Cunxiao Gao

Wavelength-Switchable and Wavelength-Tunable All-Normal-Dispersion Mode-Locked Yb-Doped Fiber Laser Based on Single-Walled Carbon Nanotube Wall Paper Absorber

We demonstrate a compact wavelength-tunable and -switchable mode-locked Yb-doped fiber (YDF) laser based on single-walled carbon nanotube (SWCNT) wall paper absorber. Two mechanisms coexist in the fiber cavity. The switchable mode-locked state can be obtained between two wavelengths depending on the fiber-loop-induced cavity birefringence. Because of the intensity-dependent transmission distribution, the proposed fiber laser can be operated in the tunable wavelength mode-locked state from 1025 to 1037 nm. The spectral bandwidth varied from 1.1 to 2.4 nm depending on the operating wavelength and the pump power with pulse duration of hundreds of picoseconds. The average wavelength spacing is 3.6 nm, which can be changed, corresponding to the birefringence of the fiber cavity. Moreover, stable wavelength-tunable mode locking is obtained at room temperature.

All-Fiber Dissipative Solitons Evolution in a Compact Passively Yb-Doped Mode-Locked Fiber Laser

Compact all-fiber all-normal dispersion Yb-doped fiber ring laser is demonstrated based on nonlinear polarization rotation technique. Dissipative solitons (DSs) with bell-shaped spectra are observed in the fiber cavity with linear chirps for the first time to our knowledge. Stable pulse width is 9.7 ps with the pulse energy of 1.2 nJ, which can be compressed to near the transformed limited pulse duration of 225 fs. The experimental result agrees well with the numerical simulations. The theoretical modeling indicates that the formation of the bell-shaped spectra is due to the combined effect of normal dispersion, nonlinearity, gain, loss, and spectral filtering effect. Different from the pulse evolution in the mode-locked fiber laser based on the wave plate and the birefringent plate, conventional DSs with rectangular-shaped spectra can be obtained by varying the polarization orientation of the cavity.

Low-repetition-rate ytterbium-doped fiber laser based on a CFBG from large anomalous to large normal dispersion

We report on the long-cavity ytterbium-doped fiber laser based on a chirped fiber Bragg grating (CFBG) to control the dispersion in the cavity. The proposed fiber lasers operating in large anomalous dispersion and large normal dispersion are intensively studied in this paper. To the best of our knowledge, this is the first time for us to give the dispersion map over such a wide range. The experimental results show that, for large anomalous dispersion, the state of soliton rains can be obtained. Nanosecond pulse is obtained in the large normal dispersion regime with spectral filter which is different from the operation mode without spectral filter. This study may pave the way to best apply the fiber laser in many fields.

Single- and dual-pulse oscillation in a passively Q-switched Nd:YAG microchip laser

Experimental investigation of single and dual pulses in a passively Q-switched Nd:YAG microchip laser with a Cr4+:YAG saturable absorber has been reported. The dual pulses consist of a main and a satellite pulse with respective spectra, intensities, and durations. It is found that the preponderant oscillating mode gives birth to the main pulse, and the other oscillating mode corresponds to the satellite pulse. Our results demonstrate that the dual-pulse emission results from double-longitudinal-mode oscillation in high pump regime.

Eye-safe, high-energy, single-mode all-fiber laser with widely tunable repetition rate

We present a novel high-energy, single-mode, all-fiber-based master-oscillator-power-amplifier (MOPA) laser system operating in the C-band with 3.3-ns pulses and a very widely tunable repetition rate, ranging from 30 kHz to 50 MHz. The laser with a maximum pulse energy of 25 \muJ and a repetition rate of 30 kHz is obtained at a wavelength of 1548 nm by using a double-clad, single-mode, Er:Yb co-doped fiber power amplifier.

All fiber supercontinuum light source using photonic crystal fibers pumped by nanosecond fiber laser pulses

A novel compact supercontinuum (SC) source using the single mode photonic crystal fibers (PCF) pumped with an all fiber MOPA fiber laser is demonstrated experimentally. A bandwidth of 700 nm is achieved by operating the pumping fiber laser at a wavelength of 1064 nm, pulse duration of 10 ns, repetition rate of 50 kHz and peak power of 1 kW. The SC generation is initiated through modulation instability (MI) which breakups the nanosecond pump pulses into picosecond or femtosecond pulses, and further broadened through nonlinear effects of PCF.

Passive Q-switched fiber laser with SESAM in ytterbium-doped double-clad fiber

A passively Q-switched ytterbium-doped double-clad fiber laser with SESAM as a saturable absorber is demonstrated experimentally. This system showed up to 18.7mW output power, up to 29.4 kHz repetition rate, a maximum pulse energy of 0.636μJ and a minimum pulse duration of 3.148 μs. The characteristics of pulse were investigated, and the theoretical analysis agree well with the experimental results.

A sub-nanosecond narrow-linewidth pulsed laser source with controllable repetition rate

A compact all-fiber sub-nanosecond narrow-linewidth Yb-doped fiber amplifier with a controllable repetition rate has been investigated. Tunable temporal pulses ranging from sub-nanoseconds to 10 ns with repetition rates from 10 kHz to 1 MHz are obtained by controlling the waveform of the injected electrical-pulse signal. Due to the practical requirements of our intended applications, a distributed feedback semiconductor laser with a wavelength of 1064 nm, pulse duration of 802 ps, repetition rate of 500 kHz and average power of 20 μW is used to seed a dual-stage single mode Yb-doped fiber amplifier. The characteristics of the amplified pulses are measured and exhibit a temporal duration of 810 ps with an average power of 31.2 mW. The gain of the amplified pulse is about 32 dB at the maximum output power. A notable feature of the amplifier pulses is that the spectral linewidth can be maintained to less than 0.1 nm during the dual-stage amplifier process. The noise level lies more than 22 dB below the peak value of the amplified spectrum, which represents an excellent signal-to-noise ratio.

Watts-level super-compact narrow-linewidth Tm-doped silica all-fiber laser near 1707 nm with fiber Bragg gratings

Watts-level ultra-short wavelength operation of a Tm-doped all fiber laser was developed by using a 1550 nm Er-doped fiber laser pump source and a pair of fiber Bragg gratings (FBGs). The laser yielded 1.28 W of continuous-wave output at 1707.01 nm with a narrow linewidth of ~44 pm by means of a 20 cm Tm-doped fiber. The dependencies of the slope efficiencies and pump threshold of the Tm-doped fiber laser versus the length of active fiber and reflectivity of the output mirror (FBG) were investigated in detail, in which the maximum average slope efficiency was 36.1%. There is no doubt that this all fiber laser will be a perfect pump source for mid-IR laser output.

The pulsed all fiber laser application in the high-resolution 3D imaging LIDAR system

An all fiber laser with master-oscillator-power-amplifier (MOPA) configuration at 1064nm/1550nm for the high-resolution three-dimensional (3D) imaging light detection and ranging (LIDAR) system was reported. The pulsewidth and the repetition frequency could be arbitrarily tuned 1ns~10ns and 10KHz~1MHz, and the peak power exceeded 100kW could be obtained with the laser. Using this all fiber laser in the high-resolution 3D imaging LIDAR system, the image resolution of 1024x1024 and the distance precision of ±1.5 cm was obtained at the imaging distance of 1km.