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Phenomenological studies of femtosecond laser ablation on optical thin films for integrated photonics
摘要： In this work, we present a well-supported procedure to fabricate ridge optical waveguides onto thin films of PLZT by femtosecond laser ablation. To achieve smooth-guiding structures that guarantee good optical performance we have studied the characteristics of ablation threshold for different kinematic conditions of fs laser machining and we have also explored the different ablation regimens for several fluences reached. Furthermore, we characterized the morphology and roughness of ridge waveguides through a modal analysis of scattering loss for waveguides conducted by single and multiple scans. An innovative phenomenological model that describes the sidewall roughness to process parameters is proposed in this paper. With this approach, it is possible to extend the manufacturing method of smooth-guiding structures to many optical thin films by fs micromachining, so as to create integrated photonics devices that can be addressed to different technological applications.
关键词： Thin films,Integrated photonics,Laser materials processing,Optical waveguides,Femtosecond laser ablation
更新于2025-09-16 10:30:52
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Three-Dimensional Laser-Assisted Patterning of Blue-Emissive Metal Halide Perovskite Nanocrystals inside a Glass with Switchable Photoluminescence
摘要： The high-precision patterning of metal halide perovskites (MHPs) is of paramount importance for their device application. Here, we demonstrate the femtosecond (fs)-laser-assisted formation of three-dimensional MHP nanocrystal (NC) patterns with strong blue photoluminescence (PL) inside an oxide glass. Our strategy enables the crystallization and erasing of CsPb(Cl/Br)3 NCs inside a glass localized around the laser focal area through a combination of fs laser irradiation and thermal treatment processes. These recoverable patterns exhibit a switchable PL associated with the laser-induced defect and the thermal healing of MHP NCs that are benefits from the soft ionic crystal structure and low formation energy of the MHPs. Due to the high stability offered by the protection of the oxide glass matrix, the laser printing of fine-structured MHP micropatterns can be repeated over multiple cycles with a high robustness compared with their colloidal process counterparts. Our results demonstrate a simple strategy for creating emissive patterns inside a stable and transparent solid matrix that could be promising for applications including information storage, three-dimensional displays, anticounterfeit labels, and information security protection.
关键词： three-dimensional patterning,perovskite nanocrystals,reversible photoluminescence,laser-assisted crystallization,femtosecond laser processing
更新于2025-09-16 10:30:52
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Fiber grating sensing interrogation system based on a modulated grating Y-branch tunable laser for core-and-cladding-integrated fiber Bragg grating temperature measurement
摘要： Numerous studies have addressed various methods to interrogate fiber Bragg gratings (FBGs). However, conventional methods are ineffective for multipeak FBG demodulation. A core-and-cladding-integrated fiber Bragg grating (FBG) temperature-interrogation system, based on a modulated grating Y-branch (MG-Y) tunable laser and home-built FBG, is proposed in this study. The sensing system comprises an MG-Y tunable laser interrogation system, a 3-dB optical fiber coupler, a core-and-cladding-integrated FBG, a heating platform, and a personal computer. The core-and-cladding-integrated FBG with two reflection peaks is sampled by the designed MG-Y laser. The FBG has a period of 534 nm and a grating length of 2000 μm. It is fabricated in a single-mode fiber by femtosecond-laser writing through the fiber coating. The interrogator is suitable for temperature measurement via the core-and-cladding-integrated FBG. In tests of the temperature-interrogation system, a temperature change from 30 to 100 ○C generates spectral shifts toward longer wavelengths for both the core and cladding reflection peaks. For the core and cladding, temperature sensing sensitivities of 111 and 113 pm/○C with linearities of 0.993 and 0.99, respectively, during heating and 117 and 120 pm/○C with linearity coefficients of 0.994 and 0.99, respectively, during cooling are achieved.
关键词： fiber Bragg grating,femtosecond-laser writing,modulated grating Y-branch tunable laser,temperature measurement,core-and-cladding-integrated FBG
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Mach-Zehnder interferometer in no-core fiber based on femtosecond laser inscribed waveguides
摘要： in-line Mach-Zehnder fiber We demonstrated a interferometer constructed by femtosecond laser written waveguides in no-core fiber. Such an interferometer device consists of a section of no-core fiber, fusion spliced with single mode fiber at its two ends. One of the interferometer arms the waveguide inscribed and the other follows the diverging light path inside the no-core fiber before arriving at the end of single mode fiber core. Such a device based on internal structure can be used not only for temperature and strain, but also index for external measurement. formed by refractive is
关键词： Waveguide,Mach-Zehnder,Femtosecond laser
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Robust all polarization-maintaining femtosecond fiber laser with various phase bias
摘要： We demonstrate a compact all polarization- maintaining mode-locked femtosecond fiber laser with three different non-reciprocal phase shifters. The achieved laser directly delivers 926 fs, 0.56 nJ pulses at the repetition rate of 88.3 MHz.
