Opt Exp ress 2003; 11: 3100-9.

8. J. Nishi et al, Recent advancesand trends in chalcogenide glass fiber technology: A review, J.Non Cryst. Solids, vol. 140, 1992,pp 199-208.

9. Y. B. Shin et al, Modification of the local phonon Modes and electron phonon coupling strengths in Dy3+ doped sulphide glasses for effic ient 1-3 µm amp lification, chemical physics Letters, vol.317, 2000, pp. 637-641.

10. Sa itoh K, Koshiba M. Chromat ic dispersion control in photonic crystal fiber: application to ultra flattened dispersion. Opt Exp ress 2003; 11: 843-52.

11. Po li F, Cucinotta A, Selleri S, Bouk AH, Tailo ring of flattened dispersion in highly nonlinear photonic crystal fibers. IEEE Photon Technol Lett 2004; 16: 1065-7.

12. M.J. Gander et.a l. Expe rimental measure ment of group velocity dispersion in photonic crystal fiber, Electron, let.35, pp.63-64(1999).

13. L.P. Shen, W.P. Huage and S.S. Jain, Design of photonic crystal fibers for dispersion related applications, Lightwave Technol, 21pp. 1644- 1651(2003).

14. Ritu Sharma, Vijay janyani, Anuradha Sharma, Design of elliptica l a ir hole PCF with hybrid square lattice for h igh birefringence and a lower zero dispersion wavelength, ijcset, vol.2,2011,pp. 238 -241.

15. Ferrando A, Silvestre E, Anderes P, Miret J.J, Anders M.V, Designing the properties of dispersion flattened photonic crystal fibers, Opt. Exp,2001;687.

16. Shen L.P, Huang W.P, Jain S.S, Design and optimization of photonic crystal fibers for broad band dispersion compensation, IEEE Photon. Technol. Lett. 2003;540.

17. G.P. Agarwa l, Nonlinear fiber optics, third ed, Academic p ress, New Yo rk, 1995.

18. Bhawana Dabas, R.K. Sinha, Dispersion characteristic of he xagonal and square lattic chalcogenide As2Se3 glass photonic crystal fiber, Opt. Co mm. 2010;283: 1331-1337.

International Journal of Engineering Research & Technology (IJERT)

ISSN: 2278-0181

Vol. 1 Issue 3, May – 2012