Tm-doped Silica Fiber Laser Research Articles

Solid Tellurite Optical Fiber Based on Stack-and-Draw Method for Mid-Infrared Supercontinuum Generation

Broadband, high-power mid-infrared (mid-IR) sources are critical for many applications. Compared to alternatives such as fluorides and chalcogenides, tellurite fibers are more robust and can handle much higher power. Tellurite fibers also have high nonlinearity and a material zero dispersion close to 2 µm, making them ideal for nonlinear processes pumped by Tm-doped silica fiber lasers. In this work, we have demonstrated solid tellurite fibers fabricated by a stack-and-draw process and investigated their potential for broadband mid-IR supercontinuum generation. We have identified that fibers with low dispersion are beneficial and that low residual hydroxyl (OH) is critical for broadband mid-IR supercontinuum generation in tellurite fibers pumped at ~2 µm.

0.5-GHz Repetition Rate Fundamentally Tm-Doped Mode-Locked Fiber Laser

We demonstrate a passively mode-locked Tm-doped silica fiber laser with 535-MHz fundamental repetition rate by employing a semiconductor saturable absorber mirror. With in-band pumping at 1590 nm, the stable mode-locked fiber laser produces up to 50 mW at an incident pump power of 558 mW. The laser operating at 1938 nm has a spectral bandwidth of 0.72 nm. After amplification, the laser pulse width is measured to be $\sim 7.9$ ps, and the time-bandwidth product is $\sim 0.46$ .

High-power ultralong-wavelength Tm-doped silica fiber laser cladding-pumped with a random distributed feedback fiber laser.

We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900–2000 nm.

400 mW narrow-linewidth Tm-doped silica fiber laser output near 1750 nm with volume Bragg grating.

A type of Tm-doped silica fiber laser with narrow-linewidth and output wavelength near 1750 nm was firstly presented, by using a 1550 nm Er-doped fiber laser pump source and a volume Bragg grating (VBG). By means of a 15 cm Tm-doped fiber, a 400 mW continuous wave (cw) at ~1750 nm with FWHW of ~54 pm was generated, corresponding to an average slope efficiency up to 23.5% with respect to absorbed pump power. The influence of gain fiber length on the spectrum wavelength has been investigated in detail. All experimental results demonstrate that this fiber laser will be an effective and promising pump source for mid-IR laser output.

A Versatile Model for Temperature-Dependent Effects in Tm-Doped Silica Fiber Lasers

We have derived a model to provide a unique insight into the temperature-dependent effects in Tm-doped silica fiber lasers with consideration of important energy transfer processes and full spectra of laser transition. By fitting experimental measurements, the dependence of emission and absorption cross sections on temperature was characterized. With careful thermal management to control the influence of thermomechanical and thermooptical effects, a good agreement was achieved between simulations and experiments, even in the kilowatt power domain. On the basis of the model, the investigation shows that the thermal distribution of ions over the Stark sublevels contributes a higher threshold and a lower laser power as the temperature increase. Fortunately, this degradation of laser performance can be largely weakened when higher pump intensity is employed. The simulations also show that lower output coupling and longer operational wavelength can mitigate the output power variation arising from the temperature. The model was further used to analyze the dependence of laser spectrum on the fiber length and pump power when temperature changes. In addition, the laser output power and temperature distribution in kW-level are also studied.

Rapid, electronically controllable transverse mode selection in a multimode fiber laser

A novel technique for the electronically-controllable generation and switching of transverse modes within a multi-mode fiber laser oscillator is presented. Preliminary results demonstrate individual transverse mode lasing and fast switching between modes with watt-level output powers. When applied to a core-pumped Tm-doped silica fiber laser with a multimode core the fundamental mode (LP₀₁), the next higher order mode (LP₁₁), or a donut-shaped LP₁₁ superposition were selectively excited with power levels in excess of 5 W. Fast switching between LP₀₁ and LP₁₁ modes at up to 20 kHz was also realized.

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

In-band pumped Ho^3+:KY_3F_10 2 μm laser

We report the first observation to our knowledge of room-temperature continuous-wave laser operation on the (5)I(7)→(5)I(8) transition of Ho(3+) ions in a KY(3)F(10) single crystal. Using a Tm-doped silica fiber laser operating at 1938 nm as a pump source, a maximum laser power of 1.8 W was obtained at a wavelength of ~2040 nm for 27 W of absorbed pump power with a slope efficiency of 19.1% with respect to absorbed power. At low cavity output coupling, the lasing wavelength shifted to 2060.5 nm. The beam propagation factor (M(2)) was measured to be <1.06 at the maximum output power, confirming fundamental transverse-mode (TEM(00)) operation. Performing a Caird analysis, we determined resonator round-trip losses and intrinsic slope efficiency of 30% and 43.8%, respectively.

