Abstract

We demonstrate, for the first time to the best of our knowledge, low-loss, Si-CMOS-compatible fabrication of single-mode chalcogenide strip waveguides. As a novel route of chalcogenide glass film patterning, lift-off allows several benefits: leverage with Si-CMOS process compatibility; ability to fabricate single-mode waveguides with core sizes down to submicron range; and reduced sidewall roughness. High-index-contrast Ge23Sb7S70 strip waveguides have been fabricated using lift-off with excellent uniformity of loss propagation and the lowest loss figure of reported to date. We also show that small core Ge23Sb7S70 rib waveguides can be fabricated via lift-off as well, with loss figures lower than 0.5 dB/cm. Additionally, we find through waveguide modal analysis that although overall transmission loss is low, the predominant source of this loss comes from scattering at the sidewalls.

© 2007 Optical Society of America

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References

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    [CrossRef]
  4. W. Chung, H. Seo, B. Park, J. Ahn, and Y. Choi, "Selenide glass optical fiber doped with Pr3+ for U-band optical amplifier," Etri J. 27, 411-417 (2005).
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2007 (2)

C. Florea, J. Sanghera, L. Shaw, V. Nguyen, and I. Aggarwal, "Surface relief gratings in AsSe glass fabricated under 800-nm laser exposure," Mater. Lett. 61, 1271-1273 (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]

2006 (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]

2005 (6)

W. Li, Y. Ruan, B. Luther-Davies, A. Rode, and R. Boswell, "Dry-etch of As2S3 thin films for optical waveguide fabrication," J. Vac. Sci. Technol. A 23, 1626-1632 (2005).
[CrossRef]

R. DeCorby, N. Ponnampalam, M. Pai, H. Nguyen, P. Dwivedi, T. Clement, C. Haugen, J. McMullin, S. Kasap, "High index contrast waveguides in chalcogenide glass and polymer," IEEE J. Sel. Top. Quantum Electron. 11, 539-546 (2005).
[CrossRef]

W. Chung, H. Seo, B. Park, J. Ahn, and Y. Choi, "Selenide glass optical fiber doped with Pr3+ for U-band optical amplifier," Etri J. 27, 411-417 (2005).
[CrossRef]

P. Lucas, D. Le Coq, C. Juncker, J. Collier, D. Boesewetter, C. Boussard-Pledel, B. Bureau, M. Riley, "Evaluation of toxic agent effects on lung cells by fiber evanescent wave spectroscopy," Appl. Spectrosc. 59, 1-9 (2005).
[CrossRef] [PubMed]

D. Sparacin, S. Spector, and L. Kimerling, "Silicon Waveguide Sidewall Smoothing by Wet Chemical Oxidation," J. Lightwave Technol. 23, 2455-2461 (2005).
[CrossRef]

T. Barwicz and H. Haus, "Three-dimensional analysis of scattering losses due to sidewall roughness in microphotonic waveguides," J. Lightwave Technol. 23, 2719-2732 (2005).
[CrossRef]

2004 (4)

2003 (1)

M. Veinguer, A. Feigel, B. Sfez, M. Klebanov, V. Lyubin, "New Application of Inorganic Chalcogenide Photoresists in Lift-off Photolitography," J. Optoelectron. Adv. Mater. 5, 1361-1364 (2003).

2001 (1)

O. Efimov, L. Glebov, K. Richardson, E. Van Stryland, T. Cardinal, S. Park, M. Couzi, and J. Bruneel, "Waveguide writing in chalcogenide glasses by a train of femtosecond laser pulses," Opt. Mater. 17, 379-386 (2001).
[CrossRef]

1999 (1)

1994 (1)

C. Xu, W. Huang, M. Stern, and S. Chaudhuri, "Full-vectorial mode calculation by finite difference method," IEE Proc. Optoelectron. 141, 281-286 (1994).
[CrossRef]

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. 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]

Etri J. (1)

W. Chung, H. Seo, B. Park, J. Ahn, and Y. Choi, "Selenide glass optical fiber doped with Pr3+ for U-band optical amplifier," Etri J. 27, 411-417 (2005).
[CrossRef]

IEE Proc. Optoelectron. (1)

C. Xu, W. Huang, M. Stern, and S. Chaudhuri, "Full-vectorial mode calculation by finite difference method," IEE Proc. Optoelectron. 141, 281-286 (1994).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron. (1)

R. DeCorby, N. Ponnampalam, M. Pai, H. Nguyen, P. Dwivedi, T. Clement, C. Haugen, J. McMullin, S. Kasap, "High index contrast waveguides in chalcogenide glass and polymer," IEEE J. Sel. Top. Quantum Electron. 11, 539-546 (2005).
[CrossRef]

J. Lightwave Technol. (3)

J. Optoelectron. Adv. Mater. (1)

M. Veinguer, A. Feigel, B. Sfez, M. Klebanov, V. Lyubin, "New Application of Inorganic Chalcogenide Photoresists in Lift-off Photolitography," J. Optoelectron. Adv. Mater. 5, 1361-1364 (2003).

