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Design of terahertz spectroscopy based optical sensor for chemical detection
摘要： In this article, a new design of circular cladding with a rotated-hexacore in photonic crystal fiber (RH-CPCF) has been suggested for chemical sensing application in the THz regime. The five layers circular cladding and two layers rotated-hexacore in circular shape are designed here. All numerical results are obtained with a procedure of finite element method and perfectly match layered boundary condition in terahertz (THz) wave propagation. After the simulation result, the proposed RH-CPCF shows the high relative sensitivity is 76.44%, 77.16% and 73.20% for three chemicals such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330) at 1 THz. On the other hand, the low confinement losses are 2.33 × 10?03 dB/m, 3.07 × 10?06 dB/m and 2.84 × 10?02 dB/m for same in three chemicals at 1 THz. Moreover, effective area, effective mode index and total power fraction in core air holes are also briefly described here. In addition, this proposed circular photonic crystal fiber (RH-CPCF) can be used especially for chemical sensing in biomedical, industrial quality control, material research, micro-optics and many communication applications in THz technology.
关键词： Terahertz sensor,Sensitivity,Optical loss profile,Photonic crystal fiber,Optical sensor,FEM based analysis
更新于2025-09-12 10:27:22
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Scale Effect of Fluorescent Waveguide in Organic Micro-Materials: A Case Study Based on Coumarin Microfibers
摘要： In the past decades, the rapid development of integrated optoelectronic devices has motivated the study of the miniaturized optoelectronic components, among which the micron or sub-micron waveguides have attracted a great deal of attention. In this regard, the waveguides made of organic materials show many advantages, such as intense fluorescence, tailor-made structure and facile crystallization. The waveguide ability was usually expressed in the form of the optical loss coefficient (denoted by <), which is mainly determined by the materials of the waveguide, and relatively low < usually corresponds to less optical loss and better propagation. The value of < was usually determined by the exponential fitting of the curves of the guided intensity (Itip/Ibody) versus the waveguiding distance (x). When the sectional size of the waveguide was down/close to the wavelength of the exerted light, the traditional evaluation is no longer valid, since < is also influenced by the diameter of the waveguide. For example, silica fibers with diameter more than one micron allow multimode waveguiding of visible and infrared light, while those with diameter of sub-micron allow single-mode operation. In case of organic waveguide, the situation becomes complicated, especially for those with size close to micron and sub-micron (range for majority organic waveguides). Except for the refraction index, the sectional size and the auto-absorption within the waveguide should also be considered. Models that accurately describes the waveguiding ability are highly demanded, but still dangling with no clues.
关键词： scale effect,organic micro-materials,fluorescent waveguide,coumarin microfibers,optical loss coefficient
更新于2025-09-12 10:27:22
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Impurities in large scale produced Nd-doped phosphate laser glasses. I. Cu ions
摘要： Impurity ions such as transition metals and rare earth metals in Nd-doped phosphate laser glasses will degrade Nd-laser performance, among which Cu is the most harmful. Divalent Cu2+ not only results in an optical loss at Nd-laser wavelength, but also reduces the energy storage for laser amplification. A large-scale production of Nd-doped phosphate laser glasses is required to meet quality demand and to realize economy of scale. To balance between the controlled impurity level in the glasses and the cost of raw materials for thousands of disks of meter-scale Nd-doped phosphate laser glasses, it is important to determine an upper limit for Nd-laser degradation due to divalent Cu2+ ions. The absorption edge of Cu singly-doped phosphate glass prepared in an oxidizing atmosphere shows the evidence of monovalent Cu+. X-ray photoelectron spectroscopy is utilized to further verify the existence of monovalent Cu+ ions in Cu, Nd codoped phosphate glass. The results show that both Cu+ and Cu2+ ions most probably coexist in Nd-doped phosphate laser glasses produced in the oxidizing atmosphere to eliminate Pt inclusions in the glasses. Accordingly, this paper discusses the extinction coefficient and the fluorescence quench factor caused by divalent Cu2+ ions, as well as their influence.
