We report the first experimental demonstration of efficient and high-power operation of a Ti:sapphire laser pumped by a simple, compact, continuous-wave (cw) fiber-laser-based green source. The pump radiation is obtained by direct single-pass second-harmonic-generation (SHG) of a 33-W, cw Yb-fiber laser in 30-mm-long MgO:sPPLT crystal, providing 11 W of single-frequency green power at 532 nm in TEM00 spatial profile with power and frequency stability better than 3.3% and 32 MHz, respectively, over one hour. The Ti:sapphire laser is continuously tunable across 743-970 nm and can deliver an output power up to 2.7 W with a slope efficiency as high as 32.8% under optimum output coupling of 20%. The laser output has a TEM00 spatial profile with M2<1.44 across the tuning range and exhibits a peak-to-peak power fluctuation below 5.1% over 1 hour.
High energy terahertz pulses are produced by optical rectification (OR) in organic crystals DAST and DSTMS by a Ti:sapphire amplifier system centered at 0.8 microns. The simple scheme provides broadband spectra between 1 and 5 THz, when pumped by collimated 60 fs near-infrared pump pulse and it is scalable in energy. Fluence-dependent conversion efficiency and damage threshold are reported as well as optimized OR at visible wavelength.
We obtained an optical-to-terahertz (THz) energy conversion efficiency of 0.5% using the tilted-pulse-front technique in lithium niobate at a cryogenically cooled temperature of 100 K pumped by amplified Ti:sapphire laser pulses with ~150 fs pulse duration at 800 nm wavelength. Compared with the optimized conversion efficiency of 0.18% achieved at room temperature, we achieved more than 2.5 times enhancement in conversion efficiency upon cryogenically cooling the crystal due to reduction of THz absorption. Further improvements to the conversion efficiency can be made by optimizing the out-coup…
We present a numerical parametric study of single-cycle electromagnetic pulse generation in a DAST/SiO2 multilayer structure via collinear optical rectification of 800 nm femtosecond laser pulses. It is shown that modifications of the thicknesses of the DAST and SiO2 layers allow tuning of the average frequency of the generated THz pulses in the frequency range from 3 to 6 THz. The laser-to-THz energy conversion efficiency in the proposed structures is compared with that in a bulk DAST crystal and a quasi-phase-matching periodically poled DAST crystal and shows significant enhancement.
Correlated photon pairs generated through spontaneous parametric down-conversion (SPDC) are a key resource in quantum optics. In many quantum optics applications, such as satellite quantum key distribution (QKD), a compact, high repetition rate pump laser is required. Here we demonstrate the use of a compact, GHz-rate diode-pumped three-element Kerr-lens-modelocked Ti:sapphire laser for the generation of correlated photon pairs at 790 nm. We verify the presence of indistinguishable photons produced via SPDC using Hong-Ou-Mandel (HOM) interferometry and observe a dip in coincidence counts with …
We report on high energy terahertz pulses by optical rectification (OR) in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) directly pumped by a conventional Ti:Sapphire (Ti:Sa) amplifier. The simple scheme provides an optical to terahertz conversion efficiency of 0.25% when pumped by a collimated laser pulses with duration of 50 fs and central wavelength of 800nm. The generated radiation spans frequencies between 0.2 and 3 THz. We measured the damage threshold as well as the dependency of the conversion efficiency on the pump fluence, pump wavelength, and pulse duration.
The thermal lensing effects in the lasing crystal appear to be dominant when the pump laser focused on the lasing crystal which causes the local heating effect. The spatial refractive index variations observed if the crystal has non-uniform temperature distribution. In the present study, the demonstration of thermal lensing effect of Brewster-cut Ti: Sapphire crystal carried out when pumped by 25 ps pulses at 80 MHz repetition rate with 532 nm central wavelength, while the average pump power controlled by the attenuator. The thermal lensing effects measured first at the ~293 K temperature and …
We report an injection-locked cw titanium:sapphire ring laser at 846 nm. It produces 1.00 W in a single frequency when pumped with 5.5 W. Single frequency operation requires only a few milliwatts of injected power.
