Figure - available from: Scientific Reports
This content is subject to copyright. Terms and conditions apply.
Source publication
Abstract A novel method for numerical modelling of noncollinear and nonlinear interaction of femtosecond laser pulses is presented. The method relies on a separate treatment of each of the interacting pulses by it’s own rotated unidirectional pulse propagation equation (UPPE). We show that our method enables accurate simulations of the interaction...
Citations
... The proposed scheme of amplification is potentially CEP stable. To prove this, we have performed complete 3 + 1D simulations of the twostage amplification process with Hussar software [28,29] based on the Unidirectional Pulse Propagation Equation [30,31]. The phase of the supercontinuum and 1030 nm pump pulse was changed in the 0-360 • range, and the phase of the generated idler beam at 3 µm was observed. ...
... The construction of the optical parametric amplifier and the crystal selection was supported with 3 + 1D numerical modeling performed with Hussar software. [28,29] We have tested generation in several nonlinear crystals: AGS, KTA, GaSe, LGS and LIO 3 , with the new damage thresholds of the crystals determined. In terms of damage thresholds, the AGS (290 GW/cm 2 ), LGS (214 GW/cm 2 ) and KTA (above 200 GW/cm 2 [39]) are superior over LIO 3 (159 GW/cm 2 ) and GaSe (85 GW/cm 2 ). ...
We present a carrier-envelope phase-stable laser pulse source continuously tunable in the 2 – 4 µm wavelength range. The source relies on two-stage optical-parametric amplification, with the first stage pumped with the second harmonic of the 200-fs ytterbium pump laser. In contrast, the fundamental 1030 nm beam pumps the second stage directly. AgGaS2 (AGS), KTiOAsO4 (KTA), GaSe, LiGaS2 (LGS), and LiIO3 (LIO3) non-linear crystals were tested and the KTA crystal proved to be the most robust. We demonstrate operation without crystal damage at higher than previously reported peak intensities for AGS (290 GW/cm2) and LGS (214 GW/cm2) and report new values of damage threshold for GaSe (85 GW/cm2) and LIO3 (159 GW/cm2).
... The latter has been studied under several strong assumptions. 5,7,13,14 This communication tries to address these three aspects with the aim of providing with a solid criterion in the design of this kind of setup and with conceptual tools in the analysis of the experimental data. ...
... On the other hand, it is customary to assume that long NLCs produce longer converted signals. 5,7,13,14 This is based on calculations that at best consider the beams to be collinear or make important simplifications about the frequency generation phenomenon. This is reasonable considering the complexity of the problem, which has found a numerical solution almost free of all approximations only recently 14 though it has not yet been implemented to the particular case of fluorescence. ...
... 7,31 In these works, the small signal gain approximation was employed, while the phase-matching and dispersion were neglected. In fact, as described in Ref. 13, previous attempts of modeling of any sort of non-collinear frequency mixing were rare and involved crude approximations. ...
Several aspects contributing to the temporal broadening in the measurement of ultrafast fluorescence by means of up-conversion wave mixing are presented: the characteristics of the sample, those of the collection optics, and the wave mixing with the gate pulse in a non-linear crystal. It is concluded that these contributions are emission wavelength dependent and can be as important as the pulse durations in determining the instrument response function in this technique.
... UPPE was first established by Kolesik et al. [47] to describe the space-time propagation of few-cycle pulse. This method was widely adapted by others [48][49][50]. Compared to the nonlinear Schrödinger equation (NLSE), the UPPE can provide a more accurate description of pulse propagation, in particular, when it comes to extremely short or broadband electromagnetic pulses. ...
The situation of self-compression and concomitant supercontinuum generation in a multipass cell is analyzed in numerical simulations. This study focuses on multipass cells that contain a dielectric slab as nonlinear medium and overcompensate the dispersion of the slab with intracavity dispersive coatings. A 2D+1 unidirectional pulse propagation equation is utilized to simulate the pulse evolution through successive passes. We observe a previously unreported effect of space-time focusing, leading to a pronounced blue shift, similar to what had been observed in filament compression experiments before. This effect competes with detrimental pulse breakup, which can nevertheless be mitigated under suitable choice of cavity parameters. We further analyze resulting coherence properties, in both the time and frequency domains. Our analysis shows highly favorable properties of multipass cell compression schemes when nonlinearity and dispersion are distributed over as many cavity passes as possible. This quasicontinuous approach is particularly promising for spectral broadening schemes that allow for stabilization of the carrier-envelope phase.
