Intracavity frequency doubling of Yb-doped fiber laser with 540–550 nm tuning

The intracavity doubling of a tunable Yb-doped fiber laser is studied. The phase effects are observed, analyzed and compensated. A smooth wavelength dependence of the second harmonic is obtained in the wavelength interval 540–550 nm. The second-harmonic output is greater than 300 mW at an LD pump power of 18 W.     

Multi-coupler side-pumped Yb-doped double-clad fiber laser

The side-coupler of angle polished method, using angle-polished multimode fiber and optical adhesive, is used to efficiently pump an Yb-doped double-clad fiber laser. The maximum coupling efficiency of 78.6% is achieved by the side-coupler for a multimode fiber with a circular core of 200μm and a double-clad fiber with a 350/400μm D-shaped inner cladding. While laser diodes (LDs) with three side-couplers are simultaneously used as pump sources, maximum output power of 1.38 W and slope efficiency of 48.9% are demonstrated in the fiber laser system.     

First diode-pumped Yb-doped solid-state laser continuously tunable between 1000 and 1010 nm

We demonstrate that the ytterbium-doped medium Yb:YSO can provide laser oscillation in the 1000–1010 nm wavelength range under diode pumping around 980 nm. Ytterbium-doped Y₂SiO₅ crystal has been chosen for its high emission cross section around 1 m combined with a strong absorption line at 978 nm. We have developed an original pumping architecture that permits us to overcome problems due to the small difference between pump and laser wavelengths. In this way, laser emission continuously tunable in the 1000–1010 nm wavelength range has been obtained with more than 100 mW of output power. This kind of laser is the first step toward a metrological source around 500 nm stabilized on an I₂ absorption line. Furthermore, 100 mW of laser light has been obtained at 998.5 nm, leading to a remarkably low quantum defect of 2.1%. PACS 42.55.Xi; 42.60.Pk; 42.72.Ai     

Random fiber laser operating at 1,115 nm

We experimentally demonstrate a random fiber laser operating at 1,115 nm using a LD-pumped Yb-doped fiber laser as the pump source. We achieve about 270 mW lasing output in a 50 km standard communication optical fiber with slope efficiency more than 28 %. A new wavelength is provided for the application of random distributed feedback fiber lasers as light sources.     

Multiwavelength L-band fiber laser with bismuth-oxide EDF and photonic crystal fiber

A multiwavelength laser comb using a bismuth-based erbium-doped fiber and 50 m photonic crystal fiber is demonstrated in a ring cavity configuration. The fiber laser is solely pumped by a single 1455 nm Raman pump laser to exploit its higher power delivery compared to that of a single-mode laser diode pump. At 264 mW Raman pump power and 1 mW Brillouin pump power, 38 output channels in the L-band have been realized with an optical signal-to-noise ratio above 15 dB and a Stokes line spacing of 0.08 nm. The laser exhibits a tuning range of 12 nm and produces stable Stokes lines across the tuning range between Brillouin pump wavelengths of 1603 nm and 1615 nm.     

High power single-mode large-mode-area photonic crystal fiber laser with improved Fabry-Perot cavity

An Yb3 -doped double-clad large-mode-area photonic crystal fiber (LMA PCF) laser with 103-W single-mode continuous-wave output power is demonstrated using an improved Fabry-Perot (F-P) configuration. The slope efficiency of 83.2% and good beam quality (M2 = 1.2±0.1) are achieved without any thermo-optical problems, dichroic mirror surface damage, and drop of the slope efficiency in this system.     

Yb-doped superfluorescent fiber source with cascaded broad fiber Bragg gratings

In this paper, the Yb-doped superfluorescent fiber source (SFS) with cascaded broad fiber Bragg gratings (FBGs) are reported. The spectral properties of this SFS with cascaded broad FBGs are described and compared with that without cascaded broad FBGs. The experimental results have shown that cascaded broad FBGs can increase the output of some special wave bands.     

Lasing characteristics of strongly pumped Yb-doped photonic crystal fiber laser

A strongly pumped Yb-doped large-mode-area photonic crystal fiber(LMA-PCF)laser is analyzed.The lasing characteristics of an improved Fabry-Perot(F-P)cavity fiber laser using LMA-PCF are studied theoretically based on a rate equation model and the exact numerical solution of the rate equations is in excellent agreement with the experimental result.     

