The use of resonant whispering gallery modes (WGMs) for sensing exhibits various drawbacks and critical points related to the microsphere and tapered optical fiber fabrication tolerance. The ...uncertainty on the fiber taper and microsphere geometry or the gap between the microsphere and the fiber taper can complicate or limit the actual use of these devices for sensing, requiring peculiar calibration of the WGM based sensing set-up. An alternative double-step approach is proposed in this paper. In particular, the geometrical parameters of the set-up are recovered preliminarily and then the rare earth parameters are recovered via simple transmittance/gain measurements. The method is based on a refined electromagnetic model of the device suitably integrated with a particle swarm optimization (PSO) approach. The percent errors made on the up-conversion coefficients C
and C
are extremely low, being 0.75%, 0.05%, respectively. The procedure is very robust. It can be applied more in general, allowing the sensing of other physical parameters via simple transmittance measurements instead of wavelength shift ones, in both microsphere and microbubble based set-up.
We present an approach coupling a limited experimental number of tests with numerical simulations regarding the design of radiation-hardened (RH) rare earth (RE)-doped fiber amplifiers. Radiation ...tests are done on RE-doped fiber samples in order to measure and assess the values of the principal input parameters requested by the simulation tool based on particle swarm optimization (PSO) approach. The proposed simulation procedure is validated by comparing the calculation results with the measured degradations of two amplifiers made with standard and RH RE-doped optical fibers, respectively. After validation, the numerical code is used to theoretically investigate the influence of some amplifier design parameters on its sensitivity to radiations. Simulations show that the RE-doped fiber length used in the amplifier needs to be adjusted to optimize the amplifier performance over the whole space mission profile rather than to obtain the maximal amplification efficiency before its integration in the harsh environment. By combining this coupled approach with the newly-developed RH RE-doped fibers, fiber-based amplifiers nearly insensitive to space environment may be designed in the future.
A refined model of a mid-IR amplifier, constituted by a tapered chalcogenide fiber coupled to an erbium-doped chalcogenide microsphere, is integrated with a global solution search procedure based on ...particle swarm optimization approach. It is implemented in a computer code in order to obtain an inversion algorithm useful to evaluate the spectroscopic parameters of rare-earth-doped glass microspheres. The rare earth parameters can be recovered by means of the optical gain measurement. The error in evaluation of the erbium lifetime τ 41 is <;3.5%. It is <;0.5% for the other lifetimes and ion-ion interaction parameters. These excellent results are obtained since whispering gallery mode electromagnetic field interacts with rare earth for long effective distances.
A squintless slot-antenna array (2-D), built on a single substrate integrated waveguide (SIW) is shown. The effort needed for designing a suitable feeding network in SIW technology is justified in ...view of obtaining lightweight, low-profile, and low-cost antennas for many applications, including direct broadcast satellite. A proper definition of an "H"-shaped subarray, made of four slot-pairs, is used to improve the input matching over a wide band. This choice allows remarkable simplification of the fabrication process, as the slots are cut directly in one of the metallic planes forming the SIW.
An erbium-doped hole-assisted optical fiber amplifier, to be employed in the third band of the optical communications, is designed and optimized via a tailor made computer code. The finite element ...method is used for the electromagnetic investigation of the microstructured fiber section. The simulation model takes into account all the rare earth physical phenomena, i.e., the pump and signal propagation, the amplified spontaneous emission, the secondary transitions pertaining to the ion-ion interactions, and so on. The device feasibility is tested via a number of simulations, realistically performed by taking into account the actual parameters pertaining to the dispersion of the germania/silica glass, the erbium emission and absorption cross sections, the propagation losses. By simulation, in the small signal operation, a gain close to 42.8 dB is demonstrated for a fiber 13-m long, using a pump power of 50 mW at the signal wavelength /spl lambda//sub s/=1536 nm, the pump and the signal being copropagating.
In recent years, the development of photonic crystal fibers has allowed novel opportunities for enhancing optical amplifier characteristics. In this field, accurate numerical modeling is a ...significant need to predict the device behavior. Conventional approaches perform this task by using methods which could yield solutions characterized by divergent or unstably convergent algorithms. Global optimization methods can be considered as efficient tools to face this problem.
In this paper, the application of particle swarm optimization to perform the design and characterization of photonic crystal fiber amplifiers is proposed. The employment of this technique shows different attractive features. In particular, solutions are found quickly and the implementation of the algorithm does not require complicated evolutionary operators. Numerical results show the effectiveness of the approach for both the design and characterization of a fiber amplifier. In fact, if considered as a design tool, the obtained numerical results are in good accordance with respect to the ones yielded by a conventional approach. If considered as a characterization tool, the algorithm performs a forecasting, allowing to determine parameters, such as homogeneous upconversion coefficients, whose computation could present difficulties when it is obtained via direct or indirect measurements.
► Employment of a method based on swarm intelligence as an optimization tool. ► Application of the method to the design of erbium doped PCF amplifiers. ► Computation of the optimal parameters maximizing the gain of a fiber amplifier. ► Solution of the fiber amplifier characterization problem.
The feasibility of a microstructured optical fiber (MOF) amplifier, made of a novel Er3+-doped chalcogenide glass, has been demonstrated via accurate simulations performed by employing an oppositely ...implemented computer code. The optical and geometrical parameters measured on the first MOF sample together with other physical constants from literature have been taken into account in the simulations. The calculated optical gain of the optimized MOF amplifier, 2.79 m long, is close to 23 dB at the signal wavelength of 1.538 mum, by using a pump power of 200 mW and a signal power of 0.1 muW.
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► A novel multicore ytterbium doped fiber laser is designed to maximize both the effective mode area and the beam quality. ► A complete home-made computer code is written. ► Talbot ...cavity is considered for the in-phase supermode selection of two multimodal multicore fiber lasers here optimized. ► Single mode multicore fiber laser shows higher performance than multimode ones, even a longer fiber cavity is required.
A novel multicore ytterbium doped fiber laser is designed, with the target of maximizing both the effective mode area and the beam quality, by means of a complete home-made computer code. It can be employed to construct high power and Quasi-Gaussian beam lasers. The novel laser configuration exploits a single mode multicore fiber and does not need Talbot cavity or other in-phase mode selection mechanisms. This is an innovative solution, because to the best of our knowledge, for the first time, we have designed a truly single-mode multicore fiber laser. For comparison we have optimized two other laser configurations which are well known in literature, both employing a multimode multicore fiber and a Talbot cavity as a feedback for the in-phase supermode selection. All three multicore fibers, constituted by the same glass, are doped with the same ytterbium ion concentration and pumped with the same input power. Multimodal fiber lasers exhibit lower beam quality, i.e. a higher beam quality factor M2, with respect to the single mode one, even if suitable Talbot cavities are designed, but they are very competitive when a more compact laser cavity is required for the same output power. The novel single mode nineteen core laser exhibits a simulated effective mode area Aeff=703μm2 and a beam quality factor M2=1.05, showing better characteristics than the other two lasers.
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