Maximum Laser Output Power Research Articles

Fully planar solar-pumped fiber laser with 0.1% slope efficiency.

A slope efficiency of 0.1% has been achieved for a fully planar solar-pumped fiber laser (SPFL) with a diameter of 30 cm and an output power of 34 mW. The fiber length is constrained to 400 m, but numerical simulations indicate that the maximum laser output power can be elevated to 113 mW by simply extending the length of the fiber and housing it in the same body. The tolerance to the solar tracking error was quantified, and the results demonstrated that more than 80% of the maximum output power can be sustained up to a ±23° tracking error. This study demonstrates the capability of the fully planar SPFL to operate without solar tracking.

Self Q-switched single-frequency all-fiber laser

Here, we propose a self Q-switched single-frequency (SF) all-fiber laser. The intra-cavity Er:Yb co-doped fiber serves not only as an active fiber for lasing but also as a fiber-type saturable absorber (SA). The self-Q-switching behavior is induced by the ground-state reabsorption of the unpumped portion of the active fiber. To achieve SF operation, double fiber loops constructed by two 3 dB optical couplers (OCs) form a cascade sub-cavity, which serves as a mode selector with a narrow bandwidth. Taking the advantage of a high damage threshold of the fiber-type SA, microjoule-level self-Q-switched SF pulses are obtained with a narrow linewidth of ∼252kHz. Combed with the measured pulse width of ∼1.766µs, the corresponding time-bandwidth product is ∼0.445, which is very close to the Gaussian transform limit. The maximum output power of the pulsed SF laser can reach ∼100mW. By stretching the fiber Bragg grating (FBG), the wavelength of the pulsed SF laser can be tuned.

Widely and fast tunable external cavity laser on the thin film lithium niobate platform

We develop an integrated external cavity laser with a broad wavelength tuning range and a fast switching speed on thin film lithium niobate (TFLN) platform. By butt coupling an InP-based optical gain chip with a TFLN external cavity chip, a hybrid lithium niobate/III-V tunable laser with a wavelength switching speed of 18 ns is achieved. Furthermore, using a cascaded external cavity filter composed of three micro-ring resonators (MRRs), the laser features an ultra-wide wavelength tuning range of 96 nm across the C + L + U bands, which is the greatest value known for tunable lasers integrated on TFLN. The maximum laser output power is 0.98 mW, with a measured side mode suppression ratio (SMSR) of better than 52 dB. The laser we developed is critical in applications such as optical sensors and wavelength routed optical switch.© 2023 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.

509 nm high power wide-tuned external cavity surface emitting laser

High power widely tunable green lasers have potential applications in many fields such as biomedicine, lidar, laser spectroscopy, laser display, underwater wireless optical communication, and fine processing of nonferrous metals. Vertical-external-cavity surface-emitting lasers, also known as semiconductor disk lasers, have the advantages of high power, good beam quality, and wide bandwidth of gain medium. In this work, a gain chip with a reverse-growth epitaxy structure and an emitting wavelength of 1018 nm is designed. In the DBR reflection spectrum, a bandwidth of 74 nm is achieved above a reflectivity of greater than 99.1%, laying a solid foundation for achieving high-power widely tunable output. The laser cavity combines a 1018 nm semiconductor gain chip, a folded mirror, and a plane mirror to construct a compact V-type resonant cavity. A class-I phase-matched LBO nonlinear crystal with a length of 10 mm is placed at the beam waist of the cavity to realize an efficient frequency doubling process to produce a 509 nm green laser. To meet the requirement for the polarization during frequency conversion and to tune the oscillating wavelength of the laser, a birefringent filter (BRF) is employed in the laser resonant cavity. When the thickness of the used BRF is 1 mm, the obtained wavelength tuning range of the fundamental laser and the frequency doubled green laser are 47.1 nm and 20.1 nm, respectively, showing a good tuning capability of the laser. The laser’s performance varies with the thickness of the BRF. When using a 2 mm BRF, a maximum power output of the frequency-doubled green laser reaches 8.23 W during continuous tuning, indicating an ideal compatibility of wide tuning characteristics with a high power output. Meanwhile, its beam quality <i>M</i> <sup>2</sup> factors are 1.00 and 1.03 in the <i>x</i>- and <i>y</i>-direction, respectively, demonstrating a near diffraction-limited excellent beam quality. This green laser also possesses a frequency doubling conversion efficiency of up to 68.2%, which can efficiently converse the fundamental laser into the frequency doubled green laser. The optical-to-optical conversion efficiency from the absorbed pump light to the frequency-doubled green light also reaches 16.6%. Meanwhile, from the spectral linewidths of the green lasers under different thickness values of BRFs it is found that the thicker the BRF, the narrower the laser line width is, which is consistent with the theoretical result.

