Gain-switched Fiber Laser Research Articles

Dysprosium gain-switched fiber laser at 3.24 µm pumped at 1064 nm

We report a dysprosium-doped gain switched fluoride fiber laser pumped at 1064 nm and emitting at 3244 nm. Pulses with energies up to 1 µJ were generated on a wide range of repetition rates between 100 kHz and 200 kHz, the highest reported for a pulsed dysprosium-doped fiber laser, producing an average output power reaching 207 mW. Stable 8.9 µJ pulses were also generated near 10 kHz, which is the highest pulse energy reported to date from a 1.1 µm band pumped dysprosium-doped fiber laser. This shows the 1.1 µm band as a valuable alternative for the pumping of dysprosium-doped fiber lasers emitting far from the emission peak and is thus of potential interest for future field applications.

Highly Efficient Multiple Watt Gain-Switched 1.7 μm All-Fiber Laser Pumped by 1.6 μm Harmonic Dissipative Soliton Resonance Pulses

Here, we firstly utilize a newly explored 1.6 μm harmonic dissipative soliton resonance (DSR) pulses as a pump source to realize a highly efficient gain-switched thulium fiber laser at 1719.52 nm. The 1.6 μm DSR pulses with a fundamental repetition rate of 360 kHz were produced from a nonlinear amplifying loop mirror (NALM) ring cavity, which directly output high power mode-locking pulses due to freedom of soliton-area limitation and pulse breaking. The harmonic mode-locking (HML) operation was achieved by properly adjusting the polarization controllers (PCs). The thulium fiber laser cavity constructed by a Fiber Bragg Grating (FBG) pair was resonantly (in-band) pumped by the 1.6 μm harmonic DSR pulses. Taking the merit of the strong absorption of Tm^3+ at 1.6 μm and the laser cavity having a low insert loss, the 1.7 μm gain-switched fiber laser with the maximum repetition rate of 2.16 MHz, corresponding to the average power of 2.826 W and the pulse energy of 1.33 μJ, was obtained at a high slope efficiency of about 71.9%. The maximum output power could exceed 3 W with a high slope efficiency of over 70%, which is the record in 1.7 μm all-fiber pulsed thulium lasers.

Power controllable gain switched fiber laser at\u2009~\u20093\xa0\u03bcm and\u2009~\u20092.1\xa0\u03bcm

Based on a hybrid pumping method consisting of a 1150 nm continuous-wave pump source and a 1950 nm pulsed pump source, we demonstrate a power controllable gain-switched fiber laser in dual wavebands at ~ 3 μm and ~ 2.1 μm. Different pumping schemes for pumping a Ho3+-doped ZBLAN fiber are studied. Using only the 1950 nm pulsed pump source, ~ 2.1 μm gain-switched pulses with single and double pulses are obtained separately at different pump powers. This phenomenon indicates that the 1950 nm pulsed pump source acts as a modulator to trigger different states of the ~ 2.1 μm pulses. Moreover, by fixing the 1150 nm pump power at 3.259 W and adjusting the 1950 nm pump power, the output power of the ~ 2.1 μm gain-switched pulsed laser is flexibly controlled while the ~ 3 μm laser power is almost unchanged, inducing the maximum output powers of 167.96 mW and 260.27 mW at 2910.16 nm and 2061.65 nm, respectively. These results suggest that the comparatively low power of the ~ 2.1 μm gain-switched pulsed laser in dual-waveband laser can be efficiently overcome by reasonably controlling the 1950 nm pump power.

1.4 W in-band pumped Dy3+-doped gain-switched fiber laser at 3.24 µm.

In this Letter, we report, to the best of our knowledge, the first demonstration of an in-band pumped gain-switched Dy3+-doped fiber laser operating at 3.24 µm. The monolithic cavity bounded by two fiber Bragg gratings was pumped by a gain-switched Er3+-doped fiber system. It produced stable nanosecond pulses in a single-pulse regime on its entire operating range from 20 kHz to 120 kHz. A record average power of 1.43 W was achieved for a repetition rate of 120 kHz, and a record pulse energy of 19.2 µJ was achieved at 60 kHz. These results represent a significant improvement in Dy3+-doped pulsed fiber laser performances and open the way to applications in the fields of remote sensing and material processing.

