The results of measurements of the emission and absorption cross section for the transition 2F5/2 -> 2F7/2 of Yb3+ ions in Al2O3 and P2O5 doped silica fibers are presented. Different techniques based on spectroscopic data, and more direct technique involving optical saturation of the transition are employed. The data obtained indicate an essential difference in cross section spectra of Yb3+ ions in alumosilicate and phosphosilicate fibers.
Silica-based thulium-doped fiber devices operating around 810 nm would extend the spectral range covered by high- power fiber devices. Using a comprehensive numerical model of the fiber we have shown that efficient lasing at 810 nm can be achieved for specific ranges of the laser cavity parameters in silica-based thulium-doped fibers with enhanced 3H4 lifetime up to 58 \mus as measured in our highly alumina-codoped fibers. We present optimization of the thulium-doped fiber and laser cavity parameters and also potential applications of the developed host material in amplifiers and broadband sou…
This paper presents the progress in the fields of the modelling and design of lanthanide ion doped chalcogenide glass fiber lasers. It presents the laser cavity designs that have been developed in order to optimize the performance of lanthanide ion doped chalcogenide glass fiber lasers. Also various numerical algorithms that have been applied for the optimization of chalcogenide glass lasers are reviewed and compared. The comparison shows that a combination of less accurate but more robust algorithms with more accurate ones gives the most promising performance.
An efficient method to fabricate transparent glass ceramic fibers containing in-situ grown Er3+-doped oxide nanoparticles is presented. Characterization of the drawn fibers exhibits low loss (0.4 dB/m) and broadened Er3+ emission spectrum. This attractive method offers new scopes for fiber amplifiers.
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…
Generally speaking, the self-sweeping effect relies on the dynamical grating formed in a gain fiber. Here, the normal self-sweeping was generated in a pump-free ytterbium-doped fiber which serves as a fiber saturable absorber and is introduced to the laser cavity by a circulator in this experiment. The sweeping rate and the sweeping range alter as usual, both of which can be controlled by the pump power. Further, a new self-pulse signal is observed and discussed in this work, which shows the difference of the self-sweeping effects between active fiber and fiber saturable absorber.
We demonstrate a 7-core erbium doped fiber amplifier employing side pumping using tapered multimode fiber. The amplifier has multicore inputs and outputs which can be readily spliced to multicore transmission fiber for amplifying space division multiplexed signals. Gain over 25dB was obtained in each of the cores over a 40-nm bandwidth covering C-band.
Here a detailed formalism to achieve an analytical solution of a lossy high power Yb-doped silica fiber laser is introduced. The solutions for the lossless fiber laser is initially attained in detail. Next, the solution for the lossy fiber laser is obtained based on the lossless fiber laser solution. To examine the solutions for both lossless and lossy fiber laser two sets of values are compared with the exact numerical solutions and the results are in a good agreement. Furthermore, steps and procedures for achieving the final solutions are explained clearly and precisely.
We experimentally analyze the average-power-scaling capabilities of ultrafast, thulium-doped fiber amplifiers. It has been theoretically predicted that thulium-doped fiber laser systems, with an emission wavelength around 2 um, should be able to withstand much higher heat-loads than their Yb-doped counterparts before the onset of transverse mode instability (TMI) is observed. In this work we experimentally verify this theoretical prediction by operating thulium doped fibers at very high heat-load. In separate experiments we analyze the performance of two different large-core, thulium-doped fib…
Soliton operation and soliton wavelength tuning of erbium-doped fiber lasers mode locked with atomic layer graphene was experimentally investigated under various cavity dispersion conditions. It was shown that not only wide range soliton wavelength tuning but also soltion pulse width variation could be obtained in the fiber lasers. Our results show that the graphene mode locked erbium-doped fiber lasers provide a compact, user friendly and low cost wavelength tunable ultrahsort pulse source.
