Research | Optical MEMS & Infrared MEMS for Consumer Applications and Environment Monitoring

a. MEMS-based mid-IR emitter, filter and detector

To ensure a safe working environment, non-dispersive mid-IR gas-sensing system is often used in the measurement of the concentrations of hazardous or combustible gases. The essential component of a NDIR gas-sensing system includes a mid-IR radiation source, a waveguide, and an IR detector. MEMS will be the core technology to realize such a handheld system.

Selected Publications:
  1. Yu-Sheng Lin, Chong Pei Ho, Kah How Koh and Chengkuo Lee, Fabry-Perot filter using grating structures, Optics Lett., vol. 38, no. 6, pp. 902-904, 2013. [PDF] [DOI]

 

b. Piezoelectric driven 2-D MEMS scanners

In the optical MEMS regime, microstructures including mirrors, lenses and gratings are driven to move or deform by actuators so that unique functions such as beam steering can be achieved. In recent years, MEMS scanners have created growing interest, fuelled in part by the emergence of handheld pico projectors, which have intriguing applications in consumable electronics, IT and the amusement industries.

In our first research attempt on MEMS scanners, we have demonstrated a silicon micromirror driven by 1x10 piezoelectric Pb(Zr,Ti)O3 beam actuators. The ten PZT actuators are electrically connected in series and 2-D scanning patterns can be obtained by biasing actuators 1-5 and 6-10 at a resonant frequency corresponding to bending and torsional modes respectively. In our subsequent effort, we separated the electrical connections to the ten piezoelectric actuators so as to allow for individual biasing of the actuators. Similar to the first design, this mew design can operate in three modes: bending, torsional and mixed. A 2-D raster scanning pattern was achieved in mixed mode when the bending and torsional modes are superimposed together. To further increase the rotation angle and reduce the driving voltage of our previous design, development work on another piezoelectric driven 2-D MEMS scanner using a single meandering S-shaped PZT actuator is explored.

Selected Publications:
  1. Kah How Koh, Takeshi Kobayashi and Chengkuo Lee, A 2-D MEMS scanning mirror based on dynamic mixed mode excitation of a piezoelectric PZT thin film S-shaped actuator, Optics Express, vol. 19, no. 15, pp. 13812-13824, 2011. [PDF] [DOI]
  2. Kah How Koh, Takeshi Kobayashi, Jin Xie, Aibin Yu and Chengkuo Lee, Novel piezoelectric actuation mechanism for a gimbal-less mirror in 2D raster scanning applications, J. Micromech. Microeng., vol. 21, no. 7, 075001, 2011. [PDF] [DOI]
  3. Kah How Koh, Takeshi Kobayashi, Fu-Li Hsiao and Chengkuo Lee, Characterization of piezoelectric PZT beam actuators for driving 2D scanning micromirrors, Sens. Actuators A: Phys., vol. 162, pp. 336-347, 2010. [PDF] [DOI]

Special Mention:
  1. Our team member cum Ph.D. student, Mr Koh Kah How received an award: Best Student Paper Award of Section 5: Optical passive devices and modules during the 16th Opto-Electronics and Communication Conference (OECC) 2011. His submitted article is "Development of actuation mechanisms for MEMS mirror using PZT thin film cantilever actuators." [LINK]

 

c. Hybrid driven (Electrothermal & Electromagnetic) 2-D MEMS scanner

A novel CMOS compatible 2-D MEMS scanner based on hybrid actuation mechanisms is proposed. Both electrothermal and electromagnetic actuations have been integrated in the same device for slow and fast scanning purposes respectively. This is different from prior MEMS scanner designs where the two orthogonal scanning axes are driven by the same actuation method. Furthermore, its CMOS compatible fabrication process allows for easy monolithic integration of integrated electronics to control the actuation. The low operating voltage makes the proposed MEMS scanner potentially suitable for mobile pico projector applications powered by batteries with limited capacity.

Selected Publications:
  1. Kah How Koh and Chengkuo Lee, A two-dimensional MEMS scanning mirror using hybrid actuation mechanisms with low operation voltage, IEEE/ASME J. Microelectromech. Syst., vol. 21, no. 5, pp. 1124-1135, 2012. [PDF] [DOI]

Special Mention:
  1. Mr. Koh received another award: 1st Prize for IEEE Region 10 Postgraduate Paper Contest 2012. His winning paper, entitled "A low voltage driven 2-D MEMS scanning mirror using hybrid actuation mechanisms" presented a new form of actuation mecahnism to drive a MEMS mirror for two-dimensional scanning display applications. [LINK]

 

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