145 W single-frequency fiber laser at 1607 nm with the seed and MOPA configuration.

In this paper, high Er concentration erbium doped fiber (EDF) and erbium-ytterbium co-doped fiber (EYDF) were fabricated for the seed and master oscillator power amplifier (MOPA) system of the single-frequency fiber laser. An in-band pumping source with the wavelength of 1535 nm was proposed to improve the efficiency in the ring-cavity. A slope efficiency of 23.

Realizing 0.7 dB/m gain in O + E band by promoting BACs-P formation in bismuth-doped phosphosilicate fiber with double-pass configuration.

The long fiber length required for the amplification of bismuth-doped fiber (BDF) has hindered its practical application. In this paper, we propose and demonstrate a feasible method to improve the active absorption of bismuth active centers (BACs) by optimizing the drawing conditions, achieving a high gain with a short fiber length. The bismuth-doped phosphosilicate fiber (BPSF) preform was fabricated by the modified chemical vapor deposition (MCVD) process and drawn into fiber under nine different conditions.

Preliminary study on the optical diagnosis of orbital rhabdomyosarcoma by Raman spectroscopy.

To investigate the Raman spectral features of orbital rhabdomyosarcoma (ORMS) tissue and normal orbital tissue in vitro, and to explore the feasibility of Raman spectroscopy for the optical diagnosis of ORMS. 23 specimens of ORMS and 27 specimens of normal orbital tissue were obtained from resection surgery and measured in vitro using Raman spectroscopy coupled to a fiber optic probe. The important spectral differences between the tissue categories were exploited for tissue classification with the multivariate statistical techniques of principal component analysis (PCA) and linear discriminant analysis (LDA).

M-type refractive index profile erbium-doped fiber for high-efficiency multicore EDFA.

Cladding-pumped multicore erbium-doped fiber is an important element for future spatial division multiplexing (SDM) amplification. We propose an M-type erbium-doped multicore fiber to achieve high-efficiency SDM amplification. The performance of cladding-pumped erbium-doped fiber with a central refractive index depression has been investigated, and the M-type fiber has better amplification performance than conventional fibers by reducing the signal mode overlap with the doped region.

High bismuth-doped germanosilicate fiber for efficient E + S-band amplification.

Bismuth-doped germanosilicate fiber (BGSF), the active media of fiber amplifiers, has attracted widespread attention. Here, we report a BGSF with a high bismuth concentration of 0.075 wt.

High-efficiency cladding-pumped Er/Yb co-doped alumino-phosphosilicate fiber for an extended L-band amplification.

Extending the gain bandwidth of L-band optical fiber amplifier has provoked a widespread interest. To date, achieving a high-efficiency extended L-band amplification remains a challenge. Here, we report a cladding-pumped Er/Yb co-doped alumino-phosphosilicate fiber, prepared by the modified chemical vapor deposition process.

4.6 kW linearly polarized and narrow-linewidth monolithic fiber amplifier based on a fiber oscillator laser seed.

In this work, a record output power of 4.6 kW linearly polarized and narrow-linewidth fiber amplifier based on an optimized fiber oscillator laser (FOL) seed was realized by employing a homemade polarization-maintaining Yb-doped fiber (PMYDF), corresponding to a slope efficiency of 79.5% and a 3 dB linewidth of 0.

Extended L-band 4-Core Er/Yb co-doped fiber amplifier based on 1018 nm cladding pumping.

The extended L-band 4-core Er/Yb co-doped fiber and amplifier (MC-EYDFA) is first proposed and demonstrated, to the best of our knowledge, for space division multiplexing combined with wavelength division multiplexing application. The fiber core co-doped with Er/Yb/P is adopted for bandwidth expansion, and the long wavelength extends to 1625 nm. Numerical simulations further show that efficient amplification and higher saturation power are achieved with the 1018 nm cladding pumping.

Er/Yb co-doped 345-W all-fiber laser at 1535 nm using hybrid fiber.