We present a design for a high-energy single stage mid-IR difference frequency generation adapted to a two-color Ti:sapphire amplifier system. The optimized mixing process is based on chirped pulse difference frequency generation (CP-DFG), allowing for a higher conversion efficiency, larger bandwidth and reduced two photon absorption losses. The numerical start-to-end simulations include stretching, chirped pulse difference frequency generation and pulse compression. Realistic design parameters for commercially available non linear crystals (GaSe, AgGaS2, LiInSe2, LiGaSe2) are considered. Comp…
The organic terahertz (THz) generation crystal BNA has recently gained traction as a valuable source to produce broadband THz pulses. Even when pumped with 800-nm light, thin BNA crystals can produce relatively high electric fields with frequency components out to 5 THz. However, the THz output when pumped with 800-nm light is limited by the damage threshold of the organic crystal. Here we report that the damage threshold of BNA can be significantly improved by physically bonding BNA to a high-thermal conductivity sapphire window. When pumped with 800-nm light from an amplified Ti:sapphire las…
We report a few-cycle, broadband, singly-resonant optical parametric oscillator (OPO) for the mid-infrared based on MgO-doped periodically-poled LiNbO3 (MgO:PPLN), synchronously pumped by a 20-fs Ti:sapphire laser. By using crystal interaction lengths as short as 250 um, and careful dispersion management of input pump pulses and the OPO resonator, near-transform-limited, few-cycle idler pulses tunable across the mid-infrared have been generated, with as few as 3.7 optical cycles at 2682 nm. The OPO can be continuously tuned over 2179-3732 nm by cavity delay tuning, providing up to 33 mW of out…
A novel method for efficient generation of high power, equalized continuous-wave supercontinuum source in an all conventional silica fiber architecture is demonstrated. Highly nonlinear fiber (HNLF) is pumped in its anomalous dispersion region using a novel, high power, L-band laser. The L-band laser encompasses a 6th order cascaded Raman amplifier which is pumped with a high power Ytterbium doped fiber laser and amplifies a low-power, tunable L-band seed source. The supercontinuum generated 35W of power with ~40% efficiency. The Supercontinuum spectrum was measured to have a high degree of fl…
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.
We demonstrate yellow laser emission using silicate glass fiber as the gain medium. By employing core pumping using widely available GaN diode lasers with emission at 445 nm, we show that Dy3+-doped aluminosilicate glass fiber can be readily excited creating sufficient gain at 581 nm. In this proof of concept demonstration, the maximum output power generated was 3 mW with a slope efficiency approximately 1.8% with respect to injected pump.
The bias-pumped gain-switched fiber laser proposed by us is considered a novel pulsed fiber laser based on a new pulsing mechanism. With a certain signal power seeding, synchronization of temporal evolution can be kept between the output signal laser and the pump. The seed laser can be supplied conveniently by a CW pump power which is named bias pump power. A pulsed pump is responsible for shaping the output pulse. Stable pulsed lasers with tunable durations can be achieved under bias pump combined with pulsed pump. In addition, the temporal shape of output pulses can be controllable based on …
The performance of mid-infrared erbium doped fiber lasers has dramatically improved in the last few years. In this paper we present a numerical model that provides valuable insight into the dynamics of a dual-wavelength pumped fiber laser that can operate on the 3.5 micron and 2.8 micron bands. This model is a much needed tool for optimizing and understanding the performance of these laser systems. Comparisons between simulation and experimental results for three different systems are presented.
