Professor Ortwin Hess

Professor Hess's research interests and his group's activities are in theoretical condensed matter quantum photonics and are currently focused on active (photonic, electronic and magnetic) metamaterials, quantum nano-photonics and spatio-temporal dynamics of (plasmonic and semiconductor) nanolasers.

Together with his  group he has made pioneering contributions to the theory of slow light in metamaterials (the ‘Trapped Rainbow’, Nature, 15 Nov 2007 and several subsequent publications in Nature), to (ultrafast) spatio-temporal dynamics and quantum fluctuations of semiconductor, quantum dot and fibre lasers as well as to the quantum theory of temperature on the nano-scale.

Professor Hess's research brings together theoretical condensed matter physics with theoretical quantum optics and embraces a broad range of theoretical approaches and computatioal techniques. In his group, a large variety of advanced computational methods and simulation tools are developed and used on parallel high-performance computing platforms at the College. On the basis of 'computational experiments' the Hess group strives to explore the rich physics of metamaterials, complex nano- and soft photonic systems and novel lasers to harness the quantum nature of electrons and photons on the nano-scale and ultrafast timescales. 

The video of the invited talk Active Nanoplasmonic Metamaterials presented at the HKUST Institute for Advanced Study "New Materials and New Concepts for Controlling Light and Waves" at the Hong Kong University of Science and Technology in Hong Kong (6 October 2012) provides a brief overview of the recent research on metamaterials and nanoplasmonics with quantum gain. 

Coherent Amplification and Noise in Nanoplasmonics and Metamaterials

How to profit from plasmonic "coherent loss" to realise broadband feedback on the nanoscale

Incorporating gain into nanoplasmonic metamaterials has recently emerged as a viable solution to ultra-low-loss operation that may lead to next-generation active metamaterials. Maxwell-Bloch models for active nanoplasmonic metamaterials are able to describe the coherent spatiotemporal and nonlinear gain and plasmon dynamics. In our ACS Nano 6, 2420-2431 (2012) paper we extend the Maxwell-Bloch theory to a Maxwell-Bloch Langevin approach;a spatially resolved model that describes the light field and noise dynamics in gain-enhanced nanoplasmonic structures.

Using a realistic example of a gain-enhanced nanofishnet metamaterial exhibiting a negative refractive index, we demonstrate the transition from loss-compensation to amplification and to nanolasing.

We observe

• ultrafast relaxation oscillations of the bright negative-index mode with frequencies just below the THz regime
• that coherent amplification and lasing are maintained even in the presence of noise and amplified spontaneous emission.

'Negative Absorption' in a Negative-Refractive-Index Metamaterial

Negative refractive index metamaterials offer the possibility of revolutionary applications, such as subwavelength focusing, invisibility cloaking and 'trapped rainbow' stopping of light. At optical frequencies, these innovative materials suffer from high dissipative losses due to the metallic nature of their constituent metamolecules.

Can this obstacle be overcome?

Yes, as demonstrated in our Letter Physical Review Letters 105, 127401 (2010)], via a double trick:

• place the gain medium in an area where the field is maximum
• exite and probe (i.e. use) the metamaterial with ultra-short optical pulses to avoid detrimental noise (amplified spontaneous emission).

The findings are a guide towards lossless and amplifying metamaterials with exciting photonic applications.

Negative Refraction in Sight

Ortwin Hess, Optics: Farewell to Flatland, Nature 455, 299 (2008).

Optical metamaterials are the key to perfect lenses, 'invisibility' cloaks and slow and stored broadband light. A three-dimensional optical metamaterial with a negative refractive index has recently been created [ Valentine, J. et al. Nature 455, 376–379 (2008) ].

The Trapped Rainbow Effect

Kosmas L Tsakmakidis, Alan D Boardman and Ortwin Hess, 'Trapped rainbow' storage of light in metamaterials. Nature 450, 397 (2007)

Here we demonstrate theoretically that an axially varying heterostructure with a metamaterial core of negative refractive index can be used to efficiently and coherently bring light to a complete standstill. In contrast to previous approaches for decelerating and storing light, the present scheme simultaneously allows for high in-coupling efficiencies and broadband, room-temperature operation. Surprisingly, our analysis reveals a critical point at which the effective thickness of the waveguide is reduced to zero, preventing the light wave from propagating further. At this point, the light ray is permanently trapped, its trajectory forming a double light-cone that we call an 'optical clepsydra'. Each frequency component of the wave packet is stopped at a different guide thickness, leading to the spatial separation of its spectrum and the formation of a 'trapped rainbow'. Our results bridge the gap between two important contemporary realms of science—metamaterials and slow light. Combined investigations may lead to applications in optical data processing and storage or the realization of quantum optical memories.

metamaterials

Metamaterials are the key to perfect lenses, 'invisibility' cloaks and slow and stored broadband light and promise novel magnetoelectronic phenomena. We study the unique properties of metamaterials with a negative or negligibly small refractive index, research new ways how they can be realized and explore novel nanoelectronic and nanophotonic phenomena of metamaterials.

