Workshop on Coherent Phenomena in Disordered Optical Systems May Random Laser - Physics & Application

Transcription

1 Workshop on Coherent Phenomena in Disordered Optical Systems May 2014 Random Laser - Physics & Application Hui CAO Depts. of Applied Physics and Physics Yale University New Haven. U.S.A

2 Random Laser - Physics & Application HuiCao Depts. of Applied Physics & Physics, Yale University Group members Jonathan Andreasen Bo Liu Heeso Noh Brandon Redding Xiaohua Wu Junying Xu Alexey Yamilov Jin-Kyu Yang Yong Ling Northwestern Univ. Robert P. H. Chang Eric Seelig Xiang Liu Yale Univ. Michael Choma Doug Stone Michael Rooks

3 Laser Essential components for a laser Gain medium Light amplification Cavity Coherent feedback Mirror Gain medium Mirror R 1 R 2 Threshold Resonance 2gL g R1 R2 e 1 2 L 2 m k c

4 Laser with Scattering Reflector Scattering medium Ruby crystals Mirror Nicolay Basov Non-Resonant Feedback Lasing Threshold 2gL 1 2e g R R 1 Ambartsumyan, Basov, Kryukov, and Letokhov, IEEE J. Quantum Electron (1966) Vladilen Letokhov

5 Photonic Bomb Instability for Amplification of Spontaneous Emission (ASE) Average path length of photon exceeds amplification length Photon multiplication Letokhov, Sov. Phys. JETP 26, 1109 (1968)

6 Laser Paint Dye molecules and scattering particles Dramatic narrowing of emission spectra Lawandy, Balachandran, Gomes & Sauvain, Nature 368, 436 (1994)

7 Light Diffusion, Absorption, Emission, and Amplification Pump light and probe light in 4-level atomic media Wiersma & Lagendijk, Phys. Rev. E 54, 4256 (1997)

8 Discrete Lasing Peaks ZnO powder DDO-PPV film HC et al, Phys. Rev. Lett. 82, 2278 (1999) Frolov et al, Phys. Rev. B 59, 5284 (1999)

9 Electromagnetic Mode Maxwell s equations ), ( 1 ), ( 0 t r E t t r H ), ( ) ( 1 ), ( 2 0 t r H r n t t r E t ) ( Complex refractive index i n r in n Boundary condition: only outgoing waves HC et al, Phys. Rev. E, 61, 1985 (2000) Jiang & Soukoulis, Phys. Rev. Lett. 85, 70 (2000)

10 Localized Modes Mode Pattern Spectrum Vanneste & Sebbah, Phys. Rev. Lett. 87, (2001)

11 ZnO Powder Average particle diameter ~ 100 nm C E C E (x) ( x) E * ( x') E( x x') dx' Exponential decay length hd = m x (m) HC et al, Phys. Rev. E 66, R25601 (2002)

12 Porous GaP k l t 6 van der Molen et al, Phys. Rev. Lett. 98, (2007)

13 Weak Scattering System Dye solution with scattering particles k l t 1 Amplification of spatially extended modes in random laser Mujumdar et al, Phys. Rev. Lett. 93, (2004)

14 Overlapping Resonances Thouless number N T 1 Excitation spectrum of a passive system Resonances are strongly overlapped spatially and Spectra al Intensity (a.u u.) spectrally Wavelength (nm)

15 Coherent Lasing Mode Lasing spectrum Lasing Mode Pattern Max ensity (a.u.) Spectral Int Wavelength (nm) Laser Field Amplitude Min Vanneste, Sebbah & HC, Phys. Rev. Lett. 98, (2007).

16 Non-Uniform Gain and Absorption Absorption outside gain region effectively reduces the size of random structure by suppressing feedback from the unpumped region, and creates localized lasing modes. Yamilov et al., Opt. Lett. 30, 2430 (2005) Andreasen & HC, Opt. Lett (2009)

17 Directional Laser Emission Local pumping of weakly scattering samples Cone shaped pump volume Angular distribution of output t intensity it Integra ted Emission Inten nsity (a. u.) Laser emission 100 m 0 Spontaneous emission Detection Angle (degree) Wu & HC, Phys. Rev. A 74, (2006)

18 Mode Interaction Mode competition for gain Gain saturation, spatial hole burning Localized modes, spatially non-overlapping, weak interaction Extended modes spatial overlapping Extended modes, spatial overlapping, strong interaction

19 Composite Lasing Modes

20 Nonlinear Dynamics Conti et al, Phys. Rev. Lett. 96, (2006); Leonetti, Conti & Lopez, Nat. Photon. 5, 615 (2011)

21 Question What is the statistical properties of random lasing modes?

22 Single-Shot Emission Spectra Dye solution with scattering particles Dye solution without scattering particles

23 Peak Spacing Statistics Dye solution with scattering particles Dye solution without scattering particles Wu & HC, Opt. Lett. 32, 3089(2007)