Theoretical and experimental study on rare-eath element-doped silicon single-mode fiber laser with two different structures of resonators

Abstract: Laser resonator is very important in the study and fabrication of lasers. The work conditions and work parameters of rare-earth element-doped optical fiber lasers with two different structures of laser resonators, i. e., the fiber ring resonator and Fabry-Perot resonator are studied. The fineness, laser resonant conditions, laser oscillation conditions and threshold inversion of these two different cavity are deduced. A series of experiments are also given. The result is very valuable to evaluate the output of optical fiber laser and can be a foundation of device fabrication. The Nd~(3 )-doped silica single-mode fiber laser pumped by Ar~ laser with a low threshold of 1.02 mW and a maximum output of more than 1 mW are presented in this paper.     

Optimization of linear cavity design of Yb-doped double-clad fiber laser

The output characteristics of a linear cavity Yb-doped double-clad fiber (DCF) laser, including the effects of fiber length, fiber loss, and output mirror reflectivity on laser output power and threshold pump power have been studied theoretically and experimentally. In this paper, the linear cavity of double-clad fiber laser (DCFL) was composed of a pair of fiber Bragg gratings, while the facet of fiber was anti-reflection (AR) coated at 1070nm to erase the Fresnel reflection. Analysis showed that the laser output increases as     

Erbium-doped CW and Q-switched fiber ring laser with fiber grating Michelson interferometer

The band-pass characteristic of fiber grating Michelson interferometer is analyzed, which acts as bothband-pass filter and Q-switch. An erbium-doped fiber ring laser based on fiber grating Michelsoninterferometer is implemented for producing single longitudinal mode CW operation with 5 MHz spectrallinewidth and up to 6 mW output power. In Q-switched operation, stable fiber laser output pulses withrepetition rate of 800 Hz, pulse width of 0.6 μs, average power of 1.8 mW and peak power of 3.4 W aredemonstrated. The peak power and average power of the Q-switched pulses are varied with the repetitionrate.     

Pulsed solid-state laser system with fiber phase conjugation and 315 W average output power

Solid-state laser sources with high average output power and high beam quality are required for numerous applications in industry and science. To improve the beam quality, stimulated Brillouin scattering (SBS) mirrors based on optical phase conjugation are used to compensate for phase distortions in master oscillator power amplifier (MOPA) systems. SBS phase conjugation in commercially available silica optical fibers facilitates the construction of high-power solid-state laser systems with high beam quality. Here we present a flash lamp-pumped, passively Q-switched Nd:YAP system which delivers an average output power of 315 W with M²=2.6 at a wavelength of 1.08 μm. Received: 11 July 2001 / Revised version: 28 September 2001 / Published online: 23 November 2001     

Design of segmented cladding fiber for femtosecond laser pulse delivery at 1550 and 1064 nm wavelengths

Segmented cladding fiber (SCF) is capable of single mode operation over an extended range of wavelengths while maintaining large mode area. In this paper we report the design of an SCF with mode area as large as 1,825  $\upmu \hbox {m}^{2}$ , suitable for delivery of high peak power femtosecond laser pulses at 1550 and 1064 nm wavelengths. An SCF with such a large-mode area is a few-moded fiber and its design requires careful choice of design parameters to have robustness against mode-coupling effects and bend loss. In this paper we address these issues and report a design of an SCF showing near distortion-free propagation of 100-fs, 53-kW peak power pulses at 1550-nm wavelength with 1,825- $\upmu \hbox {m}^{2}$ mode area through fundamental mode. The same fiber can also deliver 250-fs, 15-kW peak power pulses at 1064-nm wavelength with 1,793- $\upmu \hbox {m}^{2}$ mode area. The fiber has been analyzed by using the radial effective-index method in conjunction with transfer matrix method and the pulse propagation has been studied by solving the nonlinear Schroedinger equation by split-step Fourier method. Such a fiber would find applications in multiphoton microscopy and in biomedical engineering.     

Wavelength-tunable erbium-doped fiber laser with FBG and HiBi fiber loop mirror as reflectors

In this paper, a novel structure erbium-doped fiber laser with a linear cavity is demonstrated. The wavelength selective devices are a fiber Bragg grating (FBG) and a high birefringence (HiBi) fiber loop mirror. From 1543.8 to 1555.2 nm, 15 lasering wavelengths with side mode suppresion ratio (SMSR) > 54 dB and approximately 0.8-nm spacing have been obtained by using the comb-like reflection spectrum of fiber loop mirror and the intensity reaches about 2.5 dBm on an average. The reflectivity at different wavelengths can be tuned with different settings of polarization controller and the relative laser intensity can be controlled over a dynamic range of 13.5 dB.     