增益调制掺铥光纤激光器的数值仿真及实验研究

增益调制掺铥光纤激光器的数值仿真及实验研究

Mode-locking and self-mode-locking-like operation in a resonantly pumped gain-switched Tm-doped fiber laser

Mode-locking and mode-locking-like operation in a fast gain-switched Tm-doped fiber laser have been investigated experimentally. Applying a SESAM mirror, stable gain-switched and regular mode-locked pulses at a wavelength of ∼2μm are reported. The repetition rates of the gain-switched pulses and mode-locked sub-pulses are 50 kHz and 111 MHz, respectively. The duration of sub-pulses recorded within one gain-switched pulse envelope is ∼110 ps. Besides, in the same laser system configuration, it has been found that self-starting mode-locked resembling pulses, attributed to mode beating, can be generated. To the best of our knowledge, it is the first report on a gain-switched fiber laser where both modes of operation have been demonstrated.

Highly adaptable gain-switched fiber laser with improved efficiency.

A highly adaptable fiber laser with pulse-on-demand and precision pulse-duration tuning is presented. It is based on a compact optical design combining the gain-switching technique with the all-fiber master oscillator and pump-recovery amplifier architecture. The approach of laser-pulse stability control by compensation pumping and pulse-duration control by changing the pump wavelength are introduced. In order to prove the concept, a laser setup capable of producing laser pulses with an average power of up to 30 W and a peak power of approximately 1 kW at an improved efficiency and an arbitrary repetition rate is presented.

Watt-level gain-switched fiber laser at 3.46 μm.

We demonstrate a gain-switched fiber laser, yielding a maximum average power of 1.04 W at 3.46 μm, which is the current record of a pulsed rare-earth-doped fiber laser at the wavelength beyond 3 μm, to our knowledge. The corresponding pulse energy is 10.4 μJ with a repetition rate of 100 kHz. A dual-wavelength pumping scheme consisting of a home-made 1950 nm passively Q-switched fiber laser system with a μs-scale pulse width. A 976 nm continuous wave laser diode was used to gain-switch a double-cladding Er-doped ZBLAN fiber laser cavity. Possible laser-quenching behavior during a single-pump pulse was circumvented for the moderate pump peak power and relatively large-pump pulse width. Synchronous gain-switched pulses were achieved with a tunable repetition rate at a wide range of 55~120 kHz, which is the highest gain-switching repetition rate at this band and only limited by our pulsed-pump source. Moreover, the significance of pump pulse width for repetition rate improvement is also discussed. These results provide an available way to produce high-power pulses at the mid-infrared range of 3~5 μm.

1.7 μm wavelength tunable gain-switched fiber laser and its application to spectroscopic photoacoustic imaging.

Recently demonstrated bond-selective photoacoustic (PA) imaging has revealed the importance of 1.7μm laser sources. In this Letter, we demonstrate a gain-switched thulium-doped fiber laser with continuous tuning from 1690 to 1765nm by using an electrically driven acousto-optical tunable filter. Micro-joule laser pulses with a shot-to-shot intensity variation of 1.6% and a pulse duration of 150ns are obtained. The laser source is then harnessed to implement a PA microscopy system, of which the lateral resolution is estimated to be 15.6μm by scanning the edge of a black tape. The PA spectra of butter, rapeseed oil, and adipose tissue are measured, and they show a consistent absorption peak of around 1720nm. Photoacoustic microscopy imaging of the adipose tissue demonstrates a high optical absorption contrast of lipids and the superiority of the laser for spectroscopic PA detection.

High repetition rate gain-switched Ho-doped fiber laser at 2.103 μm pumped by h-shaped mode-locked Tm-doped fiber laser at 1.985 μm.

