Xiaolei Bai

High-Power All-Fiber Single-Frequency Erbium–Ytterbium Co-Doped Fiber Master Oscillator Power Amplifier

We report herein an all-fiber single-frequency master oscillator power amplifier (MOPA) at 1550 nm with Er/Yb-codoped active fiber and wavelength-stabilized 976-nm LD pump source. A pump-limited maximum continuous-wave output power of 56.4 W was achieved under the pump power of 150 W, with corresponding slope efficiency being 37.0%. Via the self-heterodyne method, the evolution of spectrum linewidth during the amplification was investigated for the high-power MOPA-based single-frequency fiber laser. The linewidth and relative intensity noise at the maximum output power are 4.21 kHz and -110 dBm/Hz, respectively.

Investigation on high transmission efficiency 7 × 1 pump combiner

Abstract. The 7×1 end-pumped combiner employing 105/125  μm multimode fibers as pump fibers is investigated. The theoretical analysis reveals that sufficient taper length and low refractive index of the capillary should be adopted to fabricate high transmission efficiency combiners. Based on the simulation results, we fabricate a 7×1 end-pumped pump combiner with an average transmission efficiency of 98.9% and a total return loss of 1.1‰. The measured internal operating temperature of this combiner indicates it can endure pump power of the order of kilowatts.

High-energy 100-ns single-frequency all-fiber laser at 1064 nm

A high-energy, single-frequency fiber laser with long pulse duration of 100 ns has been experimentally investigated in an all-fiber architecture. Only 34-cm long heavily Yb-doped phosphate fiber was employed in power scaling stage to efficiently suppress the Stimulated Brillouin effect (SBS). In the experiment, 0.47 mJ single pulse energy was achieved in power scaling stage at the pump power of 16 W. The pre-shaped pulse was gradually broadened from 103 to 140 ns during the amplification without shape distortion.

Switchable and tunable dual-wavelength Er-doped fiber ring laser with single-frequency lasing wavelengths

We obtain a switchable and tunable dual-wavelength single-frequency Er-doped ring fiber laser. In order to realize single-longitudinal output, two saturable-absorber-based tracking narrow-band filters are formed in 3- meter-long unpumped Er-doped fiber to narrow the linewidth via using the PM-FBG as a reflection filter. The maximum output power is 2.11 mW centered at 1550.16 nm and 1550.54 nm when the fiber laser operates in dual-wavelength mode. The corresponding linewidths of those two wavelengths are measured to be 769 Hz and 673 Hz, respectively. When the temperature around the PM-FBG is changed from 15 °C to 55 °C, the dual-wavelength single-frequency fiber laser can be tuned from 1550.12 nm to 1550.52 nm and from 1550.49 nm to 1550.82 nm, respectively.

Influence of seed power and gain fiber temperature on output linewidth in single-frequency Er3+/Yb3+ co-doped fiber amplifier

Based on the 1550 nm single-frequency Erbium-Ytterbium co-doped fiber amplifier, the output linewidth with different seed power and gain fiber temperature was experimental investigated. The results demonstrated that, to obtain the same output power, the increment of the seed power was benefit to improve the output signal to noise ratio (SNR), and to reduce the linewidth broadening. The increment of gain fiber temperature can improve slope efficiency and enhance the ASE intensity but broaden linewidth. Meanwhile, the ASE was considered as one of the reason of linewidth variation.

The research on the design and performance of 7×1 pump combiners

The 7×1 end-pumped pump combiners employing 105/125 μm multimode fibers as pump fibers are investigated. Based on the results of our theoretical analysis, sufficient taper length (TL) and low refractive index (RI) of the capillary have been adopted to fabricate high transmission efficiency combiners. A 7×1 end-pumped pump combiner with an average transmission efficiency of 98.9% and a total return loss of 1.1‰ is fabricated in experiments, which could find its application in high-power fiber laser systems.

Linewidth-narrowed 2-μm single-frequency fiber laser based on stimulated Brillouin scattering effect

A 2-μm linear-polarized single-frequency Brillouin-Thulium fiber laser (BTFL) has been experimentally investigated for linewidth narrowing. The threshold for the Brillouin pump is around 200 mW, and more than 205 mW single-frequency Stokes laser was achieved with the 793 nm pump power of 8.5 W. The linewidth of the fiber laser has been narrowed for ~8 times, from 34 to 4.6 kHz. The measured RIN of the BTFL is <-150 dB/Hz for frequency above 2 MHz, which approaches the shot noise limit.

Investigation of ASE and SRS effects on 1018nm short-wavelength Yb3+-doped fiber laser

1018nm short wavelength Yb3+-doped fiber laser can be widely used for tandem-pumped fiber laser system in 1 μm regime because of its high brightness and low quantum defect (QD). In order to achieve 1018nm short wavelength Yb3+-doped fiber laser with high output power, a steady-state rate equations considering the amplified spontaneous emission (ASE) and Stimulated Raman Scattering (SRS) has been established. We theoretically analyzed the ASE and SRS effects in 1018nm short wavelength Yb3+-doped fiber laser and the simulation results show that the ASE is the main restriction rather than SRS for high power 1018nm short wavelength Yb3+-doped fiber laser, besides the high temperature of fiber is also the restriction for high output power. We use numerical solution of steady-state rate equations to discuss how to suppress ASE in 1018nm short wavelength fiber laser and how to achieve high power 1018nm short-wavelength fiber laser.

High power single-frequency erbium-ytterbium co-doped all-fiber laser in MOPA

We report herein an all-fiber single-frequency master oscillator power amplifier (MOPA) at 1550 nm with Er/Yb-codoped active fiber and wavelength-stabilized 976-nm LD pump source. A pump-limited maximum continuous-wave output power of 56.4 W was achieved under the pump power of 150 W, with corresponding slope efficiency being 37.0%. Via the self-heterodyne method, the evolution of spectrum linewidth during the amplification was investigated for the high-power MOPA-based single-frequency fiber laser. The linewidth and relative intensity noise at the maximum output power are 4.21 kHz and −110 dBm/Hz, respectively.

Experimental Investigation on Spectral Linewidth and Relative Intensity Noise of High-Power Single-Frequency Polarization-Maintained Thulium-Doped Fiber Amplifier

We investigate the spectral linewidth and relative intensity noise (RIN) of an all-fiber single-frequency polarization-maintained master oscillator and power amplifier at 1925 nm. It is found that the linewidth of the fiber amplifier is related to the power ratio of signal laser to accumulated amplified stimulated emission noises. A 3-dB linewidth of 56 kHz is measured at a maximum output power of 45 W, resulting to a linewidth broadening of 20 kHz compared to the 36-kHz linewidth of the seed laser. The RINs of the preamplifier and the power amplifier are measured to be -108 and -90 dBm/Hz at the relaxation frequency, respectively.