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Applied Optics

Applied Optics


  • Vol. 38, Iss. 24 — Aug. 20, 1999
  • pp: 5133–5143

Temporal Soliton Switching in a Rectangular Nonlinear Directional Coupler

Anca L. Sala, Brian G. Bagley, and Robert T. Deck  »View Author Affiliations

Applied Optics, Vol. 38, Issue 24, pp. 5133-5143 (1999)

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We address the theory of temporal soliton switching in a planar geometry directional coupler constructed from silica and doped silica glass and operating at the central wavelength of 1.55 μm, significant for erbium-doped amplification. We formulate the field in the coupler in terms of the supermodes of the total structure and take account of the two transverse dimensions of the rectangular channels. In the case of the weak coupling between channels consistent with elimination of pulse breakup, the effect of the fields in the outer corner regions of the channels results in a switching intensity that differs significantly from that derived from coupled-mode theory on the basis of a slab model of the coupler.

© 1999 Optical Society of America

OCIS Codes
(190.4390) Nonlinear optics : Nonlinear optics, integrated optics
(190.5530) Nonlinear optics : Pulse propagation and temporal solitons
(230.7390) Optical devices : Waveguides, planar

Anca L. Sala, Brian G. Bagley, and Robert T. Deck, "Temporal Soliton Switching in a Rectangular Nonlinear Directional Coupler," Appl. Opt. 38, 5133-5143 (1999)

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  12. Higher-order dispersion terms, connected to additional terms in Eq. (23), are significant only in the case of pulse lengths of the order of 10 fs or less. See, for example, G. P. Agrawal, Nonlinear Fiber Optics (Academic, New York, 1989); M. Piche, J. Cormier, and X. Zhu, “Bright optical soliton in the presence of fourth-order dispersion,” Opt. Lett. 21, 845–847 (1996).
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  14. Under this condition the nonlinear response of the coupler becomes independent of the sign of n2 as demonstrated in F. J. Fraile-Pelaez, G. Assanto, and D. R. Heatley, “Sign-dependent response of nonlinear directional couplers,” Opt. Commun. 77, 402–406 (1990). More generally, in the present formalism, a dependence on the sign of the nonlinearity is produced by the terms in Eqs. (14) proportional to Qll′ and Rll′, whereas in Eqs. (37) any arbitariness in the sign of n2 is eliminated by the requirement that n2 and β″ have opposite signs.
  15. The switching power can be lowered somewhat, and the power remaining in channel 1 at powers above the switching threshold can be increased, at the expense of a further increase in the coupling length of the coupler. For example, in Ref. 2 the critical power for switching equals the peak power of the fundamental soliton, but the coupler has a coupling length Lc ≅ 6 LD. In our case, Lc ≅ 2LD and the critical switching power is approximately 2.7P0. The coupling length can be decreased significantly only for pulse lengths less than 100 fs, for which the present analysis cannot be assumed to apply.
  16. K. Yasumoto, N. Mitsunaga, and H. Maeda, “Coupled-mode analysis of power-transfer characteristics in a three-waveguide nonlinear directional coupler,” J. Opt. Soc. Am. B 13, 621–627 (1996).

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