Tilted planar Bragg grating refractometers

Tilted Bragg grating refractometers have been subject to continuous interest in recent years [1]. They operate by diffracting a well-confined core mode into a discrete set of cladding [2] or plasmonic modes [3], whose properties are dependent upon an external refractive index. Traditionally these components have been fabricated in an optical fibre platform. However, recent work from the authors has demonstrated this concept in an optical planar platform [2-5]. The key advantages of these tilted planar Bragg gratings (TPBGs) include compact multiparameter sensing, signal multiplexing and the potential to seamlessly integrate operation with microfluidics. In addition, there is an increased level of design flexibility that continues to be explored; including waveguide-to-waveguide assisted coupling [5], controllability of cladding thickness, multi-waveguide arrangements and asymmetric waveguide positioning.