Wavelength control of a Tm-doped fiber laser using nonidentical mechanical long-period fiber gratings

We present wavelength tuning operation of a Tm-doped silica fiber laser pumped by a laser diode emitting at 1.63 μm. Wavelength tuning is achieved by two nonidentical mechanical long-period fiber gratings (LPFGs) induced in a single-mode fiber using coil springs. The inter-resonance-mode passband, which is formed between the rejection bands due to the core-to-cladding mode coupling, dominates the gain peak in the fiber laser resonator. The oscillation wavelength is controlled between 1865 and 1972 nm by tuning the grating periods of the two LPFGs.

An all-fiber, resonantly pumped, gain-switched, 2 μm Tm-doped silica fiber laser

An all-fiber, gain-switched, single-mode, thulium-doped silica fiber laser operating at a wavelength of 1994.6 nm was developed. The laser was pumped by a 1.55 μm master oscillator power amplifier (MOPA) system and operated at a repetition rate ranging from 50 to 300 kHz. Different configurations of the laser cavity were tested. When operating at a 100 kHz repetition rate the laser delivered a maximum average power as high as 1.08 W with a slope efficiency of 49%. For a repetition rate of 50 kHz, stable 23 ns pulses with an energy of 15.3 μJ, corresponding to a peak power of 623 W, were achieved. We also report, to the best of our knowledge, the first demonstration of 2 μm gain-switched, mode-locked pulses with 100% modulation depth obtained in a Tm-doped fiber laser.

Stable passively Q-switched operation of Tm3+ doped silica fiber laser by anti-resonant Fabry-Perot saturable absorber

We demonstrate a diode-pumped passively Q-switched Tm-doped double-cladding silica fiber laser operating at wavelength of 1960 nm using an anti-resonant Fabry-Perot saturable absorber as passive modulation element. To determine a relatively preferable fiber length for stable cw Q-switched operation, three active fiber simples with the length of 1.1, 5.3, and 7.0 m were employed respectively in our experiments. With 1.1 m gain fiber, we generated Q-switched pulses with a pulse width of 245 ns and an average power of up to 2.2 W at a repetition rate of 620 kHz. For the longer two fiber samples, Q-switched operation with longer pulse duration, Q-switched mode-locking and cw mode-locking were observed, respectively.

Tunable Tm-doped fiber ring laser operating at 19 μm band using force-induced fiber grating as wavelength tuner

We report wavelength-tunable operation of a Tm-doped silica fiber laser by using a force-induced long-period fiber grating (LPFG) formed in a fiber ring resonator. The laser output wavelength is tuned by moving the transmission passband that is generated between adjacent resonance wavelengths due to the force-induced LPFG. By changing the grating period around 900 μm, we control the laser output wavelength between 1845 and 1930 nm.

Efficient in-band pumped Ho:LuLiF_4 2 μm laser

An efficient Ho:LuLiF(4) laser in-band pumped by a cladding-pumped Tm-doped silica fiber laser operating at 1937 nm is reported. At low-cavity output coupling, the Ho:LuLiF(4) laser yielded 5.1 W of output at a wavelength of 2066 nm for 8.0 W of absorbed pump power with a slope efficiency of 70%. At high-cavity output coupling, the lasing wavelength shifted to 2053 nm and the laser produced an output power of 5.4 W with a slope efficiency of 76%. The beam propagation factor (M(2)) was measured to be approximately 1.1 at the maximum output power confirming fundamental transverse mode (TEM(oo)) operation. The influence of resonator design on laser performance is discussed, along with prospects for further power scaling and improvement of the laser efficiency.

Multi-peak output Tm-doped silica fiber laser based on femtosecond-written multi-mode fiber Bragg grating

The all-fiber Tm-doped double-clad laser was reported, incorporating a phase mask scanning technology writing FBG directly into the Tm-doped multi-mode fiber core as cavity mirror, using 800 nm femtosecond laser sources. A fiber grating of 12 mm length was realized with a period of 1.35 μm. Pumped by the 793 nm pigtail fiber output LD, the continuous wave (CW) power could scale to 25.4 W at 1.96 μm with the slope efficiency of 38% respected to the LD output power. The output laser spectrum exhibited multi-peak, due to the multi-mode FBG reflective characteristic.

