Phosphate Fiber Research Articles

Continous-wave and passively Q-switched laser at 1.36 µm of a Nd3+-doped phosphate fiber with a Yb3+-doped inner cladding.

All-fiber continuous-wave (CW) and passively Q-switched lasers at 1.36 µm (4F3/2 → 4I13/2) by a Nd3+-doped double cladding phosphate fiber are demonstrated for the first time, to the best of our knowledge. To suppress the competitive 0.9 and 1.05 µm emission, the Yb3+ ions are intentionally introduced into the inner cladding of this Nd3+-doped fiber. CW laser at 1.36 µm with a signal-to-noise ratio over 50 dB is realized by using two fiber-type dielectric films as cavity mirrors. A 4.0% CW laser efficiency is obtained when the Nd3+-doped fiber length is 33 mm. The emission at 0.9 and 1.05 µm is well-suppressed, and no parasitic laser is observed. Taking a commercial semiconductor saturable absorber (SA) mirror as the SA, the compact 1.36-µm Q-switched laser is demonstrated, and the repetition rate of output pulses can be tuned from 230 to 522 kHz with a narrowest pulse duration of 152 ns. Our results may provide a promising way to realize 1.3 µm laser oscillation in Nd3+-doped fibers.

Toward 10-watt-level single-frequency fiber laser oscillators

High-power single-frequency laser oscillators are in great demand for some specific applications, such as quantum information and laser interferometer gravitational-wave observatories, where 10-watt or even 100-watt-level narrow-linewidth lasers with extremely low noise levels are required. In this paper, we present numerical investigations on the power scalability of single-frequency distributed Bragg reflector (DBR) ytterbium-doped phosphate fiber lasers and identify the low-quantum-defect operation approach to 10-watt single-frequency laser oscillators with the best figure of merit, defined by the ratio of the laser efficiency to the quantum defect. This research offers valuable insights for the design and development of high-power single-frequency DBR fiber laser oscillators at many other wavelengths.

Large-mode-area Nd-doped anti-resonant phosphate fiber for high-power single-mode 900 nm laser generation

In this work, we propose an Nd-doped double-layer anti-resonant phosphate fiber with a core diameter of 50 µm for high-power single-mode 900 nm laser generation. Double-layer interlaced anti-resonant elements were designed here to enhance the fundamental mode confinement capability of the large-mode-area Nd-doped fiber core. Moreover, a double-layer F-P etalon formed between the anti-resonant elements and the inner cladding was analyzed for the first time for fiber loss manipulation. Single-mode operation in the 890–907 nm band with confinement loss lower than 0.1 dB/m can be achieved from the designed fiber. More importantly, high confinement loss larger than 100 dB/m is achieved for all the fiber modes around 1060 nm for four-level gain competition suppression in 900 nm Nd-doped fiber laser generation. A 900 nm fiber amplifier simulation based on the designed Nd-doped phosphate fiber shows that the parasitic lasing or even amplified spontaneous emission around 1060 nm can be effectively suppressed and a high-efficiency hundred-watt laser at 900 nm can be anticipated.

Evaluation of alginate-coated β-tricalcium phosphate fiber scaffold for cell culture.

Ex vivo tissue engineering is an effective therapeutic approach for the treatment of severe cartilage diseases that require tissue replenishment or replacement. This strategy demands scaffolds that are durable enough for long-term cell culture to form artificial tissue. Additionally, such scaffolds must be biocompatible to prevent the transplanted matrix from taking a toll on the patient's body. From the viewpoint of structure and bio-absorbability, a β-tricalcium phosphate (β-TCP) fiber scaffold (βTFS) is expected to serve as a good scaffold for tissue engineering. However, the fragility and high solubility of β-TCP fibers make this matrix unsuitable for long-term cell culture. To solve this problem, we developed an alginate-coated β-TCP fiber scaffold (βTFS-Alg). To assess cell proliferation and differentiation in the presence of βTFS-Alg, we characterized ATDC5 cells, a chondrocyte-like cell line, when grown in this matrix. We found that alginate coated the surface of βTFS fiber and suppressed the elution of Ca2+ from β-TCP fibers. Due to the decreased solubility of βTFS-Alg compared with β-TCP, the former provided an improved scaffold for long-term cell culture. Additionally, we observed superior cell proliferation and upregulation of chondrogenesis marker genes in ATDC5 cells cultured in βTFS-Alg. These results suggest that βTFS-Alg is suitable for application in tissue culture.