A 110-W fiber laser with homemade double-clad fiber

A high-power ytterbium-doped fiber laser (YDFL) with homemade double-clad fiber (DCF) is introduced in this letter. The geometric parameter and laser characteristics of the fiber have been studied. With oneend-pumping scheme, pumped by a high-power laser diode with launching power of 280 W, a maximum continuous wave (CW) output of 110 W is obtained with an optical-to-optical efficiency of 40%.     

Hybrid-type passively and actively modelocked fiber laser with a DI-NOLM

We present a 10-GHz hybrid actively and passively mode-locked fiber ring laser with a dispersion im-balanced nonlinear loop mirror (DI-NOLM), whose nonlinear switching characteristic can make the laser operate at additive pulse modelocking (APM) mode or additive pulse limiting (APL) mode. When the laser operated at APM, 5.45 ps of transform-limited pulse series were obtained. When the laser was biased at APL region, supermode noise was suppressed and the laser output was more stable.     

Design and fabrication of Gires�CTournois interferometers for?Yb-doped photonic crystal fiber laser system

A Gires?CTournois interferometer (GTI) with large dispersion compensation was designed and fabricated according to the requirement of the Yb-doped photonic crystal fiber laser system. The designed GTI can provide an average group delay dispersion (GDD) of ?1500 fs² and a high reflectance (>99.7%) from 1030 to 1050 nm. The Ion-assisted Deposition (IAD) technique was utilized to manufacture the mirror. Good agreement between the measured and designed results both for reflectance and GDD was achieved. The reflectance during 1030?C1050 nm was above 99.5% and the GDD ripple was less than ±300 fs². The GTI was used both in the intracavity dispersion compensation and extracavity pulse compression for the Yb-doped photonic crystal fiber laser system. A mode-locked soliton pulse with a 506-fs duration was recorded. An extracavity pulse compression test showed that the GTI had identical pulse compression capability as the conventional grating pairs while the energy loss was obviously reduced. Our results demonstrated that the HDM, which was able to provide quite a large amount of negative dispersion (???8×10⁴ fs²), could be an ideal alternative to replace the dispersive compensating grating pairs for the dispersion compensation of the Yb-doped photonic crystal fiber laser system.     

High-efficiency eye-safe intracavity Raman laser at 1531 nm with SrWO4 crystal

A high-efficiency diode-end-pumped Q-switched eye-safe linearly-polarized intracavity Raman laser at 1531 nm is demonstrated, with Nd:YVO₄ as the laser medium and SrWO₄ as the Raman crystal. The highest average power of 1.93 W is achieved, with an incident pump of 15.6 W and a repetition rate of 35 kHz. The narrowest pulse duration of 4.9 ns and the highest peak power of 32.2 kW are obtained at a repetition rate of 5 kHz.     

Tunable diode laser spectroscopy of benzene near 1684 nm with a low-temperature VCSEL

We describe the application of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) with extended tuning range to the detection of benzene vapor at atmospheric pressure. A benzene absorption feature centered at 1684.24 nm was accessed by reducing the heat sink temperature of a VCSEL designed for room-temperature operation to −55°C. This allowed us to increase the injection current and thus to extend a single-scan tuning interval up to 46.4 cm⁻¹ or 13.2 nm around a central wavelength of 1687.4 nm. Five absorption lines of methane in the 5903–5950 cm⁻¹ range could be acquired within single laser scans at a repetition rate of 500 Hz. A benzene absorption feature between 5926 and 5948 cm⁻¹ was recorded for concentration measurements at atmospheric pressure using a single-pass 1.2 m absorption cell. A 50 ppmv mixture of CH₄ in N₂ was introduced into the cell along with benzene vapor to calibrate benzene concentration measurements. Benzene mixing ratios down to ∼90 ppmv were measured using a direct absorption technique. The minimum detectable absorbance and detection limit of benzene were estimated to be ∼10⁻⁴ and 30 ppmv, respectively. Using the wavelength modulation technique, we measured a second harmonic sensor response to benzene vapor absorption in air at atmospheric pressure as a function of modulation index. We conclude that a low-temperature monolithic VCSEL operating near 1684 nm can be employed in compact benzene sensors with a detection limit in the sub-ppm range.