Abstract

We experimentally demonstrate, for the first time, propagation loss reduction via graded-index (GRIN) cladding layers in high-index-contrast (HIC) glass waveguides. We show that scattering loss arising from sidewall roughness can be significantly reduced without compromising the high-index-contrast condition, by inserting thin GRIN cladding layers with refractive indices intermediate between the core and topmost cover of a strip waveguide. Loss as low as 1.5 dB/cm is achieved in small core (1.6 μm × 0.35 μm), high-index-contrast (Δn = 1.37) arsenic-based sulfide strip waveguides. This GRIN cladding design is generally applicable to HIC waveguide systems such as Si/SiO2.

© 2007 Optical Society of America

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2007 (4)

J. Hu, V. Tarasov, N. Carlie, R. Sun, L. Petit, A. Agarwal, K. Richardson, and L. Kimerling, "Low-loss integrated planar chalcogenide waveguides for chemical sensing," Proc. SPIE 6444, 64440N (2007).
[CrossRef]

J. Hu, L. Petit, X. Sun, A. Agarwal, N. Carlie, T. Anderson, J. Choi, J. Viens, M. Richardson, K. Richardson, and L. Kimerling, "Studies on Structural, Electrical and Optical Properties of Cu-doped As-Se-Te Chalcogenide Glasses," J. Appl. Phys. 101, 063520-063528 (2007).
[CrossRef]

J. Hu, V. Tarasov, N. Carlie, L. Petit, A. Agarwal, K. Richardson, and L. Kimerling, "Fabrication and Testing of Planar Chalcogenide Waveguide Integrated Microfluidic Sensor," Opt. Express 15, 2307 (2007).
[CrossRef] [PubMed]

J. Hu, V. Tarasov, N. Carlie, N. Feng, L. Petit, A. Agarwal, K. Richardson, and L. Kimerling, "Si-CMOS-compatible lift-off fabrication of low-loss planar chalcogenide waveguides," Opt. Express 15, 11798 (2007).
[CrossRef] [PubMed]

2006 (2)

L. Petit, N. Carlie, F. Adamietz, M. Couzi, V. Rodriguez, and K. C. Richardson, "Correlation between physical, optical and structural properties of sulfide glasses in the system Ge-Sb-S," Mater. Chem. Phys. 97, 64-70 (2006).
[CrossRef]

M. Wu and M. Lee, "Thermal annealing in hydrogen for 3-D profile transformation on silicon-on-insulator and sidewall roughness reduction," J. Microelectromech. Syst. 15, 338-343 (2006).
[CrossRef]

2005 (6)

2004 (1)

C. Chao and L. Guo, "Reduction of surface scattering loss in polymer microrings using thermal-reflow technique," IEEE Photon. Technol. Lett. 16, 1498-1500 (2004).
[CrossRef]

2002 (2)

M. Richardson, L. Shah, J. Tawney, A. Zoubir, C. Rivera, C. Lopez, and K. Richardson, "Photo-induced structural changes in glass," Glass Sci. Technol. 75, 121-130 (2002).

N. Feng, G. Zhou, C. Xu, and W. Huang, "Computation of full-vector modes for bending waveguide using cylindrical perfectly matched layers," IEEE J. Lightwave Technol. 20, 1976-1980 (2002).
[CrossRef]

2001 (1)

1993 (1)

M. Asobe, H. Itoh, T. Miyazawa, and T. Kanamori, "Efficient and ultrafast all-optical switching using high Δn, small core chalcogenide glass fibre," Electron. Lett. 29, 1966-1968 (1993).
[CrossRef]

Appl. Phys. Lett. (1)

M. Webster, R. Pafchek, G. Sukumaran, and T. Koch, "Low-loss quasi-planar ridge waveguides formed on thin silicon-on-insulator," Appl. Phys. Lett. 87, 231108-231110 (2005).
[CrossRef]

Appl. Spectrosc. (1)

Electron. Lett. (1)

M. Asobe, H. Itoh, T. Miyazawa, and T. Kanamori, "Efficient and ultrafast all-optical switching using high Δn, small core chalcogenide glass fibre," Electron. Lett. 29, 1966-1968 (1993).
[CrossRef]

Glass Sci. Technol. (1)

M. Richardson, L. Shah, J. Tawney, A. Zoubir, C. Rivera, C. Lopez, and K. Richardson, "Photo-induced structural changes in glass," Glass Sci. Technol. 75, 121-130 (2002).

