ABSTRACT
We experimentally investigate the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the magnitude of the complex degree of first-order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses.
ABSTRACT
The emission of dispersive waves (DWs) by temporal solitons can be described as a cascaded four-wave mixing process triggered by a pair of monochromatic continuous waves (CWs). We report experimental and numerical results demonstrating that the efficiency of this process is strongly and nontrivially affected by the frequency detuning of the CW pump lasers. We explain our results by showing that individual cycles of the input dual-frequency beat signal can evolve as higher-order solitons whose temporal compression and soliton fission govern the DW efficiency. Analytical predictions based on the detuning dependence of the soliton order are shown to be in excellent agreement with experimental and numerical observations.
ABSTRACT
We report on a theoretical and experimental study of cascaded Bragg scattering in fiber optics. We show that the usual energy-momentum conservation of Bragg scattering can be considerably relaxed via cascade-induced phase-matching. Experimentally we demonstrate frequency translation over six- and 11-fold cascades, in excellent agreement with derived phase-matching conditions.
ABSTRACT
We show that the emission of dispersive waves in nonlinear fiber optics is not limited to soliton-like pulses propagating in the anomalous dispersion regime. We demonstrate, both numerically and experimentally, that pulses propagating in the normal dispersion regime can excite resonant dispersive radiation across the zero-dispersion wavelength into the anomalous regime.
ABSTRACT
Mode locking features of single section quantum dash based lasers are investigated. Particular interest is given to the static spectral phase profile determining the shape of the mode locked pulses. The phase profile dependence on cavity length and injection current is experimentally evaluated, demonstrating the possibility of efficiently using the wide spectral bandwidth exhibited by these quantum dash structures for the generation of high peak power sub-picosecond pulses with low radio frequency linewidths.
ABSTRACT
We demonstrate the passive suppression of stimulated Brillouin scattering in meter-length fiber-ring cavities through careful control of the fiber length. Experimentally we are able to demonstrate an over sixty-times increase in the Brillouin threshold of a 0.4 m fiber ring. This very simple suppression technique greatly simplifies the design of optical parametric devices based on fiber-ring cavities.
ABSTRACT
We report theoretical, numerical, and experimental studies of cascaded phase matching in fiber frequency combs and show how this mechanism is directly connected to the dynamics of supercontinuum generation. In particular, linking cascaded four-wave mixing with direct higher-order nonlinear processes allows us to derive a simple phase matching condition that governs nonlinear symmetry breaking in the presence of higher-order dispersion. We discuss how this mechanism provides a physical interpretation of soliton-induced Cherenkov radiation and associated spectral recoil in terms of phase-matched frequency mixing pumped by bichromatic pump pairs in the soliton spectrum. Theoretical and numerical predictions are confirmed via experiments using both quasicontinuous wave and picosecond pulse excitation.
ABSTRACT
We present a χ(3) fiber parametric oscillator with high conversion efficiency from the input pump wave to the output parametric sidebands. By introducing an intracavity filter detuned from the oscillator's phase-matched frequency conversion efficiencies considerably higher than those possible when operating at the phase-matched frequency are demonstrated. Experimentally we are able to obtain a total internal conversion efficiency in excess of 93% from the pump to the Stokes and anti-Stokes sidebands.
ABSTRACT
We present a linear self-referenced measurement of the spectral amplitude and phase of a free-running quantum-dash modelocked laser diode. The technique is suitable for measuring optical signals with repetition rates up to 100 GHz. In contrast to many other linear techniques it requires no external electronic clock synchronized to the signal under test. Using this method we are able to compensate for the intracavity dispersion of the diode to demonstrate 500 fs pulses at a repetition rate of 39.8 GHz. We also use the technique to characterize the dependence of the diode's intracavity dispersion on the applied current.
Subject(s)
Algorithms , Lasers, Solid-State , Spectrum Analysis/methods , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Feedback , Quantum TheoryABSTRACT
We present an all-fiber high average power fiber optical parametric oscillator based on standard telecommunications dispersion-shifted fiber. The output of the oscillator is continuously tunable out to ±28 THz from the pump wavelength. The average power of the oscillator's output is in excess of 1.9 W in each sideband out to ±25 THz detuning. Between 5 and 14 THz detuning, the average power of the Stokes output is in excess of 3.8 W.
