Keywords IR fibers, hollow waveguides, laser power delivery, fiber sensors IntroductionInfrared (IR) optical fibers may be defined as fiber optics transmitting wavelengths greater than approximately 2 µm. The first IR fibers were fabricated in the mid-1960's from chalcogenide glasses such as arsenic trisulfide with losses in excess of 10 dB/m.(1) During the mid-1970's, the interest in developing an efficient and reliable IR fiber for short-haul applications increased partly in response to the need for a fiber to link broadband, long wavelength radiation to remote photodetectors in military sensor applications. In addition, there was an ever-increasing need for a flexible fiber delivery system for transmitting CO 2 laser radiation in surgical applications.Around 1975, a variety of IR materials and fibers were developed to meet these needs. These included the heavy metal fluoride glass (HMFG) and polycrystalline fibers as well as hollow rectangular waveguides. While none of these fibers had physical properties even approaching that of conventional silica fibers, they were, nevertheless, useful in lengths less than 2 to 3 m for a variety of IR sensor and power delivery applications. (2) 2 IR fiber optics may logically be divided into three broad categories: glass, crystalline, and hollow waveguides. These categories may be further subdivided based on either the fiber material or structure or both as shown in Table 1. Over the past 25 years many novel IR fibers have been made in an effort to fabricate a fiber optic with properties as close to silica as possible, but only a relatively small number have survived. A good source of general information on these various IR fiber types may be found in the literature. (3,4,5,6) In this paper we will review only the hollow waveguide technology with emphasis on the best and most practical hollow waveguide candidates available today. In general, both the optical and mechanical properties of IR transmitting hollow waveguides remain inferior to silica fibers and, therefore, the use of hollow guides is still limited to non-telecommunication, short-haul applications requiring only a few meters of waveguide rather than kilometer lengths common in telecommunication applications. The short-haul nature of these special IR fibers results from the fact that the guides have losses in the range of a few dB/m rather than a few dB/km. Also, hollow guides have an additional loss on bending; and they are also somewhat weaker than silica fiber. These deleterious features have slowed the acceptance of hollow guides and restricted their use today to applications in chemical sensing, thermometry, and laser power delivery. Main Subcategory Examples

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Precise comparisons of the fundamental properties of matterantimatter conjugates provide sensitive tests of charge-parity-time (CPT) invariance 1 , which is an important symmetry that rests on basic assumptions of the standard model of particle physics. Experiments on mesons 2 , leptons 3,4 and baryons 5,6 have compared different properties of matter-antimatter conjugates with fractional uncertainties at the parts-per-billion level or better. One specific quantity, however, has so far only been known to a fractional uncertainty at the parts-per-million level 7,8 : the magnetic moment of the antiproton, μ p . The extraordinary difficulty in measuring μ p with high precision is caused by its intrinsic smallness; for example, it is 660 times smaller than the magnetic moment of the positron 3 . Here we report a high-precision measurement of μ p in units of the nuclear magneton μ N with a fractional precision of 1.5 parts per billion (68% confidence level). We use a two-particle spectroscopy method in an advanced cryogenic multi-Penning trap system. Our result μ p = −2.7928473441(42)μ N (where the number in parentheses represents the 68% confidence interval on the last digits of the value) improves the precision of the previous best μ p measurement 8 by a factor of approximately 350. The measured value is consistent with the proton magnetic moment 9 , μ p = 2.792847350(9)μ N , and is in agreement with CPT invariance. Consequently, this measurement constrains the magnitude of certain CPT-violating effects 10 to below 1.8 × 10 −24 gigaelectronvolts, and a possible splitting of the protonantiproton magnetic moments by CPT-odd dimension-five interactions to below 6 × 10 −12 Bohr magnetons 11 .Within the physics programme at the Antiproton Decelerator of CERN, the properties of protons and antiprotons 5,6 , antiprotons and electrons 12 , and hydrogen 13 and antihydrogen 14,15 are compared with high precision. Such experiments, including those described here, provide stringent tests of CPT invariance. Our presented antiproton magnetic moment measurement reaches a fractional precision of 1.5 parts per billion (p.p.b.) at 68% confidence level, enabled by our new measurement scheme. Compared to the double-Penning trap technique 16 used in the measurement of the proton magnetic moment 9 , this new method eliminates the need for cyclotron cooling in each measurement cycle and increases the sampling rate.Our technique uses a hot cyclotron antiproton for measurements of the cyclotron frequency ν c , and a cold Larmor antiproton to determine the Larmor frequency ν L . By evaluating the ratio of the frequencies measured in the same magnetic field, the magnetic moment of the antiproton (in units of the nuclear magneton, the g-factor) ν ν μ μN is obtained. With this new technique we have improved the precision of the previous best antiproton magnetic moment measurement 8 by a factor of approximately 350 (Fig. 1a).Our experiment 17 is located in the Antiproton Decelerator facility, which provides bunches of 30 million antiprotons at a...

Precise knowledge of the fundamental properties of the proton is essential for our understanding of atomic structure as well as for precise tests of fundamental symmetries. We report on a direct high-precision measurement of the magnetic moment μ of the proton in units of the nuclear magneton μ The result, μ = 2.79284734462 (±0.00000000082) μ, has a fractional precision of 0.3 parts per billion, improves the previous best measurement by a factor of 11, and is consistent with the currently accepted value. This was achieved with the use of an optimized double-Penning trap technique. Provided a similar measurement of the antiproton magnetic moment can be performed, this result will enable a test of the fundamental symmetry between matter and antimatter in the baryonic sector at the 10 level.

We have applied techniques developed for IR waveguides to fabricate Ag/polystyrene (PS) -coated hollow glass waveguides (HGWs) for transmission of terahertz radiation. A loss of 0.95 dB/m at 119 microm (2.5 THz) was obtained for a 2 mm bore, 90 cm long Ag/PS HGW. We found that TE modes are supported in HGWs with thin PS films, while hybrid (HE) modes dominate when PS film thickness increases. The lowest losses are obtained for the thicker PS films and the propagation of the HE modes.