Adaptivity to changing environments and constraints is key to success in modern society. We address this by proposing “incrementalized versions” of Stable Marriage and Stable Roommates. That is, we try to answer the following question: for both problems, what is the computational cost of adapting an existing stable matching after some of the preferences of the agents have changed. While doing so, we also model the constraint that the new stable matching shall be not too different from the old one. After formalizing these incremental versions, we provide a fairly comprehensive picture of the computational complexity landscape of Incremental Stable Marriage and Incremental Stable Roommates. To this end, we exploit the parameters “degree of change” both in the input (difference between old and new preference profile) and in the output (difference between old and new stable matching). We obtain both hardness and tractability results, in particular showing a fixed-parameter tractability result with respect to the parameter “distance between old and new stable matching”.

Given a set of individuals qualifying or disqualifying each other, group identification is the task of identifying a socially qualified subgroup of individuals. Social qualification depends on the specific rule used to aggregate individual qualifications. The bribery problem in this context asks how many agents need to change their qualifications in order to change the outcome. Complementing previous results showing polynomial-time solvability or NP-hardness of bribery for various social rules in the constructive (aiming at making specific individuals socially qualified) or destructive (aiming at making specific individuals socially disqualified) setting, we provide a comprehensive picture of the parameterized computational complexity landscape. Conceptually, we also consider a more fine-grained concept of bribery cost, where we ask how many single qualifications need to be changed, and a more general bribery goal that combines the constructive and destructive setting.

We demonstrated a widely tunable Tm-doped mode-locked all-fiber laser, with the widest tunable range of 136 nm, from 1842 to 1978 nm. Nonlinear polarization evolution (NPE) technique is employed to enable mode-locking and the wavelength-tunable operation. The widely tunable range attributes to the NPE-induced transmission modulation and bidirectional pumping mechanism. Such kind of tunable mode-locked laser can find various applications in optical communications, spectroscopy, time-resolved measurement, and among others.

We present a mid-infrared (mid-IR) supercontinuum (SC) light source pumped by femtosecond pulses from a thulium doped fiber amplifier (TDFA) at 2 μm. An octave-spanning spectrum from 1.1 to 3.7 μm with an average power of 253 mW has been obtained from a single mode ZBLAN fiber. Spectral flatness of 10 dB over a 1390 nm range has been obtained in the mid-IR region from 1940 - 3330 nm. It is resulted from the enhanced self phase modulation process in femtosecond regime. The all-fiber configuration makes such broadband coherent source a compact candidate for various applications.

We propose and demonstrate a broadly wavelength tunable mode-locked thulium-doped all-fiber laser, delivering sub-400 femtosecond (fs) pulses and tuning from 1867 nm to 2010 nm. The tunable range of 143 nm, to our best knowledge, is the widest in the femtosecond mode-locked thulium-doped fiber lasers (TDFLs). The broadly tunable range and femtosecond pulse oscillation attribute to the large free spectral range and bandwidth of the fiber-based Lyot filter, benefiting from the hybrid device based compact configuration. The hybrid device, integrating wavelength-division-multiplexer, polarization-sensitive isolator and output coupler, effectively diminishes the birefringence and net dispersion.

We introduce a dynamic version of the -hard graph modification problem Cluster Editing. The essential point here is to take into account dynamically evolving input graphs: having a cluster graph (that is, a disjoint union of cliques) constituting a solution for a first input graph, can we cost-efficiently transform it into a “similar” cluster graph that is a solution for a second (“subsequent”) input graph? This model is motivated by several application scenarios, including incremental clustering, the search for compromise clusterings, or also local search in graph-based data clustering. We thoroughly study six problem variants (three modification scenarios edge editing, edge deletion, edge insertion; each combined with two distance measures between cluster graphs). We obtain both fixed-parameter tractability as well as (parameterized) hardness results, thus (except for three open questions) providing a fairly complete picture of the parameterized computational complexity landscape under the two perhaps most natural parameterizations: the distances of the new “similar” cluster graph to (1) the second input graph and to (2) the input cluster graph.

We demonstrate the generation of wavelength-tunable deep-ultraviolet pulses in a small-mode-area hollow-core fiber fabricated by tapering a nodeless tubular-type hollow-core fiber. Down-scaling of the cross-sectional geometry reduces the pump energy requirement for inducing sufficient nonlinear effects, presenting a unique opportunity for staging low-energy-threshold gas-based nonlinear optics. We report the onset of the ultraviolet light with the pump pulse energy as low as 125 nJ. Our numerical analysis shows that the frequency conversion arises due to soliton phase matching, and therefore shot-to-shot coherence of the ultraviolet emission is well-preserved. It offers a promising platform for a compact ultraviolet frequency comb source.

We demonstrate flexible single-mode transmission of a high average power 2 µm nanosecond pulse using antiresonant hollow-core fibers (AR-HCFs). 39.1 W average power is delivered using a coiled 1.7 m AR-HCF, which is designed for single-mode guidance and good higher-order mode suppression. The effect of bending on the fiber output power and beam profile is also investigated. The Gaussian-like output beam profile is maintained up to a 7.5 cm bending radius. This is the highest average power delivered by a flexible long HCF in this wavelength without the need for an enclosed controlled environment, to the best of our knowledge.