We describe experiments and theory showing the generation of counterpropagating paired photons with coherence times of about 50 ns and waveforms that are controllable at a rudimentary level. Using cw lasers, electromagnetically induced transparency and cold 87Rb atoms we generate paired photons into opposing single-mode optical fibers at a rate of approximately 12 000 pairs per second.

This Letter describes the generation of biphotons with a temporal length that can be varied over the range of 50-900 ns, with an estimated subnatural linewidth as small as 0.75 MHz. We make use of electromagnetically induced transparency and slow light in a two-dimensional magneto-optical trap with an optical depth as high as 62. We report a sharp leading edge spike that is a Sommerfeld-Brillouin precursor, as observed at the biphoton level.

We use the Stokes photon of a biphoton pair to set the time origin for electro-optic modulation of the wave function of the anti-Stokes photon thereby allowing arbitrary phase and amplitude modulation. We demonstrate conditional single-photon wave functions composed of several pulses, or instead, having gaussian or exponential shapes.PACS numbers: 42.50. Gy, 32.80.Qk, 42.50.Ex, 42.65.Lm This letter demonstrates how single photons may be modulated so as to produce photon wave functions whose amplitude and phase are functions of time. The essential feature of this work is the use of one photon of a biphoton pair that is generated by spontaneous parametric down-conversion to establish the time origin for the modulation of the second photon. This is done by using electromagnetically induced transparency and slow light to produce time-energy entangled biphotons with pulse lengths of several hundred ns, and therefore, very long as compared to the temporal resolution of single photon counting modules (about 40 ps). Once the time origin is established, the photon waveform may be modulated in the same manner as one modulates a classical pulse of light. For example, the single-photon waveform may be phase, frequency, amplitude, or even digitally modulated, with the maximum modulation frequency limited by the resolution of the detection of the first photon.As shown in Fig. 1, we use cw pump and coupling lasers to generate time-energy entangled pairs of Stokes and anti-Stokes photons that propagate in opposite directions and are collected in single mode fibers. The detection of a Stokes photon at D 1 sets the time origin for firing the function generator that drives the electro-optic modulator (EOM) that modulates the wave function of the anti-Stokes photon. This latter photon is incident on the beam splitter where it is detected by D 2 or D 3 . As shown in the following, we generate single photons whose modulated waveform is two rectangular pulses, is Gaussian or is a time reversed exponential.The method demonstrated in this letter might be used to optimally load a single photon into an optical cavity [1], or instead, to study the transient response of atoms to different single photon waveforms. In the context of light-matter interfaces, it may improve the efficiency of storage and retrieval of single photons in atomic ensembles [2]. For quantum information applications, both amplitude and phase modulators could be used to allow full control over the single photon waveforms. For example, one could a construct a single photon waveform that is a train of identical pulses with information encoded into the relative phase difference between consecutive pulses [3].The generation of single photons with controlled wave- forms has been demonstrated earlier by using the techniques of cavity-QED, i.e., by coupling a single trapped ion to a high Q cavity and using an acousto-optic modulator to shape a pumping laser that is tuned close to the resonant transition [4]. In related work Rempe and colleagues use a single Rb atom, again i...

We describe a generator of narrow-band paired photons. A single retroreflected Ti:sapphire laser is used to cool, render transparent, and parametrically pump a cloud of (87)Rb atoms. We attain a paired-photon generation rate into opposing fibers of 600 counts/s with an intensity correlation function that has a width of 5 ns, and violates the Cauchy-Schwartz criteria by a factor of 2000.

We experimentally demonstrate dramatically enhanced light-matter interaction for molecules placed inside the nanometer scale gap of a plasmonic waveguide. We observe spontaneous emission rate enhancements of up to about 60 times due to strong optical localization in two dimensions. This rate enhancement is a nonresonant nature of the plasmonic waveguide under study overcoming the fundamental bandwidth limitation of conventional devices. Moreover, we show that about 85% of molecular emission couples into the waveguide highlighting the dominance of the nanoscale optical mode in competing with quenching processes. Such optics at molecular length scales paves the way toward integrated on-chip photon source, rapid transfer of quantum information, and efficient light extraction for solid-state-lighting devices.

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We describe the observation of a sharp leading edge spike in a biphoton wave packet that is produced using slow light and measured by two photon correlation. Using the stationary phase approximation we characterize this spike as a Sommerfeld-Brillouin precursor resulting from the interference of low and high frequency spectral components. c 2008 Optical Society of America OCIS codes: 270.0270, 070.7345.Optical precursors were first described by Sommerfeld and Brillouin in 1907, and are of importance in electromagnetic theory because they ensure that the front edge of a wave packet will always travel at the velocity of light in vacuum. It was previously believed that optical precursors existed for only a few optical cycles and contributed little to the amplitude of the field [1]. However, recent theoretical [2] and experimental [3] work has shown that in a narrow-resonance atomic medium the precursor magnitude can be of the same order as the primary field and its length may be much longer than a few cycles. Precursors have been extensively studied in the gamma ray [4], microwave [5], and optical regimes [3,[6][7][8][9].In this Letter, we extend the classical concept of precursors to describe the behavior of biphoton wavepackets that are measured by correlation using single photon counting modules (SPCM). The measured wave packets are generated by using electromagnetically induced transparency (EIT) and slow light [10,11] so that the correlation time of the main body of the wave packet can be varied over the range of 50-900 ns [12]. A requirement for the sharp front edge spike to be apparent is that the optical depth (OD) be sufficiently large that the pulse length is determined by the group delay. We remark that the observation of the sharp leading edge spike, see Fig. 2(b), was not expected, and its nature was first suggested to us by Daniel J. Gauthier.A schematic of biphoton generation is shown in Fig. 1. In the presence of counter-propagating cw pump (ω p ) and coupling (ω c ) lasers, phase-matched, paired Stokes (ω s ) and anti-Stokes (ω as ) photons are spontaneously generated and propagate in opposite directions. We use a two-dimensional (2D)85 Rb magneto-optical trap (MOT) with a longitudinal length L = 1.7 cm and an aspect ratio of 25. The Stokes (σ − ) and anti-Stokes (σ + ) photons are coupled into opposing single mode fibers, and detected by two SPCMs after passage through two narrow-band optical filters (F1 and F2). With the dephasing rate of the |1 → |3 transition denoted by γ 13 = 2π × 3 × 10 6 sec −1 , the pump laser has a Rabi frequency of Ω p = 1.16γ 13 , is σ − circularly polarized, and is blue detuned from the |1 → |4 transition by ∆ p = 48.67γ 13 . The coupling laser (Ω c ) is σ + circularly polarized, and is on resonance with the |2 → |3 transition. Further experimental details are described in [12].We first note that the Glauber correlation function, or equivalently the coincidence rate versus the relative time delay τ for an ideal parametric down converter with a frequency independent gro...

We demonstrate an all-dielectric quantum electrodynamical nanowire-slab system with a single emitter that concentrates the extremely intense light at the scale of 10 × 75 nm(2). The quantum dot exhibits a record high 31-fold spontaneous decay rate enhancement, its optical saturation and blinking are strongly suppressed, and 80% of emission couples into a waveguide mode.