Comparative study of supercontinuum generation using standard and high-nonlinearity fibres pumped by noise-like pulses

Abstract

We present a systematic experimental study of supercontinuum (SC) spectra produced by propagating noise-like pulses (NLPs) from an erbium-doped figure-eight laser through sections of different lengths of standard single-mode fibre (SMF) and of high-nonlinearity fibre (HNLF), as well as their combinations. With an average input power that does not exceed 35 mW, very broad and smooth SC spectra extending over several hundreds of nm are typically observed, even when only SMF is used. However, maximal broadening and flatness are obtained through a section of about 300 m of SMF followed by 50 m of HNLF; the spectrum then spans from ~1260 nm up to ~2070 nm, with a bandwidth of 431 nm at 5.7 dB from the maximum (over 800 nm at 20 dB). Our analysis indicates that nonlinear processes are still operating even after propagation through several hundreds of meters of fibre, extending and flattening the spectrum, its maximal bandwidth being eventually limited by the strong fibre attenuation in the 2 µm region.

A Novel Low-Cost Synchronous/Asynchronous Microcontroller-Based Pulsed Laser

“…One more modern technique is Q-switching, which generates pulses through the modulation of losses in the cavity [5,6]. Another technique, mode locking, the most important technique for obtaining short and ultrashort pulses, produces pulsing when the phases of the cavity modes are locked together, summing their amplitudes [7][8][9][10] so as to generate one pulse per round trip in the cavity; hence, the period (T) corresponds to the laser cavity length [9,11]. Although in general terms pulsed lasers produce a regular train of pulses (equally spaced, identical or quasi-identical releases of energy), some pulsed lasers have the capability to generate multiple pulses during each round trip, which in some circumstances are uniformly distributed along the whole laser cavity (harmonic mode locking) [12][13][14][15]; in this case, the pulse train period is an integer submultiple of the cavity round-trip time (and the pulse repetition rate, an integer multiple of the cavity fundamental frequency).…”

“…The type of laser emission required for applications (CW or pulsed) depends on the situation: CW lasers are commonly employed in holography [19], spectroscopy [20], surface cleaning [21], orthodontics [22], ophthalmology [11], material processing [23] and so on, whereas pulsed lasers are used in metrology [2,18], micromachining [24], ophthalmology [11,25], supercontinuum generation [9,14], telecommunications [26] and more. In general terms, lasers can be classified considering the kind of lasing medium they employ, such as solid state, gas, dye, fiber optics and semiconductor lasers.…”

Principles of operation of a passively mode-locked fiber ring laser and 3D mapping of ultra-short pulses

“…A mode-locked fiber laser (ML-FL) is a device that is able to produce short and ultra-short optical pulses (ns and fs-ps). This kind of pulse finds applications in pressure sensors [1,2], gas sensors [3], micromachining of materials [4], and supercontinuum generation [5,6], among others. However, there are many implicit effects in the formation and generation of ultra-short pulses, which possibly limit their use for some specific applications.…”

“…Other PML-FLs have a figure-eight or ring configuration; for these architectures, usually an artificial SA is used, which relies on non-linear effects generated in optical fiber, so indirectly the absorbed energy through to a laser component (commonly a polarizer or an isolator) is reduced by the changes that produces the non-linear effect. The Non-linear Optical Loop Mirror (NOLM) [6,25,26], the Non-linear Amplifying Loop Mirror (NALM) [28,35] or the Non-linear Polarization Rotation (NPR) [9,29] effect are examples of artificial SA implemented in PML-FLs. Commonly, the NPR effect is the SA meachanism used in a passively mode-locked fiber ring laser (PML-FRL); the latter is studied in this paper.…”

“…In recent years, the dynamics of pulses generated by ML-FL have been studied with experimental analysis and theoretical models. Different behaviors and interactions of pulses have been investigated, which encompass different types of pulses: noise-like pulses (NLPs) [6,25,26,28], dissipative solitons [30,31], spiny solitons [32], among others. A recently developed tool, which is useful in ML-FL researches, is a 3D mapping technique of the pulse temporal profile, which helps analyzing pulse dynamics [31,[33][34][35][36].…”