Moongoo Choi

An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcement frame

We present the design, fabrication and measurement results of a comb-driven electrostatic scanning micromirror. Instead of a conventional micromirror having uniform thickness across the entire reflective surface, a diaphragm mirror plate supported by an array of diamond-shaped frame structures is fabricated monolithically. The fabrication process is a simple sequence of silicon deep etch processes on both sides of the silicon-on-insulator (SOI) substrate without the substrate bonding process. The micromirror is fabricated on the device layer of the substrate. The mirror plate undergoes a rotational motion by an electrostatic force between the movable comb electrodes connected to the micromirror and stationary comb electrode formed on the handle wafer. A scanning micromirror with a 10 µm thick diaphragm mirror plate, having a planar dimension of 1.5 × 1.5 mm2, supported by an array of 110 µm thick rhombic support frames, was fabricated and tested. A mechanical deflection angle of 8.5° at a resonance frequency of 19.55 kHz and a pressure of 7 mTorr was obtained. A prototype of the raster scanning laser projection display system was developed using the fabricated micromirror as the horizontal scanner and a galvanomirror as the vertical scanner, respectively.

Electromagnetic Two-Dimensional Scanner Using Radial Magnetic Field

In this paper, we present the design, fabrication, and measurement results of a two-dimensional electromagnetic scanning micromirror actuated by radial magnetic field. The scanner is realized by combining a gimbaled single-crystal-silicon micromirror with a single turn electroplated metal coil, with a concentric permanent magnet assembly composed of two concentric permanent magnets and an iron yoke. The proposed scanner utilizes the radial magnetic field rather than using a lateral magnetic field oriented 45deg to the horizontal and vertical scan axes to achieve a biaxial magnetic actuation. The single turn coil fabricated with electroplated copper achieves a nominal resistance of 1.2 Omega. A two-dimensional scanner with mirror size of 1.5 mm in diameter was fabricated. Maximum optical scan angle of 8.8deg in horizontal direction and 8.3deg in vertical direction were achieved. Forced actuation of the gimbal at 60 Hz and resonant actuation of the micromirror at 19.1-19.7 kHz provide slow vertical scan and fast horizontal scan, respectively. The proposed scanner can be used in raster scanning laser display systems and other scanner applications.

Robust, processable, and bright quantum dot/organosilicate hybrid films with uniform QD distribution based on thiol-containing organosilicate ligands

Robust, processable, and bright quantum dot/organosilicate (QD/OS) hybrid films with uniform QD distribution are successfully demonstrated by grafting thiol-containing polymeric organosilicate (OS) ligands to the surface of QDs. It is found that the surface modified QDs show almost the same optical properties (i.e., in terms of emission PL spectra and quantum yields (QYs)) as those of pristine QDs initially covered with oleic acids. The QD/OS hybrid films based on the surface modified QDs show the uniform distribution of QDs within the films with all the beneficial properties such as high QY, improved environmental resistance against hydrochloric acid, and excellent optical transparency in the visible range. In addition, red, green, blue, and white QD/OS hybrid films with high color purity and a down-conversion film, based on a mixture of red and green QDs, placed on top of a blue LED chip showing white emission were also successfully demonstrated with the QD/OS hybrids. We further demonstrate that cylinder-patterned QD/OS hybrid films are possible simply by applying unconventional imprint lithography. The QD/OS hybrid films with uniform distribution of QDs within the films could thus be applied as practical platforms, which have easy processability, high QY, and environmental stability, for optical devices based on functional nanocrystals.

Dual-Axis Electromagnetic Scanning Micromirror Using Radial Magnetic Field

This paper presents the design, fabrication and measurement results of a dual-axis electromagnetic scanning micromirror utilizing radial magnetic field. The scanner is comprised of a gimbaled single-crystal-silicon micromirror with a single turn electroplated metal coil, assembled passively above a concentric permanent magnet assembly. Proposed scanner utilizes the radial magnetic field rather than using the magnetic field oriented 45 ° to the horizontal and vertical scan axes to achieve a biaxial magnetic actuation[ 1,2]. Forced actuation of the gimbal and resonant actuation of the micromirror provide slow vertical scan and fast horizontal scan respectively. A dual-axis scanner with maximum scan angle of 16.1 °, mirror size of 1.5 mm in diameter, and resonant frequency of 19.7kHz is reported.

Performance of a raster scanning laser display system using diamond shaped frame supported micromirror

We describe the design, fabrication, and experimental results of a raster scanning laser display system using micromachined electrostatic scanning micromirror. The micromirror is comprised of a diaphragm mirror plate supported by an array of diamond shaped support frame, and movable comb electrodes. A prototype raster scanning laser display system using the fabricated micromirror, having optical scan angle of 16.9deg at resonance frequency of 19.55 kHz, as the horizontal scanner was developed and tested. To compensate for the nonlinear characteristics of the scanner, a simple image correction method was developed, and the projected image was analyzed and compared with the simulation results

Diamond shaped frame supported electrostatic scanning micromirror

The paper presents the design, fabrication and measurement of an electrostatic scanning micromirror having a diaphragm mirror plate supported by an array of diamond shaped frame structures. Instead of supporting the diaphragm mirror of a different material with a stiff rim structure at the circumference, the diaphragm mirror plate and the frame structure are fabricated monolithically in the same layer of single-crystal-silicon (Nee, J.T. et al., Proc. IEEE Int. Conf. MEMS, p.704-9, 2000). The scanning micromirror with a 10 /spl mu/m-thick diaphragm mirror plate, having a planar dimension of 1.5/spl times/1.5 mm/sup 2/, supported by an array of 110 /spl mu/m-thick rhombic stiffening frames, was fabricated and tested. A mechanical deflection angle of 8.5/spl deg/ at the resonance frequency of 19.55 kHz and 44% reduction of dynamic deformation (Conant, R.A. et al., Proc. IEEE/LEOS Int. Conf. Optical MEMS, p.49-50, 2000), in comparison to the conventional rectangular parallelepiped micromirror, were obtained.