Silica Fiber Laser Research Articles

Efficient single-frequency Tm:YAG crystal-derived silica fiber laser at 1.7 µm.

A single-frequency distributed Bragg reflector (DBR) fiber laser operating at 1720 nm has been demonstrated for the first time using a Tm:YAG crystal-derived silica fiber (TCDSF), to the best of our knowledge. A single-frequency laser with an over 220 mW output power was achieved from a 1.5-cm-long TCDSF when being in-band pumped by a homemade 1610 nm fiber laser. The slope efficiency reached 25.30% for the absorbed pump power. The optical signal-to-noise ratio (OSNR) of the laser was ∼69.78 dB, and the laser linewidth was ∼84.5 kHz. Additionally, the measured relative intensity noise (RIN) remained at -130 dB/Hz at frequencies above 9 MHz. The experimental results indicate that the TCDSF is a promising gain medium for single-frequency lasers at 1.7 µm.

High-efficiency, single-frequency, polarized thulium-doped silica fiber lasers.

We report on single-frequency, linearly polarized, high-concentration thulium-doped silica fiber-distributed Bragg reflector lasers operating at wavelengths between 1908 and 2050 nm with high efficiencies up to 48% and high powers up to 1 W. Low relative power noise and frequency noise are demonstrated using a low-noise pump diode.

Visible silica fiber laser based on Dy:BaF2 nanoparticle doping

A silica fiber laser based on Dy3+-doped nanoparticles (NPs) and operating at a wavelength of ∼581.5 nm is reported. Specifically, Dy-doped BaF2 nanoparticles were synthesized, and suspension doped into an aluminosilicate preform fabricated using conventional MCVD methods. Though the precursor BaF2 reacts partially with the SiO2 host, a presumed barium rich environment and localized doping persists. Spectroscopic characterization included visible emission spectrum, fluorescence decay, and loss of spectrum measurements and, where applicable, comparisons are made to previously reported Dy3+-doped silica visible fiber lasers. To the best of the author’s knowledge, this is the first report on a dysprosium NP-doped silica fiber and visible fiber laser made using this approach. This work paves the way for the development of visible silica fiber lasers with engineered local environments surrounding the rare earth ions.

Simulation of solar-pumped multicore Nd3+-doped silica fiber lasers

Simulation of solar-pumped multicore Nd3+-doped silica fiber lasers

High-efficiency radiation-balanced Yb-doped silica fiber laser with 200-mW output.

The focus of this study was the development of a second generation of fiber lasers internally cooled by anti-Stokes fluorescence. The laser consisted of a length of a single-mode fiber spliced to fiber Bragg gratings to form the optical resonator. The fiber was single-moded at the pump (1040 nm) and signal (1064 nm) wavelengths. Its core was heavily doped with Yb, in the initial form of CaF2 nanoparticles, and co-doped with Al to reduce quenching and improve the cooling efficiency. After optimizing the fiber length (4.1 m) and output-coupler reflectivity (3.3%), the fiber laser exhibited a threshold of 160 mW, an optical efficiency of 56.8%, and a radiation-balanced output power (no net heat generation) of 192 mW. On all three metrics, this performance is significantly better than the only previously reported radiation-balanced fiber laser, which is even more meaningful given that the small size of the single-mode fiber core (7.8-µm diameter). At the maximum output power (∼2 W), the average fiber temperature was still barely above room temperature (428 mK). This work demonstrates that with anti-Stokes pumping, it is possible to induce significant gain and energy storage in a small-core Yb-doped fiber while keeping the fiber cool.

Amplification at 2.3-µm in 1.9-µm thulium-doped silica fiber laser

A high-power 1.9-µm Tm3+-doped silica fiber laser generates 7.3-dB of gain at 2.3 µm when cladding- pumped with 207 W of power at 793 nm. We attribute the 2.3-µm gain to the transition 3H4 → 3H5 of Tm3+.