• negative index metamaterials
• ultralow and zero loss metamaterials
• magnetic metamaterials
• coupling of lightwaves in metamaterials
• semiconductor metamaterials
• molecular metamaterials
• quantum metamaterials 

nano-photonics and plasmonics

Metal surfaces and interfaces can support surface plasmons - density waves of free electrons. These plasmon waves can interact with photons, opening the way to a novel realm of optics - plasmo nics. When the metal surfaces are nanostructured, the possibility for true nanoscale photonics emerges at optical wavelengths. Using theoretical and advanced computational appro aches that take on board microscopic s patio-temporal properties the group studies the light-matter interaction in nanostructured metals and (molecular/nanoparticle) light scattering in structured polymer films and explores the ultrafast (sub-) femtosecond dynamics.

• optics of metal nano-forests
• functional plasmonics
• active plasmonics
• nano-photonic waveguides
• organic plasmonics
• Mie scattering by nanoparticles in polymers
• nano-structural colour
• quantum plasmonics

spontaneous emission control

Spontaneous emission of photons is one of the fundamental properties of matter. Recently it has been demonstrated that 'photonic crystals' can change the way a photon is emitted by tailoring of its environment. We model the materials properties of ordered and disordered photonic "crystals" and arrays and networks of plasmonic nano-antennas to explore the possiblity of strong control of spontaneous emission.

• control of spontaneous emission in photonic crystals
• nanoplasmonic "hot-spot" enhancement of spontaneous emission
• control of spontaneous emission by light localisation

slow light science

Slowing down light may dramatically increase the interation of photons with matter and lead to unprecedented nonlinearities, dramatically improved sensing or better efficiency of solar cells. The group studies the physics of slow lightwaves in semiconductor quantum dot nanomaterials, metamaterial heterostructures, plasmonic nanomaterials, photonic crystals and fibres and graphene.

• ultra-slow and stopped light in negative index metamaterial heterostructures
• slow and fast light pulses in quantum dot optical amplifiers
• slow light in photonic crystal waveguides
• slow nonlinear optics
• relativistic slow light effects

femto- and attosecond dynamics of materials

The conception and realisation of pulses of light that are as short as femto- or atto seconds has started to open up exciting new possibilities to observe and control the dynamic s of electrons in atoms, nano-structures, biological media and the solid-state. We study the physics of ultrafast femto- and attosecond dynamics of semiconductors, plasmonic nanomaterials and bio-molecular media by a combination of theoretical and advanced computational simulation schemes involving and taking into account the propagation of coherent electromagnetic waves (with wavelengths from the THz to the soft X-ray regimes) and matter (on various levels of sophistication).

• coherent femtosecond dynamics of semiconductors
• attosecond dynamics in nanoplasmonics
• ultrafast bio-molecular media

Physics of advanced lasers and spatio-temporal laser dynamics

The group has pioneered the field of spatio-temporal dynamics and quantum fluctuations of semiconductor lasers and continues to study the physics of advanced lasers, focussing on mirocavity or nano-lasers, new active materials and nonlinear dynamics and exploring novel concepts such as the "thermal laser". We develop new theoretial approchaes for innovative gain materials (such as quantum dots), quantum fluctuations or novel laser concepts (such as the "thermal laser") and laser cavities (such as photonic crystal fibres) that may emit coherent radiation at new wavelengths and optical pulses with durations as short as femto- or attoseconds.

• dynamics of semiconductor lasers
• quantum fluctuations of semiconductor lasers
• quantum dot lasers and amplifiers
• femtosecond dynamics of microcavity lasers
• spectral dynamics of fibre lasers and amplifiers
• the "thermal laser" concept
• random lasers 

materials for 'soft photonics'

The physics of noncrystalised ("soft") materials as well as the realization of novel photonic "crystals" such as polymer opals involve complex spatio-temporal processes all the way from macroscopic scales down to the "flow" of single molecules (such as water) through carbon nanotubes.

