1.06 $\mu$m Picosecond Pulsed, Normal Dispersion Pumping for Generating Efficient Broadband Infrared Supercontinuum in Meter-Length Single-Mode Tellurite Holey Fiber With High Raman Gain Coefficient

Abstract

Abstract-We investigate efficient broadband infrared supercontinuum generation in meter-length single-mode smallcore tellurite holey fiber. The fiber is pumped by 1.06μ μ μ μm picosecond pulses in the normal dispersion region. The high Raman gain coefficient and the broad Raman gain bands of the tellurite glass are exploited to generate a cascade of Raman Stokes orders, which initiate in the highly normal dispersion region and quickly extend to longer wavelengths across the zero dispersion wavelength with increasing pump power. A broadband supercontinuum from 1.06μ μ μ μm to beyond 1.70μ μ μ μm is generated. The effects of the pump power and of the fiber length on the spectrum and on the power conversion efficiency from the pump to the supercontinuum are discussed. Power scaling indicates that using this viable normal dispersion pumping scheme, 9.5W average output power of infrared supercontinuum and more than 60% conversion efficiency can be obtained from a 1m-long tellurite fiber with a large-mode-area of 500μ μ μ μm 2 .

Generation of a compact high-power high-efficiency normal-dispersion pumping supercontinuum in silica photonic crystal fiber pumped with a 1064-nm picosecond pulse

“…Several reasons likely contribute to the high pump-to-SC conversion efficiency: 1) a short piece of PCF is used, and the propagation loss of light in the PCF is very low; 2) with the PCF post-processing techniques, the splice loss between the DCF and PCF is very low; 3) due to the relatively narrow continuum spectrum band, the quantum defect from the pump photons to the generated photons is low. [13] The SC source is tested for several minutes at ∼ 50-W output power level and no significant change about the output power and the output spectrum is observed. While, due to the dust and mist in the air, the polished output end of the PCF could suffer an optical damage after a long time running.…”

“…As for the high Raman gain coefficient, large Raman gain bandwidth and high nonlinear refractive index n 2 of the tellurite PCF, a cascade of Raman Stokes orders was initiated in the highly normal dispersion regime. [13] Then the continuum quickly extended to long wavelengths and a broadband SC from 1060 nm to beyond 1700 nm was generated. The whole SC generation process is under the normal dispersion pumping scheme and a continuum has not been formed at the short wavelength side of the pump.…”

“…The walk-off length L W , in this case, is calculated to be 3 m between 1064 nm and 1116 nm (L W = T 0 /|β P (λ ) − β S (λ )|, where T 0 is the duration of the pulse (14 ps) and |β P (λ ) − β S (λ )| is the separation between the pump and the Stokes wave. [13] ) The attenuation of the PCF at 1064 nm is 4.5 dB/km, and the effective fiber length L eff of 3-m-long PCF is 2.987 m (L eff = [1 − exp(−α P • L)]/α P , where α P represents the optical loss of the fiber at the pump wavelength and L is the fiber length. [18] ) Since the L eff of the PCF is comparable to the L W , the walk-off effect will have an influence on the SRS generation, especially for the PCF with a long length.…”

“…[11,12] Recently, broadband SC was efficiently generated in a meterlength air suspended core single mode tellurite PCF (with a ZDW of 1380 nm and a large mode area of 500 µm 2 ), which was pumped by a 1060-nm picosecond pulse in the deep normal dispersion region. [13] There are several advantages for the normal dispersion pumping scheme: firstly, the PCF with a larger mode area can be adapted to generate the SC, which can endure more pump power; secondly, it promises to achieve a high pump-to-SC conversion efficiency and high spectral intensity with this pumping scheme. [13] High power picosecond fiber lasers and SC generation in long silica PCFs pumped by the self-made pulse lasers were demonstrated in our previous work.…”

“…[13] There are several advantages for the normal dispersion pumping scheme: firstly, the PCF with a larger mode area can be adapted to generate the SC, which can endure more pump power; secondly, it promises to achieve a high pump-to-SC conversion efficiency and high spectral intensity with this pumping scheme. [13] High power picosecond fiber lasers and SC generation in long silica PCFs pumped by the self-made pulse lasers were demonstrated in our previous work. [14][15][16][17] The average output power and the pump-to-SC conversion efficiency of these SC sources were not so promising.…”