Diode-pumped Fiber Laser Research Articles

High-power diode-pumped ytterbium-doped fiber laser at 1150 nm

A model of steady-state rate equations including amplified spontaneous emission for long-wavelength ytterbi­um-doped fiber laser is set up, which provides design principle for a practical laser system. We demonstrate a diode-pumped all-fiber Yb-doped fiber laser at 1150 nm with an output power of 33.6 W, the optical efficiency is 60%.

LD泵浦瓦级单模高掺铒中红外光纤激光器

Mid-infrared lasers have a lot of potential applications,such as laser medicine,spectroscopy and infrared countermeasures.In order to obtain a compact and potable mid-infrared laser source,a diode-pumped fiber laser emitting at 2.8μm from a heavily erbium-doped ZrF4-BaF2-LaF3-AlF3-NaF double-clad fiber was demonstrated.A fiber-coupled laser diode centered at 975nm was coupled into the inner cladding as the pumping source by an achromatic coupling system consisted of two aspheric lenses. The laser cavity was composed of a protected gold mirror butted against the rear end of the active fiber, and the other end with 4% Fresnel reflection.The 2.8μm lasing was achieved when the launched pump power was higher than 0.37 W.The experimental results indicated that the center wavelength and linewidth of free running were 2.785μm and 0.9nm,respectively.Moreover,the maximum output power of the fiber laser working at the transverse-fundamental-mode was 0.98W,corresponding to the slop efficiency of 17%.High efficient watt-level single mode mid-infrared fiber laser was obtained using the efficient energy transfer upconversion processes between Er-Er ions.

Parametric Study for Different Er3+/Yb3+ Fiber Samples Based on a Computer Model for Diode Pumped Fiber Laser

In this paper the Erbium-Ytterbium (Er3+/Yb3+) co-doped fiber laser pumped by a laser diode is simulated using the Optiwave software. The proposed model is introduced and was used to perform a parametric study on four different samples of Er3+/Yb3+ fiber A, B, C, and D differ in their core diameters and their numerical apertures. The study was done in terms of fiber length, cutoff length, output mirror reflectivity, slope efficiency, and lasing threshold. The simulation results demonstrated that the optimum fiber length is 2 m, 0.5 m, 1.7 m, and 2.3 m for type A, B, C, and D respectively. The max achieved power is 3.15 w for type C at the optimum fiber length. The cut off length is 2.1m, 1.8m, 1.9m, and 2.4m for type A, B, C, and D respectively. Max. optical power of 3.15 w at 40 % reflectivity for type C fiber. Lowest lasing threshold level is 140 mw for type D. The highest slope efficiency is 73% for type C.

Passively Q-Switched 2.8-$\mu{\rm m}$ Nanosecond Fiber Laser

A diode-pumped erbium ion-doped single-mode ZBLAN fiber laser passively Q-switched by a Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> :ZnSe crystal is reported. Mid-infrared (MIR) pulses at 2.8 μm with a pulse energy of 2.0 μJ and pulse duration of 370 ns, corresponding to a peak power of 5.34 W, are achieved at a repetition rate of 161 kHz. Our experiment demonstrates that Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> : ZnSe crystal is a promising Q-switching element for high power pulsed MIR fiber lasers.

Integrated micro-endoscopy system for simultaneous fluorescence and optical-resolution photoacoustic imaging

We present a new integrated micro-endoscopy system combining label-free, fiber-based, real-time C-scan optical-resolution photoacoustic microscopy (F-OR-PAM) and a high-resolution fluorescence micro-endoscopy system for visualizing fluorescently labeled cellular components and optically absorbing microvasculature simultaneously. With a diode-pumped 532-nm fiber laser, the F-OR-PAM sub-system is able to reach a resolution of ∼7 μm. The fluorescence subsystem, which does not require any mechanical scanning, consists of a 447.5-nm-centered diode laser as the light source, an objective lens, and a CCD camera. Proflavine is used as the fluorescent contrast agent by topical application. The scanning laser and the diode laser light source share the same light path within an optical fiber bundle containing 30,000 individual single-mode fibers. The absorption of proflavine at 532 nm is low, which mitigates absorption bleaching of the contrast agent by the photoacoustic excitation source. We demonstrate imaging in live murine models. The system is able to provide cellular morphology with cellular resolution co-registered with the structural information given by F-OR-PAM. Therefore, the system has the potential to serve as a virtual biopsy technique, helping visualize angiogenesis and the effects of anti-cancer drugs on both cells and the microcirculation, as well as aid in the study of other diseases.

Control of attractor preference by low-pass filtered noise in a multistable fiber laser

A diode-pumped erbium-doped fiber laser with pump modulation shows a large dynamic behavior including the coexistence of multiple attractors. In this work it is demonstrated numerically and experimentally that a low-pass noise filtering can control the probability for the appearance of a particular state. The results of numerical simulations with the use of a three-level laser model display good agreement with experimental results. We construct three-dimensional bifurcation diagrams of the probability using the noise amplitude and cutting frequency as control parameters. Finally, it is found the existence of one noise amplitude that cause one periodic orbit to appears more frequently compared to different noise amplitudes.

