Dual-wavelength Pumping Scheme Research Articles

High-efficiency 2.3 μm Tm:YLF laser based on 0.79 μm and 1.05 μm dual-wavelength pumping scheme

High-efficiency 2.3 μm Tm:YLF laser based on 0.79 μm and 1.05 μm dual-wavelength pumping scheme

Dual-wavelength mid-infrared laser operation at 2.8 μm and 3.6 μm in Er3+ doped fluoride fiber

This study presents a pioneering experimental demonstration of dual-wavelength laser operation at 2.8 μm and 3.6 μm in an Er3+-doped ZrF4-BaF2-YF3-AlF3 double-cladding fluoride glass fiber, fabricated in-house. The achievement is realized through the implementation of a novel dual-wavelength pumping scheme utilizing 980 nm and 1150 nm lasers. This innovative scheme enables the excitation of the lower energy level of the 2.8 μm laser transition (4I11/2) to the upper energy level of the 3.6 μm transition (4F9/2) via an excited state absorption process, resulting in simultaneous emission at 2.8 μm and 3.6 μm. The maximum laser output powers at 2.8 μm and 3.6 μm are measured at 0.96 W and 0.32 W, respectively. This groundbreaking work marks the first experimental realization of dual-wavelength laser operation at 2.8 + 3.6 μm in Er3+-doped fluoride fiber, contributing significantly to the advancement of laser technology in this spectral range.

Numerical design of an efficient Ho3+-doped InF3 fiber laser at ∼3.2 ​μm

In this work, we theoretically unlock the potential of Ho3+-doped InF3 fiber for efficient ∼3.2 ​μm laser generation (from the 5F4,5S2→5F5 transition), by employing a novel dual-wavelength pumping scheme at 1150 ​nm and 980 ​nm, for the first time. Under clad-coupled 1150 ​nm pumping of 5 ​W, ∼3.2 ​μm power of 3.6 ​W has been predicted with the optical-to-optical efficiency of 14.4%. Further efficient power scaling, however, is blocked by the output saturation with 980 ​nm pumping. To alleviate this behavior, the cascaded 5I5→5I6 transition, targeting ∼3.9 ​μm, has been activated simultaneously, therefore accelerating the population circulation between the laser upper level 5F4,5S2 and long-lived 5I6 level under 980 ​nm pumping. As a result, enhanced ∼3.2 ​μm power of 4.68 ​W has been obtained with optical-to-optical efficiency of 15.6%. Meanwhile the ∼3.9 ​μm laser, yielding power of 2.76 ​W with optical-to-optical efficiency of 9.2%, is theoretically achievable as well with a moderate heat load, of which the performance is even better than the prior experimentally and theoretically reported Ho3+-doped InF3 fiber lasers emitting at ∼3.9 ​μm alone. This work demonstrates a versatile platform for laser generation at ∼3.2 ​μm and ∼3.9 ​μm, thus providing the new opportunities for many potential applications, e.g., polymer processing, infrared countermeasures, and free-space communications.

Flat supercontinuum spanning 738-2200 nm generation in standard telecom fibers based on dual-wavelength pumping scheme

Flat supercontinuum spanning 738-2200 nm generation in standard telecom fibers based on dual-wavelength pumping scheme

Dual Wavelength Pumping Scheme for Directly Diode-Pumped 75X-nm Fiber Lasers

Dual Wavelength Pumping Scheme for Directly Diode-Pumped 75X-nm Fiber Lasers

976 nm and 808 nm dual-GSA-wavelength pumped 3 µm erbium-doped solid-state laser.

A dual-wavelength pumping scheme at 976 nm and 808 nm is proposed to improve the performance of 3 µm Er:YAP laser. 976 nm and 808 nm correspond to the ground state absorption processes of 4I15/2→I11/2 and 4I15/2→I9/2, respectively. The experimental results indicate that the introduction of 808 nm pumping not only increases the total inversion population, but also can adjust the population distribution among the sublevels in the upper and lower manifold, thus supporting higher output power and multiple wavelengths emissions. Under the single-wavelength pumping, the maximum output powers of 1.192 W and 0.223 W are obtained for 976 nm and 808 nm pumping, respectively. With regard to the 976/808 nm dual-wavelength pumping, the achievable maximum output power is 1.398 W, increased by 17.3% compared to the case of single-wavelength pumping at 976 nm. The dual-wavelength pumped Er:YAP laser can also operate in a state of multi-wavelength emissions at 2.79 µm, 2.82 µm and 2.92 µm with different dual-wavelength pump power combinations. Considering the broadband absorption characteristics of ground state absorption and the convenience of obtaining near-infrared laser diodes pumping sources, the proposed dual-wavelength pump scheme shows great potential to realize high-power, high-efficiency 3 µm erbium-doped solid-state lasers with better cost-effectiveness and more compact structure.

