Transcript Slide 1
High-Q small-V Photonic-Crystal Microcavities control of light Kirill Atlasov Ecole Polytechnique Fédérale de Lausanne (EPFL) Laboratory of Physics of Nanostructures Lausanne, Switzerland Control of light: in Nature 2 Control of Light. Us. Manipulation: create, select spectrally, guide, interact, (store), detect In a predefined way. 3 Purposes: calculus, communication, data storage courtesy MIT (http://ab-initio.mit.edu/photons) 4 Microcavities: Control of Light What to control ? - They can be used as coupling blocks and filters in photonic circuits - Control of Spontaneous Emission of a light source modify broad-band source (QWR) "speed up" atom-like source (QD) Hennessy, et al, Nature 445, 896, (2007) 5 Purcell effect Vahala, Nature, 424, 839, (2003) emitter decays by interaction with continuum rate ~ density of states per volume V DoScavity > DoSfree (resonantly) rate ~ DoS per volume V fast decay rate of emitter spont. em. directed into mode 4 Microcavities: Control of Light What to control ? - They can be used as coupling blocks and filters in photonic circuits - Control of Spontaneous Emission of a light source modify broad-band source (QWR) "speed up" atom-like source (QD) Hennessy, et al, Nature 445, 896, (2007) 6 Cavity Figure of merit: Q V So, the figure of merit is about What is it good for? Q and V Cavity Figure of merit: Q/V. What is it good for? Indistinguishable photons (identical wave packets for linear-optical quantum computation) Santori et al, Nature, 419, 594, (2002) LED exhibiting laser-like performance (β - spontaneous emission Into cavity mode) Yablonovitch in Confined electrons and photons: New physics and applications, (Burstein, Weisbuch, eds) vol. 340 NATO ASI ser.B. Plenum Press (1995) LASER (β - spontaneous emission Into lasing mode – low threshold) Few QD laser: Strauf et al, PRL 96, 127404, (2006) Strong coupling regime (transfer of energy between oscillators) Khitrova et al, Nat. Phys. 2, 81, (2006) 1 8 Vcav 1 3 ( / n ) Q 7 Photonic-crystal Microcavities In principle, any defect of the periodicity. John, PRL 58, 2486, (1987) Most practical – membrane PhC 8 9 How does it compare to other possibilities? Srinivasan et al, APL 424, 839, (2003) Vahala, Nature 424, 839, (2003) In PhC V < (λ/n)3 Noda et al, Nature 425, 944 (2003) Park et al, Science 305, 1444, (2004) 10 Interesting examples: LASERs Electrical pumping QW PhC laser Few-QD laser Strauf et al, PRL 96, 127404, (2006) β = 0.85 Park et al, Science 305, 1444, (2004) β = 0.25 11 Interesting examples: Indistinguishable photons Two-photon interference (QD in PhC) Laurent et al, APL 87, 163107, (2005) Two-photon interference (QD in micropillar) Santori et al, Nature 419, 594, (2002) If 2 indistinguishable photos collide at the beamsplitter they exit via the same port!! => 2-photon inteference Hong et al, PRL 59, 2044, (1987) Cannot arive then at different detectors at the same time Probability that two colliding photons at beamsplitter exit via two diferent ports is low (given directly by correlation) Interesting feature: Strong Light-matter Coupling (transfer of energy between oscillators) Strong coupling (photons here) 1 decay κ 2 decay γ If coupling strength between two same-energy oscillators exceeds the mean of their decay rates, the coupled system has two energies – their states split Khitrova et al, Nat. Phys. 2, 81, (2006) 12 13 Interesting feature: Strong Light-matter Coupling The decay rate (of photon) ~ 1/Q And the coupling strength g ~ 1 / V (vacuum field fluctuations per volume) Wanted: high Q small mode volume V Khitrova et al, Nat. Phys. 2, 81, (2006) transition from Purcell enhancement to Rabi splitting Interesting feature: Strong Light-matter Coupling 14 1 QD in PhC Yoshie et al, Nature 432, 200, (2004) Q = 16000 – 20000 Rabi splitting at around zero detuning When tuned, anticrossing behavior Very high-Q: Cavity geometry optimization. Q = 600 000. Akahane et al, Nat. Mater 4, 208, (2005) FT if Two mirrors FT of Gaussian envelope In real space Two different waveguides... WG 2 stretched... Bandgap -> transmission... Photons with specific energies can exist only in the WG 2 15 16 Ey Intensity (arb units) High Q: cavity termination adjustments. Polarization even odd Ex normalized frequency f (c/a) ky (2π/a) |Ex| k-space K.F Karlsson, K.A. Atlasov unpublished 0 -1 0 1 kx (2π/a) Q from 1500 goes upto >100 000 SUMMARY high Q small V Strong coupling 1 2 end additional stuff For non-lasing devices β>0.9 have been estimated (0.97) (Kress et al, PRB, 71, 241304, (2005)