RESUMO
Optical frequency combs have the potential to revolutionize terabit communications1. Generation of Kerr combs in nonlinear microresonators2 represents a particularly promising option3 enabling line spacings of tens of GHz. However, such combs may exhibit strong phase noise4-6, which has made high-speed data transmission impossible up to now. Here we demonstrate that systematic adjustment of pump conditions for low phase noise4,7-9 enables coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the comb. In a first experiment, we encode a data stream of 392 Gbit/s on a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment demonstrates feedback-stabilization of the comb and transmission of a 1.44 Tbit/s data stream over up to 300 km. The results show that Kerr combs meet the highly demanding requirements of coherent communications and thus offer an attractive solution towards chip-scale terabit/s transceivers.
RESUMO
We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition. Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. The results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum.
Assuntos
Modelos Teóricos , Óptica e Fotônica/instrumentação , Óptica e Fotônica/métodos , Compostos de Silício/química , Análise Espectral/instrumentação , Análise Espectral/métodos , Desenho de Equipamento , Análise de Elementos Finitos , Háfnio/química , Lasers Semicondutores , Microscopia Eletrônica de Varredura , Microtecnologia/instrumentação , Microtecnologia/métodos , Dinâmica não Linear , Óxidos/química , Dióxido de Silício/químicaRESUMO
We report a modulation of third-harmonic generation (THG) owing to a rotational coherence in CO(2). The variation in conversion efficiency is mostly attributed to the dependence of chi(3)(tau) on the molecular alignment. THG via type I processes mainly depends on chi(3)(tau), while type II processes are influenced by the wave packet owing to both chi(3)(tau) and Delta k(tau). Observation of the generated third harmonic also shows significant changes of the polarization state owing to the birefringence induced by the rotational wave packet. Numerical modeling shows good qualitative agreement with the experimental data.
RESUMO
We propose the use of birefringent materials to attain pulse separations suitable for pump-probe spectroscopy and spectral interferometry. By choice of material thickness and cut angle, it is possible to balance second-order dispersion while allowing for variable delays. The generated pulse pair is used to calibrate the phase response of an ultrafast liquid-crystal pulse shaper, and in the measurement of a rotational wave packet in impulsively aligned CO(2) molecules.
RESUMO
We demonstrate propagation of ultrafast laser pulses through a molecular gas acting as a transient wave plate under conditions of strong phase modulation. The resulting decomposition of a linearly polarized laser pulse into two nearly distinct, orthogonally polarized laser pulses is demonstrated with transiently aligned, linear molecules.