871 nm single-frequency fiber laser for Yb+ ion optical clock

In recent years, there has been a dramatically increasing demand for high-performance narrow-linewidth lasers for optical atomic clock and quantum applications. In this paper, we report on a single-frequency distributed Bragg reflector fiber laser operating at 871 nm that can be used to produce a 435.5 nm narrow-linewidth laser for a Yb+ clock via second-harmonic generation. Linearly polarized single-longitudinal-mode laser output with a power of 6.7 mW and a polarization extinction ratio of 29 dB was obtained by using a 3-cm long 1 wt. % neodymium (Nd3+)-doped phosphate fiber as the gain fiber.

Expanding gain bandwidth using ion-hybridized fiber for kHz-linewidth single-frequency fiber lasers at S-, C-, and L-bands: design and performance evaluation.

Single-frequency fiber lasers at S-, C-, and L-bands play a crucial role in various applications such as optical network expansion, high-precision metrology, coherent lidar, and atomic physics. However, compared to the C-band, the S- and L-bands have wavelength deviations and suffer from excited-state absorption, which limits the output performance. To address this issue, a strategy called ion hybridization has been proposed to increase the differences in site locations of rare earth (RE) ions in the laser matrix, thereby achieving a broader gain bandwidth. This strategy has been applied to an Er3+/Yb3+ co-doped modified phosphate fiber (EYMPF), resulting in gain coefficients per unit length greater than 2 dB/cm at S-, C-, and L-bands. To demonstrate its capabilities, several centimeter-long EYMPFs have been used to generate single-frequency laser outputs at S-, C- and L-bands with kHz-linewidths, high signal-to-noise ratios (>70 dB), and low relative intensity noise (<-130 dB/Hz) in a compact short linear-cavity configuration.

Fiber optic dimethyl methyl phosphate fiber optic sensor based on ZIF-8@Ag/PDDA composite film

A Michelson interference dimethyl methyl phosphate (DMMP) fiber sensor with a single-mode (SMF)-dislocated single-mode (DSMF)-hollow-core fiber (HCF) structure is proposed. To fabricate the Michelson interference structure of SMF-DSMF-HCF, one end of the DSMF was misaligned and fused to the SMF, the other end was fused to the HCF to generate a reflective surface. The structure, elemental composition, and surface morphology of ZIF-8@Ag were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy after the ZIF-8@Ag/PDDA composite was coated on the surface of DSMF. The result shows that the sensitivity and the detection limit of the sensor are 45.71 dB/ppm and 0.1431 ppb, respectively, and the response/recovery time is around 14/12 s. The sensor also has excellent selectivity and stability.

Linearly-Polarized Mode-locked Yb3+-doped Phosphate Fiber Ring-Cavity Laser at 976 nm

Linearly-Polarized Mode-locked Yb³⁺-doped Phosphate Fiber Ring-Cavity Laser at 976 nm

Broadband 1.0 µm emission in Nd3+/Yb3+ co-doped phosphate glasses and fibers for photonic applications.