IEEE J. Lightwave Technol. (1)

N. Feng, G. Zhou, C. Xu, and W. Huang, "Computation of full-vector modes for bending waveguide using cylindrical perfectly matched layers," IEEE J. Lightwave Technol. 20, 1976-1980 (2002).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

C. Chao and L. Guo, "Reduction of surface scattering loss in polymer microrings using thermal-reflow technique," IEEE Photon. Technol. Lett. 16, 1498-1500 (2004).
[CrossRef]

J. Appl. Phys. (1)

J. Hu, L. Petit, X. Sun, A. Agarwal, N. Carlie, T. Anderson, J. Choi, J. Viens, M. Richardson, K. Richardson, and L. Kimerling, "Studies on Structural, Electrical and Optical Properties of Cu-doped As-Se-Te Chalcogenide Glasses," J. Appl. Phys. 101, 063520-063528 (2007).
[CrossRef]

J. Lightwave Technol. (2)

J. Microelectromech. Syst. (1)

M. Wu and M. Lee, "Thermal annealing in hydrogen for 3-D profile transformation on silicon-on-insulator and sidewall roughness reduction," J. Microelectromech. Syst. 15, 338-343 (2006).
[CrossRef]

Mater. Chem. Phys. (1)

L. Petit, N. Carlie, F. Adamietz, M. Couzi, V. Rodriguez, and K. C. Richardson, "Correlation between physical, optical and structural properties of sulfide glasses in the system Ge-Sb-S," Mater. Chem. Phys. 97, 64-70 (2006).
[CrossRef]

Opt. Express (3)

Opt. Lett. (2)

Proc. SPIE (1)

J. Hu, V. Tarasov, N. Carlie, R. Sun, L. Petit, A. Agarwal, K. Richardson, and L. Kimerling, "Low-loss integrated planar chalcogenide waveguides for chemical sensing," Proc. SPIE 6444, 64440N (2007).
[CrossRef]

Other (1)

D. Sparacin, R. Sun, A. Agarwal, M. Beals, J. Michel, L. Kimerling, T. Conway, A. Pomerene, D. Carothers, M. Grove, D. Gill, M. Rasras, S. Patel, A. White, "Low-Loss Amorphous Silicon Channel Waveguides for Integrated Photonics," in Proceedings of 3rd IEEE International Conference on Group IV Photonics, pp. 255-257.

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Figures (3)

Fig. 1.
Fig. 1.

(a). Cross-sectional schematic of an As42S58 waveguide with Ge17Sb12S71/SiO2 double GRIN cladding layers; (b) cross-sectional view of the field along x-axis of the quasi-TE mode in the same structure with (red) and without (black) GRIN cladding layers, showing field intensity decrease at the interfaces.

Fig. 2.
Fig. 2.

(a). Bending loss of quasi-TE mode as a function of bending radius in waveguides with and without GRIN cladding at 1550 nm wavelength, indicating that GRIN design also improves waveguide bending performance besides loss reduction; (b) measured insertion loss data of the 0.75 μm As42S58 waveguides with and without GRIN cladding layers, the slopes of the fitted lines represent measured waveguide loss.

Fig. 3.
Fig. 3.

(a). Top-view SEM image of a 0.75 μm wide As42S58 waveguide bending section showing excellent pattern fidelity from lift-off; (b) Tilted view of a cleaved facet of a As42S58 waveguide coated with Ge17Sb12S71 and oxide double GRIN layers.

Tables (2)

Tables Icon

Table 1. Range of refractive indices of some glassy alloys for potential GRIN cladding applications.

Tables Icon

Table 2. Measured optical transmission losses of As42S58 strip waveguides without GRIN cladding layers (denoted as “No GRIN”), As42S58 waveguides coated with a single Ge17Sb12S71 layer (denoted as “1 GRIN”) and waveguides coated with Ge17Sb12S71/SiO2 bilayers (denoted as “2 GRIN”) at 1550 nm for three different waveguide widths.

Equations (1)

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J rough ( r ) = jωε 0 δ n 2 ( r ) E g ( r )

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