关键词： Femtosecond laser,Mode-locked lasers,All polarization?maintaining
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - High Conversion Efficiency in a System “Nonlinear-Optical Crystal Partially Filling the Cross Section of a Rectangular Waveguide”
摘要： It is shown that terahertz radiation (0.1-3 THz) can be effectively generated via optical rectification of femtosecond laser pulses in a system of a “nonlinear-optical crystal partially filling the cross section of a rectangular metal waveguide”. The numerical calculations for the phase-matching in LiNbO3, ZnTe, DAST and GaSe nonlinear optical crystals have been performed. The influence of THz radiation absorption on the efficiency of generation of coherent THz radiation in the system has been investigated.
关键词： optical rectification,femtosecond laser pulses,phase-matching,nonlinear-optical crystal,terahertz radiation
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - High Sensitivity Heterodyne Electro-Optic Sampling with 1.5-μm Laser Source
摘要： A detection module for the heterodyne electro-optic sampling of terahertz pulses composed of a GaAs plate inserted into a tapered parallel plate waveguide has been designed and fabricated. The detector was installed into a standard terahertz time-domain spectrometer with a 1.5-μm femtosecond laser as a light source. The spectral bandwidth of 3.5 THz and dynamic range of 5 orders of magnitude were experimentally demonstrated, even with a photo-conductive antenna designed for 800-nm as an emitter.
关键词： 1.5-μm femtosecond laser,GaAs plate,tapered parallel plate waveguide,heterodyne electro-optic sampling,terahertz pulses,terahertz time-domain spectrometer
更新于2025-09-16 10:30:52
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ESSE 2017 (Proceedings of the International Conference on Environmental Science and Sustainable EnergyEd.by ZhaoYang Dong) || Transverse-Load Characteristics of Long Period Fiber Gratings Fabricated By Femtosecond Laser Pulses
摘要： The transverse-load characteristics of long period fiber gratings (LPFGs) fabricated by 800 nm femtosecond laser are demonstrated and investigated. It is observed that the resonant wavelength of LPFG is dependent on the direction of applied force. When a transverse load is applied along different orientations of the LPFG, the resonant wavelength will experience red shift or blue shift. However, the transmission attenuation is gradually decreases as the applied transverse-load increases, which is independent of the direction of applied force. This is mainly due to the asymmetrical distribution of the refractive index on the cross-section of LPFG induced by femtosecond laser pulses, the load-induced birefringence lead to the rotation of optical principal axes in the LPFG.
关键词： long period fiber grating,transverse-load characteristics,femtosecond laser
更新于2025-09-16 10:30:52
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Structurally colored stainless steel processed by using femtosecond laser pulses
摘要： Structurally colored stainless steel (SS) surfaces were produced by using femtosecond laser at normal incidence at ambient conditions. The influence of laser polarization on the surface properties was investigated. The surface morphologies, roughness and color of the laser-treated surface were characterized by using environmental scanning electron microscope (ESEM), roughmeter and atomic force microscope (AFM). Results indicated that the circular polarization leads to more random structures than the horizontally linear polarization. Specimen with the highest surface roughness shows the brightest color. Different colors are cyclically exhibited by changing view angles due to different orders of diffraction. This investigation developed the technique of using femtosecond laser in situ preparation of periodic structures on 304 SS, and indicating that laser polarization is an important parameter to control surface structures to achieve different colors.
关键词： polarization,micro/nanostructure,coloration,Femtosecond laser,stainless steel
更新于2025-09-16 10:30:52
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Selective excitation of one among the three peaks of tip‐enhanced Raman spectroscopy by a shaped ultrafast laser pulse
摘要： There are generally several neighboring Raman peaks that are excited simultaneously in tip‐enhanced Raman spectroscopy (TERS). A method to selectively excite a specific Raman peak and simultaneously depress the others is required for suppressing noise and improving detection sensitivity and accuracy. In this study, we demonstrate a scheme for selective excitation of one Raman peak among three excited states in TERS by properly shaping the pump and Stokes femtosecond laser pulses. The shaped pump and Stokes pulses are transformed into time domain, discretized and reconstructed; they are then used to irradiate the TERS structure obliquely. The impulse responses at five probe points of the TERS structure are calculated followed by a Fourier transform. In these cases, the probability of one selectively excited Raman transition increases by several hundreds to tens of thousands in amplitude, whereas the others are both depressed to zero. The probe points at different positions in the tip apex do not affect the enhanced and selective excitation of one Raman transition among the three excited states.
关键词： tip‐enhanced Raman spectroscopy,femtosecond laser pulse shaping,selective excitation
更新于2025-09-16 10:30:52