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We describe a silica-based 16/spl times/16 strictly nonblocking thermooptic matrix switch with a low loss and a high extinction ratio. This matrix switch, which employs a double Mach-Zehnder interferometer (MZI) switching unit and a matrix arrangement to reduce the total waveguide length, is fabricated with 0.75% refractive index difference waveguides on a 6-in silicon wafer using silica-based planar lightwave circuit (PLC) technology. We obtained an average insertion loss of 6.6 dB and an average extinction ratio of 53 dB in the worst polarization case. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs). The total power consumption needed for operation is reduced to 17 W by employing a phase-trimming technique which eliminates the phase-error in the interferometer switching unit.

Organic electronics covered in this issue, are those in which active electronic or optoelectronic components are composed partly or entirely of organic semiconducting materials. Organic electronics is now entering its second decade as a commercial technology but in many ways is a relatively recent and emerging field. As such, significant advances are being made across a broad range of activities, from improving the understanding of very fundamental phenomena to improving manufacturing technologies.

An 8/spl times/8 optical matrix switch consisting of asymmetric Mach-Zehnder (MZ) interferometer switching units with a waveguide intersection was fabricated using silica-based planar lightwave circuits (PLC's) on a silicon substrate. This switching unit can realize a high extinction ratio and a wide operation wavelength range even if the coupling ratios of the directional couplers (DC's) consisting the switching unit, deviate greatly from the ideal value of 50%. A matrix switch with a DC-coupling ratio of 30% was fabricated to test the validity of the proposed geometry. The average insertion loss was 7.3 dB in the transverse electric (TE) mode and 7.5 dB in the transverse magnetic (TM) mode. The average extinction ratio was 31.2 dB in the TE mode and 31.3 dB in the TM mode. The wavelength range with an extinction ratio greater than 20 dB was over 100 nm.

Electroluminescent (EL) diodes utilizing metal-free phthalocyanine (H/sub 2/Pc) have been fabricated by the vacuum evaporation method. The EL characteristics of the diodes depending upon the metal cathode and the characteristics of the diodes with the coevaporated layer with 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) have been investigated. We have demonstrated the infrared electroluminescence originated from the radiative transition corresponding to the Q band of H/sub 2/Pc by taking the energy band structure into consideration.

The authors report, in detail, an integrated-optic variable group-delay dispersion equalizer based on a lattice-form programmable optical filter. The variable dispersion equalizer consists of an alternating cascade of symmetrical and asymmetrical Mach-Zehnder interferometers. An equalizer with nine symmetrical and eight asymmetrical interferometers is fabricated on a planar lightwave circuit and its dispersion varied step by step from -681 to +786 ps/nm in the operational frequency range of 16.3 GHz. The effectiveness of the equalizer is shown by compensating the dispersion of three different fibers with a single equalizer. The performance of the equalizer is also evaluated and examined by numerical investigations.

The careful analysis of far-infrared reflectivity spectra of GaSb/AlSb superlattices allows us to obtain information on intermixed Al x Ga 1− x Sb layers at the heterointerfaces, namely, average chemical composition and thickness. Complementary information on structural properties and strain relaxation processes are obtained from X-ray diffraction.

Fabrication and lasing characteristics of Nd-doped P/sub 2/O/sub 5/-SiO/sub 2/ core planar waveguide lasers are described. CW oscillation at a wavelength of 1052.5 nm was successfully demonstrated in 0.2 wt%-Nd-doped silica-based planar waveguides fabricated on a silicon substrate by flame hydrolysis deposition and reactive ion etching. The lasing threshold and slope efficiency were optimized in an 8-/spl mu/m-wide waveguide, in which a lasing threshold pump power of 26 mW and a slope efficiency of 2.0% were obtained for 805-nm pumping. The measured lasing characteristics agreed with theoretical characteristics calculated by employing finite-element waveguide analysis, indicating that the waveguide structure was well controlled by the developed waveguide fabrication technique. The possible lasing characteristics of the waveguide lasers are discussed based on this agreement. The attenuation and emission properties of the waveguides are also described. >

We describe gas-source molecular beam epitaxy (MBE) and luminescence characterization of strain Si 1− x Ge x /Si quantum wells (QWs). Successful and reproducible growth of strained QWs is demonstrated, addressing the significance of selecting a higher growth temperature to establish a high degree of structural integrity and to maintain the crystallinity in terms of “optical” quality. Excellent heterointerface transcience was evidenced by an almost perfect match between the spectral shift due to exciton confinement and the theoretical calculation. A good spatial uniformity in terms of well width and composition was obtained when QWs are grown in the adsorption/dissociation-limited growth regime.

