118 research outputs found
Generation of stable and breathing flat-top solitons via Raman assisted four wave mixing in microresonators
Flat-top-soliton (or platicon) dynamics in coherently pumped normal dispersion microresonators is important for both fundamental nonlinear physics and microcomb generation in the visible band. Here we numerically investigate the platicon generation that is initiated via Raman assisted four wave mixing instead of mode interaction. To show the possibility of generating coherent combs in the visible band, we design an aluminum nitride (AlN) microresonator with normal dispersion and investigate the comb generation dynamics in simulations. Stable platicon Kerr combs can be generated in this AlN microresonator using a 780-nm pump. Moreover, we also observe a breather platicon dynamics induced by the narrow Raman gain spectrum of crystalline AlN, which shows distinct dynamics from the dark soliton breathers reported in previous work that are dominated by Kerr effect. A phase diagram bearing the influence of the pump detuning and pump power on the breathing dynamics of the breather platicon is also computed. Furthermore, a transition to chaotic breathing is numerically observed
swTVM: Exploring the Automated Compilation for Deep Learning on Sunway Architecture
The flourish of deep learning frameworks and hardware platforms has been
demanding an efficient compiler that can shield the diversity in both software
and hardware in order to provide application portability. Among the exiting
deep learning compilers, TVM is well known for its efficiency in code
generation and optimization across diverse hardware devices. In the meanwhile,
the Sunway many-core processor renders itself as a competitive candidate for
its attractive computational power in both scientific and deep learning
applications. This paper combines the trends in these two directions.
Specifically, we propose swTVM that extends the original TVM to support
ahead-of-time compilation for architecture requiring cross-compilation such as
Sunway. In addition, we leverage the architecture features during the
compilation such as core group for massive parallelism, DMA for high bandwidth
memory transfer and local device memory for data locality, in order to generate
efficient code for deep learning application on Sunway. The experimental
results show the ability of swTVM to automatically generate code for various
deep neural network models on Sunway. The performance of automatically
generated code for AlexNet and VGG-19 by swTVM achieves 6.71x and 2.45x speedup
on average than hand-optimized OpenACC implementations on convolution and fully
connected layers respectively. This work is the first attempt from the compiler
perspective to bridge the gap of deep learning and high performance
architecture particularly with productivity and efficiency in mind. We would
like to open source the implementation so that more people can embrace the
power of deep learning compiler and Sunway many-core processor
Generation of stable and breathing flat-top solitons via Raman assisted four wave mixing in microresonators
Flat-top-soliton (or platicon) dynamics in coherently pumped normal dispersion microresonators is important for both fundamental nonlinear physics and microcomb generation in the visible band. Here we numerically investigate the platicon generation that is initiated via Raman assisted four wave mixing instead of mode interaction. To show the possibility of generating coherent combs in the visible band, we design an aluminum nitride (AlN) microresonator with normal dispersion and investigate the comb generation dynamics in simulations. Stable platicon Kerr combs can be generated in this AlN microresonator using a 780-nm pump. Moreover, we also observe a breather platicon dynamics induced by the narrow Raman gain spectrum of crystalline AlN, which shows distinct dynamics from the dark soliton breathers reported in previous work that are dominated by Kerr effect. A phase diagram bearing the influence of the pump detuning and pump power on the breathing dynamics of the breather platicon is also computed. Furthermore, a transition to chaotic breathing is numerically observed
Coherence memory and amnesia in a mode-locked laser
Self-organization of temporal modes in mode-locked lasers usually starts from
quantum noise. In this process, incoherent spontaneous emission is steered into
coherent ultrashort pulses by dissipation and nonlinearity. In this work, we
investigated self-organization dynamics in a mode-locked Mamyshev oscillator
starting from coherent pulse seeds as opposed to quantum noise. We observed
that the coherence of the seed can be remembered or forgotten depending on the
initial inverse population. The excessive nonlinearity in the coherence amnesia
regime can devastate the seed coherence, causing the oscillator to undergo a
chaotic transition lasting hundreds of round trips before regaining coherence.