Gain-switched Tm3+-doped double-clad silica fiber laser

A gain-switched Tm-doped double-clad silica fiber laser operating at a wavelength of approximately 2microm with moderate output energy of 14.7mJ per pulse and a slope efficiency of 39.5% (with respect to launched pump energy) is realized pumped at 1.064microm from a Nd:YAG laser. The gain-switched fiber laser pulses are built up by a series of relaxation spikes, and every spike pulse duration is nearly 1micros. The output wavelength becomes longer, and the slope efficiency increases with the increase in fiber length.

Efficient single-axial-mode operation of a Ho:YAG ring laser pumped by a Tm-doped silica fiber laser

Efficient single-frequency operation of a Ho:YAG ring laser at room temperature with a traveling-wave TeO2 acousto-optic modulator to enforce unidirectional operation is reported. By use of a 2-at. % Ho3+-doped 10-mm-long Ho:YAG rod, end pumped by a cladding-pumped tunable Tm-doped silica fiber operating at 1.9 microm, the Ho:YAG ring laser yielded 3.7 W of single-frequency output at 2.1 microm in a diffraction-limited TEM00 beam with M2 < 1.1 for an incident pump power of 8.8 W. The rf power required for unidirectional operation was 0.3 W and corresponded to an increase in cavity loss for the lasing direction (due to diffraction) of only 0.5%. The prospects for further improvement in efficiency are discussed.

Efficient Ho?:?YAG laser pumped by a cladding-pumped tunable Tm?:?silica-fibre laser

Highly efficient room-temperature operation of a Ho:YAG laser end pumped by a cladding-pumped tunable Tm-doped silica-fibre laser operating at 1905 nm is reported. Using a simple two-mirror resonator configuration, we obtained 6.4 W of unpolarized output at 2097 nm in a diffraction-limited TEM00 beam (with M2≈1.1) for 9.6 W of incident pump power, corresponding to a slope efficiency with respect to incident pump power of 80% and an optical-to-optical efficiency of 67%. Using a folded-resonator configuration incorporating a Brewster-angled glass plate, we obtained 5.8 W of linearly polarized TEM00 output, corresponding to an optical-to-optical efficiency of ∼60%. Due to low quantum defect heating, the depolarization loss due to thermally induced birefringence in the Ho : YAG crystal was <0.14% at the maximum available pump power, indicating that there is scope for further power scaling.

High-power wavelength-tunable cladding-pumped rare-earth-doped silica fiber lasers

We describe the design and performance of cladding-pumped silica fiber lasers with high continuous-wave output powers and broad wavelength tunability in the 1, 1.5, and 2 μm spectral ranges. An ytterbium-doped fiber laser was tuned via wavelength dependent feedback provided by an external cavity containing a diffraction grating from 1027 to 1105 nm at multi-watt power levels. Similarly, high output power and wide wavelength tunability from 1540 to 1600 nm and from 1860 to 2090 nm at multi-watt output power levels has been achieved in Er-Yb co-doped and Tm-doped silica fiber lasers, respectively. A neodymium doped fiber laser was tuned from 1057 to 1118 nm at a lower power level. Limiting factors and the prospects for further improvements in performance are considered.

High-power cladding-pumped Tm-doped silica fiber laser with wavelength tuning from 1860 to 2090 nm

A high-power double-clad Tm-doped silica fiber laser, pumped by two beam-shaped and polarization-coupled diode bars at 787 nm, was wavelength tuned by use of an external cavity containing a diffraction grating. The Tm fiber laser produced a maximum output power of 7 W at 1940 nm for 40 W of incident diode power and was tuned over a wavelength range of 230 nm from 1860 to 2090 nm, with >5-W output power over the range 1870-2040 nm. The prospects for further improvement in performance and extension of the tuning range are discussed.

10 mJ total output from a gain-switched Tm-doped fibre laser

A gain-switched cladding-pumped Tm-doped silica fibre laser operating at a wavelength of approximately 2-μm with moderate output energy is reported. When pumped with the output from a gain-switched Ti:sapphire laser, a maximum total output energy of 10.1 mJ per pump pulse is produced at a slope efficiency of 30% (with respect to launched pump energy) and, at an overall optical-to-optical efficiency of 17%. For relatively short fibre lengths, saturation of the output energy is observed with an increase in launched pump energy because of pump-induced bleaching of the pump transition. The laser has been continuously tuned using an intracavity prism over a range of 109 nm, from 1909 nm to 2018 nm.