Dooyoung Hah

A low voltage actuated micromachined microwave switch using torsion springs and leverage

In this paper, a push-pull type microwave switch is proposed, which utilizes torsion springs and leverage for low-voltage operation. The switching operation up to 4 GHz is demonstrated. The actuation voltage is /spl sim/5 V. The insertion loss of /spl sim/1 dB and the isolation as high as /spl sim/40 dB at 1 GHz are achieved by the push-pull operation.

A scanning micromirror with angular comb drive actuation

Describes a single crystal silicon, 1/spl times/1 mm/sup 2/, scanning micromirror, which incorporates a novel angular vertical comb drive actuator. Results from our model for the angular vertical comb show that a 50% higher scan angle can be achieved when compared to a staggered vertical comb of equivalent dimensions. The simplified, cost effective, silicon on insulator micro-electromechanical systems, (SOI MEMS), process features self-alignment of the fixed and moving teeth and is fabricated on a single SOI wafer. Static deflection for our fabricated device fits well with the model and a resonant mode optical scan angle of /spl plusmn/18/spl deg/ at 1.4 kHz has been measured.

Theory and experiments of angular vertical comb-drive actuators for scanning micromirrors

We report on the theory and experiments of scanning micromirrors with angular vertical comb-drive (AVC) actuators. Parametric analyses of rotational vertical comb-drive actuators using a hybrid model that combines two-dimensional finite-element solutions with analytic formulations are described. The model is applied to both AVC and staggered vertical comb-drive (SVC) actuators. Detailed design tradeoffs and conditions for pull-in-free operations are discussed. Our simulation results show that the fringe fields play an important role in the estimation of maximum continuous rotation angles, particularly for combs with thin fingers, and that the maximum scan angle of the AVC is up to 60% larger than that of the SVC. Experimentally, a large dc continuous scan angle of 28.8/spl deg/ (optical) has been achieved with a moderate voltage (65 V) for a 1-mm-diameter scanning micromirror with AVC actuators. Excellent agreement between the experimental data and the theoretical simulations has been obtained.

Surface- and bulk- micromachined two-dimensional scanner driven by angular vertical comb actuators

In this paper, we present the design, fabrication, and measurements of a two-dimensional (2-D) optical scanner with electrostatic angular vertical comb (AVC) actuators. The scanner is realized by combining a foundry-based surface-micromachining process (Multi-User MEMS Processes-MUMPs) with a three-mask deep-reactive ion-etching (DRIE) postfabrication process. The surface-micromachining provides versatile mechanical design and electrical interconnect while the bulk micromachining offers high-aspect ratio structures leading to flat mirrors and high-force, large-displacement actuators. The scanner achieves dc mechanical scanning ranges of /spl plusmn/6.2/spl deg/ (at 55 Vdc) and /spl plusmn/4.1/spl deg/ (at 50 Vdc) for the inner and outer gimbals, respectively. The resonant frequencies are 315 and 144 Hz for the inner and the outer axes, respectively. The 1-mm-diameter mirror has a radius of curvature of over 50 cm. [1454].

Angular vertical comb-driven tunable capacitor with high-tuning capabilities

This paper reports on a novel tunable capacitor with electrostatic angular vertical comb-drive (AVC) actuators. The AVC tunable capacitor creates a large offset in comb fingers through a small rotation angle-an advantage not found in conventional lateral comb-drive devices. High capacitance and large continuous tuning ratio is achieved in a compact device area. The largest tuning varactor demonstrates capacitance values between 0.27-8.6 pF-a tuning ratio of more than 31:1, the highest ever reported. The maximum quality factor Q is 273 at 1 GHz near the minimum capacitance value.

Open-loop operation of MEMS-based 1/spl times/N wavelength-selective switch with long-term stability and repeatability

We report on a microelectromechanical-systems (MEMS)-based 1/spl times/N wavelength-selective switch (WSS) with excellent open-loop stability and repeatability. The optical power fluctuation of the WSS is </spl plusmn/0.0035 dB over a 3.5-h period. The variation of optical power during 30 ON-OFF switching periods is </spl plusmn/0.0026 dB. Experiments were also performed on the analog MEMS mirror. The stability and repeatability are /spl plusmn/0.00085/spl deg/ and /spl plusmn/0.0013/spl deg/, respectively.

A self-aligned vertical comb-drive actuator on an SOI wafer for a 2D scanning micromirror

A self-aligned vertical comb-drive actuator for a two-axis tilt scanning micromirror is presented. Self-alignment between moving and fixed fingers is essential in order to avoid lateral instability leading to an in-plane rotational pull-in during an actuation. Multilayered masking films have been utilized to fabricate the self-aligned comb fingers. To generate high electrostatic torque, high-aspect ratio comb-drive actuators with 40 µm thick fingers have been realized on a silicon-on-insulator (SOI) wafer utilizing deep reactive ion etching (DRIE) technology. A delay-mask process (DMP) was employed in an etching step of a silicon device layer to assist etching of a buried oxide (BOX) layer at the bottom of narrow (5 µm) and deep (40 µm) silicon trenches. The DC mechanical scan angles of the actuators employed in the two-axis tilt, gimbal-configured micromirror were measured as ±2.1° at 48 V around an inner axis and ±1.8° at 44 V around an outer axis, respectively. The fabricated micromirror with a mirror area of 1 mm × 1 mm has mechanical resonant frequencies of 1.2 kHz around the inner axis (a mirror only) and 0.9 kHz around the outer axis (a frame and the mirror), respectively.

1/spl times/N/sup 2/ wavelength-selective switch with two cross-scanning one-axis analog micromirror arrays in a 4-f optical system

A new high-port-count wavelength-selective switch (WSS) has been realized using two cross-scanning one-axis analog micromirror arrays in a 4-f optical system. The number of output ports is increased from N to N/sup 2/, where N is the maximum linear port count limited by optical diffraction. Using surface-micromachined micromirrors with hidden vertical comb drives, large scan angles (>/spl plusmn/5/spl deg/ mechanical), low drive voltages (7 V), and high fill factors (> 96.25%) are achieved for both scanning mirrors. Experimental results for WSS are demonstrated using both two-dimensional (2-D) array of discrete collimators and monolithic 2-D collimator array. A fiber-to-fiber insertion loss ranging from 6 to 18 dB and a switching time of <700 /spl mu/s have been achieved.

Open-loop operation of MEMS WDM routers with analog micromirror array

We report on the optical performance for a reconfigurable WDM router implemented by a low-voltage analog micromirror array. The system exhibits an optical insertion loss of 5 dB and a flat-top spectral response. Both the device and the system exhibit excellent repeatability (<0.12%) and stability (<0.16%) for open-loop operation.

MEMS-actuated photonic crystal switches

A compact guided-wave optical switch is realized by integrating one-dimensional photonic crystals with microelectromechanical systems (MEMS) actuators. The ON-OFF switching is achieved by physically moving a photonic crystal defect. Experimental results show an extinction ratio of 11 dB at 1.56-/spl mu/m wavelength and a 0.5-ms time constant of the step response.