Conversely, the oscillator converges in only a few round trips for the
coherence memory regime. A heterodyne technique was developed to record the
fast varying optical phase and characterize these two regimes. Dissipative
soliton molecules were synthesized from external pulse pair seeds via the
coherence memory pathway. In this case, a plateau of the generated pulse
spacing independent from seed pulse spacing, i.e., amnesia of the seed spacing,
was observed for close spaced seed pulse pairs. Moreover, we show that pulse
seeds can be used for laser reconfiguration and pulse pattern control. Our work
paves a way to control transient pulse dynamics and steady pulse forms on
demand in mode-locked lasers
Observation of Coexisting Dissipative Solitons in a Mode-Locked Fiber Laser
We show, experimentally and numerically, that a mode-locked fiber laser can operate in a regime where
two dissipative soliton solutions coexist and the laser will periodically switch between the solutions.
The two dissipative solitons differ in their pulse energy and spectrum. The switching can be controlled by an external perturbation and triggered even when switching does not occur spontaneously. Numerical
simulations unveil the importance of the double-minima loss spectrum and nonlinear gain to the switching dynamics
Accurate Guidance Method and App Development for Assigning Parking Spaces Based on Indoor Wi-Fi
Existing parking guidance systems only provide road guidance outside the parking lot but do not provide accurate guidance to specific parking spaces inside the parking lot. By using a Kalman filter, the Grubbs test, and a neural network algorithm to improve the RSSI-based location fingerprint identification technology, an accurate location method based on indoor Wi-Fi is obtained, which implements precise route guidance and a reverse search function for parking spaces. We utilize Beidou positioning to develop a Gaode map for outdoor navigation and use an integrated system of ultrasonic detector/indicators and ground locks to manage parking spaces. Through the secondary development of an Android system and the application of a MySql database, an app for precise parking guidance was developed. The system makes full use of the Internet and parking information, eliminates information asymmetry, improves the utilization ratio of the urban static traffic resources, allocates parking spaces in real-time, breaks information islands, provides parking search and recommendation functions for users, achieves parking information-sharing, and effectively improves parking efficiency and the parking utilization ratio
Particle Swarm and Bacterial Foraging Inspired Hybrid Artificial Bee Colony Algorithm for Numerical Function Optimization
Artificial bee colony (ABC) algorithm has good performance in discovering the optimal solutions to difficult optimization problems, but it has weak local search ability and easily plunges into local optimum. In this paper, we introduce the chemotactic behavior of Bacterial Foraging Optimization into employed bees and adopt the principle of moving the particles toward the best solutions in the particle swarm optimization to improve the global search ability of onlooker bees and gain a hybrid artificial bee colony (HABC) algorithm. To obtain a global optimal solution efficiently, we make HABC algorithm converge rapidly in the early stages of the search process, and the search range contracts dynamically during the late stages. Our experimental results on 16 benchmark functions of CEC 2014 show that HABC achieves significant improvement at accuracy and convergence rate, compared with the standard ABC, best-so-far ABC, directed ABC, Gaussian ABC, improved ABC, and memetic ABC algorithms
Soliton Molecules and Multisoliton States in Ultrafast Fibre Lasers: Intrinsic Complexes in Dissipative Systems
Benefiting from ultrafast temporal resolution, broadband spectral bandwidth, as well as high peak power, passively mode-locked fibre lasers have attracted growing interest and exhibited great potential from fundamental sciences to industrial and military applications. As a nonlinear system containing complex interactions from gain, loss, nonlinearity, dispersion, etc., ultrafast fibre lasers deliver not only conventional single soliton but also soliton bunching with different types. In analogy to molecules consisting of several atoms in chemistry, soliton molecules (in other words, bound solitons) in fibre lasers are of vital importance for in-depth understanding of the nonlinear interaction mechanism and further exploration for high-capacity fibre-optic communications. In this Review, we summarize the state-of-the-art advances on soliton molecules in ultrafast fibre lasers. A variety of soliton molecules with different numbers of soliton, phase-differences and pulse separations were experimentally observed owing to the flexibility of parameters such as mode-locking techniques and dispersion control. Numerical simulations clearly unravel how different nonlinear interactions contribute to formation of soliton molecules. Analysis of the stability and the underlying physical mechanisms of bound solitons bring important insights to this field. For a complete view of nonlinear optical phenomena in fibre lasers, other dissipative states such as vibrating soliton pairs, soliton rains, rogue waves and coexisting dissipative solitons are also discussed. With development of advanced real-time detection techniques, the internal motion of different pulsing states is anticipated to be characterized, rendering fibre lasers a versatile platform for nonlinear complex dynamics and various practical applications
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