High-power diode-pumped fiber laser operating at 3 μm

A high-power diode-cladding-pumped Ho³⁺-doped fluoride glass fiber laser operating in cascade mode is demonstrated. The ⁵I₆→⁵I₇ and ⁵I₇→⁵I₈ laser transitions produced 0.77 W at a measured slope efficiency of 12.4% and 0.24 W at a measured slope efficiency of 5.2%, respectively. Using a long fiber length, which forced a large threshold for the ⁵I₇→⁵I₈ transition, a wavelength of 3.002 μm was measured at maximum output power, making this system the first watt-level fiber laser operating in the mid-IR.

In vivo near-realtime volumetric optical-resolution photoacoustic microscopy using a high-repetition-rate nanosecond fiber-laser

Optical-resolution photoacoustic microscopy (OR-PAM) is capable of achieving optical-absorption-contrast images with micron-scale spatial resolution. Previous OR-PAM systems have been frame-rate limited by mechanical scanning speeds and laser pulse repetition rate (PRR). We demonstrate OR-PAM imaging using a diode-pumped nanosecond-pulsed Ytterbium-doped 532-nm fiber laser with PRR up to 600 kHz. Combined with fast-scanning mirrors, our proposed system provides C-scan and 3D images with acquisition frame rate of 4 frames per second (fps) or higher, two orders of magnitude faster than previously published systems. High-contrast images of capillary-scale microvasculature in a live Swiss Webster mouse ear with ~6-µm optical lateral spatial resolution are demonstrated.

Multicolor diode-pumped upconversion fiber laser

We present a new method to control the power of individual spectral components of a multicolor laser by mirrors with variable air gaps and by a composite resonator configuration. We demonstrate a Pr/Yb-ZBLAN fiber laser with arbitrary spectral composition of three simultaneously emitted components at 492 nm, 520 nm, and 635 nm. With 100 mW pump power at 850 nm launched into the fiber, the total laser output exceeds 10 mW.

Femtosecond to Attosecond Optics

We continue to observe strong progress moving from femtosecond to attosecond optics. Attosecond pulses are now available in many different labs with additional gating techniques which somewhat relax the requirements for the pulse duration of the intense infrared laser pulses. The pulse repetition rate still sets a limit on the signal-to-noise ratio for attosecond pump-probe measurements, and therefore, other streaking techniques have resulted in time-resolved measurements with sub-10-attosecond accuracy. Recent improvements on high-power ultrafast diode-pumped solid-state and fiber lasers will offer alternative sources for megahertz attosecond pulse generation. First proof-of-principle experiments have been demonstrated.

Calculation of Temperature Distribution in Eccentric Multi Core Diode Pumped Fiber Lasers by Green Function Method

In this paper, the temperature distribution in fiber lasers pumped by multi diode bars located in out-of-fiber axis has been investigated semi-analytically. For this reason, we consider heat deposition in fiber lasers due to pump and the nonhomogeneous heat conduction equation has been solved by using Green function method in a cylindrical coordinate system. Our model has been used for single, double and multi pumped configuration and, for a typical fiber lasers, the results have been plotted and discussed.

The Analytical Calculation of Temperature-Dependent Propagation Constant, V No. and Waveguide Dispersion in Super-Gaussian Diode-Pumped Fiber Lasers

Fiber lasers are under considerable attention due to their high efficiency and good beam qualities [1–6]. In high power regimes, the heat generation due to pump beam [7] can influence the laser operation and beam propagation characteristics. The heat deposition in end-pumped fiber lasers changes the step-index fiber to graded-index, so the propagation parameters like V numbers, propagation constant and dispersion will be varied. In this paper, we consider a fiber laser pumped by a super-Gaussian profile [8] diode laser which is more realistic profile for high-power and multimode diode lasers with respect to top hat profile. After solving the heat conductive equation, the variation of such parameters for end-pumped Yb-doped fiber laser has been studied.

A narrow-line Erbium-doped fiber laser and its application for testing fiber Bragg gratings

We inspect the spectral features of a diode-pumped Erbium-doped fiber laser (EDFL) with a Fabry-Perot cavity composed of a wavelength-selective coupler in the form of fiber Bragg grating (FBG) and wavelength-insensitive Faraday rotator mirror (FRM). High accuracy for the spectral measurements is provided with the use of an optical heterodyne scheme where the EDFL output is mixed with radiation from a narrow-line semiconductor laser, allowing the detection of the EDFL spectra with a sub-pm resolution. The heterodyne scheme permits precise measurements of the EDFL line-width as a function of the cavity length and pump power. It is worth noticing a narrow-line (a few pm) operation of the EDFL with a short length (<3 m) cavity and low (<5) excess of pump power over the laser threshold. The spectral response of the EDFL to a slow sinusoidal modulation of a physical length of the FBG coupler is analyzed and it is shown that as high as ∼1-nm modulation of the EDFL optical spectrum is attainable at maximal modulation amplitudes. The narrow-line EDFL with a modulated generation wavelength is hereby demonstrated to be a tool for high-resolution measurements of reflection spectra of FBGs, which is to the best of our knowledge a novel application of the EDFL.

