Arnon Millo

Mid-infrared fiber-optic attenuated total reflection spectroscopy of the solid-liquid phase transition of water.

Measurements of mid-infrared (MIR) absorption spectra of water and heavy water were carried out by fiber-optic evanescent wave spectroscopy, using silver halide (AgClBr) infrared fibers. Such measurements were performed for the first time on one sample, during the solid–liquid phase transition. From the variation of the spectra with temperature we found a new isosbestic point (at 3280 cm−1 for H2O or at 2475 cm−1 for D2O) and we identified five components of the O–H (O–D) stretch band. These phenomena have provided new information about the molecular structure of water.

Silver halide single-mode fibers for the middle infrared

There is an interest in single-mode fibers that are highly transparent in the middle infrared. Such fibers would be valuable for spectroscopy, interferometry, fiber lasers, and heterodyne detection. We developed core-clad fibers made of crystalline silver halides, with external diameter 900 μm, small core diameters (50–60 μm) and an extremely small difference (∼0.004) between the indices of refraction of the core and the clad. These fibers behaved as single-mode fibers at the wavelength 10.6 μm.

Silver-halide segmented cladding fibers for the middle infrared

There is a wide interest in single-mode optical fibers for the middle infrared range of 3–30μm. These fibers will be useful for a variety of applications such as spatial filtering and interferometry. However, many technical and theoretical problems hindered the development of such fibers. Segmented cladding fibers may make it possible to combine an extremely large core area and single mode operation over a large spectral range. The design parameters may accurately control the optical properties of such fibers. We report here the design and fabrication of segmented cladding fibers made of crystalline silver halides, which are highly transparent in the middle infrared.

Thin ordered bundles of infrared-transmitting silver halide fibers

Thin, ordered bundles of fibers were extruded from AgClxBr1−x (0<x<1) crystals. They consisted of 100 individual fibers of average diameters 30–45μm, packed in tight arrays to form bundles of outer diameters 0.7–2.0mm. The bundles transmitted radiation in the spectral range of 3–20μm and exhibited relatively low transmission losses and no bending losses. The bundles were used to transmit thermal images of objects at room temperature to a distance of several meters. These thin and flexible bundles will be useful for fiber-optic thermal imaging in medical and industrial applications.

Single-mode octagonal photonic crystal fibers for the middle infrared

Single-mode optical fibers for the middle infrared are needed for many applications such as infrared fiber lasers, spatial filtering, and interferometry. Index guiding photonic crystal fibers offer many advantages over regular step-index fibers such as a wide spectral range and large core area. In this paper, we report the design and fabrication of single-mode octagonal photonic crystal fibers. These fibers were fabricated from silver halide polycrystalline materials which have high transmission in the middle infrared. The fibers showed a single-mode behavior at 10.6μm with low losses and a large mode diameter (110μm).

Single-Mode Segmented Cladding Fibers for the Middle Infrared

Single-mode (SM) fibers for the middle infrared (3-20 mum) are required for a variety of purposes, such as spatial filtering and interferometry. There has only been limited success in the development of such fibers, due to the lack of suitable materials that transmit in this spectral range. In this paper, we report the design and fabrication of SM segmented cladding fibers made of silver halide materials. The fiber design consists of a uniform core of high-refractive material that is surrounded by a cladding of alternating segments of high and low refractive indices. These fibers can maintain a SM operation over a wide spectral range with a very large core area.

Single-Mode Index-Guiding Photonic Crystal Fibers for the Middle Infrared

Single-mode optical fibers for the middle infrared (mid-IR) (m) are needed for many applications such as IR fiber lasers, spatial filtering, and interferometry. There has only been limited success in the development of such fibers, due to the lack of suitable materials that have high transmission in this spectral range. In this letter, we discuss the development and optical measurements on single-mode index-guiding photonic crystal fibers based on silver-halide crystalline materials which are highly transparent in the mid-IR. These fibers were designed to have a large core area and to maintain a single-mode operation over a wide spectral range.

Flexible ordered bundles of infrared transmitting silver-halide fibers: design, fabrication, and optical measurements

Ordered bundles of silver-halide fibers, which are highly transparent in the middle infrared, are fabricated by multiple extrusions from single crystals. We fabricate and characterize the optical properties of thin and flexible bundles of diameters of 0.7-2.0 mm that incorporate 100 individual fibers. The measurements include attenuation, resolution, cross talk, near-field scanning of single fibers in the bundle, and bending losses. Bundles of lengths of several meters transmit thermal images of bodies whose temperature is near room temperature. These bundles would be useful for medical, industrial, and military applications, and in particular for endoscopic thermal imaging.

Few modes in infrared photonic crystal fibers

Photonic crystal fibers guide light by trapping it in a periodic array of elements in the cladding area. We fabricated photonic crystal fibers by multiple extrusions of silver halide (AgClxBr1−x) crystals which are highly transparent in the middle infrared. The core of such a fiber consisted of pure silver bromide AgBr (n=2.16 at 10.6μm), and the cladding area consisted of concentric rings of fiber-optic elements made of pure silver chloride AgCl (n=1.98 at 10.6μm), which lowered the refractive index of the clad. Two types of photonic crystal fibers were fabricated, one with two concentric rings and one with five concentric rings of fiber-optic elements around the core. The characterization of the fibers, such as the power distribution, the attenuation, and the numerical aperture were measured. Both fibers behaved like regular core-clad structures. Simulations on these structures showed that each of these fibers guided a small number of modes and that adding rings to the structure lowered the number of bo...

Toward the realization of a single-mode photonic crystal fiber in the middle infrared

Photonic crystal fibers confine light within a periodic array of elements. We used multiple extrusions of silver halide (AgClxBr1-x) crystalline materials to fabricate photonic crystal fibers, which are transparent in the middle infrared (mid-IR) in the spectral range 2-20 μm. The cores of these fibers consisted of pure silver bromide (AgBr) of refractive index n=2.16, and the cladding area included concentric rings of tens of fiberoptic elements made of pure silver chloride (AgCl), of a lower refractive index n=1.98. Simulations on photonic crystal structures showed that all the fabricated fibers guide a small number of modes. Furthermore, adding rings to such a structure should lower the number of bound modes in the core. We measured the attenuation and the output power distribution of these fibers and carried out spectroscopic measurements in the mid-IR. Good correlation was found between the experimental and the theoretical results. These findings will pave the way for the fabrication of single-mode fibers in the mid-IR range.