Makoto Fujino

Monolithically cascaded micromirror pair driven by angular vertical combs for two-axis scanning

In this work, monolithically cascaded one-axis micromirrors driven by angular vertical comb drives are designed and fabricated. Using W-shaped folded-beam optics, we demonstrate two-axis scanning covering /spl plusmn/6.0/spl deg/ two-dimensional area at resonant modes of 7.5 kHz, /spl plusmn/17 V for a fast-scanning mirror and 1.2 kHz, /spl plusmn/7 V for a slow-scanning mirror. The experimental results satisfy the requirements for a surveying instrument.

Scanning micromirrors: An overview

An overview of the current state of the art in scanning micromirror technology for switching, imaging, and beam steering applications is presented. The requirements that drive the design and fabrication technology are covered. Electrostatic, electromagnetic, and magnetic actuation techniques are discussed as well as the motivation toward combdrive configurations from parallel plate configurations for large diameter (mm range) scanners. Suitability of surface micromachining, bulk micromachining, and silicon on insulator (SOI) micromachining technology is presented in the context of the length scale and performance for given scanner applications.

Dispersion dependence of linewidth in actively mode-locked ring lasers

We numerically and experimentally study the effect of cavity dispersion in actively mode-locked ring lasers. The wavelength-swept laser with quite narrow linewidth is achieved by the combination of anomalous dispersion in a linearly chirped fiber Bragg grating and self-phase modulation-induced spectral broadening in semiconductor optical amplifier. By using this technique, a wavelength sweeping with rate of 120 kHz and range of 40 nm have been successfully demonstrated.

Ultrahigh resolution OCT imaging with a two-dimensional MEMS scanning endoscope

This paper reports preliminary results from the development and application of a two-dimensional MEMS endoscopic scanner for OCT imaging. A 1 mm diameter mirror provides high aperture over large scan angle and can scan at rates of hundreds of Hz in both axes. The mirror is integrated with focusing optics and a fiber-optic collimator into a package of ~5 mm diameter. Using a broadband femtosecond laser light source, ultrahigh axial image resolution of < 5 um in tissue is achieved at 1.06 um center wavelength. Ultrahigh resolution cross-sectional and three-dimensional OCT imaging is demonstrated with the endoscope with ~12 um transverse resolution and < 5 um axial resolution.

Rigorous analysis of a volume phase holographic grism for astronomical observations

A grism typically consists of a transmission grating attached to a prism and constitutes an important optical element for spectroscopic astronomical observations. Here, we present a new type of grism that includes a volume phase holographic grating and evaluate its performance in detail using the rigorous coupled wave analysis (RCWA). Based on the knowledge gained from this evaluation we were able to design and fabricate a grism prototype with good performance.

Cascaded micromirror pair driven by angular vertical combs for two-axis scanning

In this work, monolithically cascaded one-axis micromirrors driven by angular vertical comb drives are designed and fabricated. Using W-shaped folded-beam optics, we demonstrate two-axis scanning covering /spl plusmn/6.0/spl deg/ two-dimensional area at resonant modes of 7.5 kHz, /spl plusmn/17 V for a fast-scanning mirror and 1.2 kHz, /spl plusmn/7 V for a slow-scanning mirror. The experimental results satisfy the requirements for a surveying instrument.

A widely-variable optical attenuator for multimode fibers with a MEMS micromirror

MEMS-based variable optical attenuators (VOAs) using a shutter, a mirror, or a grating have been proposed in the field of optical telecommunication [1]. The MEMS-based VOAs used in optical telecommunication, however, are not suitable for optical instruments, in which a light beam is not always single mode ( i.e. is low spatially coherent) and optical power to be regulated can substantially vary (≫ 40 dB).

Negative refractive optics

Negative refractive optics is considered to bring forth new optical functions that have been out of reach for classical optics. Since materials with a negative refractive index are difficult to find or fabricate, the photonic crystal (PhC) is currently deemed the most potential candidate bringing negative refraction into the optical regime without requiring the materials refractive index itself being negative. In this work, we first look at the optical properties of a slab lens and then analyze a common PhC structure with negative refractive behavior with respect to optical transmission, dispersion and wavefront aberration. By taking a PhC slab we determine the geometrical and physical conditions that allow it to provide imaging similar to a lens.

Rigorous evaluation of a Talbot waveguide coupler

The Talbot array Illuminator (TAIL) is well known as a diffractive element that efficiently transforms a monochromatic optical wave into an array of bright spots. To date, TAILs have been thoroughly studied both analytically and experimentally mainly within the frame of scalar diffraction theory and paraxial approximation. However, only little investigation has been done so far on what happens to the illumination characteristics when the TAILs feature size becomes of the order of the wavelength and whether illumination of less than one TAIL period can be in any way useful. In the following, we try to answer those questions by taking a look at the performance of a TAIL when acting as a coupling element to an optical waveguide. For simplicity we confine here our evaluation to optical structures that vary only in two dimensions, e.g., a slab waveguide, and TE illumination.