Silica Fiber Research Articles

972 nm single-frequency distributed Bragg reflector Yb³+-doped silica fiber laser

972 nm single-frequency distributed Bragg reflector Yb³+-doped silica fiber laser

Monolithic low-loss short-length 2.113-µm Tm-doped fiber laser oscillator made by phase-mask-assisted femtosecond-laser inscription

We report a monolithic low-loss short-length gain-switched thulium-doped fiber laser (TDFL) beyond 2.1 µm. Phase-mask-assisted 800-nm femtosecond laser exposure method was used to fabricate the monolithic laser cavity on ∼10-cm long straightened silica Tm-doped fiber (TDF) after single-shot spatial alignment. The low loss (<0.2 dB per FBG) of inscribed fiber Bragg gratings (FBGs) is comparable to the loss of FBGs made by phase-mask-assisted UV-laser exposure method, while multiple auxiliary processes of hydrogen loading and the annealing are involved in the latter fabrication. 2.113-µm lasing with 10 ns width was obtained from the gain-switched TDFL, under inband 1.55-µm core-pumping scheme. The maximum output peak power, pulse energy, and polarization extinction ratio of the TDFL were 360 W, 3.6 µJ, and >22 dB, respectively. The 2.113-µm TDFL shows slope efficiency of 29%, comparable with that in 2.1-µm gain-switched holmium doped fiber laser (HDFL), indicating that such a short-length TDFL is competitive to HDFL for lasing beyond 2.1 µm. In the time domain, it has been observed that intracavity pulsed amplified spontaneous emission in 1.8-1.9 µm is contributed to the efficient generation of the ultralong-wavelength TDFL beyond 2.1 µm, similar to the reabsorption mechanism of the previously reported long-length 2-2.2 µm TDFL. But our fabricated short-length TDFL with high peak power is obviously advantageous over its long-length counterpart for suppressing nonlinear effects occurring in the laser cavity. An additional demonstration has been carried out to generate 2.325-µm stimulated Raman scattering with 10% slope efficiency, 3.6 W peak power, and 50 nJ pulse energy in 40m-long highly nonlinear silica fiber, using the short-length gain-switched TDFL as the pump. At last, our simulation shows the feasibility to extend efficient lasing in cm-long ultrashort TDFL oscillator up to 2.2 µm, when FBGs cavity mirrors with high reflectivity and low loss can be made. It therefore indicates such a short-length TDFL a promising compact high-peak-power mid-IR laser source for applications beyond 2.1 µm.

Holmium-Doped Silica Fibers Combining High Doping and High Efficiency

Holmium-Doped Silica Fibers Combining High Doping and High Efficiency

Low-threshold broadband-tunable cascaded Raman fiber laser at 2.3 μm based on highly GeO₂-doped silica and As₂S₃ fibers

Low-threshold broadband-tunable cascaded Raman fiber laser at 2.3 μm based on highly GeO₂-doped silica and As₂S₃ fibers

Optical fibers performance parameters management under the control of spectral functional light sources with various wavelength windows and thermal effects

Abstract This paper has clarified the high speed performance signature of single-mode/multimode graded index silica-doped fibers in point to point link transceiver communication system. Fiber signal attenuation is studied versus ultraviolet wavelength region and different germanium dopant ratios added to silica fibers in point to point link. The fiber signal attenuation is also clarified versus near infrared wavelength region and different germanium dopant ratios added to silica fibers in point to point link. Fiber scattering loss is demonstrated against spectral operating wavelength region and different thermal effects of fiber temperature in point to point link. The modal fiber dispersion is investigated clearly and clarified in relation to fiber numerical aperture at different relative refractive index difference at operating spectral wavelength of 1,550 nm and 1,300 nm near infrared regions.

Broadband all-fiber mid-infrared supercontinuum generation in an As2S3-polycarbonate hybrid microtaper

Abstract We present a coherent supercontinuum (SC) spanning a 1.1–3.9 µm wavelength range from propagation in a three-stage cascade of nonlinear and dispersive fibers, including a silica fiber, a ZBLAN fiber, and a robust and dispersion-engineered As2S3 microtaper. In the first stage made of silica fiber, a pump pulse undergoes soliton fission, creating a fundamental soliton that subsequently redshifts through soliton self-frequency shift (SSFS) to a center wavelength of 2.14 μm. In the second stage made of ZBLAN fiber, the fundamental soliton becomes a higher order soliton and experiences a second round of soliton fission creating another fundamental soliton that would shift up to a wavelength of 2.86 µm via SSFS. In the third stage, the As2S3 microtaper generates a SC that covers the wavelength range of 1.1–3.9 µm. The As2S3 microwire design with a diameter of 4.4 µm and a short length of 25 mm provides anomalous dispersion and high mode confinement to the 2.86 µm soliton while mitigating propagation losses. This all-fiber passive cascade allows a small footprint and alignment-free operation. Numerical simulations match the experimental results and confirm the high coherence of the generated SC.