Monolithic ultrashort-cavity DBR gain-switched thulium doped fiber laser made by high-precision femtosecond laser direct-writing

We demonstrate a novel monolithic ultrashort-cavity distributed Bragg reflector (DBR) gain-switched thulium doped silica fiber laser. Commercial heavily thulium doped non-polarization-maintaining silica fiber was selected as the gain medium. Monolithic linear laser resonator, which includes a pair of uniform fiber Bragg gratings (FBGs) with a space of 1.0-mm inbetween, was inscribed in the thulium fiber by femtosecond-laser point-by-point (PbP) writing method. The reflectivity of either FBG is close to 100 % and the effective cavity length is calculated to be 3.5 mm. Such an ultrashort-DBR-cavity fiber laser exhibited high Q factor and low cavity loss, allowing the efficient utilization of pump power within the millimeter-long cavity. Single-longitudinal, linearly polarized, gain-switched TDFL at 2003 nm, with a recorded shortest pulse duration of 4.3 ns, a repetition rate of 50 kHz, a maximum peak power of 500 W, and single pulse energy of 2.14 μJ, has been realized, benefitted from the ultrashort cavity length.

Monolithic 2-µm single-frequency linearly-polarized gain-switched distributed feedback fiber laser by femtosecond laser direct-writing.

We report a single-frequency, linearly polarized gain-switched, distributed feedback (DFB), 2-µm thulium doped silica fiber laser (TDFL), with an effective cavity length of 2.5 mm. The cavity is based on a heavily thulium doped non-polarization-maintaining silica fiber and composed of a π-phase-shifted fiber Bragg grating (FBG) with a total FBG length of 35 mm. The DFB FBG was written by femtosecond-laser point-by-point (PbP) method. In-band pumping scheme is chosen with a 1550 nm nanosecond pulsed erbium-doped silica fiber laser pump. Single-longitudinal, linearly polarized, gain-switched TDFL at 2002 nm, with a recorded shortest pulse duration of 4.7 ns, a repetition rate of 20 kHz, a maximum peak power of 170 W, and single pulse energy of 0.8 µJ, has been obtained, benefitting from the ultrashort DFB cavity made by the femtosecond laser direct-writing method.

Er-doped silica fiber laser made by powder-based additive manufacturing

The pursuit of advanced fiber laser technologies has driven research toward unconventional manufacturing techniques. In this work, we present an erbium-doped fiber laser made using powder-based additive manufacturing. An Er3+/Al3+ co-doped silica glass rod was printed using laser powder deposition and then used as the core material in a fiber preform. The fiber drawn from the preform exhibited the complete, desired functionality linked to Er3+ doping. To demonstrate this, a standing wave laser cavity was formed with the feedback attained from the cleaved ends of the manufactured fiber. The high quality of the fiber is showcased through a low background loss, single-mode operation, a 9.4% laser slope efficiency, and an output of 4.5 mW, limited by the available pump power. This proof-of-concept opens up promising areas for rapid fabrication and development of high-performance fibers and fiber lasers.

High ytterbium concentration Yb/Al/P/Ce co-doped silica fiber for 1-µm ultra-short cavity fiber laser application.

We demonstrate a high ytterbium concentration Yb/Al/P/Ce co-doped silica fiber by conventional modified chemical vapor deposition (MCVD) technology and solution doping process. The fiber has a Yb concentration of about 2.5 wt%, and the corresponding core absorption coefficient is measured to be ∼1400 dB/m at 976 nm. The gain coefficient was measured to be approximately 1.0 dB/cm. It is found that the Yb/Al/P/Ce co-doped silica shows a lower photodarkening-induced equilibrium loss of 52 dB/m at 633 nm than the Yb/Al/P co-doped silica fiber of 117 dB/m. Using the heavily Yb3+-doped silica fiber, a compact and robust ultrashort cavity single-frequency fiber laser was achieved with a maximum output power of 75 mW and a linewidth of 14 kHz. Furthermore, a compact passively mode-locked fiber laser (MLFL) with a repetition rate of 1.23 GHz was also proposed using our developed Yb-doped fiber. The laser properties of the proposed lasers were systematically investigated, demonstrating the superior performance of this fiber in terms of photodarkening resistance and ultrashort-cavity laser application. Furthermore, utilizing an all-fiber structure based on silica-based fiber offers the significant advantage of high stability and reliability.