We present a MHz level high repetition rate gain-switched Ho-doped fiber laser at 2.103 μm using a h-shaped mode-locked Tm-doped fiber laser as the pump, for the first time. A NPR mode-locked Tm-doped ring cavity was designed as the seed, which could generate h-shaped pulses at 1.985 μm with a fundamental repetition rate of 1.435 MHz. It had a pump-dependent ns scale pulse duration with an almost unchanged peak amplitude. Then its output power and pulse energy were significantly scaled to 3.92W and 2.71 μJ, respectively based on a one-stage Tm-doped fiber based amplifier. After that, the amplified pulses were fed to a linear cavity Ho-doped fiber laser formed by a HR FBG and a perpendicularly cleaved fiber end, resulting in stable gain-switched pulses at 2.103 μm with a repetition rate of 1.435 MHz, which marks the record of gain-switched fiber lasers in this spectral region. At this repetition rate, the maximum output power of 1.13 W and pulse energy of 0.79 μJ were achieved at a high slope efficiency of 75.4% with respect to its absorbed pump power, giving the shortest pulse duration of 10.8 ns. The results indicated that the h-shaped pulses were an alternative choice for high repetition rate gain-switching in an all-fiber configuration.

A novel pulsed fiber laser: further study on the bias-pumped gain-switched fiber laser

The bias-pumped gain-switched fiber laser proposed by us is considered to be a novel pulsed fiber laser based on a new pulsing mechanism. With a certain signal power seeding, synchronization of the temporal evolution can be maintained between the output signal laser and the pump. The seed laser can conveniently be supplied with power by a CW pump; this is called bias-pump power. A pulsed pump is responsible for shaping the output pulse. Stable pulsed lasers with a tunable duration can be achieved under a bias pump combined with a pulsed pump. In addition, the temporal shape of the output pulses can be controlled based on this new pulsing mechanism. Compared with conventional gain-switched fiber lasers, a much simpler pulsed laser design can be provided by this novel pulsed fiber laser because there is no need to add a control unit to realize fast gain-switching.

Gain-switched fiber laser at 3.55 μm.

We report, to the best of our knowledge, the first demonstration of a gain-switched fiber laser operating near 3.5μm. A dual-wavelength pumping scheme consisting of a 1976nm Q-switched fiber system and a continuous-wave 976nm laser diode were used to gain-switch a monolithic erbium-doped fluorozirconate fiber laser cavity at 3.552μm. Stable pulses were produced for repetition rates ranging between 15 and 20kHz, and a record peak power of 204W was achieved at 15kHz. A quenching phenomenon was also observed at 15kHz for 1976nm pulse energies beyond 180μJ.

Stable pulse generation in a bias-pumped gain-switched fiber laser

We demonstrate gain-switched fiber laser with bias pumping plays an important role in regulating chaotic relaxation spikes. Under certain conditions the profile of output pulse from gain-switched fiber laser can keep the same shape as that of pump pulse. Bias pumping technique may have significance in increasing output stable pulse energy in gain-switched fiber laser. Gain-switched fiber laser with bias pumping may be interesting for some applications in micro-processing and thin film removal.

Widely wavelength tunable gain-switched Er3+-doped ZBLAN fiber laser around 2.8 μm.

In this paper, we demonstrate a wavelength widely tunable gain-switched Er3+-doped ZBLAN fiber laser around 2.8 μm. The laser can be tuned over 170 nm (2699 nm~2869.9 nm) for various pump power levels, while maintaining stable μs-level single-pulse gain-switched operation with controllable output pulse duration at a selectable repetition rate. To the best of our knowledge, this is the first wavelength tunable gain-switched fiber laser in the 3 μm spectral region with the broadest tuning range (doubling the record tuning range) of the pulsed fiber lasers around 3 μm. Influences of pump energy and power on the output gain-switched laser performances are investigated in detail. This robust, simple, and versatile mid-infrared pulsed fiber laser source is highly suitable for many applications including laser surgery, material processing, sensing, spectroscopy, as well as serving as a practical seed source in master oscillator power amplifiers.

Gain-switched monolithic fiber laser with ultra-wide tuning range at 2 μm.

We demonstrate a gain-switched thulium-doped fiber laser (TDFL) built in an all-fiber format producing nanosecond pulses with variable wavelength in the 2 μm waveband. The laser features tunable operation in an ultra-wide spectral region of 1765 - 2055 nm (24 THz). The nearly 300 nm tunability doubles the record tuning range of existing gain-switched fiber lasers, and to the best of our knowledge, presents the broadest tuning range that has been reported for a monolithic pulsed rare earth doped fiber laser to date. The TDFL can operate at a repetition rate of 2.5 - 100 kHz with a pulse width as short as ~200 ns. Influences of various system parameters on the laser performance are investigated in detail.

