Optical waveguides for evanescent field sensing

Abstract

A new fabrication process of ion-exchange waveguides well suited for integrated-sensor applications is presented. The process consists in burying each extremity of the waveguide few microns below the surface while its central region is located at the surface. For a single-mode waveguide at 785 nm, we measured propagation losses of 0.13 dB/cm for the buried portion, 2.80 dB/cm for the surface portion, and losses of 0.40 dB for the transition region. For this structure, we also observed a deformation of the fundamental mode. The proposed method is easy to implement and permits one to control precisely the topography of the elaborated waveguides.

Modeling of ion-exchanged glass waveguide structures

“…4(a)-(e) are normalized power contours of the fundamental mode corresponding to the cross-sections of Fig. 3, which match very well to the observed modes in [22]. Of particular interest is the lateral shift of the waveguide in cross-sections b, c, and d. This occurs as a result of the fringing field in the vicinity of the mask edge.…”

“…in the x-direction [22,23]. In this case, a second mask is deposited onto the substrate following the initial thermal exchange.…”

“…Outside of the sensing region, burial of the waveguide is desirable to improve propagation characteristics. An adiabatic transition between the two depths can be accomplished by a selective burial process [22,23], in which a mask edge is employed at a shallow angle to the axis of propagation (z-axis) (Fig. 2).…”

Optical filter design with holographic photopolymer materials and selective buried ion exchange optical waveguides

“…Light in this waveguide structure transitions from a buried waveguide to a surface waveguide section and then back to a buried waveguide [14,15]. The buried waveguide sections have nearly circular index profiles and provide a good match to fiber waveguides.…”

Single-step fabrication of surface waveguides in fused silica with few-cycle laser pulses

“…Changing n s changes the conditions for total internal reflection. When n s increases, the minimum angle for total internal reflection decreases and the steepest rays escape the waveguide [27,20].…”