Waveguides hollow

Saggese S.J., Harrington J.A., Sigel G.H., Hollow waveguides for sensor applications, Proc. SPIE 1368 (1990), San Jose, pp.2-14. 

Murthy Ch.S., Pustogov V.V., Mizaikoff B., Inberg A., Croitoru N., Trace level gas detection using mid infrared hollow waveguides, Proc. 5th Europtrode (2000), Lyon, p.275. 

The prevalently used waveguides are optical fibres. Fibre technology is standard in the UV to near-IR, but also some fibres for light transport in the mid-IR have been developed. An overview of different IR fibre materials and their characteristic performance parameters is given in Table 1. More details can be found in a number of reviews focused on the material properties of IR transmitting optical fibres26 31. For some applications, as an alternative to optical fibres also hollow waveguides may be used. 

A hollow waveguide (HWG) is essentially a hollow tube that transports light from one end to the other either by multiple mirror reflection or by total internal reflection. The hollow structure gives them several advantages (i) a high power threshold, (ii) low insertion losses, (iii) no end reflections, (iv) a small beam divergence, (v) robustness and - especially important for sensor applications - (vi) a wide spectral transmission range. 

For sensing applications, high bending losses restrict the applicability as (flexible) light pipes. Practical applications are mostly restricted to gas cells, where the hollow waveguide acts as a compact multi-reflection cell to increase the sensitivity in comparison to single-pass cells. 

Alaluf M., Dror J. and Croitoru N., Plastic hollow waveguides as transmitters and filters in mid-IR radiation, Proc. SPIE, 1991 1591 146-149. 

Worrell C., Giles I. and Adatia N., Remote gas sensing with mid-infra-red hollow waveguide, Eleclr. Lett., 28 (7) 615-617. 

Worrell C. and Gallen N., Trace-level detection of gases and vapours with mid-infra-red hollow waveguides,./. Phys. D Appl. Phys., 1997 30 1984-1995. 

Sato S., Saito M. and Miyagi M., Infrared Hollow Waveguides for Capillary Flow Cells, Appl. Spectrosc., 1993 47 (10) 1665-1669. 

Kozodoy R., Micheels R. and Harrington J., Small-Bore Hollow Waveguide Infrared Absorption Cells for Gas Sensing, Appl. Spectrosc., 1996 50 (3) 415-417. 

Campopiano, S. Bernini, R. Zeni, R. Sarro, P. M., Microfluidic sensor based on integrated optical hollow waveguides, Opt. Lett. 2004, 29, 1894 1896... 

Barber, J. P. Lunt, E. J. George, Z. A. Yin, D. Schmidt, H. Hawkins, A. R., Integrated hollow waveguides with arch shaped cores, IEEE Photonic Tech. Lett. 2006, 18, 28 30... 

Figure 1. (a) The 3x3 multiple images formed in a 2D MMI hollow waveguide (b) SEM of the 80 X 80 [xrnl silicon hollow waveguide showing the guide cross-section... 

A.Yehia, K. Madkour, H Maaty and D. Khalil, Multiple-Imaging in 2D MMI Silicon Hollow Waveguides, IEEE Phot. Technol. Lett. 16, 2072-2074 (2004). 

Fig. 9.25 Hollow waveguide for ammonia, based on capillary coated with oxazine perchlorate (adapted from Giuliani et al., 1983)...

Charlton, C.M., Thompson, B.T., and Mizaikoff, B. (2005) Hollow waveguide infrared spectroscopy and sensing. In Wolfbeis, O.S. (Ed.) Frontiers in Chemical Sensors. Springer, p. 133. 

Hollow waveguides have emerged as a very attractive alternative to solid-core IR waveguides because of the inherent advantage of their air core. However, only a few applications in medical and industrial fields have been reported. 

In such waveguides, the core can be simultaneously used for confining the light and the fluid/gas to be measured, thus achieving a high interaction between them. As an example, in optical gas detection, hollow waveguides have already improved the detection limits [117]. 

Fig. 12 Scanning electron microscopy (SEM) microphotographs of the walls and bottom of a hollow waveguide after the deep reactive ion etching process...

Fig. 14 Standard configuration of hollow-based sensors. Flow is injected from a reservoir to the microchannel that also forms the hollow waveguide. Light interacts with the flow after crossing the input membrane and the signal is read after the output membrane...

Hollow planar waveguides have been fabricated by several techniques, including physical vapor deposition and CVD of silver and dielectric layers on metallic substrates. Nevertheless, better results can be obtained by taking advantage of silicon micromachining techniques. Perhaps the most important advantage of silicon hollow waveguides over other hollow structures is the... 

Brief History of Hollow Waveguides as Gas-Transmission Cells. 143... 

Optical Considerations for Hollow-Waveguide-Based Gas Sensing. 144... 

Real-Time Direct Fourier Transform IR Hollow Waveguide Gas Analysis... 

Applications of Laser-Coupled Hollow Waveguide Gas Sensors. 158... 

C02 Lasers Coupled to Hollow Waveguide Gas-Sensing Modules. 159... 

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