Mode-locked fiber laser of 3.5 µm using a single-walled carbon nanotube saturable absorber mirror

We report on a mid-infrared fiber laser that uses a single-walled carbon nanotube saturable absorber mirror to realize the mode-locking operation. The laser generates 3.5 µm ultra-short pulses from an erbium-doped fluoride fiber by utilizing a dual-wavelength pumping scheme. Stable mode-locking is achieved at the 3.5 µm band with a repetition rate of 25.2 MHz. The maximum average power acquired from the laser in the mode-locking regime is 25 mW. The experimental results indicate that the carbon nanotube is an effective saturable absorber for mode-locking in the mid-infrared spectral region.

Intense emission at ∼3.3 µm from Er3+-doped fluoroindate glass fiber.

Fluoroindate glass fibers with an Er3+ doping concentration of ∼0.5mol% were fabricated by using a rod-in-tube method. Pumped by a 976 nm laser diode, intense emission at ∼3.3µm was obtained from a 40 cm long Er3+-doped fiber, which could be attributed to the transition 4S3/2→4F9/2 of Er3+ ions. The calculated emission cross section at ∼3.3µm was ∼3×10-26m2, which was ∼1.5 times larger than that of transitions Er3+:4F9/2→4I9/2 and Dy3+:6H13/2→6H15/2. In addition, broad emissions ranging from 3.1 µm to 3.85 µm were obtained in the Er3+-doped fiber under a 976 nm/1973 nm dual-wavelength pumping scheme. Our results indicated that Er3+-doped fluoroindate glass fibers had the potential for constructing efficient ∼3.3µm fiber lasers.

Widely Tunable Gain-Switched Er³⁺-Doped ZrF₄ Fiber Laser From 3.4 to 3.7 μm

We present wide wavelength tuning of a gainswitched Er 3+ -doped ZrF 4 fiber laser in the 3.5 μm band for the first time to our knowledge. In this case, a dual-wavelength pumping (DWP) scheme is used including a continuous wave (CW) LD at 976 nm and two home-made Tm 3+ -doped fiber lasers (TDFLs) at 1981 nm operating in Q-switched and CW regimes, respectively. At the pump repetition rate of 50 kHz, stable gain-switched pulses can always be obtained within the whole tuning range of 3397.1~3690.2 nm (~293 nm) realized with a plane ruled grating. At a wavelength of 3450.5 nm, a maximum average power of 264.5 mW with a corresponding pulse energy of 5.29 μJ and width of 1.02 μs are achieved. The effects of pump power and laser wavelength on the output characteristics have also been investigated. The results indicate that such a gain-switched laser can be a versatile pulsed source for many applications.

Enhancement of 1.8 μm emission in Er3+/Tm3+ co-doped tellurite glasses: Role of energy transfer and dual wavelength pumping schemes

Thulium (Tm3+) and erbium (Er3+)-doped tellurite glasses were synthesized and explored their spectroscopic properties for optical amplification and medical appliances. The emission at 1.8 μm of Tm3+ ions has been enhanced significantly in Er3+/Tm3+ co-doped tellurite glasses under dual pumping lasers at 808 and 980 nm. Emission cross-section of the Tm3+ ions is found to be 3.46 × 10−20 cm2 which was evaluated by utilizing the Mc-Cumber theory. The possible energy transfer mechanisms between Er3+ and Tm3+ ions under 808 and 980 nm excitations were investigated by utilizing the excitation, emission and decay curve analyses. Effect of dual wavelength pumping on the 1.5 and 1.8 μm spectral profiles is also enlightened. Decay curves of Tm3+:3H4 → 3F4 (1440 nm) transition and Er3+: 4I13/2 → 4I15/2 (1531 nm) transition in the Tm3+ singly and Er3+/Tm3+ co-doped tellurite glasses have been analyzed under 808 nm laser excitation. Energy transfer efficiency is evaluated between Er3+: 4I13/2 and Tm3+:3F4 states from the decay curves and it is found to be 83%. The results are significant and indicating that the Er3+/Tm3+ co-doped tellurite glasses could be a potential candidate for optical fiber amplification at around 1.8 μm region under dual wavelength pumping scheme.

Mode-locked and tunable fiber laser at the 3.5 µm band using frequency-shifted feedback

We report on a mid-infrared mode-locked fiber laser that uses an acousto-optic tunable filter to achieve frequency-shifted feedback pulse generation with frequency tuning over a 215 nm range. The laser operates on the 3.5 µm transition in erbium-doped zirconium fluoride-based fiber and utilizes the dual-wavelength pumping scheme. Stable, self-starting mode locking with a minimum pulse duration of 53 ps was measured using a two-photon absorption autocorrelator. The longest wavelength demonstrated was 3612 nm, and the maximum average powers achieved were 50 and 167 mW in fundamental and multi-pulse mode-locking regimes, respectively. To the best of our knowledge, this is the longest wavelength rare-earth-doped mode-locked fiber laser demonstrated. The broad tunability promises potential uses for environmental sensing applications.

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.

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.