Assembling halloysite nanotubes in nickel foam with silica fibers as scaffold for efficiently encapsulating phase change materials towards solar-thermal-electric energy conversion and management

Assembling halloysite nanotubes in nickel foam with silica fibers as scaffold for efficiently encapsulating phase change materials towards solar-thermal-electric energy conversion and management

End-pump silica-fluoride fiber combiner utilizing tapering and assembling technique for mid-infrared laser systems

End-pump silica-fluoride fiber combiner utilizing tapering and assembling technique for mid-infrared laser systems

Flexible Short Silica Fibers and Tricalcium Phosphate Synergistically Promote Bone Fracture Healing in Composite Cryogel Scaffolds.

Bone tissue engineering is a critical area of research focused on enhancing the regeneration of bone tissue, particularly in cases of complex defects. Despite inherent self-healing capabilities of bone, irregularly-shaped defects pose significant challenges for complete regeneration, thereby necessitating innovative therapeutic strategies. This study addresses these challenges by exploring the development of advanced tissue regeneration scaffolds. Here, tricalcium phosphate (TCP) is integrated with short silica (SiO2) fibers to develop 3D cryogel scaffolds, designated as SSFx@TCP. These cryogel scaffolds exhibit low density (<2mgcm- 3), high water absorption (>3500%), and favorable sustained release properties, enabling effective cellular interactions. Notably, the SSFx@TCP cryogels support cell attachment, proliferation, and differentiation, while also regulate gene expression associated with angiogenesis and osteogenesis. Furthermore, in vivo assays demonstrated that these scaffolds can effectively promote de novo bone production in a rat calvarial defect model 8 weeks post-operatively, thereby indicating their potential to mimic the natural extracellular matrix. The successful integration of bioactive components in these cryogels may be beneficial for improved clinical outcomes in bone regeneration therapies and ultimately enhancing patient care in reconstructive surgery.

Understanding the Temperature Conditions for Controlled Splicing Between Silica and Fluoride Fibers

This study explores the efficacy of thermal splicing conditions between silica and zirconium‐fluoride fibers, focusing on achieving mechanical strength between the two fibers. A comprehensive characterization of the thermal profile in the hot zone of the filament splicer was conducted using a fiber Bragg grating, providing valuable insights into its stability and overall performance. Results demonstrate mechanically strong joints and suggest a very narrow temperature window to achieve strong connection between the two materials. Moreover, we characterize the surface composition of the ZrF4 fiber using energy dispersive spectroscopy following splicing at ideal temperatures, as well as at higher and lower temperatures. This work paves the way towards future implementation of silica and fluoride fibers splicing using alternative splicing solutions such as CO2 laser system while raising interesting facts for further studies in the specific field.

Watt-level, high-efficiency single-frequency DBR Tm3+-doped YAG crystal-derived silica fiber laser oscillator at 1941 nm

Watt-level, high-efficiency single-frequency DBR Tm3+-doped YAG crystal-derived silica fiber laser oscillator at 1941 nm

Researching and determination of the strain sensitivity of the fabricated Bragg gratings

This article presents a systematic study of the stretching characteristics of polymer fiber Bragg gratings. Experimental data demonstrate that applying mechanical stretching to polymer fiber Bragg gratings enables a wide tuning range of the Bragg wavelength (over 50 nm) with high reproducibility, reversibility, and repeatability. It was also established that the strain sensitivity of polymer fiber Bragg gratings is 1.46 pm/με, which significantly exceeds the strain sensitivity of silica fiber Bragg gratings. Additionally, it is shown that the relationship between strain and the Bragg wavelength shift exhibits high linearity (correlation coefficient R² = 0.9995), ensuring the reliability of the gratings under mechanical loads. The study confirms the potential of polymer fiber Bragg gratings for use in WDM optical communication systems, fiber optic strain sensors, and medical sensors.