The initiation and propagation of hydrogen cracks in a pure iron single crystal have been investigated via notched tensile tests with simultaneous cathodic charging of hydrogen. The notch opening displacement for hydrogen crack growth when the tensile direction was parallel to [001] was much smaller than for [110] tension. Hydrogen cracks under [001] tension propagated in a straight line on the (001) plane from the notch root with only slight plastic deformation, whereas under [110] tension they propagated in a zigzag fashion with significantly larger plastic strain accompanying many slip bands. The slip band formation and the crack arrest patterns on the fracture surfaces indicate that hydrogen cracks were initiated and propagated by dislocation reactions on the slip systems in accordance with calculations for the maximum resolved shear stress distribution around the crack tip. The difference in hydrogen crack propagation between [001] and [110] oriented specimens has been explained by assuming t...

An improved 8/spl times/8 optical matrix switch was fabricated using silica-based planar lightwave circuits (PLCs) on a silicon substrate. Three improvements were made. First, the waveguide material was changed from titanium-doped silica (SiO/sub 22/-TiO/sub 2/) to germanium-doped silica (SiO/sub 22/-GeO/sub 2/) to reduce propagation loss. Second, offset driving powers were supplied to every switch unit to realize high extinction ratios. Third, the dummy switch units were modified to suppress the crosstalk through these units. The average insertion loss of the fabricated device was 3.81 db in the TE mode and 3.82 dB in the TM mode. The average extinction ratio of the switch units was 25.3 dB in the TE mode and 22.3 dB in the TM mode. The accumulated crosstalk was estimated to be less than -14 dB in the TE mode and -11 dB in the TM mode. The average driving power of the phase shifter in the on-state was 0.54 W in the TE mode and 0.52 W in the TM mode. The switching response time was 1.3 ms. The packaged 8/spl times/8 matrix switch with additional fiber-waveguide coupling loss of 2.7 dB was successfully employed in photonic multimedia switching and photonic inter-module connector system experiments. >

Specific heat measurements have been performed on single-crystalline Ce(Ru 1− x Rh x ) 2 Si 2 ( x =0.15,0.35) in various magnetic fields parallel to the c -axis. For x =0.15, the magnetic specific heat C mag shows a jump due to the spin density wave for B B c (∼3.6 T). For B c B C mag / T increases with decreasing temperature with a non-Fermi liquid (NFL) behavior. The paramagnetic Fermi liquid (FL) behavior was observed for B >6 T. For x =0.35, C mag / T shows the NFL behavior for B B >6 T.

A thin film multi-layer structure consisting of alternating layers of organic 8-hydroxyquinoline aluminium (Alq3) and aromatic diamine (TPO) has been grown by organic molecular beam deposition. The structure of the multi-layer has been confirmed by X-ray diffraction. Optical characteristics have been studied using optical absorption and photoluminescence. The photoluminescence peak of Alq3 shifts to a higher energy with decreasing layer thickness, suggesting a quantum size effect. An electroluminescent diode has also been fabricated using the Alq3/TPD multi-layer structure, and the emission characteristics have also been discussed.

A simple new technique is presented for evaluating the structural parameters of antireflection coating films formed on optical waveguide facets. SiO(x)/MgF(2) double layer AR coatings are fabricated on silica based optical waveguide facets by the thermal evaporation method. The transmission properties of the waveguides are measured in the 0.5-1.7-microm wavelength region. The structural parameters (refractive index and thickness) of the SiO(x) and MgF(2) films are determined by fitting the theoretical transmission properties to the experimental results by iteratively changing the parameters for calculation. The calculated reflectivity is in good agreement with the value measured with an optical time domain reflectometer. A graphic method for the simple determination of the parameters is also discussed.