Волоконные лазеры с солнечной накачкой без первичного концентратора.

We studied solar pumped fiber lasers without primary concentrator. A model of solar sidepumped Nd3+ doped silica fiber lasers was developed using photon tracing method. Theabsorbed power distribution, possible losses and the pumping efficiency are estimated using the model. We analyzed the estimated paramters and drawed conclutions which have many suggests for improved design of solar pumped fiber lasers. The absorption efficiency of a fiber solar laser without a primary concentrator or sun tracker was calculated to be 0.2% for a 190 m fiber. The output power of the fiber laser is 40 mW, and the conversion efficiency from sunlight to laser light is calculated to be 0.06%. The developed model allows one to estimate the overall efficiency, output power and absorption distribution of Nd3+ fiber lasers without focusing optics, enabling various investigative comparisons.

Monolithic silica fiber laser operating at 585 nm.

We report, to the best of our knowledge, the first monolithic silica fiber laser operating in the visible. The laser cavity is based on a dysprosium-doped aluminosilicate fiber bounded by a pair of fiber Bragg gratings operating at 585 nm. The yellow laser signal reaches a record output power of 147 mW. Although the pump irradiation causes photodarkening, significant reduction of the photoinduced absorption losses is demonstrated via a photobleaching process with visible light.

In vivo three- and four-photon fluorescence microscopy using a 1.8 µm femtosecond fiber laser system.

Multiphoton microscopy has enabled us to image cellular dynamics in vivo. However, the excitation wavelength for imaging with commercially available lasers is mostly limited between 0.65-1.04 µm. Here we develop a femtosecond fiber laser system that produces ∼150 fs pulses at 1.8 µm. Our system starts from an erbium-doped silica fiber laser, and its wavelength is converted to 1.8 µm using a Raman shift fiber. The 1.8 µm pulses are amplified with a two-stage Tm:ZBLAN fiber amplifier. The final pulse energy is ∼1 µJ, sufficient for in vivo imaging. We successfully observe TurboFP635-expressing cortical neurons at a depth of 0.7 mm from the brain surface by three-photon excitation and Clover-expressing astrocytes at a depth of 0.15 mm by four-photon excitation.

Ultrathin gold nanowires as broadband saturable absorbers for ultrashort pulsed lasers

Ultrathin gold nanowires (UGNWs) with a diameter of ⩽2 nm have attracted much attention because of their high aspect ratios, unusual physical properties and potential applications in nanoelectronics, sensors and photonics. Despite recent advances on UGNWs and the related devices, nonlinear optical properties of UGNWs and their application on photonic devices (e.g. ultrashort pulsed lasers) remain largely unexplored. Here we show that UGNWs can be used as broadband saturable absorbers (SAs) for constructing ultrashort pulsed lasers with an operating wavelength range from near-infrared to mid-infrared (MIR). UGNWs are prepared by using a silane-mediated approach, and then mixed with polyvinyl alcohol to form the UGNWs film. The UGNWs film not only show strong absorption from visible to MIR spectral region (over 25 μm), but also possess the nonlinear saturable absorption properties in the spectral region. As the UGNWs film SA is inserted into an erbium or thulium doped silica fiber laser cavity, stable passively mode-locked lasers at 1562.2 or 1970 nm with a pulse width of a few hundreds of femtoseconds is obtained, respectively. Especially, by inserting the UGNWs film SA into a holmium/praseodymium codoped fluoride fiber laser cavity, stable passively mode-locked laser at 2864 nm is achieved. Our results show that the UGNWs film are promising SAs for constructing broadband ultrashort pulsed lasers.

