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Light Instability of QC Lasers. Yuting Huang , 1 Yu Yao, 1 Kais Al- Naimee , 1,2 and Claire Gmachl 1 1 – Department of Electrical Engineering and MIRTHE, Princeton University, Princeton, NJ 08544 USA, and NSF-ERC, USA
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Light Instability of QC Lasers Yuting Huang,1 Yu Yao,1Kais Al-Naimee, 1,2 and Claire Gmachl1 1 – Department of Electrical Engineering and MIRTHE, Princeton University, Princeton, NJ 08544 USA, and NSF-ERC, USA 2 – Permanent address : National Institute of Applied Optics, Phys. Dep., University of Florence, Florence, Italy
Why Investigate Light Instability? • Power Instability has long been a known problem in traditional lasers but not in high profile QC lasers. 1 • Finding potential quasi-period behaviors of light instability can help make much more powerful lasers by stabilizing them on the higher power state. Fig 1. Zooming in on 7 sequential • light pulses out of 5000 pulses in P2 Laser3. . 1. K.J. Franz, J.J.J. Raftery, P.Q. Liu, A.J. Hoffman, M.D. Escarra, S.S. Howard, Y. Dikmelik, J.B. Khurgin, X. Wang, J.-Y. Fan, C. Gmachl "Negative Differential Resistance and Pulse Instabilities in Minimalized Quantum CascadeLaser Structures," Conference on Lasers and Electro-Optics (CLEO), Baltimore, MD,June 2009.. Fig 2 shows around 100 light pulses at I = 0.7 A, the current for stable light output. Fig 3 shows around 160 light pulses at I = 2.4 A, the current for extremely unstable light output.
Program and Setup • (The figure above) Easy-to-use Matlab interface monitors up to 5,000 sequential pulses • plots light output instability in the gate regions. • In the right figure a laser holder is shown. The laser is opposite to a light detector, a voltage generator, an oscilloscope and the computer.
Light Instability in Gated Regions • We choose the region of instability on each pulse as the gate region. • (In the above figure) Gate region is between the red lines. • (In the right figure) Data calculated by averaging the light power output in the gate region on each pulse may reveal the light instability pattern hidden in QC laser. • Conclusion We succeeded in developing a real time, pulse by pulse measurement system that allows monitoring laser dynamics and chaos.