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Wavelength Tuning of a 2 µm Tm-Ho fiber laser based CO 2 Sensor

Wavelength Tuning of a 2 µm Tm-Ho fiber laser based CO 2 Sensor. Marjorie Dallmann , Renjie Zhou, and Prof. Lynford Goddard Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign. Theory. Goals.

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Wavelength Tuning of a 2 µm Tm-Ho fiber laser based CO 2 Sensor

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  1. Wavelength Tuning of a 2 µm Tm-Hofiber laser based CO2 Sensor Marjorie Dallmann, Renjie Zhou, and Prof. Lynford Goddard Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign Theory Goals • Design and build a stretch tuning fiber Bragg grating (FBG) circuit • Tune the output wavelength of a 2 µm Tm-Hofiber laser by stretching the FBG • Use wavelength modulation absorption spectroscopy (WMAS) to measure CO2 concentration for monitoring spoilage of stored grain • FBG – a reflector inside an optical fiber that selectively reflects one wavelength and transmits all others • The highest absorption peak for CO2 with low-cost fiber is around 2.005 µm, the 2 µm fiber laser must be tuned to ~1 nm around this peak for WMAS • By stretching the FBG, the fiber laser output wavelength can be changed to allow for WMAS and CO2 concentration measurement 12V power source Arduino Uno Fiber Bragg Grating 90o Rotation FBG Stretching Set-Up Experimental Results Stepper Motor 1.5 µm FBG tuning Both motors are fixed on a stationary base Stepper Motor Driver Arduino Control Code Main Body Rotation function void rotateDeg(float deg, float vel){ int dir = (deg > 0)? HIGH:LOW; digitalWrite(dirpin, dir); int steps = abs(deg)*(1/0.225); float usDelay = (1/vel) * 70; for(int i=0; i < steps; i++){ digitalWrite(steppin, HIGH); delayMicroseconds(usDelay); digitalWrite(steppin, LOW); delayMicroseconds(usDelay);} } Transmission spectrum after tuning int dirpin = 2; int steppin = 3; void rotateDeg(float deg, float vel); void setup() { pinMode(dirpin, OUTPUT); pinMode(steppin, OUTPUT); rotateDeg(90, 1); } void loop() {} Original transmission spectrum Future Work • Perform wavelength modulation with 2 µm FBG and test setup • Begin to test the device for CO2 concentration measurement References • Arduino Function Code: http://bildr.org/2011/06/easydriver/ • Stepper Motor, Arduino, and Easy Driver Picture: http://bildr.org/blog/wp-content/uploads/2011/05/EasyDriver-Stepper-Motor-Driver2.png • R. Zhou et al, CO2 sensing with a 2005 nm thulium holmium co-doped fiber laser, Optical Sensors, OSA Technical Digest, paper STh2B.4, 2012.

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