Thulium-doped fibers suitable for core-pumped single-frequency lasers were fabricated by the modified chemical vapor deposition (MCVD) method. Refractive index profile, doping profile and spectral absorption was measured. High doping concentration of thulium ions should be achieved to allow for high absorption of light at a pump wavelength while the thulium ions clustering should be avoided to prevent the cooperative upconversion and quenching processes. The fabricated fibers featured pump absorption up to 70dB/m at a pump wavelength of 1611nm. The single-frequency master oscillator with a res…
We report on an ytterbium-free erbium-doped aluminophosphosilicate all-fiber laser, producing an output power of 25 W at a wavelength of 1584 nm with a slope efficiency of 30% with respect to the 976 nm absorbed pump power. The simple cavity design proposed takes advantage of fiber Bragg gratings written directly in the gain fiber. The single-mode erbium-doped aluminophosphosilicate fiber was fabricated in-house and was doped with 0.06 mol.% of Er2O3, 1.77 mol.% of Al2O3 and 1.04 mol.% of P2O5. The incorporation of aluminium and phosphorus into the fiber core allowed for an increased concentra…
Blue-enhanced, broadband supercontinuum generation in a 50 um core fluorine-doped graded-index multimode fiber is demonstrated by pumping with a 1064 nm picosecond source. Multi-octave supercontinuum spectrum extending from ~400 nm to 2,400 nm is achieved in a relatively short fiber. The measured spectrum and multimode nonlinear properties are compared to those of a germanium-doped graded-index multimode fiber. It is shown that engineering the glass composition and thus its chromatic dispersion and absorption characteristics, provides a novel and effective approach to further controlling the n…
Using a numerical model we study the frequency dependence of mode coupling gain due to stimulated thermal Rayleigh scattering in step index, Yb doped, fiber amplifiers. The frequency at the gain peak is shown to vary with core size, doping size, population saturation, thermal lensing, fiber coiling, direction of pumping, photodarkening, and pump noise spectra. The predicted frequencies are compared with measured values whenever possible.
Optical fiber tapers are used to collect photoluminescence emission at ~1.5 um from photonic crystal cavities fabricated in erbium doped silicon nitride on silicon. Photoluminescence collection via fiber taper is enhanced 2.5 times relative to free space, with a total taper collection efficiency of 53%. By varying the fiber taper offset from the cavity, a broad tuning range of coupling strength is obtained. This material system combined with fiber taper collection is promising for building on-chip optical amplifiers.
This paper describes a mode locking technique based on enhanced polarization dependent loss (PDL). The method utilizes a bent single mode fiber (SMF28) coil to induce sufficient PDL at 2 \(μ\)m wavelength region. Significant PDL in SMF28 coils is enabled since the light is much more weakly guided. A passively mode-locked thulium doped all-fiber laser is demonstrated using this simple device with polarization controllers as mode locker. The results indicate a moderate amount of 1 dB is sufficient to initiate and sustain stable mode-locking operation. We believe, to the best of our knowledge, th…
Optical emission from rare-earth-doped fluoride fibers has thus far been limited to less than 4 μm. We extend emission beyond this limit by employing an indium fluoride (InF3) glass fiber as the host, which exhibits an increased infrared transparency over commonly used zirconium fluoride (ZBLAN). Near-infrared pumping of a dysprosium-doped InF3 fiber results in broad emission centered around 4.3 μm, representing the longest emission yet achieved from a fluoride fiber. The first laser emission in an InF3 fiber is also demonstrated from the 3 μm dysprosium transition. Finally, a frequency domain…
A Core/Cladding Yb-doped fiber amplifier configuration is presented that relies on anti-Stokes fluorescence cooling for effective heat mitigation in high-power operation. In the proposed design, the inner cladding of the double clad fiber is doped with the same ion as in the core; therefore, the excess heat generated from the background absorption is removed by the anti-Stokes fluorescence in both core and inner cladding. We consider both silica and ZBLAN glasses for the host material in the Core/Cladding Yb-doped fiber amplifier. The model incorporates the spatial profiles of the signal and p…
We present an analytical solution for a radiation balanced fiber laser, in which no net heat is generated during lasing operation due to cooling by anti-Stokes fluorescence. The results are in excellent agreement with the numerical solutions. Using realistic values for fiber laser parameters, the analytical solutions presented are proposed as an economically desirable alternative to time-consuming, direct numerical calculations.
