Peng Wan

High pulse energy 2 µm femtosecond fiber laser

In the paper, a 2 µm high energy fs fiber laser and amplification system is presented based on Tm doped fibers. The seed laser was designed to generate pulse train at 2024 nm at a repetition rate of 2.5 MHz. An AOM was used as a pulse picker to further lower the repetition rate down to 100 kHz. Two-stage fiber pre-amplifiers and a high energy large mode area (LMA) fiber amplifier were used to boost pulse energy up to 54 µJ before pulse compressor with chirped pulse amplification technique. After compressor, pulse energy of 36.7µJ and pulse duration of 910 fs and were obtained.

All fiber-based Yb-doped high energy, high power femtosecond fiber lasers

Two all fiber-based laser systems are demonstrated to achieve high energy and high average power femtosecond pulsed outputs at wavelength of 1 µm. In the high energy laser system, a pulse energy of 1.05 mJ (0.85 mJ after pulse compressor) at 100 kHz repetition rate has been realized by a Yb-doped ultra large-core single-mode photonic crystal fiber (PCF) rod amplifier, seeded with a 50 µJ fiber laser. The pulse duration is 705 fs. In the high average power experiment, a large mode area (LMA) fiber has been used in the final stage amplifier, seeded with a 50 W mode locked fiber laser. The system is running at a repetition rate of 69 MHz producing 1052 W of average power before compressor. After pulse compression, a pulse duration of 800 fs was measured.

2 µm femtosecond fiber laser at low repetition rate and high pulse energy

In the paper, a 2 µm high energy fs fiber laser is presented based on Tm doped fiber at a low repetition rate. The seed laser was designed to generate pulse train at 2 µm at a pulse repetition rate of 2.5 MHz. The low repetition rate seed oscillator eliminated extra devices such as AO pulse picker. Two-stage fiber amplifier was used to boost pulse energy to 0.65 µJ with chirped pulse amplification.

High power 2 µm femtosecond fiber laser.

A high power polarization maintaining femtosecond Tm-doped fiber laser system is demonstrated. A chirped fiber Bragg grating with normal dispersion was used to compensate the anomalous dispersion from the regular fiber in the 2 µm seed oscillator to generate mode locked pulses with a pulse repetition rate of 30.84 MHz. After chirped pulse amplification, an amplified power of 78 W was obtained. The pulse was compressed by a chirped volume Bragg grating based pulse compressor. A pulse duration of 760 fs and an average power of 36 W were obtained after compressor.

Sub-50 fs pulses around 2070 nm from a synchronously-pumped, degenerate OPO

We report generation of 48 fs pulses at a center wavelength of 2070 nm using a degenerate optical parametric oscillator (OPO) synchronously-pumped with a commercially available 36-MHz, femtosecond, mode-locked, Yb-doped fiber laser. The spectral bandwidth of the output is ~137 nm, corresponding to a theoretical, transform-limited pulse width of 33 fs. The threshold of the OPO is less than 10 mW of average pump power. By tuning the cavity length, the output spectrum covers a spectral width of more than 400 nm, limited only by the bandwidth of the cavity mirrors.

Low repetition rate high energy 1.5 µm fiber laser.

In this paper, we report, for the first time, that by modulating pump beam to suppress ASE effect we realized ultra-low repetition rate output in an all fiber based Er:Yb codoped master oscillator power amplifiers (MOPA) system. Combined with pulse shaping technology, pulses with up to 205 µJ pulse energy and 200 ns pulse duration were obtained at Hz level.

156 micro-J ultrafast Thulium-doped fiber laser

A high energy, high power ultrafast Tm doped fiber laser system was successfully developed. Pulse energy of 156 μJ and average power of 15.6 W were achieved. The laser system consisted of a mode-locked 2020 nm seed oscillator and multiple-stage power amplifiers. The seed included 30 m-long dispersion compensating fiber and emitted slightly chirped pulses with spectrum bandwidth of 8 nm. The mode-locking was stable and self-started. Repetition rate of seed oscillator was 2.5 MHz. The seed pulses were stretched with anomalous dispersion fiber to the duration of 320 ps. An AOM was used as a pulse picker to lower the repetition rate. A two-stage pre-amplifier was used to boost the pulse energy to 3 μJ. Pulse energies of up to 156 μJ were obtained from the final stage of power amplifier at a repetition rate of 100 kHz. Pulse durations of 780 fs were obtained after pulse compression. High OSNR and low background noise were also achieved at this low repetition rate.

High-energy femtosecond 2-μm fiber laser

Abstract. We describe in detail a high energy, high power ultrafast thulium-doped fiber laser system. The pulse energy of 156 μJ was realized. The laser system is comprised of a mode-locked 2020-nm seed oscillator and multiple-stage power/energy amplifiers. The seed oscillator output pulses at a repetition rate of 2.5 MHz. The seed pulses were stretched with the anomalous dispersion fiber to the duration of 320 ps. An acousto-optic modulator was used as a pulse picker to lower the repetition rate. A two-stage preamplifier was used to boost the pulse energy to 3 μJ. The pulse energies of up to 156 μJ and the average power of 15.6 W were obtained from the final stage of power amplifier at a repetition rate of 100 kHz with a slope efficiency of 26%. The pulse durations of 780 fs were obtained after pulse compression. High optical signal-to-noise ratio (OSNR) and low background noise were also achieved at this low repetition rate.

Pulse shaping fiber lasers for free-space and lidar applications

Fiber laser is becoming an enabling technology for coherent Lidar applications and free space communications due to its high efficiency, compact size and reliable operation. In these applications, high extinction rate and high OSNR are musts for a fiber laser. However, current Q-switched fiber lasers and solid state lasers cannot meet these criteria. Innovative approach has to be conceived to meet the requirements. In this paper, we will discuss our researches on high energy/power ns pulsed fiber lasers. Modulation schemes for seed laser in getting various optical waveforms to accommodate pulse narrowing in high power amplification and reduce SBS, high power operation of fiber amplifiers, nonlinearity mitigation in high power fiber lasers, and trade-offs among the parameters such as OSNR, power/energy scaling, extinction ratio, interpulses background noise (contrast ratio), and efficiency will be discussed.

High energy 3 µm ultrafast pulsed fiber laser.

In the paper, a 3 µm mid-infrared (MIR) high energy ultrafast Er:ZBLAN fiber laser and amplification system is presented. The 3µm seed pulses were generated through an Yb-doped ultrafast fiber laser pumped optical parametric amplification (OPA). A pulse energy of 12.4 µJ is generated at a repetition rate of 100 kHz with a pulse duration of 103 fs. A Er:ZBLAN fiber amplifier was used to further boost the chirped pulse energy to 84 µJ.