J. Vac. Sci. Technol. A (1)

W. Li, Y. Ruan, B. Luther-Davies, A. Rode, and R. Boswell, "Dry-etch of As2S3 thin films for optical waveguide fabrication," J. Vac. Sci. Technol. A 23, 1626-1632 (2005).
[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]

Mater. Lett. (1)

C. Florea, J. Sanghera, L. Shaw, V. Nguyen, and I. Aggarwal, "Surface relief gratings in AsSe glass fabricated under 800-nm laser exposure," Mater. Lett. 61, 1271-1273 (2007).
[CrossRef]

Opt. Express (5)

Opt. Mater. (1)

O. Efimov, L. Glebov, K. Richardson, E. Van Stryland, T. Cardinal, S. Park, M. Couzi, and J. Bruneel, "Waveguide writing in chalcogenide glasses by a train of femtosecond laser pulses," Opt. Mater. 17, 379-386 (2001).
[CrossRef]

Other (2)

J. Hu, V. Tarasov, A. Agarwal, L. Kimerling, Microphotonics Center, Massachusetts Institute of Technology, 77 Mass Ave, Cambridge, M.A. 02139 and N. Carlie, L. Petit, K. Richardson are preparing a manuscript to be called "Exploration of Waveguide Fabrication From Thermally Evaporated Ge-Sb-S Glass Films."

Y. Ruan, D. Freeman, N. Madsen, R. Jarvis, A. Rode, S. Madden, and B. Luther-Davies, "Fabrication and Characterization of Submicron Chalcogenide Waveguides," presented at the Conference on Optoelectronic and Microelectronic Materials and Devices, Brisbane, Australia, 8-10 Dec. 2004

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Figures (5)

Fig. 1.
Fig. 1.

(a). Schematic cross-sectional process flow of Ge23Sb7S70 waveguide fabrication by lift-off; (b) Dimensions of fabricated Ge23Sb7S70 strip and rib waveguides.

Fig. 2.
Fig. 2.

(a). Cross-sectional SEM image of a Ge23Sb7S70 waveguide before photoresist lift-off, showing a sidewall angle of ~65° and rounded corners; (b) Submicron strip waveguide morphology measured by AFM with a sidewall RMS roughness value of (11±2) nm and top surface RMS roughness of (1.6±0.3) nm.

Fig. 3.
Fig. 3.

Measured transmission loss of single-mode 0.75 µm×0.4 µm Ge23Sb7S70 strip waveguide as a function of wavelength. Loss increases for lower wavelength values, pointing to a negligible contribution from substrate leakage loss.

Fig. 4.
Fig. 4.

Statistical distributions of loss values of 1.6 µm×0.4 µm Ge23Sb7S70 strip waveguides measured from 40 individual dies across a 6” wafer, which yield an average loss number of (2.3±0.4) dB/cm. This tight distribution of waveguide loss values suggests excellent wafer-scale uniformity of the lift-off process.

Fig. 5.
Fig. 5.

Modal profiles of (a) quasi-TE mode and (b) quasi-TM mode in a 0.75 µm wide Ge23Sb7S70 strip waveguide with 65° sidewall angle, simulated using a finite difference technique, indicating the mixed-polarization nature of the modes.

Tables (1)

Tables Icon

Table 1. Measured optical transmission losses and calculated modal parameters of Ge23Sb7S70 waveguides at 1550 nm and modal parameters for fundamental TE/TM modes calculated using a finite-difference technique.

Equations (4)

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α tot = α = α bulk _ absorption + α top _ roughness + α sidewall _ roughness + α surface _ absorption + α substrate
α bulk _ absorption = Γ core α Ge 23 S b 7 S 70
α surface _ absorption = Γ surface α surface
α tot = α = Γ core α Ge 23 S b 7 S 70 + α sidewall _ roughness + Γ surface α surface + α substrate

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