Guiding and Confining Light in Nanostructures

June 1, 2004 / Vol. 29, No. 11 / OPTICS LETTERS

1209

Guiding and confining light in void nanostructure

Vilson R. Almeida, Qianfan Xu, Carlos A. Barrios, and Michal Lipson

School of Electrical and Computer Engineering, Cornell University, 411 Phillips Hall, Ithaca, New York 14853

Received January 20, 2004

We present a novel waveguide geometry for enhancing and confining light in a nanometer-wide low-index

material. Light enhancement and confinement is caused by large discontinuity of the electric field at highindex-contrast interfaces. We show that by use of such a structure the field can be confined in a 50-nm-wide

low-index region with a normalized intensity of 20 mm22 . This intensity is approximately 20 times higher

than what can be achieved in SiO2 with conventional rectangular waveguides. © 2004 Optical Society of

America

OCIS codes: 030.4070, 130.0130, 130.2790, 230.7370, 230.7380, 230.7390, 230.7400.

Recent results in integrated optics have shown the ability to guide, bend, split, and f ilter light on chips by use

of optical devices based on high-index-contrast waveguides.1 – 5 In all these devices the guiding mechanism

is based on total internal ref lection (TIR) in a high-

Ex x

being formed by the interaction between the fundamental eigenmodes of the individual slab waveguides.

Rigorously, the analytical solution for the transverse

E-field prof ile Ex of the fundamental TM eigenmode of

the slab-based slot waveguide is

8

>1

>

>

jxj , a

> 2 cosh gS x ,

> nS

>

>

>

nH 2

nS 2 kH

>

>

Ω

æ

>

>1

nH 2 gS

>

>

cosh gS a cos kH b 2 a 1

sinh gS a sin kH b 2 a exp 2gC jxj 2 b , jxj . b

>

: nC 2

nS 2 kH

index material (core) surrounded by a low-indexmaterial (cladding); the TIR mechanism can strongly confine light in the high-index material. In recent years

a number of structures have been proposed to guide

or enhance light in low-index materials,6 – 11 relying on

external ref lections provided by...