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An improved implementation of the perfectly matched layer (PML) is developed for the Transmission Line Modelling (TLM) method based on a mapping of the symmetrical condensed node (SCN) to an analytically extended geometric space. By mapping the TLM node, a medium - circuit equivalence is developed which maps transmission line parameters from real to complex domain. This consequently modifies the TLM scatter-connect process. The PML implementation is demonstrated for canonical cases where it is shown to have a comparable absorption performance and a significantly improved temporal stability relative to previously published TLM-PML formulations.

Based on tapered Triple-Core Photonic Crystal Fiber (TCPCF), a high performance tunable Dual-Wavelength Erbium-Doped Fiber Laser (DW-EDFL) is proposed and experimentally demonstrated. The mode-coupling among three cores of TCPCF appears periodically and becomes further enhanced in tapered TCPCF, which are beneficial to form a filter to select lasing wavelength. A series of tapered TCPCFs with different taper lengths are fabricated and inserted into tunable DW-EDFL as filters. Multiple groups of tunable dual-wavelength lasing outputs are achieved by using the tapered TCPCF filter with a waist diameter of 126 μm. The maximum tunable range can reach up to 14.36 nm and the side mode suppression ratio of all lasing outputs are above 52 dB. In addition, the tunable single- and triple-wavelength lasers are also obtained. The tunable single-wavelength laser has an excellent linear response to strain and can be applied to realize a high-sensitivity strain sensor with the highest strain sensitivity of -13.1 pm/με.

Results from the electromagnetic modeling of the threshold conditions of hybrid plasmon modes of a laser based on a silver nanotube with an active core and covered with an active shell are presented. We study the modes of such a nanolaser that have their emission wavelengths in the visible-light range. Our analysis uses the mathematically grounded approach called the lasing eigenvalue problem (LEP) for the set of the Maxwell equations and the boundary and radiation conditions. As we study the modes exactly at the threshold, there is no need to invoke nonlinear and quantum models of lasing. Instead, we consider a laser as an open plasmonic resonator equipped with an active region. This allows us to assume that at threshold the natural-mode frequency is real-valued, according to the situation where the losses, in the metal and for the radiation, are exactly balanced with the gain in the active region. Then the emission wavelength and the associated threshold gain can be viewed as parts of two-component eigenvalues, each corresponding to a certain mode. In the configuration considered, potentially there are three types of modes that can lase: the hybrid localized surface plasmon (HLSP) modes of the metal tube, the core modes, and the shell modes. The latter two types can be kept off the visible range in thin enough configurations. Keeping this in mind, we focus on the HLSP modes and study how their threshold gain values change with variations in the geometrical parameters of the nanotube, the core, and the shell. It is found that essentially a single-mode laser can be designed on the difference-type HLSP mode of the azimuth order m = 1, shining in the orange or red spectral region. Furthermore, the threshold values of gain for similar HLSP modes of order m = 2 and 3 can be several times lower, with emission in the violet or blue parts of the spectrum.

A diode-pumped Q-switched Er3+:ZBLAN double-clad, single-transverse mode fiber laser is practically realized. The Q-switched laser characteristics as a function of pump power, repetition rate, and fiber length are experimentally investigated. The results obtained show that the Q-switched operation with 46 µJ pulse energy, 56 ns long pulses, and 0.821 kW peak power is achieved at a pulse repetition rate of 10 kHz. To the best of our knowledge, this is the highest-ever demonstrated peak power emitted from an actively Q-switched, single-transverse mode Er3+:ZBLAN fiber laser operating near 2.8 µm.

A spontaneous emission fiber source operating in the mid-infrared (MIR) wavelength range from 3.5 to 8 µm is demonstrated for the first time at output power levels of at least 1 mW. The source is a Pr3+-doped selenide chalcogenide, multimode, glass fiber pumped with commercially available laser diodes operating at 1.470 µm, 1.511 µm and 1.690 µm. This MIR spontaneous emission fiber source offers a viable alternative to broadband mid-infrared supercontinuum fiber sources, which are comparatively complex and costly. The MIR emission wavelength range is significant for molecular sensing applications across biology and chemistry, and in medicine, agriculture, defense, and environmental monitoring.

An electromagnetic wavelength-scale analysis of the optical characteristics of multi-nanolayer photovoltaic (PV) structures: without an antireflection coating, with an antireflection coating on the top of the structure, and with both the antireflection coating on the top and a broadband non-periodic (chirped) distributed Bragg reflector (DBR) on the bottom of the structure is performed. All the PV structures studied are based on a Si p-i-n type absorber supported by a metallic layer (Cu) and SiO2 substrate. The top-to-bottom electromagnetic analysis is performed numerically by the method of single expression (MSE). Absorbing and reflecting characteristics of the multi-nanolayer PV structures are obtained. The influence of the thicknesses and permittivities of the layers of the PV structures on the absorbing characteristics of the structures is analyzed to reveal favourable configurations for enhancement of their absorption efficiency. The localizations of the electric component of the optical field and the power flow distribution within all the PV structures considered are obtained to confirm an enhancement of the absorption efficiency in the favorable configuration. The results of the electromagnetic wavelength-scale analysis undertaken will have scientific and practical importance for optimizing the operation of thin-film multi-nanolayer PV structures incorporating a chirped DBR reflector with regards to enhancing their efficiency.

The modeling and design of fiber lasers facilitate the process of their practical realization. Of particular interest during the last few years is the development of lanthanide ion-doped fiber lasers that operate at wavelengths exceeding 2000 nm. There are two main host glass materials considered for this purpose, namely fluoride and chalcogenide glasses. Therefore, this study concerned comparative modeling of fiber lasers operating within the infrared wavelength region beyond 2000 nm. In particular, the convergence properties of selected algorithms, implemented within various software environments, were studied with a specific focus on the central processing unit (CPU) time and calculation residual. Two representative fiber laser cavities were considered: One was based on a chalcogenide–selenide glass step-index fiber doped with trivalent dysprosium ions, whereas the other was a fluoride step-index fiber doped with trivalent erbium ions. The practical calculation accuracy was also assessed by comparing directly the results obtained from the different models.

Achieving single-mode operation and highly directional (preferably unidirectional) in-plane light output from whispering-gallery (WG)-mode semiconductor microdisk resonators without seriously degrading the mode Q-factor challenges designers of low-threshold microlasers. To address this problem, basic design rules to tune the spectral and emission characteristics of microscale optical cavity structures with nanoscale features by tailoring their geometry are formulated and discussed in this paper. The validity and usefulness of these rules is demonstrated by reviewing a number of previously studied cavity shapes with global and local deformations. The rules provide leads to novel improved WG-mode cavity designs, two of which are presented: a cross-shaped photonic molecule with introduced asymmetry and a photonic-crystal-assisted microdisk resonator. Both these designs yield degenerate-mode splitting, as well as Q-factor enhancement and directional light output of one of the split modes [ABSTRACT FROM PUBLISHER]