The 1.5-µm fiber laser is widely used in the fields of laser lidar, remote sensing, and gas monitoring because of its advantages of being eye-safe and exhibiting low atmospheric transmission loss. However, due to the ∼1-µm amplified spontaneous emission (ASE) of the Er/Yb co-doped fiber (EYDF), it is difficult to improve the laser power.

3 × 1 fiber signal combiner with high beam quality Gaussian-like beam for a 10kW-level fiber laser.

We present the design and fabrication of a 3 × 1 signal combiner with high beam quality based on supermode theory. For improving beam quality, the fiber with core diameter of 34 µm and numerical aperture of 0.11 is first chosen as the output fiber.

High-efficiency cladding-pumped 4-core erbium-doped fiber with a pedestal for space division multiplexing amplification.

A cladding-pumped 4-core erbium-doped fiber (4C-EDF) with a pedestal structure has been firstly, to the best of our knowledge, proposed and fabricated for space division multiplexing (SDM) amplification. The numerical simulation shows that the index-raised pedestal around the fiber core can improve power conversion efficiency (PCE) by enhancing pump power usage. Compared with conventional 4C-EDF, the 4C-EDF with a pedestal has a gain improvement of 4.

Low-numerical aperture confined-doped long-tapered Yb-doped silica fiber for a single-mode high-power fiber amplifier.

A low-numerical aperture (NA) confined-doped long-tapered (LCT) Yb-doped fiber is proposed and fabricated by modified chemical vapor deposition combined with solution doping technique. The LCT fiber owns the core NA of ∼0.05 and the gain dopant doping diameter ratio of ∼77%, with a core/cladding diameter of 25/400 µm at both ends and 37.

Extended L-band few-mode Er/Yb Co-doped fiber amplifier with a cladding-pumped pseudo-two-stage configuration.

Spatial division multiplexing (SDM) is one of the most important technologies that may help to solve the future capacity crisis. However, to date, SDM optical amplification is still a challenge for its application. Herein, we numerically and experimentally demonstrated a few-mode Er/Yb co-doped fiber amplifier (FM-EYDFA) for extended L-band operation.

Extending the L-band amplification to 1623 nm using Er/Yb/P co-doped phosphosilicate fiber.

The gain bandwidth of the erbium-doped fiber amplifier limits the enhancement of the transmission capacity in optical fiber communication systems. This Letter reports an erbium-ytterbium co-doped phosphosilicate fiber, which is expected to increase transmission capacity by extending the L-band gain bandwidth to 1623 nm. The fiber was fabricated by modified chemical vapor deposition combined with solution doping technology.

Thermal bleaching of photodarkening and heat-induced loss and spectral broadening in Tm-doped fibers.

We demonstrate the thermal bleaching effect on a photodarkened thulium-doped fiber (TDF) in detail. The bleaching effect on visible transmission initiates at 250 °C and a complete recovery is achieved at 550 °C. Prior to the recovery, a post-irradiation heat-induced spectral loss is observed.

Bleaching of photodarkening in Tm-doped silica fiber with deuterium loading.

We demonstrate the rapid photodarkening (PD) phenomenon in Tm-doped fiber (TDF) core pumped by a laser at 1080 nm and the bleaching effect of deuterium (${{\rm D}_2}$D) on PD TDF. By ${{\rm D}_2}$D loading for seven days, the PD-induced excess loss (PIEL) in the visible (VIS) and near-infrared (NIR) region have been largely eliminated, and no degradation was observed within 30 days. PD resistance of the ${{\rm D}_2}$D pretreated TDF has been investigated as well.

Promotion of pulse peak power by halving the repetition rate based on a vector soliton.

We report on an all-fiber mode-locked repetition-rate-switch pulse operation in a Yb-doped fiber laser based on a polarization rotation vector soliton. The polarization controller (PC) in a fiber loop and a polarization-dependent isolator at the output port are incorporated into the laser resonator at the switch of the repetition rate. By adjusting the PC in the cavity, the mode locking can be switched between the fundamental repetition rate and half of it with a tiny pulse width change.

Yb doped gain guided index anti-guided fiber based on the nanoporous silica glass rod.