1.2 W single-frequency Tm3+/Ho3+ co-doped fiber oscillator at 2050 nm.

In this Letter, a watt-level single-frequency fiber oscillator at 2050 nm was demonstrated for the first time, to the best of our knowlegde, in a linear laser cavity with a piece of an un-pumped Tm3+/Ho3+ co-doped fiber serving as a saturable absorber. With delicate optimization of mode filtering effect of the dynamic gratings formed in the saturable absorber, a maximum single-frequency laser output power of 1.2 W was achieved under a total bidirectional pump power of 5.8 W at 1570 nm, and the corresponding optical efficiency is 20.7%. This is, to the best of our knowledge, the highest power of a single-frequency fiber oscillator at the wavelength above 2 µm.

10 Hz Stable Mode-locked Er-Fiber Laser

Abstract: In this paper, a stable output at the reduction repetition rate from 80 MHz mode-locked Er-doped fiber laser (EDFL) was demonstrated by adjusting the operating point for external LiNbO3 Mach-Zehnder‎ electro-optic intensity modulator to suppress harmonic mode-locked pulses. More than 70% of the laser beam was launched into the external pigtail Mach-Zehnder intensity modulator using single mode fiber with collimating lens and fiber (ferrule connector) FC adapter. The optimum values of Mach-Zehnder modulator bias voltages V0 and Vπ (half wave voltage) which resulted in maximum and minimum laser output power to leave the modulator were found at 6.5 and 0.29 V, respectively. The best modulation was achieved for the RF modulating signal with an opening time of about 8 ns. For driving voltage equal to Vπ, a clean mode-locked pulse train was generated with a pulse shape and energy similar to the input pulse, albeit with a low repetition rate. The minimum repetition rate reached as low as 10 Hz, resulting in pulse energy and peak power of 0.32 nJ and 1.5 kW, respectively. Second-harmonic generation of the low repetition rate pulse train was also produced by using a PPLN crystal. This opens up the potential for using this laser in single photon detection experiments and as a seed laser for many applications. Keywords: Er-fiber laser, Passively mode-locked fiber laser, Nonlinear polarization rotation, Mach-Zehnder modulator, Fast electro-optic modulator. PACS: Fiber lasers, 42.55.Wd, Mode locking, 42.60.Fc.

Laser operation at 1.2 µm in Ho3+-doped ZBYA glass fibers.

Powerful 1.2-µm laser operation was produced in Ho3+-doped single-cladding, in-house fabricated ZrF4-BaF2-YF3-AlF3 (ZBYA) glass fibers. The fibers were fabricated based on ZBYA glass with a composition of ZrF4-BaF2-YF3-AlF3. Pumped by an 1150-nm Raman fiber laser, the maximum combined laser output power emitted from both sides of a 0.5-mol% Ho3+-doped ZBYA fiber was 6.7 W, with a slope efficiency of 40.5%. We also observed lasing at 2.9 µm with an output power of 350 mW, which was ascribed to the transition of Ho3+:5I6 → 5I7. The effect of rare earth (RE) doping concentration and the length of the gain fiber were also investigated to determine their effect on laser performance at 1.2 µm and 2.9 µm.