Research on a Low-Loss and Low-Crosstalk Supermode Demultiplexer

ABSTRACT A novel demultiplexer with mode-degenerate output (DMDO) for the six-core supermode fiber (SSF) using finite element method (FEM) and beam propagation method (BPM) is proposed, which can achieve the multiple-input multiple-output free (MIMO-FREE) operations. The DMDO is composed of four directional mode-selective couplers, where the pure silica fiber cores in the couplers significantly minimize fiber attenuation and splicing loss. The main channel with the SSF core (SSFC) supports the supermodes LP01, LP11, LP21, and LP31, where large effective refractive index difference (ERID) between neighboring supermodes enables low crosstalk. The DMDO can achieve mode-degenerate outputs of four supermodes LP01, LP11, LP21, and LP31, which solves the mode rotation issue in the propagation system. In the range of 1530–1565 nm, extinction ratios (ERs) of supermodes LP01, LP11, LP21, and LP31are respectively maintained above 27.48, 29.07, 28.18, and 36.65 dB, while the ER of supermode LP31 is up to a maximum of 39.25 dB. The corresponding coupling efficiencies (CEs) can respectively reach −0.42, −0.22, −0.17, and −0.40 dB. According to principle of light wave reversibility, the DMDO can be used as a multiplexer.

Random Plasmonic Laser Based on Bismuth/Aluminum/Yttria/Silver Co-Doped Silica Fiber with Microcavity Shaped Tip

In this study, we demonstrate a proof of principle of an all-fiber random laser due to the plasmonic effect. This was achieved with a fiber co-doped with bismuth/aluminum/yttria/silver in which a microsphere (microcavity) at the fiber’s tip was made using a splicing machine. The presence of bismuth and silver nanoparticles in the fiber along with bismuth–aluminum phototropic centers stands behind the observed phenomenon. The effect can be attributed to the in-pair functioning of this unit as an active medium and volumetric plasmonic feedback, resulting in lasing at 807 nm under 532 nm pumping with a notably low (~2 mW) threshold.

Polarization maintaining, normal-dispersion silica fiber for dispersion compensation in ultrafast erbium and thulium-doped fiber lasers

We present a highly birefringent silica fiber with normal dispersion up to 2334 nm, designed to control a net-cavity dispersion of pulsed fiber lasers at different wavelengths. The fiber is characterized by a large normal dispersion, slowly growing from -87 ps/nm/km at 1200 nm to -42 ps/nm/km at 2000nm, and high phase birefringence exceeding 1.9 × 10−4 in this spectral range which ensures a polarization extinction ratio as high as 28 dB for a 1 m long fiber section. The industrially fabricated fiber was examined in two all-polarization-maintaining mode-locked fiber oscillators operating at central wavelengths of 1560 nm and 1980nm. We confirmed the ability to manage the dispersion of the oscillators, which worked in both anomalous and normal dispersion, maintaining stable mode-locking. Employing the developed fiber with normal dispersion has resulted in a broadening of spectral full width at half maximum from 7.8 to 44.3 nm and from 5.5 to 25.8 nm for the erbium and thulium lasers, respectively. The ability to support operation in the range of tens of MHz allows for the application of the developed laser sources in systems reducing the repetition rate via e.g. pulse picking.

In Situ Preparation of Thin-Film Q-Switches Based on Vanadium Dioxide for Pulsed Fiber Lasers

In the presented work, erbium fiber lasers operating in the pulsed mode with a nonlinear element containing a vanadium oxide saturable absorber are demonstrated. The structure of the saturable absorber is based on a segment of thinned silica fiber coated with a thin-film vanadium oxide by the method of metalorganic chemical vapor deposition. A fiber laser scheme is demonstrated that allows controlling the transmission of the internal cavity of the resonator during laser generation and deposition of a thin film. We have demonstrated a method for obtaining and annealing nanocoatings with laser generation control. We controlled the laser output parameters directly during the synthesis of the saturable absorber material. Vanadium oxides obtained in the work demonstrated the Mott–Paierls phase transition practically at room temperature. In this work, the optical characteristics of the output radiation of a fiber laser with a saturable absorber were measured. At temperatures above 70 °C, the coatings demonstrate a passive Q-switch with a repetition rate of 38 kHz and a pulse duration of 3.8 μs. At temperatures below the phase transition, a short-term mode-locking mode occurs. The transmission jump at a wavelength of about 1350 nm during structural rearrangement was 24%. For comparison, VO2 nanopowder in a polydimethylsiloxane elastomer matrix was used as a saturable absorber material. The nanopowder modulator made it possible to obtain pulses with a frequency of 27 kHz and a duration of about 7.2 μs.

Silica fiber laser emitting moderate power-stable visible output.

