Birefringence control in plasma-enhanced chemical vapor deposition planar waveguides by ultraviolet irradiation

Abstract

Complete birefringence compensation is demonstrated in plasma-enhanced chemical vapor deposition waveguides by 193-nm postexposure. A single relaxation process dominates the decay in stress anisotropy, indicating that compressive stress from the substrate leads to an elastic stress anisotropy at the core.

Ultraviolet-induced birefringence in hydrogen-loaded optical fiber

“…The characteristic curve in these cases is usually expressed with index change as a function of the natural log of the fluence. Experimental evidence supporting this model include ͑1͒ UV annealing of stress in a planar waveguide leads to a linear index change versus natural log of fluence plot, 42 indicating a single dominant bulk mechanical relaxation of the structure, ͑2͒ similar linearization of the characteristic curve of hypersensitized fiber, consistent with the removal of a second index process in the fiber leaving behind a dominant structural relaxation associated with densification, 4,5 and ͑3͒ the linearization of the characteristic curve in radiation-exposed phosphosilicate fiber where electron generation and diffusion play the dominant role. 43 Hence, there is a substantive argument that the index change of fully hydrogen-loaded fibers has a contribution that may not be structural but is indeed photorefractive-in the proposal above, suggesting preferential radial alignment at the core-cladding interface is consistent with this.…”

Engineering UV-photosensitivity in planar lightwave circuits by plasma enhanced chemical vapour deposition

“…GaAlAs-GaAs) in making III-V semiconductor waveguide modulators [26] and TM-TE mode converters in fabricating optical filters using proton exchanged Ti : LiNbO 3 waveguides [27] or even multi-quantum-well waveguide structures defined in III-V semiconductor material systems [28]. Researchers have previously shown [29] that birefringence (∼1500 nm) in PECVD grown silica-on-silicon devices, emanating due to the stress in the system, can be controlled or compensated by post exposure UV irradiation. Despite this being attractive in controlling birefringence selectively, it is an additional process step that requires additional apparatus and careful focusing and adjustment of UV laser beams.…”

The characteristic curve and site-selective laser excitation of local relaxation in glass

“…These types of index changes involve direct excitation through molecular absorption either at defect sites in the glass ͑in germanosilicate glass typical defect bands used are centred at 180, 240, and 320 nm: with the possible exception of the diamagnetic lone pair oxygen deficiency center at 240 nm, 32,33 these bands are not unambiguously identified͒ or at oxide bonds determining the band edge of the glass at ϳ150 nm. 35 In this case the photosensitive process enables a linear reduction of birefringence as a function of natural log fluence. 1.…”