We demonstrate a mid-infrared dysprosium-doped fluoride fiber laser with a continuously tunable output range of 573 nm, pumped by a 1.7 μm Raman fiber laser. To the best of our knowledge, this represents the largest tuning range achieved to date from any rare-earth-doped fiber laser and, critically, spans the 2.8-3.4 μm spectral region, which contains absorption resonances of many important functional groups and is uncovered by other rare-earth ions. Output powers up to 170 mW are achieved, with 21% slope efficiency. We also discuss the relative merits of the 1.7 μm pump scheme, including poss…
We present here the inscription of single-mode waveguides with Bragg gratings in sapphire. The waveguide Bragg gratings have a novel multi-layer depressed cladding design in the 1550 nm telecommunications waveband. The Bragg gratings have a narrow bandwidth (<0.5 nm) and have survived annealing at 1000°C. The structures are inscribed with femtosecond laser direct writing, using adaptive beam shaping with a non-immersion objective. A single-mode sapphire fiber Bragg grating is created by writing a waveguide with a Bragg grating within a 425 μm diameter sapphire optical fiber, providing signific…
We use a detailed numerical model of stimulated thermal Rayleigh scattering to compute mode instability thresholds in Tm$^{3+}$-doped fiber amplifiers. The fiber amplifies 2040 nm light using a 790 nm pump. The cross-relaxation process is strong, permitting power efficiencies of 60%. The predicted instability thresholds are compared with those in similar Yb$^{3+}$-doped fiber amplifiers with 976 nm pump and 1060 nm signal, and are found to be higher, even though the heat load is much higher in Tm-doped amplifiers. The higher threshold in the Tm-doped fiber is attributed to its longer signal wa…
We perform a numerical analysis of mid-infrared photoluminescence emitted by praseodymium (III) doped chalcogenide selenide glass pumped at near-infrared wavelengths. The results obtained show that an effective inversion of level populations can be achieved using both 1480 nm and 1595 nm laser diodes. The rate of the spontaneous emission achieved when pumping at 1480 nm and 1595 nm is comparable to this achieved using the standard pumping wavelength of 2040 nm.
We present a hundred-watt-level linearly-polarized random fiber laser (RFL) pumped by incoherent broadband amplified spontaneous emission (ASE) source and prospect the power scaling potential theoretically. The RFL employs half-opened cavity structure which is composed by a section of 330 m polarization maintained (PM) passive fiber and two PM high reflectivity fiber Bragg gratings. The 2nd order Stokes light centered at 1178 nm reaches the pump limited maximal power of 100.7 W with a full width at half-maximum linewidth of 2.58 nm and polarization extinction ratio of 23.5 dB. The correspondin…
We describe an efficient laser emission from a directly grown Er3+:YAG single-crystal fiber that is resonantly pumped using a continuous-wave (CW) laser diode at 1532 nm. In a longitudinal pumping, it emits 12.5 W at 1645 nm with a slope efficiency of 32%, which is the highest ever reported for a directly grown Er:YAG single-crystal fiber laser. Using an off-axis pumping scheme, CW output powers up to 7.3 W can be reached and in Q-switched operation, the laser produces 2 mJ pulses with a duration of 38 ns at the repetition rate of 1 kHz with an M^{2} factor below 1.8. To our knowledge this is …
We report the compact and robust coherent source operating in mid-IR based on Fe:ZnSe chalcogenide gain medium optically pumped by Er:ZBLAN fiber laser. The output power of 2.1 W with 59% slope efficiency with respect to absorbed pump power at liquid nitrogen cooling is achieved. We show that strong re-absorption at high pump power and iron ion doping concentrations leads to the continuous tuning of central wavelength from 4012 to 4198 nm. Robustness of high power Er:ZBLAN fiber laser combined with prominent spectroscopic properties of Fe:ZnSe media pave the way for the development of reliable…
By pumping thulium-doped silica-based fibers at 1.07~μm, rapid generation of absorbing centers leads to photo-induced attenuation (PIA). This detrimental effect prevents exploiting laser emissions in the visible and near infrared. We report on the characterization of the PIA versus the fiber core composition, particularly the concentration of thulium (Tm), lanthanum (La) and cerium (Ce) ions. We show that UV emision induced by Tm-Tm energy transfers is the source of photo-darkening, and that lanthanum and cerium are efficient hardeners against PIA.