In this work, the spectroscopic properties of 1.0 µm emission in Nd3+/Yb3+ co-doped phosphate glasses were systematically investigated under 808 nm excitation. Notably, broadband 1.0 µm emission with a full width at half maximum (FWHM) of 96 nm was obtained in the phosphate glass doped with 2 mol.% Nd2O3 and 1 mol.% Yb2O3. In addition, the energy transfer microscopic parameter and transfer efficiency were analyzed. What is more, multimaterial fibers with Nd3+/Yb3+ co-doped phosphate glass core and silicate cladding were successfully drawn by using the molten core method. An intense 1.0 µm amplified spontaneous emission (ASE) can be realized in a 3 cm long multimaterial fiber. More importantly, the FWHM of the ASE can reach as large as 60 nm when excited at 976 nm. These results demonstrate that the Nd3+/Yb3+ co-doped phosphate glasses and fibers are promising gain materials for amplifier and laser applications in photonics.

Fabrication of a Fish-Bone-Inspired Inorganic-Organic Composite Membrane.

Biological materials have properties like great strength and flexibility that are not present in synthetic materials. Using the ribs of crucian carp as a reference, we investigated the mechanisms behind the high mechanical properties of this rib bone, and found highly oriented layers of calcium phosphate (CaP) and collagen fibers. To fabricate a fish-rib-bone-mimicking membrane with similar structure and mechanical properties, this study involves (1) the rapid synthesis of plate-like CaP crystals, (2) the layering of CaP-gelatin hydrogels by gradual drying, and (3) controlling the shape of composite membranes using porous gypsum molds. Finally, as a result of optimizing the compositional ratio of CaP filler and gelatin hydrogel, a CaP filler content of 40% provided the optimal mechanical properties of toughness and stiffness similar to fish bone. Due to the rigidity, flexibility, and ease of shape control of the composite membrane materials, this membrane could be applied as a guided bone regeneration (GBR) membrane.

Fluoro-sulfo-phosphate fiber with long-wavelength gain for an L-band laser

In this work, a self-developed Er3+/Yb3+ co-doped fluoro-sulfo-phosphate (FSP) fiber with long-wavelength gain characteristics has been reported. The mixed-ion strategy manipulates the ligands of rare-earth ions, leading to a broad gain bandwidth (almost twice that of phosphate fiber) and excellent amplification ability at the extended wavelength (&gt;2dB/cm at the L-band). As showcases of its features, a 1617-nm fiber laser based on a 1-cm-long FSP fiber is constructed. Furthermore, an all-fiber-integrated L-band passively mode-locked laser based on a 2.2-cm-long fiber with a fundamental repetition rate of 4.3 GHz is demonstrated. The generated pulse exhibits a high signal-to-noise ratio larger than 80 dB in the radio-frequency domain and a low relative intensity noise of 0.04%.

Ultralow-quantum-defect single-frequency fiber laser.

A single-frequency distributed-Bragg-reflector fiber laser at 980 nm with a quantum defect of less than 0.6% was developed with a 1.5-cm 12 wt% ytterbium-doped phosphate fiber pumped by a 974.5-nm laser diode. Linearly polarized single-longitude-mode laser with a polarization extinction ratio (PER) of nearly 30 dB and spectral linewidth of less than 1.8 kHz was obtained. A maximum output power of 275 mW was measured at a launched pump power of 620 mW. The performance of the single-frequency fiber laser pumped at 909 nm and 976 nm was also characterized. This research demonstrated an approach to high-power single-frequency fiber laser oscillators with mitigated thermal effects.

Clustering engineering in tellurium-doped glass fiber for broadband optical amplification

Dense wavelength division multiplexing (DWDM) is recognized as one of the leading technologies for resolving the internet data traffic capacity issue. Although the successful development of rare-earth doped fiber amplifiers enables to achieve optical signal amplification in various telecommunication wavebands, their bandwidth is limited by the inherent sharp 4f electronic transition. Here, we propose the clustering engineering strategy in tellurium (Te)-doped glass fiber for broadband optical amplification. The correlation among the glass system, chemical state of Te and the optical response are systematically studied. The active Te-doped phosphate glass with intense and broadband luminescence is successfully achieved by control of the cluster state of the Te atoms. Subsequently, Te-activated phosphate fiber is successfully drawn and the optical response is transferred smoothly. Importantly, the amplified spontaneous emission and broadband optical amplification are achieved for the first time in Te-doped glass fiber. A small signal on-off gain covering an ultra-wide range of O + E + S + C + L bands is observed under excitation at 808 nm. Our results establish a critical step toward advancing Te-based photonic materials for novel broadband fiber amplifiers serviced in telecommunication system.

