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Zinc Oxide Random Laser Threshold Enhancement via Addition of Passive Scatterers
Student Research Symposium
  • Zachariah M. Peterson, Portland State University
  • Rolf Könenkamp, Portland State University
  • Robert Campbell Word, Portland State University
Start Date
7-5-2014 11:00 AM
End Date
7-5-2014 1:00 PM
  • Zinc oxide -- Electric properties,
  • Zinc oxide thin films,
  • Optoelectronic devices -- Materials -- Mathematical models,
  • Lasers,
  • Photonics -- Mathematical models,
  • Semiconductor lasers

Zinc oxide (ZnO) is a wide bandgap n-type semiconductor with a variety of optical and electrical applications and many methods of fabrication. Strong optical scattering and photoluminescence from ZnO nanoparticles and films makes the material an ideal candidate for a random laser. Previous studies have shown both incoherent and coherent random lasing from ZnO films and particles agglomerations. When used as a passive scatterer in a laser dye gain medium, the addition of ZnO has been shown to improve the threshold for lasing. By combining active scattering ZnO with a passive scatterer, MgO, we show here that the lasing threshold is reduced. We also demonstrate strong optical feedback in laser pumped ZnO nanoparticle films. Photoluminescence (PL) results show a clear amplification threshold and the resulting non-linear behavior. We find that shortening the pump pulse time by a factor 6 causes a feedback mechanism transition from Amplified Spontaneous Emission (ASE) to Non-resonant feedback (NRF). The pulse time is still longer than the excitonic lifetime (~200 ps), however the randomness from spontaneous emission is greatly reduced. NRF in our samples can be characterized by a dramatic narrowing of the photoluminescence peak around 387 nm to FWHM of ~3 nm, as well as a high degree of reproducibility in the emitted spectra. A new statistical model for the generation of random laser modes was formulated and it reproduces the experimental results. Further work will focus on studying the transition from non-resonant to resonant feedback in the nanoparticle films.

Persistent Identifier
Citation Information
Zachariah M. Peterson, Rolf Könenkamp and Robert Campbell Word. "Zinc Oxide Random Laser Threshold Enhancement via Addition of Passive Scatterers" (2014)
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