We present a 100 MHz repetition rate Yb-fiber-laser-pumped synchronously pumped optical parametric oscillator (SPOPO) delivering tunable frequency combs covering almost the entire visible spectral range. By intracavity doubling both the signal and idler combs and using collinear residual pump light, nearly continuous tuning over the range of 420-700 nm is achieved with only small gaps near the OPO degeneracy condition. Output powers range from 10 mW to 200 mW, depending on wavelength, with pulse durations below 150 fs without external compression. Frequency locking of all three collinearly out…
We demonstrate a broadband mid-infrared (MIR) frequency comb source based on difference frequency generation (DFG) in periodically poled lithium niobate (PPLN) crystal. Mid-infrared radiation is obtained via mixing of the output of a 125 MHz repetition rate Yb-doped fiber laser with Raman-shifted solitons generated from the same source in a highly nonlinear fiber. The resulting idler is tunable in the range of 2.7 - 4.2 μm with average output power reaching 237 mW, and pulses as short as 115 fs. The coherence of the MIR comb is confirmed by spectral interferometry and heterodyne beat measureme…
Lasers based on Cr$^{2+}$-doped II-VI material, often known as the Ti:Sapphire of the mid-infrared, can directly provide few-cycle pulses with super-octave-spanning spectra, and serve as efficient drivers for generating broadband mid-infrared radiation. It is expected that the wider adoption of this technology benefits from more compact and cost-effective embodiments. Here, we report the first directly diode-pumped, Kerr-lens mode-locked Cr$^{2+}$-doped II-VI oscillator pumped by a single InP diode, providing average powers of over 500 mW and pulse durations of 45 fs - shorter than six optical…
We introduce a new equation that describes the spatio-temporal evolution of arbitrary pulses propagating in a fiber-ring cavity. This model is a significant extension of the traditionally used Lugiato-Lefever model. We demonstrate spontaneous symmetry breaking as well as multistability regimes in a synchronously pumped fiber-ring cavity. The equation can be applied to virtually any type of waveguide-based ring cavity.
A temporal variation of a spectrum of excited modes in a continuously pumped erbium-doped random fiber laser (RFL), based on randomly distributed Bragg gratings, is studied. Developed phenomenological theoretical model assumes hard excitation mechanism of the eigenmodes instability. The model explains qualitatively peculiarities of the spectrum variation, observed experimentally.
Absolute output power optimization and performance of a near- to mid-infrared picosecond optical parametric oscillator (OPO) is studied at two high pump powers using a widely-tunable output coupling (OC) technique which provides 15% to 68% OC. The MgO:PPLN-based OPO is synchronously pumped at 81.1 MHz by an Yb:fiber laser with double-peak spectrum. At 2 W pump power, maximum signal (at 1.46 $μ$m) and idler (at 3.92 $μ$m) power of 670 mW and 270 mW are obtained at 27% OC at 47% total extraction efficiency and 58% pump power depletion where at 15.5 W pump power, 7.4 W signal and 2.7 W idler powe…
In this work, the spectral evolution properties in single-frequency Raman fiber amplifier (RFA) with different pump manners are analyzed theoretically for the first time based on the gain dynamics. The analysis of gain dynamics reveals that the walk-off effect in counter-pumped manner produces a natural low-pass filter in single-frequency RFA. When applying rare-earth doped fiber lasers as the pump source, the strong temporal fluctuations in the pump source lead to spectral broadening in co-pumped manner, while the natural low-pass filter in countered-pumped case can still ensure single-freque…
Space-division multiplexing (SDM), whereby multiple spatial channels in multimode and multicore optical fibers are used to increase the total transmission capacity per fiber, is being investigated to avert a data capacity crunch and reduce the cost per transmitted bit. With the number of channels employed in SDM transmission experiments continuing to rise, there is a requirement for integrated SDM components that are scalable. Here, we demonstrate a cladding-pumped SDM erbium-doped fiber amplifier (EDFA) that consists of six uncoupled multimode erbium-doped cores. Each core supports three spat…
Many fields such as bio-spectroscopy and photochemistry often require sources of vacuum ultraviolet (VUV) pulses featuring a narrow linewidth and tunable over a wide frequency range. However, the majority of available VUV light sources do not simultaneously fulfill those two requirements, and few if any are truly compact, cost-effective and easy to use by non-specialists. Here we introduce a novel approach that goes a long way to meeting this challenge. It is based on hydrogen-filled hollow-core photonic crystal fiber pumped simultaneously by two spectrally distant pulses. Stimulated Raman sca…
