We review the recent investigations on surface-mode phonons as a powerful tool for the study of solid state physics. First, the propagation characteristics of surface phonons are presented in some detail; attenuation in insulators and amplification in piezoelectric semiconductors. Second, special emphases are placed on the phonon focusing in anisotropic crystals as well as phonon reflection at stress free solid surfaces. Finally, recent topics on phonon transmission at solid-liquid helium interfaces are reviewed with emphasis on the role of the surface-mode phonons.
Wavelength calibration of commercial wavelength-stabilized He-Ne lasers (Hewlett Packard Model 5500 C) is made in comparison with an iodine stabilized He-Ne laser of NRLM. It is found that the individual wavelengths of the two calibrated lasers under thermal equilibrium are 632 991 387±2.8 fm and 632 991 333±0.8 fm respectively, while the stabilities of these lasers are ±4×10-9 and ±1×10-9 and their resettabilities, which are evaluated by repeated dischare and stabilization, are ±4×10-9 and ±3×10-9 respectively. The reproducibility of these two lasers evaluated from the wavelength differencebetween the two lasers is 8×10-8. The results show that the Hewlett Packard wavelength stabilized He-Ne lasers tested by us can be used for interferometric length measurement as a light wavelength standard with absolute wavelength of 632 991. 3 pm.
Detailed synthetic processes of a series of p-alkoxybenzylidene-p'-amino-2chloro-propyle-cinnamate and their ferroelectric properties are reported. These materials with dipole moments in the chiral part indicate larger dielectric constants (>150) and spontaneous polarization as compared with those of DOBAMBC in which the dipole moment is located separately from the chiral part. Contrary to HOBACPC (enatiotropic ferroelectric liquid crystal), OOBACPC and DOBACPC with longer alkoxy chain length indicate ferroelectric phase only in the cooling stage (monotropic). A mixture of DOBAMBC and DOBACPC indicates excellentproperties: namely wider temperature range of ferroelectricity than DOBACPC and larger ferroelectric-ity than DOBAMBC. Electro-optical effects are observed also in these liquid crystals and the threshold voltage is decreased remarkably as compared with that in DOBAMBC, which is consistent with its possessing a larger spontaneous polarization than DOBAMBC.
Recent advances in visible emission laser diodes are reviewed with emphasis on the (GaAI)-As double-heterostructure. The shortest cw lasing wavelength at room temperature so far obtained in this system is close to 700 nm, whereas the practical compatibility with 800 nm-range infrared lasers in performance and reliability is limited only to about 750 nm. For a shorter wavelength laser material, the system (AlInGa) P/GaAs may be one of the most potential candidates among quaternary III-V mixed crystals lattice-matched to binary com-pounds, in which the direct bandgap energy covers a range from 1. 91 to 2. 17 e V.
Light scattering studies on polarization fluctuation spectra near transition temperatures of KH2PO4 type ferroelectrics in GHz frequency region are reviewed. Temperature dependences of the spectra of a relaxational mode-acoustic phonon coupled system are studied theoretically and compared with the recent experimental results of pure and mixed crystals KH2(1-x)D2xPO4. A criterion is obtained of whether or not the softening of the acoustic phonon is observed by light scattering in this system. The scattering intensities and the line widths depend upon the directions of scattering wave vectors. These results are well explained by the anisotropic polari-zation fluctuations which originate from characteristic long range interactions in these substances.
Elimination of effect of stray capacitances is essential to measure the small capacitance. The stray capacitance exists between two lead wires of the measuring capacitor and between each of the lead wire and the ground. Conception of three terminal capacitor is introduced and its measuring principle of preventing effect of the stray capacitances is explained. Some measuring methods including resonance, A. C. bridge, charge-discharge and oscilla-tion methods, some of them are newly developed, are shown. Examples of useful capacitors and sensors are also shown in the last section.
The process of development and present status of moire topography are reviewed from the view point of fringe formation. Results of applications of several types of techniques to medical objects such as live human body are also demonstrated.