Effects of P co-doping on X-ray/450 nm LD induced photodarkening in Dy3+ doped silica glass and fiber laser

Effects of P-codoping on X-ray/450 nm LD induced photodarkening in Dy3+ doped silica glass and fiber were investigated to develop a visible fiber laser. P and Dy concentrations in Dy-P-doped silica glass were optimized to reduce Rayleigh scattering. It was found in optimized glass that X-ray-induced photodarkening can be well suppressed by P co-doping. 450 nm LD pumped laser oscillation was firstly observed in the fiber using optimized glass. The slope efficiency is 4.2% which is lower than those in Dy–Al-and Dy–Al–Ge-doped fibers previously reported. Contrary to the results of X-ray-induced PD, 450 nm LD-induced photodarkening easily occurred.

Radiation-induced color centers and their inhibition methods in Yb3+-doped silica fibers

Yb3+-doped silica fiber (YDF) lasers have important application prospects in space. However, YDFs face various types of harsh ionizing radiation (such as protons, electrons, and γ-rays) during space missions. Radiation-induced darkening (RD), primarily because of the generation of color centers at a microscopic scale, can seriously deteriorate the laser performance of the YDFs. In this review, the nature, formation mechanism, and suppression methods of color centers in YDFs are introduced.

Flexible chalcogenide glass large-core multimode fibers for hundred-watt-level mid-infrared 2-5 µm laser transmission

The rapidly-developed high-power mid-infrared 2-5 µm laser technology requires a compact, flexible low-loss glass fiber for power delivery or laser generation. With the broadest bandwidth of low-loss transmission window in mid-infrared region amongst all mid-infrared glass fibers, chalcogenide glass fiber is the best candidate covering the whole 2-5 µm range. Multi-hundred-watt high-power delivery for 5.4-µm CO laser was previously demonstrated in a multimode chalcogenide fiber with a 1-mm-diameter large core, at the cost of giving up one of the most desirable fiber advantages, the flexibility. Indeed, chalcogenide glass fibers with decent flexibility have never exhibited hundred-watt-level power transmitting capability in the 2-5 µm range. In this paper, we have experimentally demonstrated 100-watt-level power transmission in multimode As2S3 chalcogenide fibers, using a customized high-power 2-µm thulium doped silica fiber laser source. With effective forced cooling, the multimode As2S3 fiber with 200 µm core diameter can resist incident laser power of 120 W and deliver transmitted power of 63 W. Nano-sized scattering center related laser damage mechanism and the cylindrical heat transfer model have been proposed to explain the high-power damage process of chalcogenide glass fibers. The calculation is in good agreement with the experiments. It is promising to further enhance the transmitted power above 100 W in flexible chalcogenide glass large-core fibers.

Radiation‐induced darkening and its suppression methods in Yb3+‐doped silica fiber core glasses

AbstractYb3+‐doped silica fiber (YDF) laser has important applications in space. However, the darkening effect caused by space ionizing radiation (called RD effect), which is due to the generation of color centers at the microscopic scale, can significantly deteriorate the performance of the YDF laser. This review mainly includes three aspects. First, we briefly introduce space radiation environment and challenges that optical fibers encounter in space. Second, we review the nature and generation mechanism of color centers responsible for RD in YDFs. Finally, we systematically introduce five methods to inhibit RD and their inhibition mechanisms.

High-power and highly-efficient laser operation of Tm3+:Ho3+-codoped silica fiber lasers emitting at 2.1 μm and 2.2 μm

High-power and highly-efficient laser operation of Tm³⁺:Ho³⁺-codoped silica fiber lasers emitting at 2.1 μm and 2.2 μm

Diode pumped visible Dy3+-doped silica fiber laser: Ge-co-doping effects on lasing efficiency and photodarkening

We present the first demonstration of visible laser oscillation in the Dy3+-doped silica fiber pumped by a 451 nm InGaN laser diode. It was found that Ge-co-doping plays the following important roles of laser oscillation: (1) to reduce the Rayleigh scattering loss, (2) to suppress the X-ray-induced and pump-induced photodarkening (PD), and (3) to increase lasing slope efficiency. In a fiber with 0.46 wt% Dy, 1.8 wt% Ge, and 0.54 wt% Al, the slope efficiency is 22.0% at 582.5 nm, and the maximum output power is 18.4 mW.