... The key component of the amplifier is a PM NPE based environmentally stable fiber oscillator [16] seeding a two-stage fiber amplifier that employed an ytterbium-doped photonic crystal fiber (rod) in the final booster stage. Parameters of each of the amplification stages were numerically simulated and optimized for the system efficiency using the modified pulse propagation algorithm developed in [17]. The maximum energy of the pulses available at the central wavelength of 1030 nm was 50 mJ, with the pulse repetition frequency fixed at 300 kHz. ...
Surface-enhanced Raman spectroscopy (SERS) is a research method in which a lack of cost-effective, versatile platforms with high enhancement factor (EF) is still a major obstacle to its widespread use. The platforms should be also easy to manufacture, stable in time (for weeks or even for months) and manufactured with a highly reproducible method.
We demonstrate SERS platforms based on silicon modified on the surface by laser ablation and covered with SERS-active metal. The substrates were fabricated by a femtosecond laser, thus the method is simple, very fast and creates highly uniform SERS platforms in a large number. The platform was tested with para-mercaptobenzoic acid (p-MBA) in terms of sensitivity and reproducibility. The calculated EF was at the level of 10⁸ and the standard deviation (SD) gives 7 % for 10⁻⁶ M solution of p-MBA based on the intensity of the band at 1073 cm⁻¹. Optimized SERS substrate also exhibits excellent stability for up to six months.
We also give the proof-of-concept of using our platform and, for the first time, the SERS analysis of the most important human opportunistic fungal pathogen Candida spp. (Candida glabrata, Candida albicans SN148 and Candida albicans BWP17). Finally, the chemometric analysis in the form of Principal Component Analysis (PCA) allowed to strain differentiation of Candida spp., and to distinguish the studied Candida species from Gram-positive bacterial samples with Staphylococcus aureus. Our results demonstrate that the proposed SERS platform is a perfect substrate for detection, identification and differentiation between fungal and bacterial pathogens using SERS technique.
Hopf‐type bifurcation dynamics, a universal phenomenon existing in numerous physical systems, has recently been observed in mode‐locked erbium‐doped fiber lasers with anomalous or normal net dispersion. This study demonstrates the real‐time experimental observation of double‐Hopf‐type breathers in an all‐normal dispersion all‐polarization maintaining ytterbium‐doped fiber laser instead. It is shown that the breather frequency can be modulated periodically by the additional oscillation with increasing amplitude in response to increased pump power until a stationary dissipative soliton is formed. The possible explanation of the observed double‐Hopf‐like bifurcation dynamics is discussed by exploring the numerical approach that combines the interplay of the population inversion in the laser medium with the pulses energy. The results provide additional building blocks for further understanding laser physics and can help in optimizing fiber cavity designs. Hopf‐type bifurcation dynamics is a universal phenomenon existing in numerous physical systems. This study demonstrates the real‐time experimental observation of double‐Hopf‐type breathers in ultrafast fiber lasers, where the breather frequency is modulated by an additional oscillation. These results may significantly contribute to a more profound understanding of laser physics, and bring attractive perspectives for several cutting‐edge technological applications.
Light beams with broad spectral bandwidth are indispensable for the generation of ultrashort light pulses. Here, the generation of broadband ultrashort light pulses from narrowband seeds in transparent media is demonstrated. Broadband light pulses with a spectral width of hundreds of nanometers can be generated seeding with narrowband light pulses. The full spectral bandwidths of the narrowband seeds are several nanometers. Broadband ultrashort pulses from about 500 nm to 1020 nm are obtained seeding with a light beam at around 900 nm with 9 nm full spectral bandwidth. The temporal and spatial parameters of the generated broadband pulses are measured and analyzed. A new method for the generation of wavelength tunable broadband ultrashort lights is presented. The broadband light beam generation phenomenon can be explained by ping-pong four wave mixing (PPFWM) process, which helps us to understand all the optical parametric processes visually. The generated broadband pulses have potential applications in ultrafast spectroscopy and ultrafast pump-probe experiments.
