Surface-relief gratings with high spatial frequencies were first fabricated using a direct imprinting process with a glassy carbon mold at the softening temperature of phosphate glass. A grating with maximum height of 730 nm and 500 nm period was formed on the glass surface by the pressing at the softening temperature of glass under constant pressure of 0.4 kN/cm(2). Phase retardation of 0.1 lambda was observed between TE-polarized and TM-polarized light at 600 nm wavelength.

Sawtooth activity on HT-7 tokamak has been investigated experimentally mainly by using soft x-ray diode array and magnetic probes. Their behaviors and occurrences are correlated closely to the discharge conditions: the electron density N e , the electron temperature T,, the safety factor qa on plasma boundary and wall condition etc. When central line-averaged electron density N e ( 0 ) is over 2 . 0~1 0 '~c m -~, major sawtooth activity emerges with a period of up to 6.5 ms and a fluctuation amplitude of up to 2-30 % of SXR radiation signal. In some cases such as the safety factor between 4.2-4.7 and 2,15=3.0-6.0, a monster sawtooth activity often emerges without apparent deterioration of plasma confinement and without major disruption. During these events, abundant MHD phenomena are observed including partial sawtooth oscillations. In this paper, the observed sawtooth behaviors and their dependence on the and their dependence density Ne and wall condition in ohmically heated plasma are introduced, the results are discussed and presented.-PACS: 52.70.La, 52.55.Fa

Mold shape has been optimized to fabricate one-dimensional glass gratings with a high aspect ratio. Comparison of experimental and simulated results demonstrated that a periodic groove with a tilted sidewall, a parabolic top tooth, and a large width was preferable to imprint high-aspect-ratio gratings on a glass surface. In particular, a mold with a parabolic top tooth and a wide groove was effective to increase the aspect ratio. In the case of a mold with a 500 nm period, a grating of 540 nm height could be imprinted under the respectively optimized imprinting parameters of 430 C, 5 MPa, and 5 min.

One-dimensional periodic sub-wavelength structures (SWSs) with a period of 300 nm were fabricated on a bismuth germanoborate glass plate by a direct glass nanoimprint method using SiC molds. The borate glass had a refractive index of 1.82 at 587.6 nm wavelength, an internal transmittance higher than 80% at a thickness of 3 mm in the visible wavelength region, and a deformation temperature of 468°C. SWSs with height of a few hundred nanometers were simultaneously fabricated on both surfaces of the glass plate by the glass nanoimprint at 488°C for 120 s with 8 MPa in pressure. The SWSs showed form birefringence. A phase retardation of 0.23 λ was observed between transverse electric (TE)-and transverse magnetic (TM)-polarized beams at 400 nm wavelength.

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