CW-to-pulse conversion using temporal Talbot array illuminators

Abstract

We report on the linear conversion of continuous-wave (CW) laser light to optical pulses using temporal Talbot array illuminators (TAIs) with fractional orders 1/q(q≤10), implemented by use of multilevel PM and dispersive propagation in a chirped fiber Bragg grating. The generated, sub-nanosecond optical pulse trains have repetition rates in the gigahertz range and show the presence of satellite pulses originated by the finite electrical modulation bandwidth (7.5 GHz). Though this fact impacts the resulting extinction ratio, an experimental comparison with time and Fresnel lenses indicates that temporal TAIs represent compact systems with high light gathering efficiency (>87%) at moderate values of compression (q≤8), which can be tailored in repetition rate, gain, or width, through the fractional Talbot order for its use in pulse compression systems fed by CW light.

Several new directions for ultrafast fiber lasers [Invited]

“…For instance, a highbandwidth intensity modulator can carve pulses out of a continuous-wave (CW) beam by attenuating the beam in a desired pulse sequence. Techniques with greater efficiency (up to unity in some cases) have been demonstrated using rapid amplitude or phase modulation schemes based on time-lenses [74][75][76], temporal zone plates [77], temporal holograms [78,79], or the temporal Talbot effect [80], followed by a dispersive delay line that compresses the modulated beam into a pulse train. The improved efficiency can reduce the number of amplification stages needed; however, these techniques generate a repetitive pulse train, rather than individual pulses, and are therefore less versatile than techniques such as direct intensity modulation.…”

Ultrashort pulse generation from binary temporal phase modulation

“…Results can then be normalized by the Talbot length z T defined as: where Δf is the frequency spacing between two non‐zero spectral components ( Δf = 2 f 0 in our ideal case). After a propagation distance of z T /4, the phase modulation is converted into a binary intensity modulation (red curve, Figure 3(B)), typical of a Talbot array illuminator 25‐27 . After z T /2, a continuous wave is reconstructed as expected from the self‐imaging process.…”

Arbitrary Energy‐Preserving Control of Optical Pulse Trains and Frequency Combs through Generalized Talbot Effects

“…1) Temporal phase sequences, 2) optical spectra of the obtained pulse trains, 3) instantaneous power traces of the obtained pulse trains. Reproduced with permission . Copyright 2017, Optical Society of America.…”

“…[123,124] Finally, it is worth mentioning that Talbot-based methods have also been used for energy-preserving manipulation of continuous-wave (CW) signals. R. Fernández-Pousa et al demonstrated efficient CW-to-pulse conversion through a methodology based on the reviewed energy redistribution methods [125] (experimental examples shown in Figure 21). This can be interpreted as the time-domain counterpart of the Talbot array illuminator (TAI), a process by which a plane wave is focused into a set of localized bright spots through the interplay of a spatial phase mask and free-space propagation.…”

“…Last but not least, as mentioned above, beyond their interest for application to the control of repetitive waveforms, the outlined wave energy redistribution strategies could be generalized to a wider variety of signal processing scenarios, such as for manipulation of arbitrary aperiodic signals. [125,129] Hence, the Talbotbased methodology outlined and reviewed herein opens a myriad of promising new avenues for advanced arbitrary energy-efficient waveform generation, processing and control, of potential broad practical interest.…”