Gain-switched Thulium-doped Fiber Laser Research Articles

Monolithic ultrashort-cavity DBR gain-switched thulium doped fiber laser made by high-precision femtosecond laser direct-writing

We demonstrate a novel monolithic ultrashort-cavity distributed Bragg reflector (DBR) gain-switched thulium doped silica fiber laser. Commercial heavily thulium doped non-polarization-maintaining silica fiber was selected as the gain medium. Monolithic linear laser resonator, which includes a pair of uniform fiber Bragg gratings (FBGs) with a space of 1.0-mm inbetween, was inscribed in the thulium fiber by femtosecond-laser point-by-point (PbP) writing method. The reflectivity of either FBG is close to 100 % and the effective cavity length is calculated to be 3.5 mm. Such an ultrashort-DBR-cavity fiber laser exhibited high Q factor and low cavity loss, allowing the efficient utilization of pump power within the millimeter-long cavity. Single-longitudinal, linearly polarized, gain-switched TDFL at 2003 nm, with a recorded shortest pulse duration of 4.3 ns, a repetition rate of 50 kHz, a maximum peak power of 500 W, and single pulse energy of 2.14 μJ, has been realized, benefitted from the ultrashort cavity length.

High repetition rate gain-switched thulium-doped fiber laser pumped by 1.6 μm noise-like pulses

We demonstrate a watt-level 2 μm high repetition rate gain-switched thulium-doped fiber laser (TDFL) pumped by 1.6 μm noise-like pulses (NLPs). Served as pump pulses, the hundred nanoseconds level NLPs from a mode-locked fiber laser are amplified to ~8 μJ by an Er:Yb co-doped fiber amplifier. Referring to simulative and experimental results of the gain-switched TDFL, the cavity parameters are adapted for the performance of the gain-switched pulse. The TDFL generates 1940 nm gain-switched pulses with the minimum pulse duration of 14.7 ns in the cavity length of 14 cm. The maximum output power reaches 2.44 W. The research firstly reports a gain-switched TDFL pumped by noise-like pulses and provide a method to generate high repetition rate gain-switched short pulse.

High-energy all-fiber gain-switched thulium-doped fiber laser for volumetric photoacoustic imaging of lipids

We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic (PA) imaging of lipids. The laser cavity is constructed by embedding a short piece of gain fiber between a pair of fiber Bragg gratings (FBGs). Through using three pairs of FBGs with operation wavelengths at 1700, 1725, and 1750 nm, three similar lasers are realized with a cavity length of around 25 cm. Under a maximum pump energy of 300 μJ at 1560 nm, laser pulse energies of 58.2, 66.8, and 75.3 μJ are, respectively, achieved with a minimum pulse width of < 16.7 ns at a repetition rate of 10 kHz. Volumetric imaging of lipids is validated through scanning a fat beef slice with a PA microscopy system incorporated with the newly developed source, and a lateral resolution of 18.8 μm and an axial resolution of 172.9 μm are achieved. Moreover, the higher shooting speed of the developed source can potentially allow for increasing at twice the frame rate of current intravascular PA imaging.

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

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.

Repetition-Rate-Switchable and Self-Mode-Locked Pulses Generation From a Gain-Switched Thulium-Doped Fiber Laser and Their Amplification Properties

We report on repetition-rate-switchable and self-mode-locked pulses generation from a gain-switched thulium-doped fiber laser. Stable pulse trains were gain-switched by a home-made, pulsed Erbium/Ytterbium codoped fiber amplifier. The pulse repetition rate (PRR) of stable output pulse trains can be switched as 1/4, 1/3, and 1/2 times of that of the pump pulse train. Besides, the gain-switched mode-locked pulses were also achieved in the same cavity. By following three-stage thulium-doped fiber amplifiers, the average output power of the stable gain-switched pulses was scaled to 115 W with the PRR of 100 kHz, corresponding to a pulse energy of about 1.15 mJ. The amplification properties of the gain-switched mode-locked pulses were also characterized and discussed.

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.