Stable Gain-Switched Thulium Fiber Laser With 140-nm Tuning Range

We demonstrate a gain-switched thulium fiber laser that can be continuously tuned over 140 nm, while maintaining stable nanosecond single-pulse operation. To the best of our knowledge, this system represents the broadest tuning range for a gain-switched fiber laser. The system simplicity and wideband wavelength tunability combined with the ability to control the temporal characteristics of the gain-switched pulses mean this is a versatile source highly suited to a wide range of applications in the eye-safe region of the infrared, including spectroscopy, sensing and material processing, as well as being a practical seed source for pumping nonlinear processes.

1 mJ nanosecond all-fiber thulium-doped fiber laser at 2.05 μm.

A high energy all-fiber format nanosecond thulium-doped fiber laser at 2050 nm with a master oscillator power amplifier (MOPA) configuration is presented in this paper. The seed oscillator is a linearly polarized gain-switched fiber laser pumped by a 1550 nm fiber laser. The output pulse of the seed has a polarization extinction ratio (PER) better than 16 dB with a maximal output power of 470 mW. After two-stage double- cladding fiber amplifiers, the average power at 40 kHz was boosted up to 40.5 W. The output pulse has a maximum pulse energy of 1 mJ with a pulse width of 100 ns, which corresponds to a peak power of 10 kW. To the best of our knowledge, it is the highest single pulse energy ever reported for a nanosecond thulium-doped all-fiber MOPA system at 2050 nm.

Compact tunable dual-wavelength mid-infrared optical parametric oscillator pumped by high power gain-switched fiber laser

We report, to the best of our knowledge, the first demonstration of a gain-switched fiber laser pumped tunable dual-wavelength optical parametric oscillator (OPO) operating around 3–5 µm. A homemade APMgLN crystal was used as the nonlinear material. A ‘figure-of-h’ shaped pump pulse was employed to improve the nonlinear conversion efficiency of the OPO. A maximum total idler output power of 4.82 W was obtained under pump power of 44.6 W with corresponding pump-to-idler conversion efficiency of 10.5%. The idler wavelengths were measured to be 3.34 and 3.65 μm at a temperature of 40 °C, which can be successfully tuned with a rate of about 2 nm °C−1 by adjusting the working temperature of the APMgLN crystal from 20 °C to 80 °C.

Compact high power mid-infrared optical parametric oscillator pumped by a gain-switched fiber laser with "figure-of-h" pulse shape.

We demonstrate a compact high power mid-infrared (MIR) optical parametric oscillator (OPO) pumped by a gain-switched linearly polarized, pulsed fiber laser. The gain-switched fiber laser was constructed with a piece of Yb doped polarization maintaining (PM) fiber, a pair of fiber Bragg gratings written into the matched passive PM fiber and 6 pigtailed pump laser diodes working at 915 nm with 30 W output peak power each. By modulating the pulse width of the pump laser diode, simple pedestal-free pulse shape or pedestal-free trailing pulse shape ("figure-of-h" as we call it) could be achieved from the gain-switched fiber laser. The laser was employed as the pump of a two-channel, periodically poled magnesium oxide lithium niobate-based OPO system. High power MIR emission was generated with average output power of 5.15 W at 3.8 μm channel and 8.54 W at 3.3 μm channel under the highest pump power of 45 W. The corresponding pump-to-idler conversion efficiency was computed to be 11.7% and 19.1%, respectively. Experimental results verify a significant improvement to signal-to-idler conversion efficiency by using "figure-of-h" pulses over simple pedestal-free pulses. Compared to the master oscillator power amplifier (MOPA) fiber laser counterpart, the presented gain switched fiber laser is more attractive in OPO pumping due to its compactness and simplicity which are beneficial to construction of OPO systems for practical MIR applications.

Short pulsed gain-switched fiber laser with improved efficiency utilizing unabsorbed pump recovery.

A simple solution for increasing the slope efficiency of a gain-switched fiber laser based on Yb-doped active fiber is presented. By adding a fiber amplifier stage, which recovers the unabsorbed pump light from the gain-switched oscillator, a significant increase in slope efficiency is achieved. The pulses at 1030-nm wavelength have an FWHM of 28 ns and a peak power of 2.3 kW.