We theoretically and experimentally demonstrate a novel mode-locked ytterbium-doped fiber laser with a saturable absorber based on nonlinear Kerr beam cleanup effect. The saturable absorber was formed by a 2-m graded-index multimode fiber and a single-mode fiber segment served as a diaphragm. With an all-normal-dispersion-fiber configuration, the laser generated dissipative soliton pulses with pulse duration of 26.38 ps and pulse energy more than 0.25 nJ; output pulses could be compressed externally to 615.7 fs. Moreover, the self-starting mode-locking operation of this laser exhibited a high …
We propose a robust spectral beam combining scheme using wavelength dependent polarisation rotators and polarization beam combiners. We successfully demonstrated the concept for two Yb-doped fiber lasers at 1064nm and 1092nm up to a total input power of 90W. The results reveal a very good combining efficiency and the potential for scaling to high power operations in this method of beam combining.
We present some of our research activities dedicated to doped silica-based optical fibers, aiming at understanding the spectral properties of luminescent ions, such as rare-earth and transition metal elements. The influence of the local environment on dopants is extensively studied: energy transfer mechanisms between rare-earth ions, control of the valence state of chromium ions, effect of the local phonon energy on thulium ions emission efficiency, and broadening of erbium ions emission induced by oxide nanoparticles. Knowledge of these effects is essential for photonics applications.
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 demonstrate the broadband supercontinuum (SC) generation in photonic crystal fiber (PCF), highly nonlinear fiber (HNLF) and ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber with a passively mode-locked erbium-doped fiber laser (EDFL). The passively mode-locked EDFL incorporates a CNT-based saturable absorber and has achieved a pulse width of 620 fs with a pulse repetition rate of 18 MHz. The spectral broadening phenomena inside each fiber has been observed with respect to the variation in seed pulse power. The SC spectrum bandwidth of 1050 nm, 1400 nm, and 2000 nm has been achieved using PCF, HNLF, an…
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 …
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…
Erbium-doped ZBLAN is the most commonly used glass for mid-infrared fiber lasers. In this paper we quantify the energy dynamics of the erbium ions which is important for improving the performance of mid infrared fiber lasers. Previous studies have found a discrepancy between the strength of inter-ion energy transfer measured in bulk Er:ZBLAN and the strength required to explain current fiber laser performance. We have measured the energy transfer of the 4I13/2 + 4I13/2 -> 4I15/2 + 4I9/2 energy transfer process directly in a range of fibers for the first time.
Coherent combining is demonstrated in a clad pumped Yb doped double core fiber laser. A slope efficiency of more than 70 % is achieved with 96 % of the total output power on the fundamental mode of one of the two cores. This high combining efficiency is obtained when both cores are coupled via a biconical fused taper in a Michelson interferometer configuration.
Ytterbium (Yb) doped fiber lasers are known to be affected by the creation of color centers during lasing (socalled photodarkening (PD)). In a previous work, this defect creation was investigated from a spectroscopic point of view, showing the presence of traces (ppb) of thulium (Tm) in the Yb doped fiber. It was shown that Tm has a strong impact on the defect creation process involved in PD. In this paper, we compare the results from the literature with our Tm hypothesis, without finding any contradiction. Moreover, this hypothesis can be an explanation for the discrepancies in the literature…
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 contribution we investigate the transversal mode instability behavior of an ytterbium doped commercial 20/400 fiber and obtain 2.9 kW of output power after optimizing the influencing parameters. In this context, we evaluate the influence of the bend diameter and the pump wavelength within the scope of the absorption length and the length of the fiber. Furthermore with a newly developed fiber we report on 4.4 kW of single-mode output power at 40 cm bend diameter.