We report a heavily Yb/Al/B/F co-doped high silica rod with a negative refractive index relative to pure silica. The high silica rod was fabricated from nanoporous silica rod using glass phase-separation technology. To lower the refractive index, B and F were simultaneously introduced into the silica rod and the optical properties of the silica rod were investigated.

High coupling efficiency technology of large core hollow-core fiber with single mode fiber.

With the research of hollow-core fiber with large core diameter, the coupling efficiency from hollow-core fiber with large core diameter to single-mode fiber is difficult to increase through the traditional technology, we proposed a novel coupling method to improve the coupling efficiency by attaching a pure silica small ball at the front end of single-mode fiber, the coupling efficiency of 50% from hollow-core fiber with a large core diameter of 110 µm to single-mode fiber can be achieved.

Mitigation of mode instability in laser oscillators based on deuterium loading.

Ytterbium-doped fiber (YDF) loaded with deuterium is used herein to mitigate mode instability. Experimental results reveal that this method can increase the mode instability threshold in a laser oscillator. Specifically, when the YDF was loaded with deuterium over two- and four-week periods, the mode instability threshold power increased from ∼459 W to ∼533 W (16%) and to ∼622 W (35%), respectively, but the respective laser efficiencies were almost unaffected (71.

Gain-tailored Yb/Ce codoped aluminosilicate fiber for laser stability improvement at high output power.

A gain-tailored Ge-free Yb/Ce codoped aluminosilicate fiber is fabricated by MCVD combined with solution doping technique. Through regulating the temperature in the tube and designing the solution doping process, the refractive index profile of this fiber is close to a step-index without any center dip. The laser performance of this fiber is proved through contrast experiments with conventional fiber in a kW-level MOPA setup.

Double negative curvature anti-resonance hollow core fiber.

We report on a double negative curvature anti-resonance hollow core fiber, in which, the cladding is constituted of 6 large tubes and 6 small tubes arranged in a staggered pattern. The simulation shows that the loss of the fiber can reach or even exceed the loss of double-clad negative curvature anti-resonance hollow core fibers in short wavelength band, due to the staggered arrangement of two kind of tubes and the double negative curvature on the core boundary. The best single mode performance with a loss ratio as high as 100,000 between LP mode and LP mode is obtained due to simultaneously inhibited LP modes and LP modes in the fiber structure.

Broadband 2 μm amplified spontaneous emission of Ho/Cr/Tm:YAG crystal derived all-glass fibers for mode-locked fiber laser applications.

Broadband ∼2  μm amplified spontaneous emissions with a full width at half-maximum (FWHM) varying from ∼206 to ∼234  nm were obtained from the Ho/Cr/Tm:yttrium aluminum garnet (YAG) crystal derived fibers, which were drawn using a molten core method. The core-cladding structure of the as-drawn fibers was preserved completely, and the core was found to be amorphous. What is more, an all-fiber-integrated passively mode-locked laser based on an 8 cm long Ho/Cr/Tm:YAG crystal derived all-glass fiber was built which, to the best of our knowledge, is the first demonstration of a mode-locked fiber laser in a similar YAG derived fiber.

Numerical investigation of GHz repetition rate fundamentally mode-locked all-fiber lasers.

GHz repetition rate fundamentally mode-locked lasers have attracted great interest for a variety of scientific and practical applications. A passively mode-locked laser in all-fiber format has the advantages of high stability, maintenance-free operation, super compactness, and reliability. In this paper, we present numerical investigation on passive mode-locking of all-fiber lasers operating at repetition rates of 1-20 GHz.

Robust Q-switching based on stimulated Brillouin scattering assisted by Fabry-Perot interference.

Q-switching operation based on stimulated Brillouin scattering (SBS) has been developed for decades due to its inexpensive configuration, high pulse energy output, and the potential to be free from wavelength and material limitations. However, unstable and uncontrollable pulse output affected by SBS's stochastic nature hinders its development. In this work, we demonstrated a unique robust SBS-based Q-switched all-fiber laser.