两微米瓦级掺铥短光纤激光器

High-power operation of diode-pumped fiber lasers at wavelength near 2 microns are demonstrated with short length of heavily Tm3+-doped silica glass fibers. With 7-cm long fiber, a laser at near 2 microns is obtained with the threshold of 135 mW, maximum output power of 1.09 W, and slope efficiency of 9.6% with respect to the launched power from a laser diode at 790 nm. The output stability of this fiber laser is within 5%. The dependence of the performance of fiber lasers on the operation temperature and cavity configuration parameters is also investigated.

Fractional Photothermolysis for Photoaging of Hands

Laser treatment for photoaging of the hands should ideally address pigmentary alteration as well as associated skin roughness and wrinkling. Fractional resurfacing has been previously shown to effectively treat facial rhytids and dyschromia. We examined the effect of fractional resurfacing for photoaging of the hands. Ten patients (skin phototypes II to IV) with hand photodamage were randomized to receive five treatments with a 1,550-nm diode-pumped erbium fiber laser (Fraxel SR, Reliant Technologies) laser on either the right or left hand. Treatments were performed at settings of 8 to 9 mJ/microscopic treatment zone and density of 2,500 microscopic treatment zones/cm2. Subjective assessments by the patients and investigator were performed for skin roughness, wrinkling, and pigmentation using a 5-point scale. Skin biopsies were taken at baseline and at 1 and 3 months. Patient subjective assessment and physician clinical assessment at 1 and 3 months revealed a mean 51% to 75% improvement in skin pigmentation and 25% to 50% improvement in skin roughness and wrinkling. Biopsies of the skin showed increased density of dermal collagen. Patients experienced transient erythema and edema and none had scarring or other adverse effects. This was a small study. Fractional resurfacing appears to be an effective and safe treatment modality for correcting both the pigmentary and the textural aspects of photoaging of the hand.

Directly diode-pumped holmium fiber lasers

Sensitizer-free holmium-doped silica and fluoride mid-infrared fiber lasers are pumped using a high-power diode laser operating at 1148 nm. A maximum output power of 162 mW at 2.86 microm was produced at a slope efficiency of 24% using Ho(3+), Pr(3+)-doped fluoride fiber. Using Ho(3+)-doped silica fiber, a maximum output power of 55 mW at 2.1 microm was generated at a slope efficiency of 27%, a value limited by the presence of pump excited state absorption.

Development of a high-pulse-energy Q-switched Tm-doped double-clad fluoride fiber laser and its application to the pumping of mid-IR lasers

A diode-pumped Q-switched Tm-doped double-clad fluoride fiber laser is reported providing up to 90 microJ pulse energy (160 ns, 100 kHz, i.e., 9 W of average power). The dependence of the fiber laser's repetition rate on pump power and modulator repetition rate was investigated. By amplification even higher pulse energies of 410 microJ could be generated. In a second stage of the setup the Q-switched fiber laser serves as a pump for a gain-switched tunable Cr2+:ZnSe laser. The pulse energies reported are to the author's knowledge the highest generated by Tm-doped fluoride fiber lasers or amplifiers today.

Efficient operation of diode-pumped single-frequency thulium-doped fiber lasers near 2 μm

Efficient operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber. At 1893 nm, the single-frequency fiber laser has a pump threshold of 30 mW, a slope efficiency of 35%, and maximum output power of 50 mW with respect to the launched power of single-mode pump diodes at 805 nm. To the best of our knowledge, this is the highest lasing efficiency achieved in single-frequency fiber lasers operating near 2 micro m. Frequency noise of the single-frequency fiber laser at 1893 nm has been characterized and compared with that of single-frequency fiber lasers at 1 and 1.55 micro m.

Locking of self-oscillation frequency by pump modulation in an erbium-doped fiber laser

Frequency locking of self-oscillations in a diode-pumped erbium-doped fiber laser by external modulation of the diode current is studied experimentally. The coexistence of locking and unlocking regimes is detected. The condition for onset of the bistability and dependences of the frequency detuning on the modulation frequency and amplitude are established. Transitions to torus-chaos are also demonstrated.

Continuous-wave and giant-pulse operations of a single-frequency erbium-doped fiber laser

We present a compact diode-pumped single-frequency single-polarization erbium-doped fiber laser with fiber Bragg gratings (FBGs) written in the active fiber itself. The single-polarization regime was obtained by applying uni-axial stress to one of the two FBGs forming the cavity. The laser is shown to operate in two regimes-quasi-continuous-wave regime with a few-percent of modulation in the output power and a giant-pulse regime accessible under sinusoidal pump modulation.