A non-destructive method for measuring the resonant absorption coefficient of rare-earth-doped optical fibers is introduced. It can be applied to a broad range of fiber designs and host materials. The method compares the side-collected spontaneous emission at two arbitrary locations along the fiber as a function of the pump wavelength to extract the absorption coefficient. It provides an attractive and accurate alternative to other available techniques. In particular, the proposed method is superior to the cut-back method, which destroys the sample and is prone to inaccuracies due to the cladd…
In this contribution, a comprehensive experimental study of photoluminescence from Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber samples is discussed. The selenide-chalcogenide multimode fiber samples co-doped with 500 ppm of Pr3+ ions and 500 ppm of Dy3+ ions are prepared using conventional melt-quenching. The main objective of the study is the analysis of the pumping wavelength selection on the shape of the output spectrum. For this purpose, the Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber samples are illuminated at one end using pump lasers operating at the wavelength…
Core-clad fibers on the basis of high-purity 1300 ppmw Pr(3+)-doped Ga-Ge-As-Se and 2000 ppmw Pr(3+) -doped In-Ge-As-Se-I glasses have been prepared. The minimum optical losses of the fibers are at the level of 1 dB/m in the wavelength range, where there is no influence of the praseodymium absorption. At present, it is the best result obtained for core-clad rare- earth-doped chalcogenide fibers with high dopant concentration. The fibers exhibit the broadband luminescence in the spectral range of 3.5-5.5 micron. The values of luminescence lifetime at the wavelength of 4.7 micron are within 6.5-…
Chirped fiber Bragg gratings in Yb-doped fiber lasers allow tuning the net cavity dispersion, thus enabling access to pulse dynamics beyond the typical all-normal-dispersion dissipative soliton regime. This Letter demonstrates an ultrafast dispersion-managed all-polarization-maintaining fiber oscillator mode-locked with a nonlinear optical loop mirror. Using a chirped fiber Bragg grating inside the oscillator, it can work at net cavity dispersion in the range from -0.098 ps$^2$ up to +0.067 ps$^2$ and above at the wavelength of 1 $\mathrmμ$m. Depending on the configuration, the system can deli…
Photonic crystal fibers doped with silver nanoparticles exhibit the Kerr nonlinearity that can be positive or negative depending on wavelength and vanishes at a specific wavelength. We study numerically how the simultaneous presence of a zero-nonlinearity wavelength (ZNW) and a zero-dispersion wavelength affects evolution of soliton and supercontinuum generation inside such fibers and find a number of unique features. The existence of negative nonlinearity allows soliton formation even in the normaldispersion region of the fiber, and the ZNW acts as a barrier for the Raman-induced red shift of…
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 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 present a comprehensive theoretical and experimental investigation of a dual-wavelength, bismuth-doped fiber (BDF) laser operating near 1700 nm based on cascaded cavities. The BDF provides optical gain from 1650 nm to 1800 nm when pumped at 1550 nm; the laser cavity is defined by a 90% mirror on one end and two fiber Bragg gratings (FBGs) separated by a length of BDF on the other. The laser can operate at either wavelength alone or both wavelengths simultaneously by simple adjustment of the pump power. Experimental results correlate well simulations based on a theoretical model of the laser…
Tellurite glass fibers with embedded nanodiamond are attractive materials for quantum photonics applications. Reducing the loss of these fibers in the 600-800 nm wavelength range of nanodiamond fluorescence is essential to exploit the unique properties of nanodiamond in the new hybrid material. The first part of this study reported the origin of loss in nanodiamond-doped glass and impact of glass fabrication conditions. Here, we report the fabrication of nanodiamond-doped tellurite fibers with significantly reduced loss in the visible through further understanding of the impact of glass fabric…
Dynamic population gratings (DPGs) in rare-earth doped fibers are prevalent devices in fiber lasers for the production of single-longitudinal-mode emission, Q-switched pulses, and wavelength self-sweeping regimes. This study presents a transition from Q-switched state to continuous wave (CW) state, accompanying irregular mode-hopping, in an erbium-doped fiber laser with a heavily-doped DPG centered at 1549.95 nm. Our results demonstrate that the transition between these two states can be achieved by adjusting the pump power. The repetition frequency of the Q-switched pulse increases monotonica…
Rare earth (RE) doped silica-based optical fibers with transparent glass ceramic (TGC) core was fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of post-ceramming. The main characteristics of the RE-doped oxyde nanoparticles namely, their density and mean diameter in the fibers are dictated by the concentration of alkaline earth element used as phase separating agent. Magnesium and erbium co-doped fibers were fabricated. Optical transmission in term of loss due to scattering as well as some spectroscopic character…
