The Experts below are selected from a list of 591 Experts worldwide ranked by ideXlab platform
Richard P. Mildren - One of the best experts on this subject based on the ideXlab platform.
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pump probe measurements of the Raman Gain Coefficient in crystals using multi longitudinal mode beams
IEEE Journal of Quantum Electronics, 2015Co-Authors: Alexander Sabella, David J Spence, Richard P. MildrenAbstract:The effect of multi-longitudinal-mode interference on pump–probe Raman Gain measurements is studied as the functions of laser linewidth and correlation between the pump and probe temporal structures. For Raman linewidths typical of crystals, correlations that develop between the pump and the probe increase the Raman amplification beyond the ideal single longitudinal mode case, leading to inflated Raman Gain Coefficient values. We show that the linewidth correction factors used previously are valid only for uncorrelated beams and small Gain factors. Taking into account these considerations, a Raman Gain Coefficient for a diamond of 3.80 ± 0.35 cm/GW is reported at a pump wavelength of 1.864 $\mu \text{m}$ (polarizations parallel to a $\langle 110\rangle $ crystal axis).
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deep ultraviolet diamond Raman laser
Optics Express, 2011Co-Authors: Eduardo Granados, David J Spence, Richard P. MildrenAbstract:We present a synchronously pumped diamond Raman laser operating at 275.7 nm pumped by the 4th harmonic of a mode locked Nd:YVO4 laser. The laser had a threshold pump pulse energy of 5.8 nJ and generated up to 0.96 nJ pulses at 10.3% conversion efficiency. The results agree well with a numerical model that includes two-photon absorption of the pump and Stokes beams and uses a Raman Gain Coefficient of diamond of 100 cm/GW. We also report on the observation of nanometer scale two-photon assisted etching of the diamond crystal surfaces.
Pierre Bourdon - One of the best experts on this subject based on the ideXlab platform.
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fourth order cascaded Raman shift in asse chalcogenide suspended core fiber pumped at 2 μm
Optics Letters, 2011Co-Authors: M Duhant, W Renard, G Canat, Thanh Nam Nguyen, F Smektala, Johann Troles, Quentin Coulombier, Perrine Toupin, Laurent Brilland, Pierre BourdonAbstract:Cascaded Raman wavelength shifting up to the fourth order ranging from 2092 to 2450 nm is demonstrated using a nanosecond pump at 1995 nm in a low-loss As38Se62 suspended-core microstructured fiber. These four Stokes shifts are obtained with a low peak power of 11 W, and only 3 W are required to obtain three shifts. The Raman Gain Coefficient for the fiber is estimated to (1.6±0.5)×10−11 m/W at 1995 nm. The positions and the amplitudes of the Raman peaks are well reproduced by the numerical simulations of the nonlinear propagation.
M Ibsen - One of the best experts on this subject based on the ideXlab platform.
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highly efficient Raman distributed feedback fibre lasers
Optics Express, 2012Co-Authors: Jindan Shi, Shaiful Alam, M IbsenAbstract:We demonstrate highly efficient Raman distributed feedback (DFB) fibre lasers for the first time with up to 1.6W of continuous wave (CW) output power. The DFB Bragg gratings are written directly into two types of commercially available passive germano-silica fibres. Two lasers of 30cm length are pumped with up to 15W of CW power at 1068nm. The threshold power is ~2W for a Raman-DFB (R-DFB) laser written in standard low-NA fibre, and only ~1W for a laser written in a high-NA fibre, both of which oscillate in a narrow linewidth of <0.01nm at ~1117nm and ~1109nm, respectively. The slope efficiencies are ~74% and ~93% with respect to absorbed pump power in the low-NA fibre and high-NA fibre respectively. Such high conversion efficiency suggests that very little energy is lost in the form of heat through inefficient energy transfer. Our results are supported by numerical simulations, and furthermore open up for the possibility of having narrow linewidth all-fibre laser sources in wavelength bands not traditionally covered by rare-earth doped silica fibres. Simulations also imply that this technology has the potential to produce even shorter R-DFB laser devices at the centimetre-level and with mW-level thresholds, if Bragg gratings formed in fibre materials with higher intrinsic Raman Gain Coefficient than silica are used. These materials include for example tellurite or chalcogenide glasses. Using glasses like these would also open up the possibility of having narrow linewidth fibre sources with DFB laser oscillating much further into the IR than what currently is possible with rare-earth doped silica glasses.