Efficient theoretical model and numerical simulation for optimization of gain-switched thulium-doped fiber lasers

We demonstrate an effective and simplified theoretical model of the in-band-pumped gain-switched thulium-doped fiber laser in which the effective pump power and effective population density are defined as the approximation of spatial variables. The numerical simulation results based on the model are in good agreement with the experimental data. The parameters of the pump source and the cavity configuration are considered in our numerical model for the optimization of the laser system. The pump condition in which the pulse distortion can be avoided is presented.

High-Power Highly Linear-Polarized Nanosecond All-Fiber MOPA at 2040 nm

We demonstrate a nanosecond all-fiber master oscillator power amplifier with linear-polarized output at 2040 nm, seeded by an in-band-pumped gain-switched thulium-doped fiber laser, which can directly output tens-of-microjoules pulses with designable pulse duration and Gaussian-like pulse profile. After only two stages of amplification, we achieve an average power of 70 W at a pulse width of 114 ns and a repetition rate of 10 kHz, corresponding to a pulse energy of 7 mJ and a peak power of 53.8 kW. Benefit from the on-site polarization control technique we proposed, a polarization extinction ratio (PER) of 25 dB at the highest output is also obtained. To the best of our knowledge, this is the highest power nanosecond all-fiber laser reported at 2-μm waveband and the PER is also a record among high-power fiber lasers.

High Power Supercontinuum Generation in Fluoride Fibers Pumped by 2 $\mu{\rm m}$ Pulses

High power supercontinuum generation in fluoride step-index optical fibers pumped with 2- μm pulses delivered by a gain-switched thulium-doped fiber laser and amplifier system is reported. An output average power of 1.25 W in the ~ 1.8-4.15 μm spectral band and 1.82 W in the ~ 1.8-3.65 μm band was achieved for two fluorozirconate fibers of different parameters. The first demonstration of Watt-level supercontinuum generation in a fluoroindate fiber is also demonstrated. The achieved output SC powers are the highest ones ever reported for fluoride fibers pumped with 2- μm gain-switched optical pulses.

Temporal characteristics of gain-switched thulium-doped fiber laser near threshold

The temporal output characteristics of an all-fiber gain-switched thulium-doped fiber laser near threshold are investigated experimentally and numerically. The pulse repetition rate and pulse energy of the 1550 nm pump source are found to be two important parameters that affect the laser performance. Adjusting these two parameters, three different output working states, namely no lasing state, unstable state, and steady state, are observed experimentally. Particularly, in the unstable state relatively stable output pulse trains with repetition rate trisecting (PRR 1/3) and halving (PRR 1/2) with respect to the pump source are found. The experimental results together with corresponding numerical simulation afford a deep insight into the related lasing mechanisms.

