A 250-microm-bore size and 50-cm-length hollow-glass waveguide (HGW) coated with a thin film of silver has been used to transport laser pulses at 800 nm from a Ti:sapphire oscillator. The silver film is deposited by a liquid-phase process. The measured transmission of this silver-coated HGW is 95%, which is considerably higher than the transmission of HGWs with no coating, as reported by other groups. The image of the output beam taken at different distances from the fiber output shows that a single HE11 mode couples to free-space modes from the exit of the fiber. Considerable spectral broadening can be obtained with high-intensity femtosecond pulse when this waveguide is filled with argon. This HGW can be used for such applications as beam transport and optical-pulse compression.

Metal sulfide dielectric thin films have been deposited using dynamic wet chemistry processing on silver coated hollow glass waveguides (HGWs). The sulfides used were cadmium sulfide (CdS) and lead sulfide (PbS); both films have excellent infrared transparency and high refractive index contrast. The thickness of these thin films can be tailored to minimize the attenuation of the HGW over specific infrared wavelengths. We have made both single and multiple dielectric (2 and 3 layer) metal coated HGWs using CdS and PbS deposited over an inner Ag layer. The straight lowest loss measured at 1.55 microm for a 1,000-microm bore Ag/CdS/PbS/CdS HGW was 0.06 dB/m. This loss is three times less than that measured for a single layer Ag/CdS coated HGW at 1.55 microm.

An all-fiber-optic infrared multispectral radiometer for measurements of temperature and emissivity of graybodies at near-room temperature was constructed. Different spectral regions in the radiometer were obtained by use of hollow glass waveguides (HGWs) as filters. Using HGWs instead of bulk filters was advantageous because each HGW can be used as two different spectral filters when a dual-band IR detector is used. In addition, HGWs are much cheaper than the bulk IR filters that are usually used in such applications. For one graybody with a mean emissivity of 0.71, the estimated mean errors obtained for sample temperature, ambient temperature, and sample emissivity for all measured temperatures were 0.50% (approximately 1.65 K), 0.48% (approximately 1.4 K), and 7.3% (approximately 0.052) respectively. For a second graybody with a mean emissivity of 0.8 the estimated mean errors were 0.35% (approximately 1.2 K), 0.48% (approximately 1.4 K), and 5.0% (approximately 0.04), respectively.

Coherent IR fiber optic bundles for use in IR imaging from 2 to 12 m are fabricated from rigid hollow-glass waveguide arrays. The bore of each hollow glass tube in the bundle is coated with thin films of metallic Ag followed by AgI for enhanced reflectivity. The coating of the rigid bundle is done using liquid phase chemistry techniques applied to all tubes simultaneously. The hollow-glass arrays are composed of up to 900 individual tubes with bore sizes as small as 50 m. Several rigid hollow-core arrays are used to transmit an IR image of a small loop of hot wire and a sample of tissue heated by a CO 2 laser.

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