The group develops new effective theoretical models (such as a nonlinear Maxwell model) describing the highly nonlinear flow and structural dynamics of anisotropic fluids (such as polymers) and simulates the microscopic (nonequilibrium) molecular dynamics of nano-confined water and formation of polymer opal films from (core-shell) polymer spheres on the basis ofequilibrium and nonequilibrium molecular dynamics computer simulation.

• rheo-chaos in Maxwell model fluids
• 3D elastic turbulence in complex fluids
• molecular transport through carbon nanotubes
• formation of polymer opal films

1. Optical Chirality in Self-Assembled Nanoplasmonic Metamaterials, META 2013, Sharjah United Arab Emirates (18 – 22 March 2013). 
2. Slow and Stopped-Light Lasing in Active Nanoplasmonic Metamaterials, Advances in Slow and Fast Light VI, SPIE Photonics West, San Francisco, USA (4 – 7 Feb 2013)
3. Amplification and Lasing in Nano-plasmonics and Metamaterials: An Overview, Physics and Simulation of Optoelectronic Devices XXI, SPIE Photonics West, San Francisco, USA (4 – 7 Feb 2013).
4. Nanoplasmonics and Optical Metamaterials with Gain: From Loss-Compensation to Nano-Lasing, NanoMeta 4, Seefeld, Austria (2 – 6 Jan 2013). 
5. Amplification and Lasing in Nano-Plasmonic Metamaterials, Metamaterials, Plasmonics and Transformation Optics, HKUST, Hong Kong (3 – 7 Oct 2012).
6. Slow and Stopped Light in Metamaterials, Metamaterials 2012, St Petersburg, Russia (17 – 22 Sep 2012).
7. Amplification and Lasing in Nanoplasmonic Metamaterials, SPIE Optics and Photonics, Metamaterials, San Diego, CA (Aug 2012).
8. Slow and Stopped Light in Plasmonic Metamaterials, ICTON 2012, Coventry, UK (2 – 5 July 2012).
9. Nonlinear Lasing Dynamics in Nanoplasmonic Metamaterials, Laser Optics 2012, St Petersburg, Russia (25 – 29 June 2012).
10. Dynamics of Amplified Spontaneous Emission and Lasing in Nanoplasmonic Metamaterials, PECS-X Santa Fe, New-Mexico, USA (3 – 8 June 2012).
11. Loss-Compensation, Light Amplification and Lasing in Nanoplasmonic Metamaterials, Meta’12, Paris (19 – 22 April 2012).
12. Nanoplasmonic Meta-Lasers, Meta’12, Paris (19 – 22 April 2012).  
13. Stopped Light in Metamaterials, Meta’12, Paris (19 – 22 April 2012).
14. Nonlinear Lasing-Dynamics of Gain-Enhanced Nanoplasmonic Metamaterials, Photonics Europe, Brussels April 2012.
15. Metamaterials with Gain, APS March Meeting, Boston, 27 Feb 2012.
16. Amplified stopped light in metamaterials waveguides, Advances in Slow and Fast Light V, SPIE Phtonics West, San Francisco 22 – 24 Jan 2012.
17. Stopping and Controlling Light in Amplifying Metamaterials, Passive Components and Fiber-Based Devices, Shanghai, China (13 – 16 Nov 2011).
18. Extreme Control of Light in Nano-Plasmonic Metamaterials: From ‘Trapped Rainbows’ and Femtosecond Nano-Solitons to Metamaterial Lasers, Nonlinear Optics and Complexity in Photonic Crystal Fibers and Nanostructures", Ettore Majorana Foundation and Centre for Scientific Culture in Erice, Sicily (8 – 13 Nov 2011).
19. Light Amplification and Lasing in Nano-Plasmonic Metamaterials, APS Laser Science Annual Meeting (LS XXVII), San Jose, California, USA (16 - 20 October 2011).
20. Dynamics of Amplification and Gain in Nano-Plasmonic Metamaterials, Active Photonic Materials IV, SPIE Optics+Photonics 2011, San Diego, California, USA (21 - 25 August 2011).
21. Dynamics of Amplification and Gain in Plasmonic Metamaterials, International Conference on Materials for Advanced Technologies, Symposium "Metamaterials", Singapore (26 June - 1 July 2011).
22. Theory and Modeling of Gain in Nano-Plasmonics and Metamaterials, Integrated Photonics Research, Silicon and Nano Photonics (IPR), Toronto, Canada (12 - 16 June 2011).
23. Gain in negative-refractive-index slow-light waveguides, Advances in Slow and Fast Light IV, SPIE Photonics West, San Francisco, California, USA (22 - 27 January 2011). 