24 Peak Height Statistics Dye solution with scattering particles Dye solution without scattering particles I I P I I I I = -2.7, P I I e = Wu & HC, Phys. Rev. A 77, (2008)

25 Question How coherent is random laser emission?

26 Temporal Coherence z Temporal coherence length is determined by spectral bandwidth of laser emission 2 2ln2 z ct c Noginov et al, Opt. Mater. 12, 127 (1999); Papadakis et al, J. Opt. Soc. Am. B 24, 31 (2010)

27 Young s double slit experiment Spatial Coherence

28 Tailoring Spatial Coherence by Varying Pump Region MFP=500 m d=215 m = m Wavelength (nm) MFP=500 m d=290 m = m Wavelength (nm) MFP=500 m d=390 m = m Wavelength (nm)

29 Tailoring Spatial Coherence by Changing g Scattering Strength Weaker scattering MFP=500 m d=215 m = m Wavelength (nm) Stronger scattering MFP=50 m d=215 m = m Wavelength (nm) B. Redding, M. Choma, & HC, Opt. Lett. 36, 3404 (2011).

30 Second-Order Coherence Emission intensity or photon number fluctuations G 2 I 2 2 I I Single-mode coherent light: G 2 1 Single-mode chaotic light: G 2 2

31 Emission Intensity Statistics of Nonresonant Feedback Laser Fluctuation of total emission intensity is suppressed dby gain saturation. ti Intensity fluctuation of individual mode remains large due to mode interaction. G 2 2 Ambartsumyan et al. Sov. Phys. JETP 26, 1109 (1968)

32 Photon Statistics of Random Laser with Resonant Feedback ngth (nm) Wavele G Time (ps) P/P th HC et al, Phys. Rev. Lett. 86, 4524 (2001)

33 Nonlinear Effect in Random Laser Strong third-order nonlinearity n n 0 n 2 I Liu et al, Phys. Rev. Lett. 91, (2003); Appl. Phys. Lett. 83,1092 (2003).

34 Partially-Ordered Random Laser? 2.0 Optimal degree of disorder Strongest light confinement Yamilov & HC, Phys. Rev. A, 69, (2004) Mode (ps) me of Lasing Lifeti Degree of disorder

35 Short-Range Order GaAs membrane Spatial Fourier spectra Localized mode Coupled mode Noh et al., Phys. Rev. Lett. 106, (2011)

36 Deterministic Aperiodic Structure The Rudin-Shapiro structure creates localized modes with well-defined frequencies and positions Yang et al., Appl. Phys. Lett. 97, (2010)

37 Light Transport in Amplifying Random Media In a diffusive system below lasing threshold Effect of coherent amplification on transport: Enhances long-range correlation Increases fluctuation of transmission & reflection Pushes a diffusive system towards localization Yamilov, HC et al, Phys. Rev. E 70, (2004); Phys. Rev. B 71, (2005); Phys. Rev. E 74, (2006); Physica B 405, 3012 (2010).

38 Amplification Enhances Interference Effect Returning field E = E 1 + E 2 + L 1 In the absence of gain L 1 < L 2 E 1 > E 2 L 2 Weak interference In the presence of gain Longer path, more amplification E 1 ~ E 2 Stronger interference

39 Light Localization Induced by Random Imaginary Permittivity Basiri, Bromberg, Yamilov, Cao, Kottos, arxiv

40 Physics Random lasers are complex, open, nonlinear chaotic systems. Mesoscopic transport, laser physics, nonlinear optics, quantum optics, statistical physics, quantum chaos, nonlinear dynamics, atomic physics

41 Application Microlaser X-ray laser, -ray laser Galaxy maser, stellar laser Optics & Photonics News, 16, 24 (2005)

42 Speckle-free Laser Imaging Lens AF S Iris IP Source Obj Obj CCD Random Laser He:Ne Laser Redding, Choma & HC, Nature Photonics 6, 355 (2012)

43 Spatial cross talk Object Coherent e illumination I E 2 2 E 1 2 E E1 E2 2 E1 E2 cos( ) 2 2 Incoherent illumination Camera Camera Camera I I 1 I 2

44 On-chip Electrically-Pumped Semiconductor Random laser Development of a New Light Source for Massive Parallel Confocal Microscopy and Optical Coherence Tomography

45

46 Ideal Illumination Source Random Lasers Lasers acy/ nce Degener al Radian Photon D Spectra High Low Thermal white light Light emitting diodes Superluminescent Diodes Pinhole filtered white light Low High Spatial Coherence