A high slope efficiency of 12%, a stabilized output power of 250 mW at a wavelength of 581.8 nm, and what we believe to be a record peak output power of 450 mW have been achieved from a diode-pumped high concentration Dy3+:BaF2 nanoparticle (NP)-doped silicate fiber laser. The performance is primarily attributed to a reduction in the overall background loss within the cavity and a higher Dy3+ concentration in the pre-synthesized NPs. Almost 60% of the initial laser power remains in the steady state after several hours of the fiber being pumped by high-power 450 nm radiation, suggesting a modified local rare-earth ion environment. Such an environment likely leads to moderate photodarkening resistance, which results from the reduced energization of nearby precursor defects in the aluminosilicate glass, typically forming strongly absorbing defect centers. The result opens the door to a new class of lasers that exploits the remarkable material properties of silicate glass for the efficient generation of visible light.

Exploring the Weathering and Accelerated Environmental Aging of Wave-Transparent Reinforced Composites.

Approaches to retain or improve wave-transparent composite properties received ongoing attention. Silica glass fiber composites are being utilized in wave transparency applications owing to their excellent dielectric properties. During operational service life, they are exposed to ambient and harsh environments, which degrade their performance and properties. The objective is to evaluate the progressive degradation of silica fiber wave-transparent composite material's properties and overall performance. Silica fiber/epoxy wave-transparent composites (SFWCs) were fabricated by stacking high-silica glass cloth (HSG) plies via multi-layer compression and curing at 150 °C (14 hrs) and were investigated upon one-year real-time weathering and 20-year accelerated aging (Hallberg peck model). The morphology of one-year-aged SFWC composite was found to be better than that of 20-year-aged SFWC, where relatively weakened interfacial bonding and composite structure were observed. One year weathering the dielectric constant (εr) was increased to 4.34%, and dielectric loss (δ) was found to be 5.6%, whereas upon accelerated conditions (equivalent to 20 yrs of ambient conditions), εr was significantly raised 30.63% from its original value (3.2), and δ was increased 22.8% (0.035). In the 20-year aged SFWC composite, the maximum absorbed moisture was 3.1%. Tensile strength dropped from 147.8 MPa to 136.48 MPa, and compressive strength from 388.54 MPa to 374.41 MPa. Upon aging (from 1 year of weathering to 20 years of accelerated aging), SFWC composite properties and functional performance were lowered but remained reasonable. SFWC properties, as revealed by microscale characterization, can contribute to the determination of the impact of deterioration and useful service life in respective microelectronics wave transparency applications.

Coaxial Cable Distributed Strain Sensing: Methods, Applications and Challenges.

Distributed strain sensing is a powerful tool for in situ structural health monitoring for a wide range of critical engineering infrastructures. Strain information from a single sensing device can be captured from multiple locations simultaneously, offering a reduction in hardware, wiring, installation costs, and signal analysis complexity. Fiber optic distributed strain sensors have been the widely adopted approach in this field, but their use is limited to lower strain applications due to the fragile nature of silica fiber. Coaxial cable sensors offer a robust structure that can be adapted into a distributed strain sensor. They can withstand greater strain events and offer greater resilience in harsh environments. This paper presents the developments in methodology for coaxial cable distributed strain sensors. It explores the two main approaches of coaxial cable distributed strain sensing such as time domain reflectometry and frequency domain reflectometry with applications. Furthermore, this paper highlights further areas of research challenges in this field, such as the deconvolution of strain and temperature effects from coaxial cable distributed strain sensor measurements, mitigating the effect of dielectric permittivity on the accuracy of strain measurements, addressing manufacturing challenges with the partial reflectors for a robust coaxial cable sensor, and the adoption of data-driven analysis techniques for interrogating the interferogram to eliminate concomitant measurement effects with respect to temperature, dielectric permittivity, and signal-to-noise ratio, amongst others.

Preparation and performance study of a Tm3+-doped silica optical fiber by sol-coating and laser drawing technology

High-concentration Tm3+-doped silica optical fibers have significant application value in areas such as single-frequency lasers. This paper investigates the sol-coating in the silica capillaries process and CO2 laser drawing technology and successfully fabricates a Tm3+-doped single-mode silica optical fiber. The core composition adopts a Tm-La-Al-Si system; the Tm3+ doping concentration is 0.5 mol%; the core and cladding diameters are 5 and 130 µm, respectively; and the numerical aperture (NA) is 0.28. A laser seed source with a wavelength of 1940 nm is established, and the laser gain characteristics of the optical fiber are tested. The small-signal net gain coefficient at the wavelength of 1940 nm is measured to be 0.15 dB/cm. The sol-coating method employed in this study enhances the doping concentration of Tm ions, while the laser drawing technique mitigates ion diffusion effects. The results indicate that this Tm3+-doped silica fiber preparation method offers a novel, to the best of our knowledge, approach for manufacturing high-concentration doped silica fibers and holds significant reference value for related research fields.