ABSTRACT
We present a heterodyne measurement of the spectral amplitude and phase of periodic optical signals. In contrast to previous techniques this measurement requires no optical modulation of either the signal or the local oscillator, places much relaxed tunability requirements on the optical local oscillator, and requires no electronic clock to be passed to the receiver. We present measurements of the spectral amplitude and phase of 20 GHz 33% return-to-zero, and 66% carrier-suppressed return-to-zero optical signals, as well as a passively modelocked optical source with in excess of 100 modes.
Subject(s)
Optical Devices , Spectrum Analysis/instrumentation , Computer-Aided Design , Equipment Design , Equipment Failure AnalysisABSTRACT
We present an investigation of the statistics of the gain fluctuations of a fiber optical parametric amplifier pumped with a temporally incoherent pump. We derive a simple expression for the probability distribution of the gain of the amplified optical signal. The gain statistics are shown to be a strong function of the signal detuning and allow the possibility of generating optical gain distributions with controllable long-tails. Very good agreement is found between this theory and the experimentally measured gain distributions of an incoherently pumped amplifier.
ABSTRACT
We experimentally investigate the performance of a fiber optic parametric amplifier pumped with a temporally incoherent pump. The measured gain curves are compared with both a simple theory capable of predicting the maximum attainable mean incoherent parametric gain and full numerical simulations of the nonlinear Schrödinger equation. Parametric gain slopes seven times higher than that of an equivalent coherently pumped parametric amplifier are reported.
ABSTRACT
We present a widely tunable low-threshold chi(3) optical parametric oscillator. The oscillator cavity is formed by butt coupling dichroic mirrors to either end of a highly nonlinear index-guiding photonic crystal fiber. This yields a singly resonant Fabry-Perot oscillator with a high feedback fraction for the resonant parametric sideband. The tuning range of the output parametric sideband stretches from 23 to 164 THz above the pump frequency. The threshold power of the oscillator is only 15 W.
ABSTRACT
We show that the combined action of parametric gain and Raman scattering can lead to the complete suppression of an input optical signal in a single-pump parametric amplifier. This suppression is due to an interference between the two parametric gain modes. The interference occurs only at a set of discrete combinations of pump power, phase mismatch, and frequency detuning. Experimentally we are able to demonstrate over 95% (13 dB) suppression of an input signal in an amplifier with a peak parametric gain of only 6 dB.
ABSTRACT
The real part of the Raman susceptibility is shown to have a strong influence on the peak parametric gain of single-pump parametric amplifiers. This results in a 35% variation in the peak parametric gain over the frequency range 0-30 THz. We are able to experimentally demonstrate this effect in a photonic crystal fiber and obtain good agreement between the experimentally measured and theoretically predicted gains.
ABSTRACT
A high-conversion-efficiency widely-tunable all-fiber optical parametric oscillator is described. It is based on modulation instability in the normal dispersion regime near the fiber's zero-dispersion wavelength. A 40 m long dispersion-shifted fiber is used in a synchronously pumped ring cavity. We demonstrate continuous sideband tuning from 1300 to 1500 nm and 1600 to 1860 nm by tuning the pump wavelength between 1532 and 1556 nm. Internal conversion efficiencies of up to 40% are achieved.
ABSTRACT
We investigate the combined effect of Raman and parametric gain on single-pump parametric amplifiers. The phasematched parametric gain is shown to depend strongly on the real part of the complex Raman susceptibility. In fused silica fibers this results in a significant reduction in the available parametric gain for signal detunings beyond 10 THz. We are able to experimentally measure this effect for signal detunings ranging from 7 to 22 THz. Finally we discuss the implications of these results for the design of broadband optical parametric amplifiers.
ABSTRACT
We report on the observation of cross-phase modulation instability in a highly nonlinear photonic crystal fiber. In such fibers the presence of higher orders of dispersion results in a complex phase-matching curve. We are able to observe this behavior experimentally and obtain excellent agreement between the measured and predicted shifts.
ABSTRACT
Polarization modulation instability (PMI) in birefringent photonic crystal fibers has been observed in the normal dispersion regime with a frequency shift of 64 THz between the generated frequencies and the pump frequency. The generated sidebands are orthogonally polarized to the pump. From the observed PMI frequency shift and the measured dispersion, we determined the phase birefringence to be 5.3 x 10(-5) at a pump wavelength of 647.1 nm. This birefringence was used to estimate the PMI gain as a function of pump wavelength. Four-wave mixing experiments in both the normal and the anomalous dispersion regimes generated PMI frequency shifts that show good agreement with the predicted values over a 70 THz range. These results could lead to amplifiers and oscillators based on PMI.
