Silica Fiber Laser Research Articles

Centimeter-scale Yb-free heavily Er-doped silica fiber laser.

The laser behavior of a centimeter-scale Er3+/Al3+ codoped silica fiber with core numerical aperture and core diameter of 0.15 and 8μm, respectively, is reported. The core glass was prepared by the sol-gel method combined with high-temperature sintering; it contained Er3+ ion concentration as high as 1.32×1020 ions/cm3 and an Al/Er mole ratio of 10. The high doping homogeneity of Er3+ ions in the fiber core was confirmed by an electron probe microanalyzer element scanning, long Er3+: I13/24 emission lifetime of 11.4ms, and low refractive index fluctuation of fiber core (±1×10-4). The signal gain of fibers with 4.6cm, 10cm, and 16cm lengths was tested in the 1500-1620nm range. A gain of 7dB is achieved at 1560nm in a 16-cm-long EDF under 230mW pump power. Aimed for CO2 sensor application, the laser behavior of Er/Al codoped fiber was tested at 1572nm. A slope efficiency of 12% and an output power of 15mW were achieved in a 10-cm-long fiber under 166mW absorbed pump power. The newly developed silica fiber is promising for use in high-repetition-rate lasers.

High Average Power Thulium-Doped Silica Fiber Lasers: Review of Systems and Concepts

Thulium-doped fiber lasers (TDFLs) have had the second highest growth in average output power next to ytterbium-doped fiber lasers. This has been enabled by access to high power, high brightness ∼790-nm pump diodes in conjunction with the cross-relaxation process that improves laser efficiency. While numerous high power TDFLs have been recently demonstrated, a 1-kW result from 2010 remains the highest output power system reported to date. This paper reviews these systems and the concepts behind high power TDFLs. The spectroscopic properties of Tm3+ -doped silica are first detailed, revealing complex processes and large variations among published measurements. Notable multi-100 W TDFLs are then summarized, with outputs ranging from 1908 to 2130 nm. Another route for power scaling is to in-band pump with another TDFL to enable >90% efficiencies. Both 790- and 1900-nm pumped TDFL architectures are theoretically modeled based on currently available systems. Hindered by high background losses and available pump sources, achieving >4 kW like ytterbium-fiber systems will be a substantial challenge.

高功率掺铥石英光纤激光器研究进展

高功率掺铥石英光纤激光器研究进展

Solid Tellurite Optical Fiber Based on Stack-and-Draw Method for Mid-Infrared Supercontinuum Generation

Broadband, high-power mid-infrared (mid-IR) sources are critical for many applications. Compared to alternatives such as fluorides and chalcogenides, tellurite fibers are more robust and can handle much higher power. Tellurite fibers also have high nonlinearity and a material zero dispersion close to 2 µm, making them ideal for nonlinear processes pumped by Tm-doped silica fiber lasers. In this work, we have demonstrated solid tellurite fibers fabricated by a stack-and-draw process and investigated their potential for broadband mid-IR supercontinuum generation. We have identified that fibers with low dispersion are beneficial and that low residual hydroxyl (OH) is critical for broadband mid-IR supercontinuum generation in tellurite fibers pumped at ~2 µm.

A 1030 nm single-frequency distributed Bragg reflector Yb-doped silica fiber laser

We demonstrate a single-frequency fiber distributed Bragg reflector (DBR) laser operating at 1030 nm by using a 1.1 cm long commercially available highly Yb-doped silica fiber. The DBR fiber laser has a threshold pump power of 5 mW, and the maximum output power is over 160 mW with a slope efficiency of 27% relative to the launched pump power. The linewidth of the laser at 1030 nm is 6 kHz. With the aid of only a 5 cm long amplifier stage, the output power is scaled up to 306 mW with a slope efficiency of 51.5%.

Impact of cerium and lanthanum on the photo-darkening and photo-bleaching mechanisms in thulium-doped fibre

Photo-darkening prevents developing of new applications of rare-earth doped silica fibre lasers or amplifiers operating at wavelengths shorter than 1μm or at any wavelength at high power. The photo-darkening is characterized by a decrease of the laser intensity during amplification. In this article, we are interested in Tm-doped fibres. This ion offers many potential optical transitions spanning from 0.45 to 1.9μm. Several interesting transitions can be excited via up-conversion, using one pump around 1μm. However, this scheme induces a particularly fast and intense photo-darkening, enough to prevent amplification in the short wavelengths region (0.45–0.9μm). To mitigate this effect, we co-dope the fibres with cerium or lanthanum ions. By characterizing the steady state values of photo-darkening and its characteristic times, we demonstrate the beneficial role of Ce and La on the bleaching mechanisms.

