Deep reinforcement learning for self-tuning laser source of dissipative solitons

Increasing complexity of modern laser systems, mostly originated from the nonlinear dynamics of radiation, makes control of their operation more and more challenging, calling for development of new approaches in laser engineering. Machine learning methods, providing proven tools for identification, control, and data analytics of various complex systems, have been recently applied to mode-locked fiber lasers with the special focus on three key areas: self-starting, system optimization and characterization. However, the development of the machine learning algorithms for a particular laser system, while being an interesting research problem, is a demanding task requiring arduous efforts and tuning a large number of hyper-parameters in the laboratory arrangements. It is not obvious that this learning can be smoothly transferred to systems that differ from the specific laser used for the algorithm development by design or by varying environmental parameters. Here we demonstrate that a deep reinforcement learning (DRL) approach, based on trials and errors and sequential decisions, can be successfully used for control of the generation of dissipative solitons in mode-locked fiber laser system. We have shown the capability of deep Q-learning algorithm to generalize knowledge about the laser system in order to find conditions for stable pulse generation. Region of stable generation was transformed by changing the pumping power of the laser cavity, while tunable spectral filter was used as a control tool. Deep Q-learning algorithm is suited to learn the trajectory of adjusting spectral filter parameters to stable pulsed regime relying on the state of output radiation. Our results confirm the potential of deep reinforcement learning algorithm to control a nonlinear laser system with a feed-back. We also demonstrate that fiber mode-locked laser systems generating data at high speed present a fruitful photonic test-beds for various machine learning concepts based on large datasets

Investigation of the influence of the nucleon pairing force on the octupole deformation of uranium and thorium isotopes in the mean-field approximation

In the Hartree-Fock-Bogolyubov approximation and the axial symmetry of nuclei with Skyrm forces SkM∗, the properties of U with A = 220 – 232 and Th with A = 218 – 230 isotopes were calculated. In addition, the properties of U and Th near the neutron drip line A = 280 – 292 were calculated. Pairing of nucleons in nuclei is described by pairing forces of zero radius of action of a mixed type with different sets of pairing force constants. In our calculations, we used constrained conditions on the parameters of quadrupole β₂ and octupole β₃ deformations of nuclei. It is shown that for the considered U isotopes, as well as Th isotopes, the deformation of the β₃ nuclei strongly depends on the choice of the parameters of the nucleon pairing force.У наближенні Хартрі-Фока-Боголюбова та аксіальної симетрії ядер із силами Скірма SkM∗ проведено розрахунки властивостей ізотопів U з A = 220 – 232 і Th з A = 218 – 230. Додатково проведені розрахунки властивостей U і Th біля границі нейтронної стабільності A = 280 – 292. Спарювання нуклонів у ядрах описується силами спарювання нульового радіуса дії змішаного типу з різними наборами констант сил спарювання. У розрахунках використовувалися накладені умови на параметри квадрупольної β₂ і октупольної β₃ деформацій ядер. Показано, що для розглянутих ізотопів U, як і ізотопів Th, деформація ядер β₃ сильно залежить від вибору параметрів сили спарювання нуклонів

Inverse design of mode-locked fiber laser by particle swarm optimization algorithm

A wide variety of laser applications, that often require radiation with specific characteristics, and relative flexibility of laser configurations offer a prospect of designing systems with the parameters on demand. The inverse laser design problem is to find the system architecture that provides for the generation of the desired laser output. However, typically, such inverse problems for nonlinear systems are sensitive to the computation of the gradients of a target (fitness) function making direct back propagation approach challenging. We apply here particle swarm optimization algorithm that does not rely on the gradients of the fitness function to the design of a fiber 8-figure laser cavity. This technique allows us to determine the laser cavity architectures tailored to generating on demand pulses with duration in the range of 1.5–105 ps and spectral width in the interval 0.1–20.5 nm. The proposed design optimisation algorithm can be applied to a variety of laser applications, and, more generally, in a range of engineering systems with flexible adjustable configurations and the outputs on demand

Properties of Fe, Ni and Zn isotope chains near the drip-line

The location of proton and neutron drip-lines and the characteristics of the neutron-deficient and the neutron-rich isotopes Fe, Ni and Zn on the basis of Hartree-Fock method with Skyrme forces (Ska, SkM*, Sly4) taking into account deformation was investigated. The calculations predict a big jump of deformation parameter up to β ~ 0.4 for Ni isotopes in the neighborhood of N ~ 62. The manifestation of magic numbers for isotopes ⁴⁸Ni, ⁵⁶Ni, ⁷⁸Ni and also for the stable isotope in the respect to neutron emission ¹¹⁰Ni which is situated beyond the neutron drip-line is discussed.На основі метода Хартрі-Фока з силами Скірма (Ska, SkM*, Sly4) при врахуванні деформації досліджено положення протонної і нейтронної границі стабільності і характеристики нейтронодефіцітних і нейтрононадлишкових изотопів Fe, Ni и Zn. Розрахунки зазбачають, що для изотопів Ni в околі N ~ 62 спостерігається великий стрибок величини параметра деформації до β ~ 0.4. Обговорюються прояви магічних чисел для изотопів нікеля ⁴⁸Ni, ⁵⁶Ni, ⁷⁸Ni, а також для нейтроностабільного изотопа ¹¹⁰Ni , який знаходиться за межами границі стабильності.На основе метода Хартри-Фока с силами Скирма (Ska, SkM*, Sly4) при учете деформации исследовано положение протонной и нейтронной границы стабильности и характеристики нейтронодефицитных и нейтроноизбыточных изотопов Fe, Ni и Zn. Расчеты предсказывают, что для изотопов Ni в окрестности N ~ 62 наблюдается большой скачок величины параметра деформации до β ~ 0.4. Обсуждается проявление магических чисел для изотопов никеля ⁴⁸Ni, ⁵⁶Ni, ⁷⁸Ni, а также для нейтроностабильного изотопа ¹¹⁰Ni, который находится за пределами границы стабильности

Elastic Scattering Phenomenology

We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered “good”, are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions

International standard atmosphere - a tool for technological measurement sovereignty in the aerospace industry

When designing aircraft for agriculture, all calculations are carried out for the International Standard Atmosphere (ISA) conditions, which makes it possible to compare the results of calculations and flight tests of several aircraft conducted in different climatic zones by recalculating the test results to the parameters of the International Standard Atmosphere, “placing” all aircraft in the same conditions - ISA conditions. Historically, the materials for the development of international standards in the field of ISA were developed in the USSR and formed the basis of international standards ISO, which in turn became the basis of documents ICAO 7488/3 of the International Civil Aviation Organisation (ICAO) and subsequently became state documents on standardisation identical to international standards ISO. The above works were carried out within the framework of the international technical subcommittee on standardisation ISO/TC 20/SC 6 “standard atmosphere”, formed in 1980 as part of the international standardisation body ISO/TC 20/SC 6 “standard atmosphere”. Standardisation is the basis for the unity of measurements. In the Russian Federation, the technical committee on standardisation TC 484 “Standard Atmosphere” was established. The developed model of the International Standard Atmosphere allows us to compare the results of calculations and flight tests of several aircrafts conducted in different climatic zones by recalculating the test results to the parameters of the International Standard Atmosphere, “placing” all aircrafts in the same conditions - ISA conditions. With the development of aviation and space technology, the list of atmospheric parameters subject to normalisation and standardisation is expanding