Analysis of Polarization-Maintaining Waveguide Used in Resonance Integrated Optical Gyro

Abstract:

Resonance integrated optical gyroscope, Polarization-maintaining waveguide, Single-mode condition, Birefringence. Abstract. A polarization-maintaining (PM) waveguide used in Resonance Integrated Optical Gyro (RIOG) is theoretically proposed. Three essential factors determining the PM performance, which are the single-mode condition, birefringence and core index, are analyzed and optimized respectively. The single-mode rectangular waveguide is obtained by analyzing the propagation mode of the rectangular waveguide. A high birefringence waveguide design method is brought up according to the theory of geometrical birefringence, realized by changing the cross-sectional shape of the waveguide. The effect that the core index contributes to the birefringence is also discussed, and an optimal core index of the waveguide to reach maximal birefringence is determined in the condition of single-mode transmission. The high birefringence PM Waveguide with geometrical birefringence of 1.5×10-4 is obtained by theoretical analysis, the simulation results shows that the polarization cross-talk in RIOG is obviously improved.

• Periodical: Key Engineering Materials (Volume 503)
• Pages: 156-162
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.503.156
• Online since: February 2012
• Authors: Hui Lan Liu, Ru Ya Li, Huai Yong Yu, Jun Jie Wang, Zhi Chao Jiao
• Keywords: Birefringence, Polarization-Maintaining Waveguide, Resonance Integrated Optical Gyroscope, Single-Mode Condition

References

[2]

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[3] Where VI=k0t(n12-n02)1/2 is normalized frequency of slab waveguide I, and bI=( N12-n02)/(n12-n02) is its normalized refractive index. A range of the thickness of the waveguide t can be obtained from Eq.2. Base on this range, a series of width w which satisfy single mode condition can be calculated. At operating wavelength of 1550nm, when waveguide refractive index for cladding is 1.4452; for core is 1.4566, the w and t relationship can be shown as Fig. 4. Fig. 4 The relationship for w and t under single mode condition The dark region in Fig. 4 shows the size of the rectangular waveguide that satisfies single mode condition. The range of width decreased as thickness increases. Vice versa, decreasing the thickness of the waveguide may bring a wider range of width to choose from. The upper boundary of the region in Fig. 4 has the meaning of the maximum width wmax that satisfies single mode condition to the fixed thickness of the waveguide. For different thickness t, the maximum width wmax can be seen in Table 1. Table 1 Relationship of t and wmax under single mode condition t(μm) 1.50 1.75 2.00 2.25 2.50 2.75 wmax(μm) 9.17 8.22 7.54 7.02 6.63 6.32 t(μm) 3.00 3.25 3.50 3.75 4.00 4.25 wmax(μm) 6.06 5.86 5.69 5.54 5.42 5.32 The rectangular waveguide is to connect with single mode fiber, whose mode field diameter is 9μm. Thus, the cross-section of the single mode rectangular waveguide design here needs to be as large as possible, which means the maximum width is preferred when the thickness of the waveguide is determined. Birefringence. Linear birefringence of optical waveguide is mainly initiated by two factors: geometrical factor and stress. Geometrical linear birefringence is caused by the fact that the cross-section of the optical waveguide is not an ideal circle[[] Ou Haiyan, Lei Hongbing, Yang Qinqing Wang Hongjie and Wang Qiming: Theoretical Analysis on Polarization Characteristics of Silicon-Based Silica Optical Waveguide Devices (Chinese). Acta Optica Sinica, Vol. 21(1), 2001, pp.122-124

[4] Where nx and ny represent the effective refractive index of the two orthogonal polarization fundamental mode E11x and E11y, and n1=( nx+ny)/2. According to the Marcatili' method we introduced before, when core refractive index is 1.4566 and cladding refractive index is 1.4452, the relationship between cross-section shape and effective refractive index nx, ny can be given from dispersion equations[[] Katsunari Okamoto: Fundamentals of Optical Waveguides. (Elsevier Academic Press, United States of America 2006, pp.29-31

DOI: 10.1109/3.199254