External laser intensity modulation based on a MEMS micro-mirror for photo-acoustic gas sensing

Li Li, George Stewart, Graham Thursby, Norhana Arsad, Deepak Uttamchandani, Brian Culshaw, Yiding Wang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

An external laser intensity modulation system based on a micro-electromechanical systems (MEMS) mirror is presented in this paper, for application to gas sensing. The micro mirror is driven by the electrothermal actuator. The rotation direction is decided by the relative position between the driving actuator and the axis of micro-mirror. In contrast to the traditional technique of current modulation of tunable diode lasers where wavelength modulation (WM) is combined with intensity modulation (IM), the IM can be separated from WM and wavelength tuning through the external modulation furnished by the mirror reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror with 2mm diameter. The mirror is attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. There are four electrothermal actuators orthogonal to each other that are connected to the circular mirror. Double-loop serpentine springs are used to attach the four actuators to the micro mirror. Each three-beam actuator is attached to a spring at one end that connects the actuator to the mirror and fixed to the substrate at the other end. The actuators are of two different types regarding length: 1.8 mm from hereon called the long actuator and 1.35 mm called the short actuator. Characterizing the frequency response and measuring the modulation performance of the MEMS mirror is presented in this work. Intensity modulation depth from very low values to about 100 percent can be achieved through adjusting the MEMS mirror's reflection position and driving voltage. The intensity-modulated laser source is used for photoacoustic gas sensing in order to recover the target gas absorption line profile based on tunable diode laser spectroscopy. The target gas is 1 percent acetylene balanced by nitrogen and the target absorption line is P17 of acetylene at 1535.39nm. Good agreement between experimental results and theoretical simulations is obtained.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
Volume7657
DOIs
Publication statusPublished - 2010
Externally publishedYes
Event5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems - Dalian
Duration: 26 Apr 201029 Apr 2010

Other

Other5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems
CityDalian
Period26/4/1029/4/10

Fingerprint

Micromirror
Micro-electro-mechanical Systems
microelectromechanical systems
MEMS
Actuator
Mirrors
Modulation
Sensing
Gases
Acoustics
Mirror
mirrors
Laser
Actuators
modulation
actuators
acoustics
Lasers
gases
lasers

Keywords

  • Electrothermal actuator
  • External laser intensity modulation
  • Micro-electromechanical systems
  • Micro-mirror

ASJC Scopus subject areas

  • Applied Mathematics
  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Li, L., Stewart, G., Thursby, G., Arsad, N., Uttamchandani, D., Culshaw, B., & Wang, Y. (2010). External laser intensity modulation based on a MEMS micro-mirror for photo-acoustic gas sensing. In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 7657). [76570M] https://doi.org/10.1117/12.864033

External laser intensity modulation based on a MEMS micro-mirror for photo-acoustic gas sensing. / Li, Li; Stewart, George; Thursby, Graham; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding.

Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7657 2010. 76570M.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Li, L, Stewart, G, Thursby, G, Arsad, N, Uttamchandani, D, Culshaw, B & Wang, Y 2010, External laser intensity modulation based on a MEMS micro-mirror for photo-acoustic gas sensing. in Proceedings of SPIE - The International Society for Optical Engineering. vol. 7657, 76570M, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, Dalian, 26/4/10. https://doi.org/10.1117/12.864033
Li L, Stewart G, Thursby G, Arsad N, Uttamchandani D, Culshaw B et al. External laser intensity modulation based on a MEMS micro-mirror for photo-acoustic gas sensing. In Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7657. 2010. 76570M https://doi.org/10.1117/12.864033
Li, Li ; Stewart, George ; Thursby, Graham ; Arsad, Norhana ; Uttamchandani, Deepak ; Culshaw, Brian ; Wang, Yiding. / External laser intensity modulation based on a MEMS micro-mirror for photo-acoustic gas sensing. Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7657 2010.
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abstract = "An external laser intensity modulation system based on a micro-electromechanical systems (MEMS) mirror is presented in this paper, for application to gas sensing. The micro mirror is driven by the electrothermal actuator. The rotation direction is decided by the relative position between the driving actuator and the axis of micro-mirror. In contrast to the traditional technique of current modulation of tunable diode lasers where wavelength modulation (WM) is combined with intensity modulation (IM), the IM can be separated from WM and wavelength tuning through the external modulation furnished by the mirror reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror with 2mm diameter. The mirror is attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. There are four electrothermal actuators orthogonal to each other that are connected to the circular mirror. Double-loop serpentine springs are used to attach the four actuators to the micro mirror. Each three-beam actuator is attached to a spring at one end that connects the actuator to the mirror and fixed to the substrate at the other end. The actuators are of two different types regarding length: 1.8 mm from hereon called the long actuator and 1.35 mm called the short actuator. Characterizing the frequency response and measuring the modulation performance of the MEMS mirror is presented in this work. Intensity modulation depth from very low values to about 100 percent can be achieved through adjusting the MEMS mirror's reflection position and driving voltage. The intensity-modulated laser source is used for photoacoustic gas sensing in order to recover the target gas absorption line profile based on tunable diode laser spectroscopy. The target gas is 1 percent acetylene balanced by nitrogen and the target absorption line is P17 of acetylene at 1535.39nm. Good agreement between experimental results and theoretical simulations is obtained.",
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