3 W narrow-linewidth ultra-short wavelength operation near 1707 nm in thulium-doped silica fiber laser with bidirectional pumping

We have developed an ultra-short wavelength operation of all-fiber Tm-doped laser system, in which the laser system was structured in a FBGs based linear cavity with FBG associated bidirectional pump mechanism at 1550 nm. The laser yielded 3.15 W of continuous-wave output at 1706.75 nm with a narrow-linewidth of ~50 pm. A high reflectivity FBG (HR-FBG) at 1550 nm was used to reflect the residual pump light and achieve the bidirectional pump mechanism. The maximum slope efficiency was improved from 23.2% without HR-FBG to 42.1% with HR-FBG at 1550 nm and the lowest pump threshold was reduced from 1.6 to 0.8 W accordingly. In the experiment, we have also investigated the dependencies of the slope efficiencies and pump threshold of the laser versus the length of active fiber and reflectivity of the output mirror (FBG) in detail. It is indisputable that the development of 1.7 μm silicate fiber lasers with Watt-level output power will open up a number of promising application windows.

1064 nm超短腔DBR单频掺镱硅酸盐光纤激光器

1064 nm超短腔DBR单频掺镱硅酸盐光纤激光器

0.5-GHz Repetition Rate Fundamentally Tm-Doped Mode-Locked Fiber Laser

We demonstrate a passively mode-locked Tm-doped silica fiber laser with 535-MHz fundamental repetition rate by employing a semiconductor saturable absorber mirror. With in-band pumping at 1590 nm, the stable mode-locked fiber laser produces up to 50 mW at an incident pump power of 558 mW. The laser operating at 1938 nm has a spectral bandwidth of 0.72 nm. After amplification, the laser pulse width is measured to be $\sim 7.9$ ps, and the time-bandwidth product is $\sim 0.46$ .

High-power ultralong-wavelength Tm-doped silica fiber laser cladding-pumped with a random distributed feedback fiber laser.

We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900–2000 nm.

High-peak-power single-oscillator actively Q-switched mode-locked Tm3+-doped fiber laser and its application for high-average output power mid-IR supercontinuum generation in a ZBLAN fiber.

A single-oscillator actively Q-switched mode-locked (QML) thulium-doped silica fiber laser is presented and used to pump a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber for mid-infrared (mid-IR) supercontinuum (SC) generation. The fiber laser provided high-peak-power levels directly from the oscillator delivering single mode-locked pulse energies up to 48 μJ, being 2-4 orders of magnitude higher than conventional continuous wave mode-locked lasers. By pumping a ZBLAN fiber specially designed for high-output-power SC generation, 7.8 W have been achieved in all spectral bands with a spectrum extending to 4.2 μm.

Single-frequency distributed Bragg reflector Nd doped silica fiber laser at 930 nm.

We report a single-frequency distributed Bragg reflector (DBR) fiber laser at 930 nm for the first time, to the best of our knowledge. A ∼2.5 cm long commercial highly neodymium-doped silica fiber was utilized as the gain medium to achieve ∼1.9 mW laser output. The single longitudinal mode operation of this laser was verified by a scanning Fabry-Perot interferometer. This fiber laser is suited for seeding high-power 930 nm narrow-linewidth laser amplifiers, which can be used to generate coherent single-frequency pure blue light through frequency doubling.

Heavily Ho^3+-doped lead silicate glass fiber for ~2 μm fiber lasers

A heavily Ho3+-doped lead silicate glass with low content of hydroxyls was prepared in this paper. Luminescent properties of this glass were characterized. Peak emission cross section reached 3.07 × 10−21 cm2 around 2055 nm and lifetime of Ho3+: 5I7 was fitted to be 1.31 ms. A single-cald fiber was prepared using this glass as the core. An all-fiber configuration was constructed. Under in-band core-pump of a silica fiber laser, a single-mode maximum 60 mW was realized in a 6 cm-long fiber, which shows high potential for single-frequency fiber lasers applications.

295 mW output, frequency-stabilized erbium silica fiber laser with a linewidth of 5 kHz and a RIN of -120 dB/Hz.