Development of a Mode-Locked Fiber Laser Utilizing a Niobium Diselenide Saturable Absorber

The saturable absorber of niobium diselenide (NbSe2), with a wide working bandwidth and excellent nonlinear optical response, was prepared using liquid-phase exfoliation. Its saturation intensity and modulation depth were 5.35 MW/cm2 and 6.3%, respectively. Stable mode-locking with a center wavelength of 1558.7 nm of an erbium-doped fiber laser based on a NbSe2 saturable absorber was successfully achieved. The maximum average output power of the mode-locked laser was 6.93 mW, with a pulse width of 1.3 ps and a repetition rate of 25.31 MHz at a pump power of 550 mW. The results show that NbSe2 is a promising photoelectric modulation material owing to its excellent nonlinear optical properties.

Kerr-lens mode-locking of an Yb:CLNGG laser.

We report on a Kerr-lens mode-locked laser based on an Yb3+-doped disordered calcium lithium niobium gallium garnet (Yb:CLNGG) crystal. Pumping by a spatially single-mode Yb fiber laser at 976 nm, the Yb:CLNGG laser delivers soliton pulses as short as 31 fs at 1056.8 nm with an average output power of 66 mW and a pulse repetition rate of ∼77.6 MHz via soft-aperture Kerr-lens mode-locking. The maximum output power of the Kerr-lens mode-locked laser amounted to 203 mW for slightly longer pulses of 37 fs at an absorbed pump power of 0.74 W, which corresponds to a peak power of 62.2 kW and an optical efficiency of 20.3%.

Wireless optical power transmission based on the off-axis VECSEL of long resonator

We present laser generation in a several-meters-long air cavity using an optically pumped semiconductor gain chip for wireless optical power transmission applications. Theoretical calculations showed that stable laser oscillation can be realized in long laser oscillation cavities of more than 500 cm. Moreover, the laser oscillation can be maintained even when the output mirror of the laser is off-axis, which is useful in the alignment of energy charging terminals. A lens was inserted into the cavity to adjust the intra-cavity beam, and the beam radius on the gain chip surface sufficiently increased to match a large pump spot and achieve high output power. Laser generation in an external air cavity of 200 cm was realized, and the maximum output laser power of more than 705.4 mW was achieved. The off-axis range of the output mirror surpassed 19 mm. Moreover, the output laser power decreased by 5.5 % (from 586.4 to 554.2 mW) when the length of the external air cavity was increased from 100 to 200 cm. However, the off-axis range increased by 40.7 % (13.5 to 19 mm). Thus, the longer external cavity laser made it easier to align the laser beam and charging terminal.

High-power and efficient orthogonally-polarized dual-wavelength Nd:YLF laser

We demonstrate an actively Q-switched orthogonally-polarized dual-wavelength laser at 1047.4 nm and 1053.4 nm with high average power and high efficiency. The gain competition between dual-wavelength lasers is effectively suppressed by using two Nd:YLF crystals as laser gain medium. Investigations concerning different resonator structures and pulse repetition frequency were conducted to achieve the best performance of this laser. Under the total incident pump power of 32.7 W, a maximum dual-wavelength laser output power of 13.4 W is obtained at the pulse repetition rate of 30 kHz, corresponding to an optical conversion efficiency of 41%. For 1047.4 nm and 1053.4 nm lasers, the maximum average output powers are as high as 7.6 W and 5.8 W, respectively, and they also demonstrate good output power stability and beam quality. This orthogonally-polarized dual-wavelength laser has significant practical applications in various fields, such as terahertz radiation generation, precision metrology, laser radar, and spectral analysis.

