Infrared transmissive, hollow plastic waveguides with inner Ag–AgI coatings

Abstract

Hollow polycarbonate waveguides with thin-film coatings of Ag-AgI were fabricated by liquid-phase chemistry methods. These hollow waveguides, which have bore sizes ranging from 500 to 2000 microm and lengths as long as 2 m, are transmissive from 2 to more than 20 microm. The lowest loss of 0.02 dB/m was obtained for a straight 2000 microm bore guide at 10.6 microm. This is to our knowledge the lowest loss measured for any IR fiber at CO2 laser wavelengths. The bending losses were found to increase as 1/R, where R is the radius of the bend. These waveguides were able to withstand 18 W of CO2 laser input power for bore sizes greater than 1000 microm.

Single mode operation with mid-IR hollow fibers in the range 51-105 µm

“…The results show an almost linear behavior, as predicted by Matsuura et al [21], thereby supporting the notion that an additional contribution to the total losses originates from light scattering due to surface roughness of the inner HCW metallic layer. …”

“…By producing a hollow fiber with a specific dielectric thickness layer, the transmission spectrum of the waveguides can be tailored for different spectral wavelength ranges. The optimal dielectric film that minimizes propagation losses into the fiber for a wavelength of λ = 5 µm is 0.46 µm, assuming that the refractive index n d of silver iodine at this wavelength is 1.965 [21]. The actual thickness of the AgI layer, calculated from the Fourier transform infrared spectrometer, is about 0.56 µm [9].…”

Quantum cascade laser light propagation through hollow silica waveguides

“…Reduced loss can be obtained using hollow polycarbonate waveguides, which can be made with bore diameters up to 2000 μm while retaining a good level of flexibility [3]. The propagation of light through cylindrical hollow metallic waveguides was originally analysed by Marcatili and Schmeltzer [23] and was later expanded upon by Miyagi and Kawakami [13] to include analysis of the influence of the dielectric layer.…”

“…These attenuation coefficients were calculated for a wavelength of 7.8 μm using the following optical constants: n = 8.48, κ = 45.0 and n d = 2.1 [22]. Ellipsometry can be used to measure these optical constants as demonstrated by George and Harrington [3] who obtained values of n = 4.98, κ = 33.82 for silver and n d = 1.95 for silver iodide at 10.6 μm. The data show a significant reduction in attenuation for lower-order modes and the 1/a 3 variation with bore diameter that was highlighted in Eq.…”

Flexible hollow polycarbonate fiber for endoscopic infrared laser treatment

“…Plastic tube [5,6] and extruded polycarbonate tubing [7] were used as supporting tubes for hollow optical fiber. They are safer base tubes than the glass capillary.…”