Efficient laser operation with low loss Nd3+-doped phosphate glass fiber under direct pumping

For the first time, we have demonstrated efficient 1054 nm laser output with low loss Nd3+-doped phosphate glass fibers at room temperature using an 888 nm laser diode as the direct pumping source. Therein, the home-made Nd3+-doped phosphate glass fiber is the key for laser performance improvement. The transmission loss of the large-core single-cladding Nd3+-doped phosphate fibers prepared by the novel peeled-off isolated stacked extrusion method is as low as 1.1 dB/m at ∼1 μm. On this basis, a low-loss Fabry-Perot cavity is constructed by precisely controlling the relative distance between the fiber end facet and the cavity mirror with a microscope. The record-breaking optical-to-optical efficiency of Nd3+-doped phosphate glass fiber lasers, 50.2% is achieved with the maximum output power of 6.71 W. During laser operation, the output laser power does not roll over, even at high pump powers. The output laser power is limited only by the available pump power. This work will lay a solid foundation to the high-power fiber laser fabrication, and will find many applications in the future.

Injection-locked highly Yb3+-doped uncoupled-61-core phosphate fiber laser.

Uncoupled multicore fibers are promising platforms for advanced optical communications, optical computing, and novel laser systems. In this paper, an injection-locked highly ytterbium (Yb3+)-doped uncoupled-61-core phosphate fiber laser at 1030 nm is reported. The 61-core fiber with a core-to-core pitch of 20 μm was fabricated with the stack-and-draw technique. Each core doped with 6-wt.% Yb3+ ions has a diameter of 3 μm and numerical aperture of 0.2. Linearly polarized single-frequency output of 9.1 W was obtained from the injection-locked cavity with a 10-cm-long gain fiber at a pump power of 23.6 W. The injection locking of all 61 cores was confirmed by inspecting the longitudinal modes of the individual lasers with a scanning Fabry-Perot interferometer. The performance of the injection-locked 61-core fiber laser was characterized and compared to that of the free-running operation in terms of optical spectrum, near- and far-field intensity profiles, and relative intensity noise.

Narrow-Linewidth Single-Frequency Ytterbium Laser Based on a New Composite Yb3+-Doped Fiber

Fiber single-frequency lasers are currently being actively developed, primarily due to the growing number of applications that require compact and reliable narrow-band sources. However, the most developed single-frequency fiber lasers based on phosphate fibers have the disadvantages of low mechanical strength of both the phosphate fibers themselves and their splices. In this paper we demonstrate a single-frequency laser based on a new composite Yb3+-doped active fiber. The core of this fiber is made of phosphate glass with a high concentration of ytterbium ions and its cladding is made of standard silica glass. This structure ensures a higher splicing strength of the fiber compared to the phosphate fibers and provides high resistance to atmospheric moisture. Despite the multimode structure of this fiber, we achieved stable single-frequency lasing with an average power of 10 mW and a spectral contrast of more than 60 dB in the scheme with a short (1.1 cm) cavity formed by two fiber Bragg gratings. We believe that further optimization of this fiber will make it possible to create powerful and reliable single-frequency lasers in the one-micron wavelength range.

Single-frequency fiber laser at 880 nm.