Folded-resonator LD side-pumped acousto-optically Q-switched Nd:YAG/SrWO4 solid-state Raman laser

A folded cavity of LD side-pumped acousto-optically Q-switched Nd:YAG/SrWO4 solid-state Raman laser is designed. The effects of the thermal focal length and resonator length on the resonator modes are analyzed. The appropriate mode sizes at laser crystal and Raman crystal are designated to realize low SRS threshold, high conversion efficiency and high beam quality. The folded-resonator LD side-pumped acousto-optically Q-switched Nd:YAG/SrWO4 solid-state Raman laser is realized, and the 1st Stokes laser at 1180 nm with high output power, high single pulse energy and high beam quality is obtained. The maximum output power of the 1st Stokes laser at 1180 nm is 2.89 W, optical–optical efficiency is 4 %, the single pulse energy is 0.96 mJ, and the shortest pulse is 35.5 ns. By analyzing the output spectrum and beam quality, it is shown that the beam spatial profile mode is well distributed, and the experimental results verify the rationality of the cavity mode design.

3.96 kW All-Fiberized Linearly Polarized and Narrow Linewidth Fiber Laser with Near-Diffraction-Limited Beam Quality.

In this paper, we realize a 3.96 kW all-fiberized and polarization-maintained (PM) amplifier with narrow linewidth and near-diffraction-limited beam quality. Based on a master oscillator power amplifier (MOPA) configuration seeded with phase-modulated single-frequency laser, a 3.96 kW signal laser is achieved with a 3 dB linewidth of 0.62 nm at the pump power of 5.02 kW. At the maximum output power, the polarization extinction ratio (PER) is ~13.9 dB, and the beam quality (M2 factor) is M2x = 1.31, M2y = 1.41. As far as we know, this is the maximum output power of PM narrow linewidth fiber laser with near-diffraction-limited beam quality and all-fiber format.

Fabrication and characterizations of Tm:Lu2O3 transparent ceramics for 2 μm laser applications

2 at.% Tm:Lu2O3 ceramics were fabricated by vacuum sintering plus hot isostatic pressing (HIP) from nano-powders without sintering aids. The resultant powders consist of spherical particles with the diameter of about 100 nm. The HIP post-treated ceramic sample has fine grains and clean grain boundaries, whose in-line transmittance reaches 82.1% at 2000 nm (1.3 mm thickness). The mechanical, thermal, and spectral properties were also investigated systematically. The thermal conductivity of the Tm:Lu2O3 transparent ceramics is 10.2 W·m−1·K−1 at room temperature. The absorption and emission cross-sections are 0.35 × 10−20 cm2 at 796 nm and 1.13 × 10−20 cm2 at 1943 nm, respectively. The laser performance was tested in quasi-continuous wave (QCW) conditions. A maximum laser output power of 0.45 W was obtained with a slope efficiency of 16.0%. Results indicate that Tm:Lu2O3 transparent ceramics is a promising gain medium for 2 μm laser applications.

2m-distance external cavity VECSEL for wireless charging applications.

We characterize laser generation in an ultralong air cavity (several meters in length) using an optical-pumped semiconductor gain chip for laser wireless charging applications. The study realizes laser generation in an external air cavity with a length of 200 cm, for the first time, and achieves a maximum output laser power of more than 86.3 mW. Furthermore, the laser oscillation can be maintained even when the output mirror of laser is off-axis within 1.6 cm. Thus, a long external cavity laser would ease the alignment between the laser beam and charging terminal, making it suitable for laser wireless charging applications.

Self-Q-switched Tm:YAP vortex laser by thermal-lensing effect

We demonstrated a self-Q-switched Gaussian laser mode and a Laguerre-Gaussian (LG0,1) laser mode at 1937.9 nm, which was directly generated by thermal lensing effect in a Tm:YAP laser. By building a Mach-Zehnder interferometer, the helical nature of the wavefront is checked. The experimental maximum output power of LG01 pulsed vortex laser was 83 mW with the repetition rate of 75.46 kHz and pulse width of 1.711 μs, corresponding to the peak power of 0.64 W and single pulse energy of 1.10 μJ. The self-Q-switched Tm:YAP vortex laser is compact and provides a convenient way to construct 2 μm pulsed vortex laser source.