We present a tunable, hybrid waveguide-fiber optical parametric oscillator (OPO) synchronously pumped by an ultra-fast fiber laser exploiting four-wave mixing (FWM) generated in silicon nitride waveguides. Parametric oscillation results in a 35 dB enhancement of the idler spectral power density in comparison to spontaneous FWM, with the ability of wide wavelength tuning over 86 nm in the O-band. Measurements of the oscillation threshold and the efficiency of the feedback loop reveal how an integration of the OPO on a single silicon nitride chip can be accomplished at standard repetition rates …
In this letter, we report a compact, low-power laser diode-pumped, all-fiber polarization-entangled photon pair source based on periodically-poled silica fiber technology. The all-fiber source offers room-temperature, alignment-free, turn-key operation, with low power consumption, and is packaged into a fanless, portable enclosure. It features a broad biphoton spectrum of more than 100nm with a concurrence that is greater than 0.96 for polarization entanglement. The source is stable over at least 10 hours of continuous operation, achieving coincidence-to-accidental ratios of more than 2000 con…
We present a 2-\mum frequency comb based on a reliable mode-locked Er:fiber laser with 100 MHz repetition rate. After shifting the spectrum of the amplified Er:fiber comb to longer wavelengths, a single-clad Tm/Ho:fiber is used as a self-pumped pre-amplifier to generate a coherent and broadband spectrum centered at 1.93 \mum. Subsequently, a cladding-pumped Tm:fiber amplifier boosts the system to a maximum output power of 4.8 W at 1.96 \mum. After compression in a compact grating compressor, our amplified Er:fiber/Tm:fiber hybrid system delivers as much as 2.9 W with a pulse duration of 141 fs…
Fiber fuse effect can occur spontaneously and propagate along optical fibers to cause wide-spread damage; it threatens all applications involving optical fibers. This paper presents two results. First, it establishes that the initiation of fiber fuse (IFF) in silica fibers is caused by defect-induced absorption. Critical temperatures and critical optical powers for IFF are simulated for the first time using a 3D solid-state heat transfer model with heat source generated by defect-induced absorption. In this method, formation energies of the defects can be uniquely determined, which offers crit…
We report on the writing of chirped volume Bragg gratings using 400 nm femtosecond pulses and the phase-mask inscription technique in the pure silica inner cladding of the gain fiber. The usefulness of such fiber component is demonstrated as a pump reflector in a cladding-pumped all-fiber laser. A reflectivity of 53% for the residual pump power guided in the cladding of the highly multimode 125 microns fiber is achieved, allowing for significant pump recycling in the fiber laser cavity which therefore optimizes the overall laser performances. As proof of concept, adding this pump reflector at …
Ultrafast optical excitation with intense mid-infrared and terahertz pulses has emerged as a new tool to control materials dynamically. As most experiments are performed with femtosecond pulse excitation, typical lifetimes of most light-induced phenomena in solids are of only few picoseconds. Yet, many scientific applications require longer drive pulses and lifetimes. Here, we describe a mid-infrared pump - terahertz-probe setup based on a CO$\mathrm{_2}$ laser seeded with 10.6 $\mathrmμ$m wavelength pulses from an optical parametric amplifier, itself pumped by a Ti:Al$\mathrm{_2}$O$\mathrm{_3…
In this letter, the impact of pump configuration on the modal instabilities (MI) threshold of high power fiber amplifiers is investigated. Using a time dependent computer model based on the optical beam propagation method (BPM), the effect of bidirectional pumping on the MI threshold of high power fiber amplifiers is explored and compared to that of a co-pumped configuration. Simulation results indicate that the bidirectional pumping increases the instabilities threshold by a factor of 30% with respect to the co-pumped scheme. We attribute this threshold enhancement to a weaker strength of the…
An analytically expression for the temperature dependence of the signal gain of an erbium-doped fiber amplifier (EDFA) pumped at 1480 \textit{nm} are theoretically obtained by solving the propagation equations with the amplified spontaneous emission (ASE). It is seen that the temperature dependence of the gain strongly depends on the distribution of population of Er$^{3+}$-ions in the second level. In addition, the output pump power and the intrinsic saturation power of the signal beam are obtained as a function of the temperature. Numerical calculations are carried out for the temperature ran…