24. Nonlinear spatio-temporal dynamics and control of quantum dot and microcavity lasers, CMMP10, University of Warwick, UK (14 - 16 December 2010). 
25. Gain in negative-index metamaterials and slow-light waveguides, Metamaterials: Fundamentals and Applications III, SPIE Optics+Photonics 2010, San Diego, California, USA (1 - 5 August 2010). 
26. Trapped Rainbow Storage of Light in Metamaterials, 5^th Forum on New Materials, Electromagnetic Metamaterials Symposium, Montecatini Terme, Tuscany, Italy (13 – 18 June 2010).
27. Trapped rainbow storage of light in nanophotonic materials, Optical Data Storage, Boulder, Colorado, USA (23 – 26 May 2010).
28. Plasmonic Metamaterials, Plasmonics, Institute of Physics, London, UK (10 May 2010).
29. Trapped rainbow storage of light in metamaterials, Metamaterials, Brussels, Belgium, (12 – 16 April 2010)
30. Recent developments in the study of slow light in complex photonic materials, Advances in Slow and Fast Light III, San Francisco, California, USA (25-26 Jan 2010).
31. Nanophotonic Metamaterials, Metamaterials and Plasmonics (16 Dec 2009)
32. Slow and Stored Light in Metamaterials, IoP (Dec 2009)
33. Optics of Metal Nanocomposites, Metamaterials: Fundamentals and Applications II conference at SPIE Optics + Photonics 2009, San Diego CA, USA (2 – 6 August 2009).
34. The trapped rainbow effect for broadband slow light and light storage, CLEO Europe – EQEC 2009, Munich (14 – 19 June 2009).
35. The Trapped Rainbow Effect: Slow Broadband Waves Through Negative Phase Shifts, ETOPIM8 – 8^th International Conference on Electrical Transport and Optical Properties of Inhomogeneous Media, Rethymnon, Crete (7 – 12 June 2009).
36. Slow Light and Light Storage in Plasmonic Metamaterials, Nanophotonics and Metamaterials Joint CLEO/IQEC Symposium, CLEO/IQEC 09 (31 May – 5 June 2009).
37. Nanophotonics and Metamaterials, Taiwan (2009)
38. The Trapped Rainbow and storage of light, East-West Summit on Nanophotonics and Metamaterials, Data Storage Institute, Singapore (27 April 2009)
39. Ultraslow and Stored Broadband Light in Metamaterials, Advances in Slow and Fast Light II at Photonics West 2009 (San Jose, Jan 2009).
40. Stopping Light in Zero- and Low-Loss Metamaterial Waveguides, Naples (18 – 19 Dec 2008).
41. Slow and Stopped Light in Metamaterials, Numerical Simulation of Optoelectronic Devices NUSOD-08 in Nottingham, UK (1 – 5 September 2008).
42. Slowing Down the Light with Metamaterials. First Mediterranean Photonics Conference in Ischia, Italy (25 – 28 June 2008).
43. Slow Light in Metamaterial Heterostructures at Advances in Slow and Fast Light at Photonics West 2008 (San Jose, Jan 2008).
44. Ultrafast Dynamics and Slow Light in Quantum Dot Lasers. COST 288 meeting in Zaragoza, Spain (Oct 2007).
45. Slow Light in Left-Handed Metamaterial Heterostructures. Photonic Metamaterials at Optics & Photonics 2007 (San Diego, California USA 26 – 30 August 2007).
46. Slow Light in Left-Handed Metamaterial Heterostructures. IoP Condensed Matter and Materials Physics Conference (Leicester, 11 – 13 April 2007).
47. Simulation of Complex Photonic Materials and Devices SPIE Conference Complex Mediums V: Light and Complexity (Denver, August 2004).
48. Computational Modelling of the Ultrafast Spatio-Temporal Dynamics of Quantum Dot Lasers and Amplifiers, 3^rd International Conference Computational Modeling and Simulation of Materials (30 May – 4 June 2004, Acriceale, Sicily).
49. Designed Nano-Photonic Materials: Physik und Simulation, WE-Heraeus Conference Computational Material Science, Halle/Saale (September 2002).
50. Finite-Difference Time-Domain Simulation of Photonic Crystal Defect Structures WE-Heraeus-Sommerschool “Photonic Crystals” (Wittenberg, July 2002).
51. Mesoscopic Theory and Simulation of Quantum Dot Lasers, Numerical Simulation of Semiconductor Optoelectronic Devices (NUSOD-02), 25 – 27 Set 2002, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland