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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
Journal of Lightwave Technology, 2011Co-Authors: Jindan Shi, Xian Feng, Peter Horak, K K Chen, Peh Siong Teh, Shaiful Alam, Wei H Loh, D J Richardson, M IbsenAbstract:We investigate efficient broadband infrared supercontinuum generation in meter-length single-mode small-core tellurite holey fiber. The fiber is pumped by 1.06 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 1.06 μm to beyond 1.70 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, 9.5 W average output power of infrared supercontinuum and more than 60% conversion efficiency can be obtained from a 1 m long tellurite fiber with a large mode area of 500 μm2 .
M Duhant - One of the best experts on this subject based on the ideXlab platform.
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fourth order cascaded Raman shift in asse chalcogenide suspended core fiber pumped at 2 μm
Optics Letters, 2011Co-Authors: M Duhant, W Renard, G Canat, Thanh Nam Nguyen, F Smektala, Johann Troles, Quentin Coulombier, Perrine Toupin, Laurent Brilland, Pierre BourdonAbstract:Cascaded Raman wavelength shifting up to the fourth order ranging from 2092 to 2450 nm is demonstrated using a nanosecond pump at 1995 nm in a low-loss As38Se62 suspended-core microstructured fiber. These four Stokes shifts are obtained with a low peak power of 11 W, and only 3 W are required to obtain three shifts. The Raman Gain Coefficient for the fiber is estimated to (1.6±0.5)×10−11 m/W at 1995 nm. The positions and the amplitudes of the Raman peaks are well reproduced by the numerical simulations of the nonlinear propagation.
V G Savitski - One of the best experts on this subject based on the ideXlab platform.
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Absorption Coefficient and Raman Gain in CVD diamond as functions of pump wavelength: Towards efficient diamond Raman lasers
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE IQEC, 2013Co-Authors: V G Savitski, Sean Reilly, Walter Lubeigt, Alan J. KempAbstract:The design of diamond Raman lasers is contingent upon the wavelength dependence of the absorption Coefficient and the Raman Gain Coefficient in chemical vapour deposition (CVD) grown diamond. Optical absorption in CVD diamond results mainly from the presence of substitutional nitrogen. The absorption Coefficient increases at shorter wavelengths and can be significant for diamonds with substitutional nitrogen concentrations of the order of a few hundred parts per billion (ppb). This absorption should be taken into account during measurements of the Raman Gain. The dependence of the absorption and Raman Gain Coefficients on the pump wavelength will determine the useful spectral range for diamond Raman lasers.
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steady state Raman Gain in diamond as a function of pump wavelength
IEEE Journal of Quantum Electronics, 2013Co-Authors: V G Savitski, Sean Reilly, Alan J. KempAbstract:The variation in the Raman Gain Coefficient in single-crystal diamond for pump wavelengths between 355 and 1450 nm is measured. Two techniques are used: a pump-probe approach giving an absolute measurement and a stimulated Raman oscillation threshold technique giving a relative measurement. Both approaches indicate that the Raman Gain Coefficient is a linear function of pump wavenumber. With the pump polarized along a ; direction in the crystal, the Raman Gain Coefficient measured by the pump-probe technique is found to vary from 7.6 ± 0.8 for a pump wavelength of 1280 nm to 78 ± 8 cm/GW for a pump wavelength of 355 nm. With the established dependence of the Raman Gain Coefficient on the pump wavelength, the Raman Gain Coefficient can be estimated at any pump wavelength within the spectral range from 355 up to 1450 nm.
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characterization of single crystal synthetic diamond for multi watt continuous wave Raman lasers
IEEE Journal of Quantum Electronics, 2012Co-Authors: V G Savitski, M D Dawso, D. Urns, Ia Friel, Jennifer E. Hastie, A J KempAbstract:A continuous-wave diamond Raman laser is demonstrated with an output power of 5.1 W at 1217 nm. This Raman laser is intracavity pumped by a side-pumped Nd:YLF rod laser: a 43-fold brightness enhancement between the Nd:YLF and diamond Raman lasers is observed, with the M2 beam propagation factor of the diamond Raman laser measured to be <; 1.2. Although higher output powers are demonstrated in a similar configuration using KGd(WO4)2 (KGW) as the Raman laser material (6.1 W), the brightness enhancement is much lower (2.5 fold) due to the poorer beam quality of the KGW Raman laser (M2 <; 6). The Raman Gain Coefficient of single-crystal synthetic diamond at a pump wavelength of 1064-nm is also measured: a maximum value of 21±2 cm/GW is returned compared to 5.7±0.5 cm/GW for KGW at the same wavelength.