We report on our realization of a high power holmium doped fiber laser, together with the validation of our numerical simulation of the laser. We first present the rare absolute measurements of the physical parameters that are mandatory to model accurately the laser-holmium interactions in our silica fiber. We then describe the realization of the clad-pumped laser, based on a triple-clad large mode area holmium (Ho) doped silica fiber. The output signal power is 90 W at 2120 nm, with an efficiency of about 50% with respect to the coupled pump power. This efficiency corresponds to the state of …
Here, we demonstrate all-fiber direct amplification of 11 picosecond pulses from a gain-switched laser diode at 1063nm. The diode was driven at a repetition rate of 40MHz and delivered 13$μ$W of fiber-coupled average output power. For the low output pulse energy of 0.33pJ we have designed a multi-stage core pumped preamplifier based on single clad Yb-doped fibers in order to keep the contribution of undesired amplified spontaneous emission as low as possible and to minimize temporal and spectral broadening. After the preamplifier we reduced the 40MHz repetition rate to 1MHz using a fiber coupl…
In this article, we explore how cryogenic cooling of the Ti:sapphire laser crystal greatly reduces thermal lensing by over an order of magnitude because of two factors: (i) the increase in the thermal conductivity of the crystal, and (ii) the decrease in the temperature dependence of the refractive index. We obtained analytical expression of the focal length of thermal lens for the pump inside the laser crystal being a Gaussian beam. Through analysis of the laser cavity stability, we found that in order for the relative difference between the optimal laser cavity path lengths in the horizontal…
We developed a new holmium-doped triple-clad fiber (Ho-3CF), reducing the clad diameter to improve the overlap between pump and doped-core, and the holmium concentration to reduce the influence of ion clustering on the laser efficiency. We illustrate here the performance of this fiber in a laser oscillator configuration. The laser emission is centered at 2.12 $μ$m by a fiber Bragg grating, and the active fiber is pumped in the clad by a 1.94 $μ$m thulium-doped fiber laser. The slope efficiency reaches 73% with respect to absorbed power (60% considering coupled power), for a maximum signal powe…
We report on an ultralow noise optical frequency transfer from a remotely located Sr optical lattice clock laser to a Ti:Sapphire optical frequency comb through telecom-wavelength optical fiber networks. The inherent narrow linewidth of the Ti:Sapphire optical frequency comb eliminates the need for a local reference high-finesse cavity. The relative fractional frequency instability of the optical frequency comb with respect to the remote optical reference was $6.7(1) \times 10^{-18}$ at 1 s and $1.05(3) \times 10^{-19}$ at 1,000 s including a 2.9 km-long fiber network. This ensured the optical…
A compact and versatile femtosecond mid-IR source is presented, based on an optical parametric oscillator (OPO) synchronously pumped by a commercial 250-MHz Er:fiber laser. The mid-IR spectrum can be tuned in the range 2.25-2.6 μm (signal) and 4.1-4.9 μm (idler), with average power from 20 to 60 mW. At 2.5 μm a minimum pulse duration of 110 fs and a power of 40 mW have been obtained. Active stabilization of the OPO cavity length has been achieved in the whole tuning range.
We demonstrated all-fiber amplification of 11 ps pulses from a gain-switched laser diode at 1064 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 $μ$W of fiber-coupled average output power. For the low output pulse energy of 325 fJ we have designed a multi-stage core pumped pre-amplifier in order to keep the contribution of undesired amplified spontaneous emission as low as possible. By using a novel time-domain approach for determining the power spectral density ratio (PSD) of signal to noise, we identified the optimal working point for our pre-amplifier. After the pre…
We report on the generation of 6.1 mJ, 3.8 fs pulses by the compression of a kHz Ti:sapphire laser in a large-aperture long hollow fiber. In order to find optimal conditions for spectral broadening at high pulse energies, we explore different parameter ranges where ionization or the Kerr effect dominates. After identifying the optimum parameter settings, large spectral broadening at high waveguide transmission is obtained. The intense 1.5-cycle pulses are used for high-harmonic generation in argon and neon.