Transmission bandwidth properties of GeO(2)-P(2)O(5)-doped silica graded-index fibers have been investigated. Theoretical results obtained from Olshansky's theory are represented in the form of a bandwidth map with profile parameter alpha on the vertical axis and wavelength lambda horizontally. The material dispersion sigma(m)(lambda) and the optimal profile parameter alpha(opt)(lambda) determined by the glass refractive-index measurement are used for calculating the transmission bandwidth. It is confirmed that the estimated results from the bandwidth map agree with the experimental results of transmission bandwidth measurements at lambda = 0.82,1.06,1.27, and 1.52 microm for twenty GeO(2)-P(2)O(5)-doped silica graded-index fibers with different alpha values.

Ring resonators composed of GeO/sub 2/-doped silica waveguides fabricated on silicon substrates by a flame hydrolysis deposition method are described. GeO/sub 2/-doped silica waveguides are developed to provide a lower propagation loss than that of TiO/sub 2/-doped silica waveguides. Since the finesse and transmission at resonance is determined mainly by total loss in the ring, the loss characteristics of the fundamental components are investigated in detail. Experimental and theoretical investigations show that a finesse of the ring resonator for GeO/sub 2/-doped silica waveguides is about 2.7 times higher than that for TiO/sub 2/-doped silica waveguides with the same transmission at resonance. >

The fabrication and characteristics of a hybrid-integrated optical gate matrix switch were studied. The switch was composed of a silica-based single-mode guided-wave circuit and two InGaAsP gate array chips, each of which comprised eight laser diode optical gates. The gate array chips were assembled on the guided-wave circuit using a hybrid integration technique. The insertion loss of the fabricated 4*4 matrix switch was scattered among switching paths and ranged from 26 to 33 dB. The switch was applicable to a 400 Mb/s signal system with a bit error rate of 10/sup -9/. The numerical analysis shows that the residual reflectivity at the LD gate and waveguide facets caused the loss scattering among the paths and that reduction of the residual reflectivity is essential for improving the switch characteristics. >

The present state of understanding of surface cracking in low C low alloy steel slabs in the continuous casting (CC) and direct rolling (DR) processes is outlined. Hot cracking of the CC slab surfa...

In clinical chemistry, a necessary step performed is the isolation of plasma from whole blood, and effective sample preparation techniques are needed for the development of miniaturized clinical diagnostic devices. This study demonstrates the use of passive microfluidic devices, which operating entirely on capillary action, for on-chip isolation of plasma from whole blood. Using these devices, several to several tens nanoliter volumes of plasma were effectively separated from a single drop of whole blood in 2 minutes. This study may have broad implications in the design of lab-on-a-chip devices for bioanalytical applications.

The effectiveness of a variable group-delay dispersion equaliser in compensating for the dispersions of various lengths of fibre is explained. The variable dispersion equaliser has a lattice-form programmable optical filter configuration and its dispersion can be varied from -681 to 786 ps/nm. The dispersion of three different fibres has been compensated for with a single equaliser.

An integrated-optic dispersion equalizer has been fabricated on a planar lightwave circuit (PLC) for the first time. The PLC optical dispersion equalizer can compensate for both negative and positive fiber dispersion values. In a preliminary experiment, we successfully compensated for the chromatic dispersion of a 20 km-long 1.3 /spl mu/m zero-dispersion fiber at 1.55 /spl mu/m. >

Recently many kinds of large-scale planar lightwave circuit (PLC) have been developed for use in optical communication systems. Since the characteristics of large scale PLCs depend on the losses in waveguides, PLC performance can be improved by reducing such losses. The propagation losses in silica-based waveguides have been evaluated by using long waveguides such as that shown in Fig. 1. The lowest loss value ever reported with silica-based long waveguides is 3.5 dB/m [1]. This was obtained in a 1.6-m long waveguide with a relative index difference Δ of 0.75%. It was deduced that the main reason for the loss is the scattering ascribed to the fluctuation of the refractive index and the core-cladding interface. This means that lower loss waveguides can be fabricated using lower Δ waveguides, though these require larger bending radii, and therefore a lager circuit size. This indicates that the minimum Δ value should be determined by taking account of the size of the substrate on which the long waveguides are laid out. Here we report the fabrication and loss characteristics of a 10-m long waveguide with a Δ of 0.45 % which has a very low loss of 1.7 dB/m.