Black phosphorus Q-switched and mode-locked mid-infrared Er:ZBLAN fiber laser at 35 μm wavelength

With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 3.5 um have become a fascinating area of research. However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region. Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 3.5 um. Here, we fabricated a 3.5-um saturable absorber mirror (SAM) by transferring liquid-phase exfoliated BP flakes onto a gold-coated mirror. With the as-prepared BP SAM, we realized stable Q-switching and continuous-wave mode-locking operations in the DWP Er:ZBLAN fiber lasers at 3.5 um. To the best of our knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 3.5 um spectral region. The research results will not only promote the development of 3.5-um pulsed fiber lasers but also open the photonic application of two-dimensional materials in this spectral region

Theoretical modelling of dual-wavelength pumpedYb3 + –Tm3 + co-doped silica fibre laser

Numerical simulations have, for the first time to our knowledge, been carried out to characterize theYb3 + –Tm3 + co-doped silica fibre laser (YTFL), defined by a fibre grating and an end mirror, by usingthe rate equations, which take into consideration both the energy transfer processes fromYb3 + toTm3 + ions and the cross-relaxation processes among differentTm3 + ions. A dual-wavelength pumping scheme with one at 805 nm and the other at 975 nm is usedto pump the YTFL. We have investigated the wavelength-dependent output power ofthe YTFL, from 1750 to 2200 nm, which takes its maximum output power at ∼ 1800 nm. The effect of the cross-relaxation processes in theTm3 + -doped silica fibre laser has been studied. The results indicate that these processes are beneficialto the laser and should be considered in the theoretical modelling. The influence of theYb3 + concentration on the characteristics of the YTFL has also been analysed and the results show thatYb3 + dopants can improve the output power and slope efficiency of the laser.

Structured-Core GeO$_{2}$-Doped Photonic-Crystal Fibers for Parametric and Supercontinuum Generation

We demonstrate efficient broadband four-wave-mixing (FWM) generation at the particular frequency detuning of ~150 THz from a 1064-nm sub-nanosecond laser pump in innovative structured-core germanium-oxide (GeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )-doped photonic crystal fibers (PCFs). Remarkably, the latter PCF has a small-diameter highly concentrated germanium rod in the core center that enables fine tuning of the FWM wavelengths. The generated anti-Stokes radiation at ~700 nm is subsequently used as secondary pump for generating a bright visible supercontinuum in the fundamental mode from 370 nm to beyond 1750 nm, when splicing the GeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -doped PCF to a pure-silica PCF, whose zero-dispersion wavelength is set in-between the pump and anti-Stokes wavelengths, consistently with the standard dual-wavelength pumping scheme.

Dual-Wavelength-Pumped Supercontinuum Generation in an All-Fiber Device

We experimentally demonstrate supercontinuum generation with a novel dual-wavelength pumping scheme. The dual-wavelength pump source and supercontinuum generation were realized one after another in a fusion spliced all-fiber device. The spectrum, extending from as short as 360 nm to beyond 1750 nm, is very flat. The all-fiber configuration makes the source very compact.

Thulium-doped silica-based optical fibers for cladding-pumped fiber amplifiers

We present preparation and spectroscopic characterization of thulium-doped fibers with enhanced 3H4 fluorescence lifetime obtained by codoping with alumina. With an alumina content of 10mol%, a fluorescence lifetime of 58μs is achieved. For the first time we study and optimize the thulium-doped fiber amplifier (TDFA) with a dual-wavelength (800+1400nm) pumping scheme, where the pump at 800nm propagates in the cladding and the pump at 1400nm propagates in the core. In the study we use numerical simulations and experimentally obtained fiber characteristics. The results are compared with those obtained for numerical simulation of a TDFA pumped at a single wavelength in the 1050nm band.

Wavelength Tunability of a Coupler and Air-Gap Etalon Controlled High-Efficiency $L$-Band Mode-Locked Erbium-Doped Fiber Laser

Mode-locked erbium-doped fiber laser with a full L-band wavelength tunability from 1567 to 1612 nm by controlling the ratio of its output coupler is demonstrated, which exhibits intracavity gain of 34 dB and maximum output power of 91 mW. The dual-wavelength (980 and 1480 nm) bidirectional pumping scheme enhances quantum efficiency and power conversion ratio to 42% and 37%, respectively. Continuous-wave lasing linewidth of 0.02 nm is obtained with the introduction of an intracavity air-gap Fabry-Peacuterot filter made by polishing the fiber connector end. A 45-nm wavelength tunablility with pulsewidth of 2.4 ps and linewidth of 6.8 nm are observed under mode-locking regime. Tuning resolution of 0.3 nm and wavelength-dependent power variation of <1.2 dB are also reported

Modeling S and C-band optical amplification in thulium and erbium codoped fluoride fiber

Theoretical model for Er 3+, Tm 3+ codoped fluoride fiber based on the rate and propagation equations has been established by considering the energy transfer process between Er 3+ and Tm 3+, Er 3+ absorption in S-band as well as Tm 3+ absorption in C-band. The spectral gain as functions of the Er 3+ concentration, the fiber length, the pump power has been investigated. Two pumping schemes have been considered and compared with respect to their spectral gains. In the case of Er 3+ and Tm 3+ codoped fluoride fiber pumped by 0.15 W at 800 nm and 0.3 W at 1410 nm, a gain of 20 dB or more can be achieved in the range of 1450–1560 nm. The results show that significant S + C-band gain can be achieved by codoping Er 3+ in Tm 3+ doped fluoride fiber and using the dual-wavelength pumping scheme.