Self-similar Pulse Compression Research Articles

Tapered photonic crystal fiber based on artificial intelligence-design for pulse compression

In this study, we employ a deep neural network(DNN) to achieve rapid prediction of dispersion and effective mode area in Pb-silicate photonic crystal fiber. Subsequently, this prediction model is used to drive a particle swarm optimization(PSO) algorithm to design tapered Pb-silicate photonic crystal fibers for pulse compression. The designed fibers exhibit an increasing nonlinear index profile, enabling self-similar pulse compression(SSPC) of pulses at a wavelength of 2μm. In compliance with fundamental soliton conditions, a 0.566 m tapered PCF achieves notable pulse compression. It reduces the initial pulse width of 1.76 ps to 52 fs, achieving a remarkable compression factor of 33.92, while maintaining a quality factor of 1.01 and less than 5.4% pedestal energy. In scenarios where fundamental soliton conditions are not met, a 1.74 m tapered PCF also achieves significant compression. It compresses a pulse with a width of 1.76 ps and a peak power of 1 kW to a pulse width of 13.7 fs and a peak power of 24.82 kW, resulting in a compression factor of 129. The proposed approach overcomes the empirical reliance inherent in manual design and significantly reduces computational demands, enabling the design of pulse compression fiber tapers tailored to input pulse shapes.

Nearly Self-Similar Pulse Compression in Horizontally Slotted Waveguides at 2.0 μm

Nearly Self-Similar Pulse Compression in Horizontally Slotted Waveguides at 2.0 μm

Self-similar pulse compression in a tapered Pb-silicate photonic crystal fiber at 2 µm

We report a 2-µm all-fiber nonlinear pulse compressor based on a tapered Pb-silicate photonic crystal fiber (PCF), which is capable of achieving large compression with low pedestal energy. A tapered Pb-silicate photonic crystal fiber with increased nonlinear coefficients is proposed for achieving self-similar pulse compression (SSPC) at 2 µm. The dynamic evolution of the fundamental order soliton is numerically analyzed based on the designed tapered fiber. After pulse compression in a tapered fiber with a length of 2.2 m, an initial 1.76 ps pulse can be compressed to 88 fs, increasing the peak power from 4.4 to 86 W with a compression factor of 20 and a quality factor of 98%. The results reveal that exponential variation yields superior compression performance and provides a promising solution for generating high-power femtosecond pulses at 2 µm.

Investigation of Multimode Self-Similar Pulse Compression in Tapered Photonic Crystal Fibers

In this paper, we theoretically investigate the multimode self-similar pulse compression (MM-SSPC) in tapered photonic crystal fibers. To expand the self-similar theory beyond single-mode scenarios, we have discovered through analytical analysis that the width of the input pulse has a significant impact on perturbing the MM-SSPC process. We proceed to solve the multimode generalized nonlinear Schrödinger equation using numerical methods for various input pulse widths, which leads to the observation of three distinct types of multimode pulse compression. MM-SSPC only takes place when the input pulse width is comparatively longer. Our numerical results are consistent with the predictions of analytical calculations. Our results demonstrate that by using input pulses of 2.5 ps in duration, three modes can be compressed in a self-similar manner to 200 fs, which corresponds to a compression factor of 12.5. Finally, We establish the minimum input pulse width required to enable the MM-SSPC to function for the three specific modes of interest. Our findings provide an effective guidance to design pulse compressor for the generation of pedestal-free, high-energy femtosecond pulses.

Simultaneous Pulse Combination and Nearly Self-Similar Pulse Compression in Tapered Silicon Waveguides at Around 2.0 μm

Nonlinear pulse compression technology permits practitioners to produce ultrashort pulses for integrated frequency comb generation and optical coherence tomography. However, on-chip simultaneous combination and compression of two pulses at 2.0 μm is a complex nonlinear dynamic that has never been reported. Here, we demonstrate that two raised cosine pulses with the same center wavelengths of 2.0 μm are firstly coalesced into a single combined pulse and then realize nearly self-similar compression in the dispersion exponentially decreasing silicon waveguide, where the final compressed pulse was reduced from 200 fs to 49 fs with a compression factor of 4.08. Additionally, the peak power of the compressed pulse steadily rises to 2.16 times of the initial peak power. For further development, we also illustrate two input pulses with different center wavelengths to realize effective combination and self-similar compression. These results shed new insights into the potential of dispersion engineering waveguides for low-power integrated applications at 2.0 μm.