Summary form only given. Electroluminescence diode based on molecularly doped conducting polymer (MDPC) with the structure of Cathode/MDPC/Anode and also Cathode/MDPC/Hole transport layer/Anode have been fabricated utilizing soluble conducting polymer such as poly(2,5-dialkoxy-p-phenylene vinylene) and fluorescent molecule such as 8-hydroxyquinoline aluminum. Electroluminescence intensity and spectrum have been found to depend on concentration of molecule, applied voltage and thickness of the layers. The obtained results are explained by taking the electronic energy states of conducting polymer and molecule into consideration. Dynamic characteristics have been also discussed.

An arrayed-waveguide grating multiplexer with SiO2-on-SiO2 structure is fabricated in order to achieve polarisation insensitivity. A negligible wavelength response dependence on polarisation of 0.01 nm, which corresponds to a birefringence of –9 × 10-6, is realised in a 16 channel arrayed-waveguide grating multiplexer with a wavelength spacing of 0.8 nm.

A 256 channel arrayed waveguide grating with a 25 GHz spacing was fabricated on a 4 inch Si wafer using 1.5% Δ silica-based waveguides with a minimum bending radius of 2 mm. By improving the fabrication methods of 1.5% Δ waveguides, we have obtained an on-chip loss of 2.7 – 4.7 dB, a far-end crosstalk of < –40 dB and a polarisation-dependent wavelength shift of < 0.025 nm.

A polarisation-insensitive arrayed-waveguide grating multiplexer is successfully fabricated on an Si substrate by adjusting the thermal expansion of dopant-rich silica-based glass to that of Si. The change in wavelength due to polarisation was kept to within 0.03 nm in a 1 × 8 arrayed-waveguide grating multiplexer with a flat and wide passband having a 3 dB bandwidth of 0.9 nm and a wavelength spacing of 1.6 nm.

A 32/spl times/32 arrayed-waveguide grating multiplexer with uniform-loss and cyclic-frequency characteristics has been fabricated on a silica-based planar lightwave circuit. The device consists of an 80-channel arrayed-waveguide multiplexer with 100 GHz spacing and 32 optical combiners which are connected to the 72 output waveguides of the multiplexer. The peak-to-peak loss and channel centre frequency variations are 1.2 dB and 22.3 GHz, respectively, for entire 32/spl times/32 input/output combinations. These values have been substantially improved from conventional arrayed-waveguide multiplexers with peak-to-peak loss and centre frequency variations of 4.7 dB and 75.6 GHz respectively.

An optical add/drop multiplexer that enables full access to 16 individual wavelength channels has been fabricated on the planar lightwave circuit (PLC). The device consists of four arrayed-waveguide gratings which are connected through 16 double-gate thermo-optic switches. The crosstalk characteristics of the optical switches have been improved by adopting a double-gate configuration. The on-off crosstalks from main input or add port to main output or drop port are less than -28.4 dB and the on-chip insertion losses are 7.8-10.3 dB, respectively.

The crosstalk of an arrayed waveguide grating multiplexer with a channel spacing of 10 GHz was reduced by trimming a-Si films deposited on the arrayed waveguides. This static phase compensation enables a stable multiplexer to be made which features a low crosstalk of

The authors demonstrate a novel multiwavelength simultaneous monitoring (MSM) device using silica-based arrayed-waveguide grating (AWG). In the present MSM device, the spectral transmission loss characteristics of the two diffraction beams are devised to cross at the signal wavelength. It is applicable to the unequally spaced WDM systems aiming at the suppression of four-wave mixing problems. The slope coefficient of the discrimination curve was ~–0.94 dB/GHz and the monitoring range was ±0.37 nm in the fabricated MSM for use in 8 ch unequally spaced WDM systems.

The higher order (third order) dispersion of dispersion shifted fibre has been successfully compensated by using a lattice-form programmable filter fabricated on a planar lightwave circuit. The equaliser offers a dispersion slope of -15.8 ps/nm/sup 2/ over 170 GHz in the 1.55 /spl mu/m region. The effectiveness of the equaliser has been confirmed by the pulse transmission experiment in which the trailing ripples of pulses caused by the higher order dispersion of 300 km dispersion shifted fibre have been eliminated.

The authors report the Rayleigh backscattering distributions of 10 m long silica-based waveguides fabricated on one substrate. These were obtained using a range-extended optical low coherence reflectometer. The results reveal that the best sample waveguide has a uniform loss of 1.7 dB/m throughout its length, and that although the others have loss increases due to defects, the main regions which are free of the defects have the same uniform loss. This uniformity indicates that the 1.7 dB/m loss is not caused by the ~200 bends in each waveguide.

