Modulational Instability Laser Research Articles

Ytterbium gain band self-induced modulation instability laser

We demonstrate an ytterbium gain band self-induced modulation instability laser. A highly nonlinear holey fiber is used to provide the anomalous dispersion required for bright soliton generation at 1 microm. The all-fiber integrated source yields a 40 GHz train of 4 ps pulses at a wavelength of 1064 nm.

Self-induced modulational instability laser revisited: normal dispersion and dark-pulse train generation

We study theoretically and experimentally the so-called self-induced modulational instability laser and show that the passive mode-locking mechanism that is at play in this laser relies on a dissipative four-wave mixing process that leads to generation of a dark-pulse train in the normal-dispersion regime.

Modulational-instability σ-resonator fiber laser

A modulational-instability laser with a resonator in a sigma configuration has been developed. The importance of a suitable intracavity filter for removing the autocorrelation background of the output signal is shown. A pulse train with a repetition rate of 107 GHz determined by the Fabry-Perot etalon used in the resonator was obtained at 1.56mum .

Impedance-matched modulational instability laser for background-free pulse train generation in the THz range

By means of a three-mode Fourier truncation procedure we develop an analytical model for the study of the modulational instability laser. The simple expressions we obtain allow us to address the problem of background field generation which accompanies pulse train formation in the device. We show that, under certain conditions, the laser can be impedance matched so that the background field is suppressed by destructive interference at the cavity output. Our analytical predictions are confirmed by numerical simulations of the complete mathematical model (propagation equation plus cavity boundary conditions). The important issue of our analysis is that it demonstrates the possibility to generate background-free ultrashort pulse trains with repetition rates in the THz range from cw pump beams of a few tens of mW.

Polarisation-stable operation of modulation-instability laser using non-polarisation-maintaining fibres

The authors propose a novel configuration of modulation-instability laser which can realise polarisation-stable operation without using polarisation-maintaining fibres. Polarisation-stable pulse trains with a repetition rate of 98.8 GHz are obtained.

Self-induced modulational-instability laser

We analyze the transition from passive mode locking into the novel modulational-instability regime of erbiumdoped fiber lasers. By including in the cavity an anisotropic loss, we observed, depending on the polarization setting, the generation of either single pulses as short as 435 fs or a continuous-wave train of 3.5-ps-long solitons at a repetition rate of 76 GHz. Even with no anisotropic losses in the cavity, soliton trains at a repetition rate of as high as 130 GHz were still observed. We believe that this is the first observation of a self-induced modulational-instability laser.

Characteristics of a visible modulation instability fiber laser

Cross-phase modulation has been harnessed to construct a modulation instability laser operating at 514.5 nm. The laser output consists of orthogonally polarized upshifted and downshifted sideband pulses separated in wavelength by 2.1 nm from the pump. The laser configuration has been found to generate a much more stable source of terahertz modulated light pulses than the single-pass configuration previously used to demonstrate modulation instability in the visible. The extra stability arises from the feedback, which provides a seed for the modulation, and hence a reduction in the pump power necessary compared with the single-pass configuration, which in turn reduces the Raman gain, and the asymmetry of the sideband amplitudes. The sideband pulses can be combined to generate a modulated envelope of 4-THz oscillations with a duration of 10-15 ps. >

Noise characteristics of cross-phase modulation instability light

The noise characteristics of cross-phase modulation instability visible light produced in high-birefringence fibres have been investigated. Noise measurements were made on single sidebands, and on the intensity difference between upshifted and downshifted sidebands using single pass and fibre-laser configurations. The intensity difference noise for the single pass configuration was reduced by more than 25 dB below the single sideband noise, which was typically 35 dB above shot noise. Under certain conditions the intensity difference noise of the modulation instability laser sidebands could be reduced to the shot noise level, while the single sideband noise from the modulation instability laser could be reduced to 2 dB above shot noise. Raman gain on the low frequency sideband and attenuation in the fibre limited the attainable noise reduction.

The modulation instability laser. II. Theory

For pt.I see ibid., vol.25, no.9, p.2036-44 (1989). A general analysis of the modulation instability laser (MIL) in a nonlinear dispersive cavity is presented. The theory of the feedback-induced modulational instability is derived. By introducing the pump depletion within one circulation of the pump pulse, the steady-state MIL oscillation can be predicted. The ripple frequency is equal to the modulation instability frequency. >