Journal of Optics

, Volume 38, Issue 2, pp 75–87

Transformation relationship of directional coupler with multimode interference coupler and two mode interference coupler

Research Article


In this paper, a simple effective index model of directional coupler (DC) with coupling gap refractive index, different from cladding region, has been presented. Using this model, we have shown for the first time the transition from DC to two mode interference (TMI) coupler by decreasing coupling gap and transition from DC to multimode interference (MMI) coupler-based general interference by enhancing refractive index of coupling gap towards refractive index of waveguide core. It is seen that DC with coupling gap ∼0.02µm is equivalent to TMI coupler and DC with coupling region refractive index ∼0.43% less than that of core region is equivalent to MMI coupler. It is also seen that the reduction of beat length is more in TMI coupler than that for MMI coupler, during transformation of DC to TMI and MMI coupler.

Key words

Directional coupler Two mode interference Multimode interference SEIM Coupled mode theory 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    D. Marcuse, “Directional couplers made of non identical asymmetric slabs. Part 1: synchronous couplers”, J Lightwave Tech, LT-5(1), 113–118 (1987)CrossRefADSGoogle Scholar
  2. 2.
    K.S. Chiang, “Effective index method for the analysis of optical waveguide couplers and arrays: an asymptotic theory”, J Lightwave Tech, 9(1), 62–72 (1991)CrossRefADSGoogle Scholar
  3. 3.
    K.S. Chiang, “Analysis of the effective-index method for the vector modes of rectangular-core dielectric waveguides”, IEEE Trans Microwave Theory Tech, 44(5), 692–700 (1996)CrossRefGoogle Scholar
  4. 4.
    H.A. Haus, W.P. Huang, S. Kawakami and N.A. Whitaker, “Coupled-mode theory of optical waveguides”, J Lightwave Tech, LT-5(1), 16–23 (1987)CrossRefADSGoogle Scholar
  5. 5.
    A.W. Synder, “Coupled-mode theory of optical fibers”, J Opt Soc Am” 62(11), 1267–1277 (1972)CrossRefADSGoogle Scholar
  6. 6.
    A.K. Das and P.P. Sahu, “Compact Integrated optical devices using high index contrast waveguides”, IEEE Wireless Opt Commun Network Conf, IEEE explore Digital No-01666673, 1–5 (2006)Google Scholar
  7. 7.
    H. Nishihara, M. Haruna and T. Suhara, Optical Integrated Circuits, McGraw-Hill (1985)Google Scholar
  8. 8.
    P.A. Besse, E. Gini, M. Bachmann, H. Melchion, “New 2×2 and 1×3 multimode interference couplers with free selection of power splitting ratios”, J Lightwave Tech, 14, 2286–2292 (1996).CrossRefADSGoogle Scholar
  9. 9.
    L.B. Soldano and E.C.M. Pennings, “Optical multi-mode interference devices based on self-imaging: principles and applications”, J Lightwave Tech, 13(4), 615–627 (1995)CrossRefADSGoogle Scholar
  10. 10.
    P.P. Sahu, “A tapered structure for compact multimode interference coupler”, IEEE Photon Tech Lett, 20(8), 638–640 (2008)CrossRefADSMathSciNetGoogle Scholar
  11. 11.
    P.P. Sahu, “Compact multimode interference coupler with tapered waveguide geometry”, Opt Commun, 277(2), 295–301 (2007)CrossRefADSGoogle Scholar
  12. 12.
    H.P. Chan, C.K. Chow and A.K. Das, “A wide-angle X-junction polymeric thermo optic digital switch with low crosstalk”, IEEE Photon Tech Lett, 15(9), 1210–1212 (2003)CrossRefADSGoogle Scholar
  13. 13.
    P.P. Sahu, “Polarization independent thermally tunable EDFA gain equalizer using cascade Mach-Zehnder coupler”, Appl Opt, 47(5), 718–724 (2008)CrossRefADSGoogle Scholar
  14. 14.
    P.P. Sahu, “Polarization insensitive thermally tunable add/drop multiplexer using cascaded Mach-Zehnder coupler”, Appl Phys B: Lasers and Optics, 92, 247–252 (2008)CrossRefADSGoogle Scholar
  15. 15.
    M.K. Chin, C.W. Lee, S.Y. Lee and S. Darrnawan, “High-index-contrast waveguides and devices”, Appl Opt, 44(15), 3077–3086 (2005)CrossRefADSGoogle Scholar

Copyright information

© Optical Society of India 2009

Authors and Affiliations

  1. 1.Dept. of Electronics & Communication EnggTezpur UniversityNapaamIndia

Personalised recommendations