An optical add/drop multiplexer (ADM) that enables full access to 16 individual wavelength channels has been fabricated on a planar lightwave circuit (PLC). The device consists of three arrayed-waveguide gratings which are connected by 16 thermo-optic switches. The on-off crosstalk for the main input to the main output port is less than -24 dB and that for the main input to the drop port is about -13 dB. The fibre-to-fibre insertion losses are 7-8 dB and 3-4 dB when signals are coupled to the main input port and to the add port, respectively.< >

The propagation loss characteristics of silica-based optical waveguides with various bending curvatures fabricated on 5 inch Si wafers are investigated. Low loss waveguides more than lm long with a Δ of 0.75% are successfully fabricated and the loss is found to be independent of the curvature radius over 5mm. A minimum loss of 3.5dB/m at ∼1.55 μm is obtained in a waveguide 1.6 m long.

An increase in the photoinduced refractive-index change Δn in silica-based optical waveguides on silicon is described. The increase is attained by the consolidation of a core film in a reducing atmosphere. A maximum Δn of 3.9 × 10−4 is obtained for the TE mode by UV laser irradiation at 248nm. This is four times larger than that in conventional waveguides.

2×16 optical splitters are fabricated using SiO2-based waveguides on an Si substrate. These splitter circuits consist of one wavelength-insensitive 2×2 coupler and 14 Y-branch elements. The circuit chip is set in a frame with a low expansion coefficient, and input and output fibre frames are connected to opposite ends of the circuit frame. The resulting module is 14 mm wide, 105 mm long and 8 mm thick. The mean and standard deviation of the insertion loss are 13.0 and 0.4 dB, respectively, at wavelengths of both 1.3 and 1.55 μm.

A compact and stable ring laser at 1.3 μm was demonstrated using an InGaAsP semiconductor laser amplifier (SLA) and a silica-based optical waveguide ring resonator with an FSR of 2 GHz on an Si substrate. Two end facets of the SLA were coupled to lensed optical fibres, the other ends of which were attached without alignment to the waveguide resonator through fibre guiding grooves. A low threshold current of 17 mA was obtained in the ring laser.

A 1×128 optical power splitter is fabricated by integrating 127 Y-branch waveguide elements on a 3 inch silicon wafer using silica waveguide technology. The average measured excess loss of this splitter is 3.2 dB including fibre-waveguide coupling loss.

The effect of microstructure on the toughness of the heat-affected zone (HAZ) in a 785 MN m−2 HSLA steel has been investigated with narrow-gap welds. Various microstructure regions, i.e. a coarse-g...

The effects of aging at 773 K on hydrogen embrittlement in Ni–30Cr (wt-%) alloys having two levels of P have been investigated by considering the grain-boundary segregation of impurity atoms and the Ni2 Cr ordered-phase formation. Aging at 773K suppressed intergraular fracture and reduced the susceptibility to hydrogen embrittlement in the low-P alloy. Such behaviour can be explained in terms of the grain-boundary strengthening caused by the segregation of C atoms. During aging at 773 K, the Ni2Cr ordered phase formed and the deformation mode changed from wavy slips to coplanar slip with paired dislocations, and then to coplanar slip with microtwins. In the low-P alloy, this change of deformation mode induced step-like cracks which may have occurred by the separation of either the {111} slip planes or the microtwin interfaces. In the high-P alloy, aging for short times caused C segregation to the grain boundaries which suppressed intergranular fracture. However, aging for longer times induced dras...

Loss increases due to the chemical reactions of hydrogen are investigated for GeO 2 -doped, GeO 2 . F-doped, and pure silica core fibers. Dissolved hydrogen gas causes the hydroxyl loss increase as well as the short-wavelength loss increase in the first two fiber types at high temperatures. The short-wavelength loss increase is attributed to two kinds of ultraviolet absorption increases. Doping fluorine reduces both of these loss increases as well as enhances the activation energy of the hydroxyl formation.