关键词： Cu2+,fluorescence quench factor,optical loss,Cu+,Nd-doped phosphate laser glass,XPS
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Ultra Low-Loss Silicon Waveguides for 200 mm Photonics Platform
摘要： We demonstrate ultra-low optical losses in silicon waveguide by applying a smoothing annealing with no morphological deformation. We reach record-low losses at 1310nm with 0.1 dB/cm in single mode waveguide, while the performances of the other devices of the platform are preserved.
关键词： waveguide,roughness,Silicon photonics,Optical loss,annealing
更新于2025-09-12 10:27:22
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Ultranarrow-waveguide AlGaAs/GaAs/InGaAs lasers
摘要： We have designed, fabricated and studied ultranarrow-waveguide heterostructure lasers emitting in the spectral range 1000 – 1100 nm. The lasers have been characterised by current – voltage, light – current, far-field intensity distribution and internal optical loss measurements. The ultranarrow-waveguide lasers have been shown to have a threshold current density of ~75 A cm–2, internal quantum efficiency near 100 % and internal optical loss near the lasing threshold under 1 cm–1, which corresponds to the level of standard heterostructures. We have demonstrated the possibility of obtaining up to 5 W of output power in continuous mode and up to 30 W in pulsed mode, with a beam convergence (FWHM) of 17.8°. The slope of the internal optical loss as a function of pump current for the ultranarrow-waveguide lasers can be markedly lower than that in lasers with a standard design, but internal quantum efficiency drops to 40 % with increasing pump current. The use of barrier layers in ultranarrow-waveguide lasers makes it possible to substantially reduce the drop in internal quantum efficiency.
关键词： absorption coefficient,internal optical loss,ultranarrow waveguide,energy barrier,pulsed pumping,semiconductor laser
更新于2025-09-11 14:15:04
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Measurements of internal optical loss inside an operating laser diode
摘要： An experimental technique for measuring internal optical loss in high-power edge-emitting semiconductor lasers is demonstrated. The technique is based on coupling a probe beam into the waveguide of a pulse-pumped laser diode. It allows measuring free-carrier absorption (FCA) in a laser heterostructure at di?erent temperatures and at pump current levels up to 30 kA/cm2. Measurement results are presented for two laser heterostructure designs, which vary in the waveguide doping level and material. For both heterostructures, the pump current increase induces a signi?cant rise in FCA and a corresponding increase in internal optical loss, from 0.4–0.7 cm?1 at the threshold current to 2–2.5 cm?1 (65 °C, 27 kA/cm2). The gradient of the FCA current dependence is lower for the laser heterostructure with a doped GaAs waveguide, while the heterostructure with an undoped AlGaAs waveguide displays a larger increase in FCA but better internal quantum e?ciency at high currents. These results show that the proposed experimental method has signi?cant potential.
关键词： internal optical loss,heterostructure,free-carrier absorption,laser diode,high-power lasers
更新于2025-09-11 14:15:04
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[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || PT-Symmetry on-a-Chip: Harnessing Optical Loss for Novel Integrated Photonic Functionality
摘要： The development of non-Hermitian parity-time (PT) symmetric quantum mechanics has offered a powerful platform to engineer novel device functionality for integrated photonics. In this chapter, we review the chip-scale applications of PT-symmetry in photonic devices, including the implementation of the unidirectional reflectionless PT metamaterial, coherent asymmetric light-light switching, and orbital angular momentum (OAM) laser on-chip. We study the optical analogy of non-Hermitian PT systems, manipulate the complex refractive index properties such as gain/loss modulation, and investigate the unique wave transport characteristics near the exceptional point (EP) to achieve these intriguing on-chip functionalities.
关键词： light-light switching,orbital angular momentum laser,optical loss,non-Hermitian quantum mechanics,integrated photonics,PT-symmetry,unidirectional reflectionless,exceptional point
更新于2025-09-10 09:29:36