Katsutoshi Muto

Mirror-type optical branch and switch

An optical branch and switch based on a unique mirror effect were fabricated by varying the amount of Ti diffused in a LiNbO(3) waveguide, and their properties were investigated. In this type of optical branch, the branching ratio of the light intensity could be varied by the electric field as well as by the separating angle and the effective indices of the waveguides. The main features of this optical switch are (1) small and simple electrode form and (2) a separating angle large enough to accommodate a number of switches on a single substrate. The ratio of the optical branch light intensity to that of the main waveguide was varied from 0.10 to 12.4 by applying the electric field from 0 V/microm to 8 V/microm.

Ferroelasticity in ReP5O14 (Re : La-Tb)

The ferroelasticity of rare earth pentaphosphates, ReP 5 O 14 (Re : La, Ce, Pr, Nd, Sm, Eu, Gd and Tb) which belongs to the species mmmF2/m is studied by DSC, Weissenberg camera and polarizing microscope. Anomaly of heat capacity at the ferroelastic transition point (second order), ferroelastic hysteresis loop, space group in para phase ( Pncm a =8.822, b =9.142, c =13.13 A at 150°C LaP 5 O 14 ), temperature dependence of ferroelastic order parameter and indicatrix are obtained.

Oxygen penetration into CaF2:Sm2+ crystals

Abstract The diffusion of O −− ions into CaF 2 :Sm 2+ crystals has been directly observed by means of the decoloration of the crystals. In the presence of water vapor the O −− ions penetrate easily into the crystals, but in an O 2 atmosphere penetration is quite limited. The penetration is isotropic, and the activation energy for diffusion is estimated to be 45±4 Kcal/mole. The dependence of the Sm 3+ fluorescence on the penetration process has also been investigated. The emission spectrum of Sm 3+ ions in the transparent zone shows the presence of both Type I ( C 3 ) and Type II ( C 4 ) centers. It was found that Sm 3+ ions are charge compensated not only by O −− ions but also by interstitial − ions, in spite of thermal treatment in an H 2 O atmosphere. The emission spectrum in the opaque zone shows only Type I centers.

Holographic storage in U-doped LiNbO(3).

A single LiNbO(3) crystal doped with U ions is a new sensitive phase holographic material with high diffraction efficiency and with long thermal decay time of a hologram. The energy density of a 4880-A beam from an Ar-ion laser required to reach 40% diffraction efficiency is about 1 J/cm(2) for a 1.2-mm thick crystal. Diffraction efficiency of a hologram stored in an U-doped LiNbO(3) crystal was scarcely reduced from its initial value when the crystal was held at room temperature for 150 days.

Absorption spectra and Zeeman effects of Tm3+ in CaF2

Abstract The absorption spectra of Tm 3+ in CaF 2 were analyzed by the concentration series method at 4·2 ° K. Systems of lines, belonging to Tm 3+ ion centers of different structure, are isolated from the general spectra. Some of structures of Tm 3+ ion centers were made clear by studying optical Zeeman effects and a change of absorption lines during thermal treatment. The tetragonal crystal field parameters and g -value of the upper state are also discussed.

Electrooptic Light Beam Deflection with Sr0.75Ba0.25Nb2O6 Prism

An experimental investigation was performed on the electrooptic light beam deflection with a Sr0.75Ba0.25Nb2O6 isosceles prism at 6328 A. Although measured deflection angle was large (e.g. 3m rad. for an electric field of 6 kV/cm), deflection characteristic was considerably nonlinear and what is called butterfly hysteresis loop was observed in the ferroelectric phase. Sign and magnitude of the polarization were easily changeable and the coercive field was found to be as low as 1.3 kV/cm at 33°C. The electrooptic effect is dominated by a quadratic term with respect to the polarization. The unclamped value of the quadratic electrooptic g-coefficient g33 was determined to be 0.14 m4/C2. An electrically-induced spot distortion was observed, which was most remarkable at the polarization reversal.

Nonresonant Energy Transfer from Er3+ to Yb3+ in LaF3

Energy transfer in LaF3; Er, Yb is studied by observing the lifetimes of Er3+ in excited states and the excitation spectra both at room temperature and at 77 °K. It is found that the energy transfer from Er3+ (4S3/2→4I13/2) to Yb3+ (2F7/2→2F5/2) is associated with the emission of three phonons of about 350 cm−1, and that the energy transfer from Er3+ (2H9/2→4F9/2) to Yb3+ accompanied by the absorption of phonons takes place.

Mirror-type optical switch array.

Two optical switches were integrated on a single LiNbO(3) substrate to construct an array. Two switches were connected by a thin film waveguide in such a way that one of the outputs of the first switch leads to the entrance of the second switch. As an array, one input of the first switch fans out to three outputs controlled by an electrical signal. When no electric field is applied to either of the two switches, the relative outputs of the three terminals were 1.92, 0.05, and 0.01. When a field of 6 V/microm was applied only to the first switch, the three terminals responded to 0.02, 1.80, and 0.05. The relative outputs of the terminals switched to 0.01, 0.01, and 1.80 when both switches were activated.