Optical-waveguide chemical sensors

Figure 5.20 — Reversible flow-through optical waveguide gas sensors using a reagent immobilized on the inner walls of the tube for the determination of moisture (water) (A) and sulphur dioxide (B). For details, see text. (Reproduced from [64] and [65] with permission of the American Chemical Society and Elsevier Science Publishers, respectively).

Fig. 2. Cross-section through a optical fiber chemical sensor composed of a fiber waveguide, an optically responsive workmg chemistry. The outer overcoat may he the optical isolation, or a layer of immobilized enzyme.

Polina R.J., Klainer S.M., A field-hardened, optical waveguide hybrid integrated-circuit, multi-sensor chemical probe and its chemistry, Proc. SPIE-Int. Soc. Opt. Eng. 1997 3105 71... 

Optical sensors (Figure 1) can be defined as devices for optical monitoring of physical parameters (pressure1, temperature2, etc.) or (bio)chemical properties of a medium by means of optical elements (planar optical waveguides or optical fibres). Chemical or biochemical fibre-optic sensors3 are small devices capable of continuously and reversibly recording the concentration of a (bio)chemical species constructed be means of optical fibres. 

In recent years, the evolution of the technological components required for IR sensor systems has been denoted by a significant miniaturisation of light sources, optics and detectors. Essentially, an IR sensor consists of (i) a polychromatic or monochromatic radiation source, (ii) a sensor head and (iii) a spectral analyser with a detector. As sensors where all optical elements can be included in the sensor head are the exception rather than the rule, also various optics, waveguides and filters may form essential parts of IR-optical chemical sensors. Another important building block, in particular when aiming at sensors capable of detecting trace levels, are modifications of the sensor element itself. 

Burke C.S., Polerecky L., MacCraith B.D., Enhanced polymer waveguide platforms for absorption-based optical chemical sensors, Proc. S.P.I.E., 2002 4876 848-855. Opto-Ireland 2002 Optics and Photonics Technologies and Applications (Galway, Ireland, 2002 ). 

Sol-gel coating technique for optical chemical sensors and biosensors is now in extensive research phase. For example, the side-coating of optical fibers or waveguides in evanescent-wave sensors it is particularly important to control precisely the sensitivity determining parameters, such as the coating thickness and length45. 

Butler, T. M. Igata, E. Sheard, S. J. Blackie, N., Integrated optical Bragg grating based chemical sensor on a curved input edge waveguide structure, Opt. Lett. 1999, 24, 525 527... 

Goddard, N. J. Hulme, J. Malins, C. Singh, K. Fielden, P. R., Asymmetric anti resonant reflecting optical waveguides (ARROW) as chemical sensors, Analyst 2002, 127, 378 382... 

Horvath, R. Skivesen, N. Larsen, N. B. Pedersen, H. C., Reverse symmetry waveguide for optical biosensing, In Frontiers in Chemical Sensors. Novel Principles and Techniques Orellana, G. Moreno Bondi, M. C., Eds. Springer Series on Chemical Sensors and Biosen sors Springer, Berlin, 2005, Vol. 3, 279 301... 

For almost 20 years, the optical waveguide sensor has been used for the label-free, evanescent-field detection of chemical or biological reactions taking place in the close vicinity of the waveguide surface. This includes numerous applications within the fields of chemical and biological sensing, where in... 

Lukosz W, Nellen PM, Stamm C, Weiss P (1990) Output grating couplers on planar waveguides as integrated optical chemical sensors. Sensors Actuators B Chem 1 585-588... 

---