The optical constants of cubic boron nitride were determined for the first time in the vacuum ultraviolet.The fundamental optical-absorption edge determined from these optical constants is 6.1~0.2 eV.The cubic form of boron nitride (cBN) exhibits various interesting characteristics such as semiconducting properties, ' high optical band gap, extreme hardness, and high melting point. Because of these characteristics, the application of this material to the active devices operating at high temperature will be important in the near future. ' However, the experimental studies relevant to the electronic band structures have not been performed yet, although several theoretical studies on the electronic band structures were already performed.Recently, large single crystals of cBN were successfully synthesized by applying the temperature-difference method, which utilizes LiCaBN2 as a solvent at 55 kbar and 1800 C. Using these crystals the determination of optical constants of cBN becomes possible and is the purpose of the present study.Measurements of reAectance and transmittance spectrum were carried out at beam line 1 of SOR-RING (0.38-GeV electron storage ring) of the Institute for Solid State Physics using a 1-m Seya-Namioka-type monochromator in the photon energy range from 2 to 23 eV. Figure 1 shows the reAectance spectrum of a yellow crystal of cBN whose area is nearly 5 mm . Because the top and bottom surfaces of the crystal are not parallel to each other, the reAected light only from the top surface can be detected. Here, incident light is polarized in the plane of incidence and is deAected by 10 from the normal direction with respect to the surface of the crystal. The transmittance spectrum of a 0.16-mm-thick crystal is shown in Fig. 2. Here, light is incident normal to the surface of the crystal. The absolute value of the reAectance and transmittance shown in Figs. 1 and 2 is multiplied by certain factors, respectively, such that the value of the refractive index at a photon energy of 2. 10 eV is equal to 2. 117, which was determined by Gielisse et a/. ' Here, it is assumed from Fig. 2 that the value of the extinction coefficient is zero at this photon energy.

The surface‐emitting laser can be fabricated monolithically via planar technology and mass‐produced for applications to laser discs and optical IC's for optical communication. However, the transverse mode control in the surface‐emitting laser, which is important to laser oscillation, has not been well studied. This paper discusses the transverse mode control for the surfaceemitting laser and clarifies the shape of the single transverse mode in the structure. As a result of the calculation for a laser wavelength of 1.3 μm, if the composition of the waveguide core (the carrier‐confining layer) is λ = 0.93 μm in a structure where a waveguide is built in the cavity, the waveguide radius must be less than 2 μm. For a structure where only the active layer is embedded, the radius of the reflector must be 3 to 4 μm or the radius of the active region must be 5 to 7 μm when the reflector radius is 10 μm. Therefore, even in the surface‐emitting laser, the transverse mode control can be achieved relatively easily.

Silicon-hydrogen bonds in silicon oxide films were detected for the first time by applying surface-sensitive X-ray photoelectron spectroscopy and were confirmed by measuring infrared absorption. The areal density of silicon-hydrogen bonds in native oxides formed in a hot solution of HNO3 is estimated to be nearly 2×1014 cm-2, and is much larger than that formed in a solution with a composition of NH4OH:H2O2:H2O=1:1.4:4.

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An important issue in the polymerization of a polymer film by plasma-enhanced chemical vapor deposition (PECVD) is how to control the polymer structure. As is generally recognized, it is extremely difficult to control the process because it is very complex. For example, various precursors in the plasma arise from fragmentation of source monomers, which can easily change by varying the plasma conditions. High-energy electrons and ions in the plasma bombard the surface of the deposited film and affect the chemical reaction on the film. Moreover, the droplets that arise from the reactor wall by sputtering will accumulate on the film. However, if we aim to fabricate only a photonically functional polymer film, we will be able to find a solution. In this paper, we propose copolymerization from two types of monomers; one type is used as jointing materials by cracking, and the other is used as a photonic functional segment without serious deformation. This difference of action arises from a difference in the formation enthalpy. To confirm this idea, as an initial step, we copolymerized a film from a mixture of benzene (C 6 H 6 ) as the functional segment and cyclohexene (C 6 H 10 ) as the jointing material under the low radio frequency power. The deposited film consists of sp 2 bonding clusters surrounded by sp 3 bonded (alkyl) networks. We confirmed that the sp 2 bonding clusters mostly belong to phenyl, with a few belonging to olefins arising from decomposed C 6 H 6 . In addition, the amount of sp 2 bonding increases proportionally with increasing ratio of C 6 H 6 in the mixture, and the ratio of phenyl in the film becomes comparable to that of polystyrene. From these facts, we speculate that C 6 H 10 acts as the jointing material and C 6 H 6 as the functional segment. Additionally, we introduced tetrafluorocarbon (CF 4 ) to the plasma. CF 4 decomposes with a smaller energy than C 6 H 10 , and it forms mainly fluorine and CF 3 radicals. The fluorine radical pulls out hydrogen from the film and reacts to form dangling bonds in the film. Moreover, we speculate that they will terminate the dangling bonds.