We report the results of an optical design study of a multilayer mirror that provides high reflectivity in the 400 eV region. First, the material pair selection rule proposed by Yamamoto was applied to examine the coating materials. Using the optical constants table by Palik, we calculate the Fresnel coefficients for various materials at angle of incidence of 60 deg. Following the selection rule, we looked for two materials yielding strong reflection at interfaces where the distance between two points of the Fresnel coefficients on the complex plane is far apart, as well as small absorption in the multilayer structure. Then film thicknesses of the multilayer structure were optimized by numerical calculation using IMD software, which results in practical high reflectivity between 43 to 50% on the Sc/Si, Sc/Mg, and Sc/Cr multilayer mirrors at the photon energy of 397.5 eV. In this presentation, we also report grazing incidence x-ray reflectivity results for multilayer mirrors deposited by a magnetron sputtering method.
To bring global optimization capability on optical design of a focusing objective in soft X-ray region, we describe novel design approach by combining analytical and numerical methods based on geometric optics. We assume two-spherical mirror objective of glazing-incidence configuration. First, relationship between system layout parameters, i.e., radii of curvatures and mirror separations, and focus length is derived with paraxial approximation, to describe all feasible mirror layouts with constant focal length. Then, focusing property of the mirror objectives are computed by applying numerical raytracing method, to seek practical optical designs with low aberrations. As design examples, the proposed method is applied to a two-spherical-mirror objective for one-dimensional focusing of soft X-ray high harmonics. We successfully find three kinds of practical designs with low aberration. The calculation results show that we can expect small spot size close to 100 nm on the focal plane, for the case that the objective has moderate focal length (f = 100 mm) and numerical aperture (NA = 0.02). These results indicate that the proposed approach is capable of global optimization of the mirror objective with glazing-incidence configuration.
We developed a craft kit of "Color Mixer" to understand easily the principle of reproducing colors while enjoying the craftwork with mixing colors using three LEDs. We will report on the composition of the kit and its outreach activity.
A phase-shifting interferometry (PSI) using a multi-longitudinal-mode blue laser diode was developed. Since the
longitudinal modes of a laser diode are located almost at even interval and changes synchronously with the injection
current, by setting an optical path difference between two arms of an interferometer in such a way that makes the
contrast of interferogram to be a maximum, the phase shift required for PSI can be obtained by changing the injection
current. Moreover, in such a condition, the PSI system works even mode hops occur. Theory and experimental results for
measuring the transmitted wavefront of an aspheric DVD pickup lens are presented.
A digital phase-measurement interferometer using a tunable SHG blue laser at 410nm was developed. This system enables us to test high NA lenses used in high-density optical storage devices. Excellent features such as wavelength tunability, narrow spectral linewidth, and wavelength stability, make the SHG laser very suitable as a light source for a phase-shifting interferometer working at blue-violet wavelength region. We investigated the tuning characteristic of the SHG laser as a function of DBR-section current and found that the wavelength-changing ratio was 0.0017nm/mA. An unbalanced Twyman-Green interferometer with the SHG laser was composed to measure the transmitted wavefront of an optical pickup lens with a NA of 0.85. The theory and experimental results are presented.
We present a new interference microscope for quantitative measurement of transparent objects. High precision measurement is achieved by applying the phase-shifting interferometry to an ordinary transmission optical microscope. In that microscope, a bi-prism inserted between a magnifying lens and an observation plane is used as both a beam splitter and a phase shifter. The phase shift required for phase extraction using the phase-shifting technique is introduced by laterally shifting the bi-prism with a piezoelectric transducer. The diffraction caused by the vertex of the bi-prism is avoided by placing a thin wire at the center position of an intermediate image plane. Experimental results for measuring the refractive index distribution of an optical waveguide and the thickness of a biological sample are presented to demonstrate the usefulness of the this method.
In this paper, we present an ac optical balanced homodyne detection system which enables us to detect both the amplitude and phase of the surface optical nonlinear signal. In this system, a balancing scheme and an unique lock-in detection method using fundamental interference signal as a reference has been employed. This system enables us to simultaneously measure, with extremely high sensitivity of 3 aW and high precision, both the intensity and phase of a very weak surface SHG signal. Experimental results of simultaneous measurement of the intensity and phase in surface second-harmonic waves generated from native-oxidized Si (111) surfaces is presented.
We present a new type of phase-shifting microscope that enables us to quantitatively measure the phase distribution of a transparent microscopic object. In this microscope, a Fresnel's biprism is used to make the object wave and a reference wave to interfere. The biprism is laterally moved by a piezoelectric transducer to produce the phase shift between the two waves required for phase extraction using the phase shifting technique. The diffraction caused by the vertex of the biprism is avoided by placing a thin wire at the center position of an intermediate image plane. The technique described here can be easily applied to an ordinary optical microscope, moreover, this technique can also be applied to an electron holographic interference microscope using an electron biprism. Experimental results for measuring the refractive index distribution of an optical waveguide are presented.
An ac optical balanced homodyne detection system was developed to simultaneously measure the intensity and phase in surface second-harmonic generation. Extremely high sensitivity of 3 aW (6 photon/sec) has been achieved by use of a lock-in amplifier, in which an interference signal of fundamental waves is used as a reference signal. Experimental results of simultaneous measurement of the intensity and phase in surface second-harmonic waves generated form native-oxidized Si(111) surfaces is presented.
The pump wavelength dependence of the optical second harmonic generation from Si(100)-2x1 has been investigated by use of a tunable Ti:Sapphire laser. Significant enhancement of second harmonic signal around pump wavelength of 850 nm was observed. Such an enhancement is considered be caused by resonance related to Si surface dangling-bond states.
The method of measurement of two-dimensional flatness of etalons are proposed. Fundamental idea is to measure diameters of interference rings produced on CCD camera. The reproducibility is about (lambda) /1800.
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