We demonstrate the frequency stabilization of a high output power, erbium silica fiber laser by utilizing a (13)C2H2 (acetylene) absorption line at 1538.8 nm and a H(13)C(14)N (hydrogen cyanide) absorption line at 1549.73 nm. We introduced a novel short ring cavity configuration and pump power feedback control to suppress the intensity noise of the laser output, which is caused by the relaxation oscillation of erbium ions. As a result, we succeeded in simultaneously obtaining a stable single-frequency oscillation with an output power of over 290 mW, a linewidth of 5 kHz, and a low relative intensity noise (RIN) of -120 dB/Hz. The frequency stabilities reached 2.8 × 10(-11) and 6.9 × 10(-11) for an integration time of 1 s with a (13)C2H2 and a H(13)C(14)N absorption line, respectively.

Air-Clad Holmium-Doped Silica Fiber Laser

We report the design, fabrication, and operation of an air-clad holmium-doped fiber laser that was manufactured by directly milling the rare-earth-doped preform. This silica fiber laser operates at 2.1 μm with a slope efficiency of 49.7%, and is in-band pumped with a 1.94-μm thulium fiber laser. To the best of our knowledge, this is the first demonstration of an air-clad holmium-doped fiber laser.

Interferometric technique for investigation of nonradiative transition kinetics in silica-fiber laser media.

A novel tool for investigation of nonradiative processes in active solid-state laser media is proposed. The technique is based on using an interferometer for population-kinetics detection by means of resonantly enhanced nonlinearity. The advantages of this method in comparison with traditional luminescence-kinetics techniques are verified on the example of decay time measurements for nonradiative 4I(11/2)→4I(13/2) transition in an Er3+-doped active optical fiber.

Single frequency, 5 ns, 200 μJ, 1553 nm fiber laser using silica based Er-doped fiber.

A 1553 nm Er-doped fiber master-oscillator-power-amplifier (MOPA) laser system providing pulses with a 6 kHz repetition rate, 5 ns duration, ~210 μJ energy, ~300 MHz linewidth, and with a near diffraction limited beam quality, was developed. A gain fiber as short as 0.7 m in length was utilized in order to relax the SBS effect. To the best of our knowledge, thus generated peak power of 40 kW is the highest one obtained from a single frequency Er-doped silica fiber laser. The pulse quality was verified by frequency conversion with a periodically poled lithium niobate nonlinear crystal (PPLN) for second harmonic generation. A pulse energy as high as ~100 μJ was achieved at 776.6 nm with a moderate incident energy of 133 μJ, indicating an energy conversion efficiency of 75%.

400 mW narrow-linewidth Tm-doped silica fiber laser output near 1750 nm with volume Bragg grating.

A type of Tm-doped silica fiber laser with narrow-linewidth and output wavelength near 1750 nm was firstly presented, by using a 1550 nm Er-doped fiber laser pump source and a volume Bragg grating (VBG). By means of a 15 cm Tm-doped fiber, a 400 mW continuous wave (cw) at ~1750 nm with FWHW of ~54 pm was generated, corresponding to an average slope efficiency up to 23.5% with respect to absorbed pump power. The influence of gain fiber length on the spectrum wavelength has been investigated in detail. All experimental results demonstrate that this fiber laser will be an effective and promising pump source for mid-IR laser output.

Actively mode-locked Tm(3+)-doped silica fiber laser with wavelength-tunable, high average output power.

A diode-pumped, actively mode-locked high-power thulium (Tm3+)-doped double-clad silica fiber laser is demonstrated, providing an average output power in mode-locked (continuous wave) operation of 53 W (72 W) with a slope efficiency of 34% (38%). Mode-locking in the 6th-harmonic order was obtained by an acousto-optic modulator driven at 66 MHz without dispersion compensation. The shortest measured output pulse width was 200 ps. Owing to a diffraction grating as cavity end mirror, the central wavelength could be tuned from 1.95 to 2.13 μm. The measured beam quality in mode-locked and continuous wave operation has been close to the diffraction limit.

Multiwavelength thulium-doped silica fiber laser incorporating an all-fiber phase modulator

A novel multiwavelength thulium-doped silica fiber laser incorporating an all-fiber phase modulator is first presented in 2μm band. In the laser cavity, a phase modulator with a modulation frequency is efficient and beneficial to overcome the mode competitions. A polarization maintaining fiber Sagnac loop mirror is used as the filter. Large number of lasing wavelengths can easily and conveniently obtained at a proper modulation frequency under room temperature. The fiber laser can achieve ten output channels within a 15dB bandwidth from 1982nm to 1998nm.