Nonlinear photoresponse of high damage threshold titanium disulfide nanocrystals for Q-switched pulse generation

A passively Q-switched Er-doped fiber laser with two wavelength at 1530 nm and 1556 nm wavelength was designed based on the titanium disulfide (TiS2) saturable absorber, the ultra-fast modulator was fabricated with TiS2 by the liquid-phase exfoliation and spin-coating methods and transferred onto a fiber ferrule. In the experiment, two single-mode 980 nm pump sources were applied in order to detect the high damage threshold of TiS2. The shortest pulse duration and maximum output power of the stable self-starting Q-switched fiber laser are 1.45 µs and 3.93 mW, respectively. The adjustable range of the repetition rate is from 25.8 kHz to 126.8 kHz with about 100 kHz tuning range, and the pulse with energy up to 39.3 nJ. Our experimental results conclusively suggest that TiS2 nanocrystals were advanced nanomaterial with high damage threshold would have extensive application prospects in the field of pulse fiber lasers.

Graphene-based passive Q-switching of a Dy3+,Tb3+:LuLiF4 yellow laser

We report solid-state continuous-wave (cw) and Q-switched lasers directly emitting in the yellow spectral region, which include a Dy3+,Tb3+:LuLiF4 crystal as the laser material and a single-emitter blue laser diode (LD) as the pump source. Without resorting to any nonlinear conversion process, a maximum output power of 351 mW is obtained for the cw yellow laser with a slope efficiency of 15% at the wavelength of 573.9 nm. For generating the Q-switched yellow laser, a monolayer graphene is used as the saturable absorber. The maximum average output power of the Q-switched yellow laser is determined to be 85 mW. The shortest pulse width is obtained as approximately 596 ns, which corresponds to a repetition rate of 78 kHz. The calculated pulse energy and peak power are nearly 1.1 μJ and 1.8 W, respectively. Overall, the proposed approach exhibits immense potential for fabricating compact and economical solid-state cw and Q-switched yellow lasers.

Fabrication of Fiber Bragg Gratings by Visible Femtosecond Laser for Multi-kW Fiber Oscillator

In this paper, we fabricate a pair of fiber Bragg gratings (FBGs) in large mode area double cladding fiber (LMA-DCF, core/inner cladding diameter: 20/400 μm) by visible (515 nm) femtosecond laser and phase mask for the first time to the best of our knowledge. Then this pair of FBGs are utilized to construct a high power fiber oscillator operated near 1080 nm. The maximum output laser power is more than 3.2 kW with a slope efficiency of ∼77.9%, and the beam quality factor M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is about 1.28. The FBGs are simply fixed on water-cooling plate without any special package, and the temperature of the FBGs is about 40 °C at the maximum output power. Our research work confirms the reliability of visible femtosecond laser in fabrication of FBGs intended to be applied in high power fiber oscillators.

Compact, Hybrid III-V/Silicon Vernier Laser Diode Operating From 1955–1992 nm

The 2 µm waveband is capable of enabling pervasive applications. The demonstration of the hollow-core photonic bandgap fiber and the thulium-doped fiber amplifier has highlighted the fiber propagation and amplification aspects of fiber communications, indicating its potential as an adjunct to present communication infrastructure at the O/C bands. The above is especially imperative given the current concerns with regards to the upper bandwidth limit of the single-mode fiber. Furthermore, the waveband could facilitate many more applications such as LIDAR and free-space communication. However, water absorption (OH-) is high at most of the 2 μm waveband and this will impact the optical insertion loss of applications implemented in the wavelength region. The relative low water absorption region of the waveband falls within 1950 – 2000 nm. As such, the development of a hybrid/heterogeneous III-V/silicon laser source that operates within the region is important for 2 µm silicon photonics. In this work, we demonstrate a III-V/Si hybrid tunable laser operating from 1955 - 1992 nm for the first time. Room temperature continuous wave operation is achieved with a maximum laser output power of 8.1 mW. This wavelength-tunable laser operates specifically within the low water absorption window, indicating good wavelength suitability for applications at the 2 μm waveband.