Shenggui Fu

Switchable dual-wavelength ytterbium-doped fiber laser based on a few-mode fiber grating

The authors propose and demonstrate a simple switchable dual-wavelength Ytterbium-doped fiber laser based on a few-mode fiber grating. The laser can be designed to operate in stable dual-wavelength or wavelength-switching modes, due to the polarization hole burning enhanced by the few-mode fiber grating. The lasing lines may be controlled only by a polarization controller. Stable operation is achieved at room temperature when the wavelength separation is 0.9 nm.

Switchable multiwavelength ytterbium-doped double-clad fiber laser based on a multimode fiber grating

A simple switchable multiwavelength double-clad fiber laser using a multimode fiber Bragg grating (MMFG) as a wavelength selective component is demonstrated. The MMFG is fabricated directly in the active double-clad fiber, resulting in low splicing loss and compact configuration. By properly adjusting the polarization controller in the cavity, the double-clad fiber laser can stably operate at different multiwavelength states at room temperature. At lower pump levels, the laser can be switched between single- and dual-wavelength operations, while at higher pump levels the laser can switch between dual- and triple-wavelength operations. The slope efficiency of the system is 41% with the maximum output power of 6.2 W.

High-power broadband superfluorescent source with a Yb-doped double-cladding fiber

A high-power and broadband super-fluorescent source (SFS) based on an Yb-doped double-cladding fiber is described. The source is pumped at 976 nm from a laser diode by end-pumping system. The SFS generated a maximum 100 mW of broadband emission centered at 1066nm, with an about 40nm FWHM spectrum. The basic characteristics of the superfluorescent source, such as the output power and output linewidth, have been analyzed and studied.

Polarization characteristics of the large-mode-area fiber amplifier applied in coherent combination

Built on the maser oscillator power amplifier configuration including a single mode erbium-doped fiber laser used as the signal source and a large-mode-area Erbium/Ytterbium double-clad fiber used as the gain medium, the polarization states of the signal light and the amplified signal light are experimentally investigated. The results show that the polarization degree of the output of the amplifier is low without taking any polarization control measure; after inserting a polarizer in the loop of the signal source, the degree of polarization is improved evidently and the stability of the polarization state becomes better, whether for continuous wave operation or for mode-locked operation. The mode-locked operation had a little lower polarization degree and a better PSs stability than the continuous wave operation of the output of the amplifier. When introducing a polarizer in the loop of the signal, the instability of the polarization state of the output of amplifier is mainly caused by the polarization parameter azimuth. So, the combination use of a polarizer and a polarization controller is supposed to improve the polarization degree and the stability of the output of the amplifier, furthermore, polarization-maintaining gain fiber is recommended to be used to avoid the random perturbation of the environment. This work offers an important experimental basis for the control of the PS in the laser beam coherent combination.

A novel all-fiber self-organization coherent erbium-doped fiber laser

A novel all-fiber self-organization Michelson coherent Erbium-doped fiber laser (MCEDFL) has been proposed and demonstrated. The laser system is composed of two independent branch lasers. The two arms of the active interferometer are spliced to a 3dB 2×2 coupler. A fiber Bragg Grating (FBG) with 95% reflectivity is spliced to one port of the coupler. It acts as wavelength selective filter and common reflection mirror to make the two branch arms emit laser with the same wavelength, which can conform to the coherent constraint exactly. The high reflection mirror of each laser cavity is composed of a 3dB fiber loop mirror (FLM). The other output port of the coupler is spliced to an isolator that acts as the MCEDFLs output port. Any feedback from this port into the MCEDFL is prevented by the isolator. When each of the two lasers is pumped to 100mW independently, the output power is 12.1mW and 16.2mW respectively. By adjusting the polarization controller (PC), the two lasers attain coherent coupling, the output power is 34.5mW, which is more than two times the output power of any single laser. Furthermore, we bring forward and discuss a novel factor to denote the effect of coherent combination—coherent coupling factor. Herein the value of coherent factor is 1.12. The advantages of the coherent fiber, such as simple structure, high efficiency and single frequency etc, can make coherent coupling easier.

Efficient tunable multiwavelength Yb3+-doped double-clad fiber laser

We present a tunable multi-wavelength Yb3+-doped double-clad fiber laser based on a Fabry-Perot filter (FPF). By adjusting the FPF, the number of lasing wavelength and their spaces are controlled which is in agreement well with the numerical analysis. The laser can oscillate at different number of wavelengths from one to ten while the oscillation is quite stable. In ten-wavelength laser, the system allows us to extract more than 1.5 W with a slope efficiency of 67%.

Analysis of the guided modes in triangular photonic crystal fibers using a full-vectorial numerical method

Properties of the photonic bandgaps effect and guided modes in triangular photonic crystal fibers have been studied by means of a full-vectorial plane-wave expansion method. Photonic crystal fibers under consideration consist of a triangular array of microscopic holes forming a two-dimensional photonic crystal cladding and a defect as their core. The photonic band-structure for photonic crystal cladding structures and the field intensity distribution of defect mode with various air-filling fractions and defect size are calculated. Guidance mechanisms in photonic crystal fibers with different configuration are also investigated.

Synchronously pumped mode-locked Yb3+-doped fiber laser

A synchronously pumped mode-locked Yetterbium-doped Fiber Laser which has the advantages of simple design and broad applications is obtained when the pump semiconductor laser current is modulated sinusoidally at the appropriate frequency. Steady pulses were obtained on harmonic mode-locked status. At the repetition rate of 623kHz,the pulse width is about 50ns,the average output power is 2.34 mW.