Co-existence of strongly and weakly localized random laser modes

Recent theoretical work on random lasing predicts that the occurrence of narrow lasing spikes can be caused by both localized and extended modes of light1,2,3. Typical random lasing spikes have been observed in powders of zinc oxide nanoparticles4, but identifying the possible degrees of localization of such modes has until now been an open issue5. In this Letter we present an experimental procedure that directly extracts the area of localization of the modes. This method relies on the investigation of micro-structured fields of zinc oxide powder, which also allows direct correlation to the local structural properties of the ensemble of subwavelength particles by scanning electron microscopy. We find that lasing from both localized and extended modes can be observed simultaneously. Our observation also corroborates the prediction that localized modes have a lower loss rate than that of extended modes5. Whether the electromagnetic fields in random lasers are localized or extended is a topic of ongoing debate. Now, the localization of modes in micro-structured ZnO powder is experimentally determined and lasing from both kinds of modes (localized and extended) shown to exist simultaneously.

[1]  Patrick Sebbah,et al.  Selective Excitation of Localized Modes in Active Random Media , 2001 .

[2]  John,et al.  Strong localization of photons in certain disordered dielectric superlattices. , 1987, Physical review letters.

[3]  B Shapiro,et al.  Random resonators and prelocalized modes in disordered dielectric films. , 2002, Physical review letters.

[4]  Diederik S. Wiersma,et al.  The physics and applications of random lasers , 2008 .

[5]  Roberto Righini,et al.  Localization of light in a disordered medium , 1997, Nature.

[6]  Ad Lagendijk,et al.  Spatial extent of random laser modes. , 2007, Physical review letters.

[7]  Renato Torre,et al.  Amplified extended modes in random lasers. , 2004, Physical review letters.

[8]  S. Adachi,et al.  Optical constants of ZnO , 1997 .

[9]  C. Klingshirn,et al.  ZnO: From basics towards applications , 2007 .

[10]  Demetrios Anglos,et al.  Random laser action in organic–inorganic nanocomposites , 2004 .

[11]  Hui Cao,et al.  Lasing with resonant feedback in weakly scattering random systems. , 2007 .

[12]  Robert P. H. Chang,et al.  Random laser action in semiconductor powder , 1999 .

[13]  C. Klingshirn,et al.  Absolute external luminescence quantum efficiency of zinc oxide , 2008 .

[14]  P. Anderson.  Absence of Diffusion in Certain Random Lattices , 1958 .

[15]  Robert P. H. Chang,et al.  Random lasing in closely packed resonant scatterers , 2004 .

[16]  C. Briskina,et al.  Characteristic properties of ZnO random laser pumped by nanosecond pulses , 2006 .

[17]  Stefan Rotter,et al.  Strong Interactions in Multimode Random Lasers , 2008, Science.

[18]  C. Klingshirn,et al.  Surface-state related luminescence in ZnO nanocrystals , 2007 .

[19]  G. Maret,et al.  Observation of Anderson localization of light in three dimensions. , 2007, Journal of the Optical Society of America. A, Optics, image science, and vision.

[20]  K. Thonke,et al.  Lasing dynamics in single ZnO nanorods. , 2008, Optics express.

[21]  Roman J. B. Dietz,et al.  Random lasing in ZnO nanocrystals , 2009 .

[22]  S. John.  Electromagnetic absorption in a disordered medium near a photon mobility edge , 1984 .

[23]  Hui Cao,et al.  Lasing in random media , 2003 .

[24]  R. Dietz,et al.  Lasing in single ZnO nanorods after fs‐ and ns‐pulsed excitation , 2009 .