Superplasticity of a 25 pct Cr-6.5 pct Ni-3 pct Mo-0.14 pct N δ/γ duplex stainless steel has been studied with particular emphasis on the microstructural change during deformation. Two large superplastic elongations are obtained at temperatures around 1323 K in δ/γ duplex phase region and 1173 K where σ phase particles precipitate dynamically at a strain rate of ~10−3 s−1. During deformation in the higher temperature region, fine Widmanstatten γ particles coarsen and coarse γ grains formed during the prior treatments are broken into spherical particles, resulting in a homogeneous dispersion of γ particles within the σ-ferrite matrix. The dynamic recrystallization of soft σ-ferrite matrix occurs locally in the region where the strain reaches some critical value, and the final microstructure consists of equiaxed σ and γ grains. In the case of lower temperature deformation, a eutectoid decomposition of δ-ferrite into γ and σ phases occurs. The relatively soft γ grains which are severely deformed by hard σ particles recrystallize dynamically, and these processes lead to the γ/σ equiaxed duplex structure. The extremely large superplasticity of this alloy can mainly be explained in terms of the above microstructural change during deformation.

Initial ohmic heating experiments in JT-60 were performed for a three month period of April-June 1985. A maximum plasma current of 1.6 MA was obtained for both divertor and limiter discharges. Low-q discharges of qeff=2.5 and high density discharges of 4.8*1019 m-3 in line-averaged density were obtained in the divertor configuration. In divertor discharges radiated loss from the main plasma can be kept at 20-30% of the ohmic input.

The effect of σ-phase morphology on the tensile properties of δ-ferrite-austenite duplex stainless steels has been investigated. The ductility of specimens deformed at temperatures below 673 K was largely reduced by the precipitation of the σ-phase, but exhibited quite a large temperature dependence, similar to that of the brittle-ductile transition in ferritic steels. A lamellar structure consisting of layers of austenite and a σ-phase-austenite cellular structure was formed by aging a specimen solution treated in the δ-ferrite-austenite duplex phase region. When this specimen was deformed at lower temperatures, transverse microcracks originating from the cleavage fracture of σ-phase particles were linked by large longitudinal cracks, and final fracture occurred with the shearing of austenite layers. On deformation at higher temperatures, the coalescence of micro voids formed by the decohesion of σ-phase/austenite interfaces led to final fracture, with a large reduction in area. The transition te...

The effects of microalloying elements such as V and Nb on the high temperature deformation properties of low alloy martensites have been investigated by means of slow strain rate tensile tests at various temperatures. It was confirmed that the precipitations of fine carbonitrides, such as V(C.N) and NbC, are quite effective in reducing the high temperature ductilities. In particular, it has been concluded that the most detrimental effects on ductility arise from the dynamic trapping of the mobile dislocations generated at prior austenite grain boundaries by the simultaneous precipitation of V(C.N) or NbC. The cyclic repetition of such a process would result in strain concentration in the vicinity of prior austenite grain boundaries, and microvoids would form at the cementite/matrix interfaces on these boundaries, leading to intergranular ductile fracture.

The present state ofunderstanding ofsurface cracking oflow carbon low alloy steel slabs in the continuous casting (CC) and the direct rolling (DR) processes are outlined. Hot cracking ofCC slab surfaces can be explained in terms of carbonitride precipitation behaviour. In addition to y grain boundary precipitation, the matrix strengthening due to dynamic precipitation and the existence ofsofter layers along the boundaries such as ferrite or precipitation-free zones (PFZs) play an important role for intergranular ductile fracture. Hot cracking during the DR process can also be explained by a similar mechanism with dynamic sulphide precipitation, although the strain rate region in the ductility trough is much larger than in the CC process. Furthermore, a well-known effect ofcarbon on hot cracking susceptibility in both CC andDR processes can be explained mainly in terms of γ grain growth during the solidification process in the mould. Some methods to prevent surface cracking are also discussed.

This paper presents gamma-ray irradiation effects on OH-loss increase due to the chemical reaction of H 2 for GeO 2 -doped and GeO 2 . P 2 O 5 -doped fibers. When H 2 diffuses into irradiated fibers (γ-H 2 treatment), OH-loss increase occurs even at room temperature. Moreover, OH-loss increases due to dissolved H 2 in irradiated fibers are larger than those in unirradiated fibers at high temperatures. These OH-loss increases are attributed to irradiation-induced defects with which H 2 reacts to form OH ions. When H 2 -dissolved fibers are irradiated, the OH-loss increases are larger than those in the γ-H 2 -treated fibers at room temperature. These larger loss increases are thought to be caused by the reaction of the unstable radical and dissolved H 2 , which are excited by the irradiation.