Efficient, high peak power Tm:YLF laser

We demonstrate efficient generation of diode pumped, passively cooled Tm:YLF laser end-pumped by 25-W fiber coupled laser diode. Over 5 W of output power was achieved for 25-W pumping laser and for elongated 120-mm cavity. For the free-running and Q-switching regimes the output spectrum was centered at 1908-nm with linewidth less than 7 nm. In the experiments on active Q-switching up to 5.5 mJ of output energy was demonstrated with pulse duration of 11 ns, corresponding to ~0.5 MW of peak power. Full Text: PDF References Jabczynski, J.K., Gorajek, L., "High repetition rate, high peak power, diode pumped Tm:YLF laser," Laser Phys. Lett. 6 (2), 109-112 (2009) CrossRef Sha, J.J., Shen, D.Y., Zhao, T., Yan, X.F., "High power and highly efficient operation of a Tm:YAG laser in-band pumped at 1617 nm", Laser Phys. Lett. 10, 075801 (2013) CrossRef Guillemet, S., "High pulse energy sub-nanosecond Tm-doped fiber laser". Proc. SPIE 8237, Fiber Lasers IX: Technology, Systems, and Applications, 82373V (2012) CrossRef Swiderski, J., Maciejewska, M., Kwiatkowski, J. and Mamajek, M., "An all-fiber, resonantly pumped, gain-switched, 2 ?m Tm-doped silica fiber laser", Laser Phys. Lett. 10, 015107 (2013). CrossRef Swiderski, J. and Michalska, M., "Generation of self-mode-locked resembling pulses in a fast gain-switched thulium-doped fiber laser," Opt. Lett. 38, 1624-1626 (2013) CrossRef Kwiatkowski, J., Jabczynski, J. K., Gorajek, L., Zendzian, W., Jelinkowa, H., Sulc, J., Nemec, M., Koranda, P., "Resonantly pumped tunable Ho:YAG laser", Laser Phys. Lett. 6 (7), 531-534 (2009) CrossRef Kwiatkowski, J., Jabczynski, J.K., Zendzian, W., Swiderski J., Gorajek, L. and Galecki, L., "Resonantly pumped acousto-optically Q-switched hybrid Ho:YAG laser", Laser Phys. Lett. 8 (4), 281-285 (2011) CrossRef Gallian, A., Fedorov, V. V., "Hotpressed ceramic Cr2+:ZnSe gain-switched laser", Opt. Express 14, 11694?11701 (2006) CrossRef Creeden, D., Ketteridge, P., "Mid-infrared ZnGeP2 parametric oscillator directly pumped by a pulsed 2 ?m Tm-doped fiber laser," Opt. Lett. 33, 315-317 (2008) CrossRef Swiderski, J. and Maciejewska, M., "Watt-level, all-fiber supercontinuum source based on telecom-grade fiber components", Appl. Phys. B 109, 177-181 (2012) CrossRef Swiderski, J. and Michalska, M., "Mid-infrared supercontinuum generation in a single-mode thulium-doped fiber amplifier", Laser Phys. Lett. 10, 035105 (2013) CrossRef Swiderski, J., Michalska, M. and Maze, G., "Mid-IR supercontinuum generation in a ZBLAN fiber pumped by a gain-switched mode-locked Tm-doped fiber laser and amplifier system," Opt. Express 21, 7851-7857 (2013) CrossRef

Linearly polarized and narrow-linewidth pulse generation at high repetition rate from an all-fiber gain-switched Thulium-doped fiber laser

Abstract Narrow-linewidth and linearly polarized operation at high repetition rate of an all-fiber gain-switched Thulium-doped fiber laser is presented. The laser produces stable 135 ns pulses with maximum average output power of 960 mW at repetition rate of 500 kHz, corresponding to maximum pulse energy of 1.92 μJ and a slope efficiency of 55.1% with respect to 1.55 μm pump power. The center wavelength of 1926.7 nm with a spectral bandwidth of

A theoretical and experimental investigation of an in-band pumped gain-switched thulium-doped fiber laser

In this paper, the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber (TDF) laser is investigated. The analytical formulations of pump energy threshold, peak power extraction efficiency, and pulse extraction efficiency are derived through analyzing the interaction process between the pump pulse and the laser pulse. They are useful for understanding, designing, and optimizing the in-band pumped TDF lasers in a 1.9 μm–2.1 μm wavelength region. The experiment with an all-fiber gain-switched TDF laser pumped by a 1.558-μm pulse amplifier is conducted, and our experimental results show good agreement with theoretical analysis.

Generation of self-mode-locked resembling pulses in a fast gain-switched thulium-doped fiber laser

We report on a generation of self-starting mode-locked resembling (MLR) pulses in an all-fiber, gain-switched Tm(3+)-doped fiber laser operating at 2 μm wavelength, which we believe to be the first demonstration of such an approach. The laser delivers 100% modulated MLR pulses within an envelope of ~30 ns gain-switched pulse at a repetition rate of 30 kHz. The maximum average output power is 0.4 W and the maximum peak-power of MLR pulses can be as high as 1.1 kW. The performance of the laser is described.

All-Fiber Gain-Switched Thulium-Doped Fiber Laser Pumped by 1.558 μm Laser

We present an all-fiber gain-switched thulium (Tm) doped fiber laser operating in the eye-safe region at 1940 nm. The fibre Bragg gratings (FBGs) inscribed by phase mask technology are used as cavity mirrors, and the transmission spectra of FBGs are also measured. The output characteristics are studied at pulse repetition frequencies of 10, 20 and 30 kHz, and the maximum output powers of 28.9, 67.0 and 71.0 mW are achieved under incident pump powers of 122, 247 and 250 mW. The narrowest pulse width of 29 ns and shortest pulse built-time of 140 ns are obtained at 10 kHz. The relation between pulse built-time and cavity length are discussed.