Single-frequency fiber lasers with extremely low noise and narrow spectral linewidth have found many scientific and practical applications. There is great interest in developing single-frequency fiber lasers at new wavelengths. In this paper, we report a single-frequency Nd3+-doped phosphate fiber laser operating at 880 nm, which is the shortest demonstrated wavelength for a single-frequency fiber laser thus far, to the best of our knowledge. An output power of 44.5 mW and a slope efficiency of 20.4% with respect to the absorbed pump power were obtained with a 2.5-cm-long 1 wt.% Nd3+-doped phosphate fiber. Our simulation results show that higher single-frequency laser output can be achieved with 1.5 wt.% or 2 wt.% Nd3+-doped phosphate fiber with mitigated ion clustering.

Ultrafast fiber laser at 0.9 µm with a gigahertz fundamental repetition rate by a high gain Nd3+-doped phosphate glass fiber.

Fiber lasers, owing to the advantages of excellent beam quality and unique robustness, play a crucial role in lots of fields in modern society. Developing optical glass fibers with superior performance is of fundamental importance for wide applications of fiber lasers. Here, a new Nd3+-doped phosphate single-mode fiber that enables a high gain at 0.9 µm is designed and fabricated. Compared to previous Nd3+-doped silica fibers, the developed phosphate fiber exhibits a significant gain promotion, up to 2.7 dB cm-1 at 915 nm. Configuring in a continuous-wave fiber laser, this phosphate fiber can provide a slope efficiency of 11.2% in a length of only 4.5 cm, about 6 times higher than that of Nd3+-doped silica fiber. To showcase its uniqueness, an ultrafast fiber laser with ultrashort cavity is constructed, such that an ultrashort pulse train with a fundamental repetition rate of up to 1.2 GHz is successfully generated. To the best of our knowledge, this is the highest fundamental repetition rate for mode-locked fiber lasers at this wavelength range - two orders of magnitude higher than that of prior works. These results indicate that this Nd3+-doped phosphate fiber is an effective gain medium for fiber amplifiers and lasers at 0.9 µm, and it is promising for two-photon biophotonics that requires long-term operation with low phototoxicity.

Mathematical Modeling and Some Novel Studies on Er3+ and Er3+/Yb3+ Co- Doped Phosphate Glasses and Fiber Optics Amplifiers for Applications in Renewable Energy

Er3+ and Er3+/Yb3+ Co-doped Phosphate Glasses and Fiber Optics Amplifiers have recently gained importance among the researchers working in the field of Renewable energy. Er has the electronic configuration [Xe]4f126s2, so Er3+ has 11 f electrons ([Xe]4f11). With such a large number of electrons in its f-shell, many different values of L, S and J are possible. The valence electron configuration of Yb+3 (from YbCl3) is 4f135s25p6, which has crucial implications for the chemical behaviour of Yb+3. Also, the size of Yb+3 governs its catalytic behaviour and biological applications. This paper presents the detailed scientific analysis of the related phenomena like - energy transfer efficiency, and the important breakthroughs in the subject. For the optimum utilization of these for Renewable energy, a good knowledge of these glasses and amplifiers is necessary. With this objective in view, the technical analysis of the Er3+ and Er3+/Yb3+ Co-doped Phosphate Glasses and Fiber Optics Amplifiers have been briefly presented. In addition, some of the recent novel important studies have been reviewed.

Diode-pumped 1.15 W linearly polarized single-frequency Yb3+-doped phosphate fiber laser.

Compact and robust high-power single-frequency laser oscillators are in great demand for some specific applications where narrow-linewidth lasers with extremely low noise are required. In this paper, we report a single-mode-diode-pumped watt-level single-frequency Yb3+-doped phosphate fiber laser at 1050 nm based on an all-fiber distributed Bragg reflector cavity. A maximum output power of 1.15 W with a slope efficiency of 66% was achieved with 18-mm-long 8 wt.% Yb3+-doped phosphate fiber. Stable, single-longitudinal-mode lasing with a spectral linewidth of 9.6 kHz and polarization extinction ratio of ∼30 dB was obtained.