Low pedestal sub-17 fs pulse generation through cascaded self-similar compression in photonic crystal fibers

We propose a realistic numerical model based on cascaded self-similar pulse compression to generate low pedestal ultrashort pulses at 2.5 µm. Self-similarity in photonic crystal fibers (PCFs) has been attained by modelling exponentially dispersion decreasing and exponentially nonlinearity increasing chalcogenide PCFs. The tapered PCF (TPCF) model is theoretically designed using the fully vectorial effective index method (FVEIM) to obtain accurate effective refractive index, group velocity dispersion (GVD), and Kerr nonlinearity values with low computation time. Initially, fundamental soliton compression in As2S3 tapered PCF is being investigated for the pedestal-free reduction of the pulse width. Subsequently, the compression factor is further enhanced in the As2Se3 PCF-based nonlinear optical loop mirror. The numerical outcomes reveal a compression of 1 ps pulse down to a pulse width of 16.6 fs with a peak power of 116 W in a total fiber length of L = 61 cm.

Self-similar pulse compression by suspended core photonic crystal fiber with cubic-quintic nonlinearities

An enhanced self-similar pulse compression with suspended core photonic crystal fiber has been theoretically studied. The proposed model well support the essential criteria of having very low dispersion and increased nonlinearity with increasing suspension factor resulting high compression rate within short length of the fiber. Unlike the conventional tapering methods, the suspended core photonic crystal fiber can achieve the self-similar conditions more easily and reduces the practical difficulties to achieve the desired fiber parametric values. We have also studied the possible deformations of the fiber and temperature variations that can effect the pulse compression process and compression factor.

Nearly Self-Similar Pulse Compression of High-Repetition-Rate Pulse Trains in Tapered Silicon Waveguides

We numerically demonstrate a feasible way to generate a high-repetition-rate ultrashort soliton train from a dual frequency beat signal on a chip-scale silicon waveguide. A train of well-separated solitons is formed in the designed novel tapered silicon waveguide. Through the self-similar pulse compression, the pulse duration of the input pulse train is compressed from 1.5625 ps to 123.4 fs at the telecomm wavelength. Besides, the pulse propagation consists of two stages: pulse shaping and pulse compression, where the raised-cosine pulse train is evolved into the hyperbolic secant pulse train and further realize an efficient self-similar compression. The results deepen our understanding of nonlinear propagation in silicon waveguides, and open the possibility of high-repetition-rate pulse trains functionalities for ultrahigh-capacity optical communication and micro-machining in a monolithic CMOS platform.

Self-similar picosecond pulse compression for supercontinuum generation at mid-infrared wavelength in silicon strip waveguides

Self-similar pulse compression has important application in highly coherent supercontinuum (SC) generation. In this paper, we numerically present the mid-infrared self-similar picosecond pulse compression in a tapered suspended silicon strip waveguide, which is designed with exponentially decreasing dispersion profile along the direction of propagation. When the variation of the Kerr nonlinear coefficient γ(z), linear and nonlinear losses, higher-order nonlinearity, and higher-order dispersion are taken into consideration, the simulation result shows that a 1 ps input pulse centered at wavelength 2.8μm could be self-similarly compressed to 47.06 fs in a 3.9-cm waveguide taper, along with a compression factor Fc of 21.25, quality factor Qc of 0.78, and negligible pedestal. After that, the compressed pulse is launched into a uniform silicon strip waveguide, which is used for the generation of SC. We numerically demonstrate that the coherence of the generated SC by the compressed pulse can be significantly improved when compared to that generated directly by the picosecond pulse. The simulation results can be used to realize on-chip mid-infrared femtosecond light source and highly coherent supercontinuum, which can promote the development of on-chip nonlinear optics.

Self-Similar Chirped Pulse Compression in the Tapered Silicon Ridge Slot Waveguide

We propose a practical scheme to realize high-degree pulse compression in tapered silicon ridge slot waveguide with exponentially decreasing dispersion. Firstly, we design the tapered silicon ridge slot waveguide, which is simple to fabricate and works at the telecommunication wavelength. In the self-similar pulse compression, the initial 1 ps pulse can be compressed to 82.53 fs at the wavelength of 1550 nm and the corresponding peak power is 7.11 times compared to the initial pulse. Besides, we also investigate the multiplicity of the effect of perturbation in initial chirp, peak power and linearly decreasing dispersion in the pulse compression process. By employing these optical properties, we further make a detailed comparison of the numerical results for the generalized nonlinear Schrodinger equation and pulse parameter equations.