We report on a long wavelength emitting rare earth doped fiber laser with emission centered at 3.5 μm and tunable across 450 nm. The longest wavelength emission was 3.78 μm, which is the longest emission from a fiber laser operating at room temperature. In a simple optical arrangement employing dielectric mirrors for feedback, the laser was capable of emitting 1.45 W of near diffraction limited output power at 3.47 μm. These emission characteristics compliment the emission from quantum cascade lasers and demonstrate how all infrared dual wavelength pumping can be used to access high lying rare…
In this paper, we report an experimental study of noise features of polarized and unpolarized amplified spontaneous emission (ASE) with narrow optical bandwidth, registered from a conventional low-doped erbium fiber. We demonstrate that ASE noise can be considered as train of Gaussian-like pulses with random magnitudes, widths, and inter- pulse intervals. The statistical properties of these three parameters of noise pulsing are analyzed. We also present the results on the influence of ASE noise upon optical spectrum broadening, produced by self-phase modulation at propagating along communicati…
Recent advances in power scaling of fiber lasers are hindered by the thermal issues, which deteriorate the beam quality. Anti-Stokes fluorescence cooling has been suggested as a viable method to balance the heat generated by the quantum defect and background absorption. Such radiation-balanced configurations rely on the availability of cooling-grade rare-earth-doped gain materials. Herein, we perform a series of tests on a ytterbium-doped ZBLAN optical fiber to extract its laser cooling-related parameters and show that it is a viable laser cooling medium for radiation-balancing. In particular,…
A ytterbium doped silica optical fiber has been cooled by 18.4K below ambient temperature by pumping with 20W of 1035nm light in vacuum. In air, cooling by 3.6K below ambient was observed with the same 20W pump. The temperatures were measured with a thermal imaging camera and differential luminescence thermometry. The cooling efficiency is calculated to be 1.2+-0.1%. The core of the fiber was codoped with Al3+ for an Al to Yb ratio of 6:1, to allow for a larger Yb concentration and enhanced laser cooling.
We experimentally demonstrate spatial beam self-cleaning in an Yb-doped graded-index multimode fiber taper, both in passive and active configurations. The input laser beam at 1064 nm was injected for propagation from the small to the large core side of the taper, with laser diode pumping in a counterdirectional configuration. The Kerr effect permits to obtain high-beam quality amplification with no accompanying frequency conversions. As a result, our nonlinear taper amplifier may provide an important building block for multimode fiber lasers and amplifiers.
We demonstrate self-started unidirectional dissipative soliton operation and noise-like pulse operation in an all-normal-dispersion bidirectional Yb-doped fiber laser mode-locked by nonlinear polarization rotation. The laser works unidirectional once mode locking was achieved due to the cavity directional nonlinearity asymmetry along with the nonlinear polarization rotation mode locking mechanism.
We investigate theoretically a fiber laser passively mode-locked with nonlinear polarization rotation. A unidirectional ring cavity is considered with a polarizer placed between two sets of a halfwave plate and a quarterwave plate. A master equation is derived and the stability of the continuous and mode-locked solutions is studied. In particular, the effect of the orientation of the four phase plates and of the polarizer on the mode-locking regime is investigated.
In this contribution a numerical model is developed to study the time dynamics of photoluminescence emitted by Tb3+ doped multimode chalcogenide-selenide glass fibers pumped by laser light at approximately 2 microns. The model consists of a set of partial differential equations (PDEs), which describe the temporal and spatial evolution of the photon density and level populations within the fiber. In order to solve numerically the PDEs a Method of Lines is applied. The modeling parameters are extracted from measurements and from data available in the literature. The numerical results obtained su…
The dynamics of dissipative solitons (DSs) are explored in a high repetition rate normal-dispersion erbium-doped fiber laser for the first time. Despite of the high fundamental repetition rate of 129 MHz and thus the low pulse energy, a DS train with a dechirped pulse width of 418 fs, period-doubling of single and dual DSs, as well as 258 MHz 2nd-order harmonic mode-locking of DSs can be observed in the fiber laser with increasing pump power and appropriate settings. A transmitted semiconductor saturable absorber and a wavelength division multiplexer/isolator/tap hybrid module are employed to …
We report on an environmentally stable, Yb-doped, all-normal dispersion, mode-locked fibre laser that is capable of creating broadband pulses with ultra-low repetition rates. Specifically, through careful positioning of fibre sections in an all-PM-fibre cavity mode-locked with a nonlinear amplifying loop mirror, we achieve stable pulse trains with repetition rates as low as 506 kHz. The pulses have several nanojules of energy and are compressible down to ultrashort (< 500 fs) durations.
