Toke Lund-Hansen

Experimental realization of highly efficient broadband coupling of single quantum dots to a photonic crystal waveguide

We present time-resolved spontaneous emission measurements of single quantum dots embedded in photonic crystal waveguides. Quantum dots that couple to a photonic crystal waveguide are found to decay up to 27 times faster than uncoupled quantum dots. From these measurements beta-factors of up to 0.89 are derived, and an unprecedented large bandwidth of 20 nm is demonstrated. This shows the promising potential of photonic crystal waveguides for efficient single-photon sources. The scaled frequency range over which the enhancement is observed is in excellent agreement with recent theoretical proposals taking into account that the light-matter coupling is strongly enhanced due to the significant slow-down of light in the photonic crystal waveguides.

Size dependence of the wavefunction of self-assembled InAs quantum dots from time-resolved optical measurements

Jeppe Johansen, Søren Stobbe, Ivan S. Nikolaev, Toke Lund-Hansen, Philip T. Kristensen, Jørn M. Hvam, Willem L. Vos, and Peter Lodahl COM · DTU, Department of Communications, Optics, and Materials, Nano · DTU, Technical University of Denmark, DTU Building 345V, DK-2800 Kgs. Lyngby, Denmark Center for Nanophotonics, FOM Institute for Atomic and Molecular Physics (AMOLF), Amsterdam, The Netherlands Complex Photonics Systems, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands

Observation of non-Markovian dynamics of a single quantum dot in a micropillar cavity

All-solid-state cavity quantum electrodynamics (CQED) systems based on quantum dots (QDs) in nanophotonic cavities provide a promising platform for practical implementations of quantum information protocols. The ability to enter the coherent-coupling regime was demonstrated by recording detuning-dependent emission spectra [1] proving that the QD-cavity coupling is so strong that there is ‘memory’ in the system, i.e. non-Markovian effects. The influence of phonons on these effects has also been studied [2].

Pump-To-Signal Intensity Modulation Transfer Characteristics in FOPAs: Modulation Frequency and Saturation Effect

This paper reports a comprehensive study of pump-to-signal intensity modulation transfer (IMT) in single-pump fiber optic parametric amplifiers (FOPAs). In particular, the IMT is studied for the first time for high-frequency fluctuations of the pump as well as in the saturated gain regime. The IMT cut-off frequency in typical single-pump FOPAs is around 100-200 GHz. The possibilities to shift this frequency based on dispersion and nonlinearities involved in the parametric gain are discussed. The severe IMT to the signal at low modulation frequencies can be suppressed by more than 50% in the gain saturation regime with respect to the linear gain operation. Experimental results confirm the validity of the numerical study.

Experimental investigation of pump-to-signal noise transfer in one-pump phase insensitive fibre optic parametric amplifiers

This paper presents a detailed experimental characterization of the relative intensity noise (RIN) transferred from the pump to the signal in one-pump phase insensitive fibre optic parametric amplifiers. We extend an existing experimental and theoretical work towards higher frequencies, showing for the first time a strong wavelength dependence of the RIN transfer over a 30 GHz modulation frequency range. Good agreement is obtained between the measured RIN transfer and the predictions of a simple theoretical model.

Extinction ratio and gain optimization of dual-pump degenerate-idler phase sensitive amplifiers

Numerical optimization of dual-pump degenerate-idler phase sensitive amplifiers is performed for Al-doped and standard highly nonlinear fibers. Design considerations for operating the PSAs at an optimum combination of gain and extinction ratio are discussed.

Saturation effect on pump-to-signal intensity modulation transfer in single-pump phase-insensitive fibre optic parametric amplifiers

A numerical and experimental characterization of how signal gain saturation affects the transfer of the intensity modulation of the pump to the signal in single-pump phase-insensitive fibre optic parametric amplifiers is presented.

High-frequency RIN transfer in fibre optic parametric amplifiers

Fibre optic parametric amplifiers (FOPAs) are versatile devices for amplification at arbitrary wavelengths, as well as a wide range of optical signal processing applications, including switching, wavelength conversion, regeneration, pulse generation etc [1]. Transfer of intensity fluctuations from the pump to the signal (hereafter referred to as relative intensity noise transfer, RINT) affects the quality of the amplified signal due to the pump power dependence of the gain and the ultrafast nature of the Kerr nonlinearity [1–4]. For high-speed signal processing applications, the pump may be modulated at several hundreds of GHz or Gbit/s and it is therefore important to quantify the RINT at such high frequencies. To the best of our knowledge, the frequency dependence of pump-to-signal RINT has only been investigated theoretically and experimentally in single-pump FOPAs for low intensity modulation frequencies (IMFs) (<10 GHz) [3], where the RINT is frequency independent. However, when the IMF of the pump is of the order of the reciprocal walk-off delay induced by group velocity mismatch between the pump and signal, the effect of walk-off can no longer be neglected. In this work, the high-frequency RINT behaviour is investigated numerically in single pump FOPAs.

Pump-to-signal intensity modulation transfer in saturated-gain fiber optical parametric amplifiers

The pump-to-signal intensity modulation transfer in saturated degenerate FOPAs is numerically investigated over the whole gain bandwidth. The intensity modulation transfer decreases and the OSNR improves when the amplifier operates in the saturation regime.

Low-Loss Tunable All-in-Fiber Filter for Raman Spectroscopy

We show a novel in-line Rayleigh-rejection filter for Raman spectroscopy, based on a solid-core Photonic Crystal Fiber (PCF) filled with a high-index material. The device is low-loss and thermally tunable, and allows for a strong attenuation of the Rayleigh line at 532nm and the transmission of the Raman lines in a broad wavenumber range.