Self-similar pulse compression by defective core photonic crystal fiber with cubic–quintic nonlinearities

We propose a class of photonic crystal fiber called as defective core photonic crystal fiber which can fulfill the self-similar condition for pulse compression in a relatively simple means, without the necessity for a complex approach of changing the size of air holes in the cladding. The proposed model obeys exponential decrease (increase) in dispersion (nonlinearity) along the fiber length and hence compresses the pulse under self-similar technique. We also study the effect of system parameters such as initial dispersion, nonlinearity and chirping in the self-similar compression and compared with adiabatic compression. Using extended nonlinear Schrödinger equation, we have taken into account the effect of quintic nonlinearity on the pulse compression. In the proposed configuration, the quintic nonlinearity shows only a weaker effect in the compression as compared to the cubic nonlinearity. In the present system, we show that the self-similar technique is superior with high degree of compression than the adiabatic route of compressing the pulse. The effect of fiber loss is also taken into account and the critical fiber loss coefficient for compression is estimated.

Mid-Infrared Self-Similar Pulse Compression in a Tapered Tellurite Photonic Crystal Fiber and Its Application in Supercontinuum Generation

In this paper, we design a tapered tellurite photonic crystal fiber (TTPCF) with nonlinear coefficient increasing along the propagation direction, and demonstrate the mid-infrared self-similar pulse compression of the fundamental soliton in such a TTPCF. When the variation of group-velocity dispersion, higher-order dispersion, higher-order nonlinearity, and linear loss are considered, a 1 ps pulse at wavelength 2.5 μm can be compressed to 62.16 fs after a 1.63-m long propagation, along with the negligible pedestal, compression factor F c of 16.09, and quality factor Q c of 83.16%. Then the compressed pulse is launched into another uniform tellurite PCF, where highly coherent and octave-spanning supercontinuum (SC) is generated. Compared to the initial picosecond pulse, the compressed pulse has much larger tolerance of noise level for the SC generation. Our research results provide a promising solution to realize the fiber-based mid-infrared femtosecond pulse source for nonlinear photonics and spectroscopy.

Mid-infrared self-similar compression of picosecond pulse in an inversely tapered silicon ridge waveguide

On chip high quality and high degree pulse compression is desirable in the realization of integrated ultrashort pulse sources, which are important for nonlinear photonics and spectroscopy. In this paper, we design a simple inversely tapered silicon ridge waveguide with exponentially decreasing dispersion profile along the propagation direction, and numerically investigate self-similar pulse compression of the fundamental soliton within the mid-infrared spectral region. When higher-order dispersion (HOD), higher-order nonlinearity (HON), losses (α), and variation of the Kerr nonlinear coefficient γ(z) are considered in the extended nonlinear Schrodinger equation, a 1 ps input pulse at the wavelength of 2490 nm is successfully compressed to 57.29 fs in only 5.1-cm of propagation, along with a compression factor Fc of 17.46. We demonstrated that the impacts of HOD and HON are minor on the pulse compression process, compared with that of α and variation of γ(z). Our research results provide a promising solution to realize integrated mid-infrared ultrashort pulse sources.

High Degree Picosecond Pulse Compression in Chalcogenide-Silicon Slot Waveguide Taper

In this paper, we propose and design a chalcogenide (As2S3)-based slot waveguide taper with exponentially decreasing dispersion profile to realize high-degree pulse compression of low-power chirped solitons. Based on the waveguide taper designed, pulse compression of fundamental solitons, and chirped 2-soliton breather are both investigated numerically. With self-similar pulse compression scheme, a 1 ps input pulse is compressed to 81.5 fs in 6 cm propagation. By using 2-soliton breather pulses, a 1 ps chirped pulse is compressed to 80.3 fs in just 2.54 cm. This is the first demonstration of the feasibility of high-degree nonlinear pulse compression in As2S3-based slot waveguide taper.

Efficient Pulse Compression Using Tapered Photonic Crystal Fiber at 850 nm

By using appropriate self-similar scaling analysis, we delineate the generation of linearly chirped solitary pulses in photonic crystal fiber (PCF) at 850 nm to obtain the short pulses with large compression factor and minimal pedestal energy when compared to adiabatic compression scheme. The dispersion and nonlinearity varying nonlinear Schrödinger equation aptly models the pulse propagation in such a PCF. The analytical results demand that the effective dispersion must decrease exponentially while the nonlinearity must increase exponentially in the PCF. Thus, based on the analytical results, we propose the new design of tapered PCF by varying the pitch and diameter of the air hole. We adopt the projection operator method to derive the pulse parameter equations which indeed very clearly describe the self-similar pulse compression process at different parts of the PCF structures. As we are interested in constructing compact compressor, we also introduce another designing of PCF by filling chloroform in the core region. The chloroform filled tapered PCF exhibits low dispersion length for efficient pulse compression with low input pulse energy over small propagation distances.