Hongxin Su

Wavelength tunable Yb3+-doped double-clad photonic crystal fiber laser

Wavelength tunable high power lasers are desired for many applications, such as spectroscopy, sensing and nonlinear optics, etc. A tunable Yb3+-doped photonic crystal fiber laser based on a blazed grating in Littrow configuration is demonstrated. The active fiber used in the experiment is a double-clad Yb3+-doped PCF which contains an Yb3+-doped core of 23 μm in diameter and a holy inner clad of 420 μm in diameter. The laser resonator is composed of a dichroic reflective mirror and a blazed grating which is set in Littrow configuration. To reduce reflection the fiber end near to the grating is polished into an angle of 8 degree. Wavelength tunable output with a range form 1035.425 nm to 1111.770nm is realized. The output power of the laser at different wavelengths is flatten within 0.8 dB. At the available maximum pump power of 12.11 W, the maximum output power of 3.45 W is obtained at 1064.085 nm, which corresponds to a slope efficiency of 35.9%. Degree of polarization of the output at different pump level are all more than 0.87.

Study on the output characteristics of a large-core Yb-doped double clad fiber laser

The output characteristics of a large-core double clad fiber (DCF) laser are experimentally investigated in this paper. The fiber laser is fabricated with 5m Yb-doped DCF that consists of a 30μm diameter core and a 400/340μm D-shape inner clad. The measured spectra show that the wavelength of laser is not stable at low pump levels, and the wavelength tends to be stabilized at 1074nm until the pump power is increased to a level far over the threshold. The maximum output power of 7.2W is obtained at an input pump of 11W with a FWHM of about 6nm. The slope efficiency and the total conversion efficiency are 84% and 65.5%, respectively.

All-fiber designed narrow line-width 1.55μm double cladding fiber lasers

To develop 1.55μm high power lasers with compactness, narrow spectral line-width and high wavelength stability suitable for practical applications, EY-DCFLs built in all-fiber configuration are investigated. The experimental setups are composed of Er3+/Yb3+ co-doped double-clad gain fiber, multimode 976nm pump laser diode, double-clad fiber Bragg gratings (FBGs) and (1+1)x1 side pump couplers. FBGs with different reflectivity are applied as output reflectors, and forward-pump scheme and backward-pump scheme are performed respectively. As the efficiency and the spectral stability are considered simultaneously, EY-DCFL with low reflective FBG mirror and in backward-pump manner is more desirable. In the optimized all-fiber EY-DCFL, the maximum output power with an optical-optical efficiency of more than 17% is up to 1.5 W, and the wavelength is defined at 1550.8nm with a line-width about 0.03nm.

Numerical simulation on output performance of continuous-wave Raman silicon lasers

To understand the physical process of SRS lasing in SOI waveguides and to optimize the performance of continuouswave Raman silicon lasers, in this paper numerical simulation on the output characteristics of continuous-wave Raman silicon lasers with different parameters is performed. Based on power propagation equations in SOI waveguides and boundary conditions, the output powers as functions of the launched pump power, the gain length, the reflectivity of the output end, and the effective mode area of the SOI waveguide are presented. It is shown that two-photon absorption (TPA) and free-carrier absorption (FCA) lead to a significant reduction to the output power of continuous-wave Raman silicon lasers, which is in good agreement with the experimental reports. Numerical analysis predicts that in the absence of TPA and FCA there are optimum values for the silicon waveguide length, the effective mode area and the output reflectivity, respectively.

Narrow linewidth, wavelength-stable Er/Yb co-doped fiber MOPA source operating at 1547.8 nm

In this paper, we demonstrate the output characteristics of a kind of all-fiber optical source based on Er3+/Yb3+ co-doped double-clad fiber (EY-DCF) in a master oscillator-power amplifier (MOPA) configuration. The amplifier is composed of a 10m long EYDCF, two isolators at both input and output terminals, and a 976nm pump diode connecting with the EYDCF via a side-pump fiber coupler. A DFB diode laser operating at 1547.8nm serves as the master oscillator. A maximum output power of 1.16W is obtained. The gain of the fiber amplifiers is up to 30.7dB. The wavelength centered at 1547.8nm with a spectral width no more than 0.02nm shows longtime stability.

Optimum design of DBR Er/Yb co-doped double cladding fiber laser

To optimize the performance of Er3+/Yb3+ co-doped double cladding fiber laser (EY-DCFL), the output characteristics of DBR EY-DCFLs with different parameters are investigated theoretically and experimentally. The output powers as functions of the launched pump power, the gain fiber length, as well as the reflectivity of the output mirror are presented by numerical simulation based on rate equations and power propagation equations. Experimental study on the output power, the spectral properties and the time-domain stability of DBR EY-DCFLs with different reflectivity is carried out. In the optimum condition, up to 2W output power at 1550.8nm is obtained with a slope-efficiency of 53.8% and a 3dB bandwidth of about 0.02nm.

Output characteristics of LMA Yb3+-doped photonic crystal fiber lasers

The output characteristics of fiber lasers built with large-mode-area(LMA) Yb3+-doped double-clad PCF are experimentally investigated. The gain fiber used in the experimental setup is a LMA Yb3+-doped double-clad PCF, which contains an Yb3+-doped core of 23μm in diameter and a holy inner clad of 420μm in diameter. In the forwardoutput configuration the maximum output is 3.43W and the slope efficiency is 34.6%. At the same pump power, the maximum output in the backward-output configuration is 3.63W and the slope efficiency is 38%. The spectra show that the fiber lasers in both forward-output and backward-output configurations produce multi-wavelength output in a range from 1067nm to 1076nm and unstable. Single wavelength output at 1067.5 nm with a FWHM of about 0.2nm is demonstrated by using a dual-end-output configuration, and a maximum output of 4.25W with a slope efficiency of 44.1% is obtained.

Investigation of stimulated Raman scattering in a phosphorus-doped silica fiber

In this paper the SRS characteristic of a phosphorus-doped fiber made for RFLs is experimentally investigated. At an averaged pump power of 0.5W we observe three spectral lines in the output spectrum, which correspond to the first order Stokes of silica at 1.12μm, the third order Stokes of silica or the first order Stokes of P2O5 at 1.24μm, and the fourth order Stokes of silica at 1.31μm, respectively. When the pump power is increased to the maximum value of 2W, there in the spectrum appears a continuum near 1.54μm with a FWHM of more than 50nm. The expected fifth Stokes of silica at 1.39μm and the second Stokes of P2O5 at 1.48μm are not observed. We demonstrate that the fiber loss in the region of 1-1.5μm plays an important role in the development of SRS in phosphorus-doped fibers.