52. Modelling of Photonic Crystals with the FDTD-Method, WE-Heraeus-Seminar "Microoptics" (Bad Honnef,22 – 24 April 2002).
53. Femtosekunden-Dynamik aktiver Halbleiter-Wellenleiter-Strukturen: Mikroskopische Dynamik und experimentelle Analyse Photonik-Symp., Baden b. Wien (23 – 25 September 2001).
54. Raumzeitliche Dynamik und Quantenfluktuationen in Halbleiterlasern und Photonischen Kristallen im Licht der Informationstechnologie, Physikertagung Hamburg 2001 der Deutschen Physikalischen Gesellschaft.
55. Femtosecond Dynamics of Active Semiconductor Waveguides – Microscopic Analysis and Experimental Investigations. Cleo-Europe’00, Nice, France (10 — 15 September 2000).
56. Theory and Simulation of Spatially Extended Semiconductor Lasers. International Spring School on Fundamental Nonlinear Laser Dynamics, Texel, The Netherlands (March 2000).
57. Control of Spatio-Temporal Filamentation Dynamics in Semiconductor Lasers. Second Euroconference on Trends in Optical Nonlinear Dynamics: „Control of Complex Behaviour in Optical Systems and Applications“, in Münster, Germany (7 —10 October 1999).
58. Spatio-Temporal Dynamics and Quantum Fluctuations of Semiconductor Lasers International Workshop „Dynamics of Semiconductor Lasers“, Weierstrass-Institut, Berlin, Germany.
59. Ultrafast optical pattern dynamics of coupled surface-emitting semiconductor laser arrays. International Seminar on „Topological Defects in Non-Equilibrium Systems and Condensed Matter“, Focus-period on Optical Patterns and Defects, Max Planck Institute for the Physics of Complex Systems (Dresden) (12 – 16 July 1999).
60. Controlling complex temporal and spatiotemporal dynamics in semiconductor lasers by delayed optical feedback. Physics and Simulation of Optoelectronic Devices VII in San Jose, California, USA (23 – 29 January 1999).
61. Spatio-Temporal Dynamics and Quantum Fluctuations of VCSELs and coupled VCSEL Arrays. Summer School and European Optical Society Topical Meeting on Semiconductor Microcavity Light Emitters, Centro Stefano Franscini, Monte Verita, Ascona, Switzerland (20 – 25 September 1998).
62. Controlling Coupled Semico nductor Lasers. 178. WE-Heraeus-Seminar „Pattern Formation in Nonlinear Optical Systems“, Bad Honnef (22 —25 June 1997).
63. Control of Complex T emporal and Spatio-Temporal Dynamics in Semiconductor Laser. SIAM Conference, Snowbird, Uta (May 1997).
64. Controlling Temporal and Spatio-Temporal Dynamics in Multi-Stripe Semiconductor Laser Arrays, European Semiconductor Laser Workshop''''96 in Palma de Mallorca (18 – 19 April 1996).
65. Spatio-Temporal Dynamics of Vertical Cavity Surface Emitting Lasers. European Quantum Electronics Conference EQEC''''9 6, Hamburg (8 – 14 Sep 1996).
66. Generalized Maxwell Model Equations for the Static and  Dynamic Nonlinear Flow Behavior, STATPHYS 19, in Xiamen, China (31 July — 4 August 1995). 
67. Microscopic Dynamic Aspects in Self-Focusing and Filamentation of High-Power Semiconductor Lasers, Laser''''95 , Munich (19 —23 June 1995).
68. Spatio-Temporal Instabilities in Semiconductor Lasers, International SPIE Photonics West ''''95 Conference: Physics and Simulation of Optoelectronic Devices III in San Jose, California, USA (4 —10 February 1995).

1. Active Nanophotonic Metamaterials: From Loss-Compensation to Ultrafast Nanolasing, META 2013, Sharjah United Arab Emirates (18 a?? 22 March 2013).
2. Extreme Control of Light in Metamaterials: From a??Trapped Rainbowsa?? to Nanoplasmonic Meta-Lasers. CUDOS Workshop, Shoal Bay, Australia (31 Jan a?? 4 Feb 2012). 
3. Slow and Stored Light in Metamaterials, PHOTONICS - 2010, Guwahati, India (11 a?? 15 December 2010).
4. Slow light in nanophotonic materials a?? From a??Trapped Rainbowsa?? to Quantum Memories, 15^th European Conference on Integrated Optics, ECIO 2010, Cambridge, UK (7-9 April 2010).
5. Slow and stopped light in metamaterials: the trapped rainbow, Metamaterials conference at SPIE Photonics Europe, Strasbourg (7-10 April 2008).