The Experts below are selected from a list of 8145 Experts worldwide ranked by ideXlab platform
Jing Zhang - One of the best experts on this subject based on the ideXlab platform.
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experimental observation of a topological band gap opening in ultracold fermi gases with two dimensional spin orbit coupling
Physical Review Letters, 2016Co-Authors: Zengming Meng, Lianghui Huang, Peng Peng, Liangchao Chen, Chuanwei Zhang, Pengjun Wang, Jing ZhangAbstract:The topological band gap in a Fermi gas is controlled by tuning the polarization of Raman Lasers that create a perpendicular Zeeman field, leading to a band gap opening.
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experimental observation of a topological band gap opening in ultracold fermi gases with two dimensional spin orbit coupling
Physical Review Letters, 2016Co-Authors: Zengming Meng, Lianghui Huang, Peng Peng, Liangchao Chen, Chuanwei Zhang, Pengjun Wang, Jing ZhangAbstract:The recent experimental realization of synthetic spin-orbit coupling (SOC) opens a new avenue for exploring novel quantum states with ultracold atoms. However, in experiments for generating two-dimensional SOC (e.g., Rashba type), a perpendicular Zeeman field, which opens a band gap at the Dirac point and induces many topological phenomena, is still lacking. Here, we theoretically propose and experimentally realize a simple scheme for generating two-dimensional SOC and a perpendicular Zeeman field simultaneously in ultracold Fermi gases by tuning the polarization of three Raman Lasers that couple three hyperfine ground states of atoms. The resulting band gap opening at the Dirac point is probed using spin injection radio-frequency spectroscopy. Our observation may pave the way for exploring topological transport and topological superfluids with exotic Majorana and Weyl fermion excitations in ultracold atoms.
David J Spence - One of the best experts on this subject based on the ideXlab platform.
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spectral and polarization effects in cascaded narrow linewidth diamond Raman Lasers
Laser Congress 2020 (ASSL LAC) (2020) paper ATu2A.5, 2020Co-Authors: E Granados, Richard P Mildren, Daniel T Echarri, K Chrysalidis, Valentin Fedosseev, Vaila A Leask, B A Marsh, S G Wilkins, S M Olaizola, David J SpenceAbstract:We study theoretically and experimentally the spectral and polarization effects occurring when cascading stimulated Raman scattering processes in diamond. We demonstrate an efficient, few-GHz linewidth, broadly tunable, multi-Stokes comb for spectroscopic applications.
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high power continuous wave Raman frequency conversion from 1 06 µm to 1 49 µm in diamond
Optics Express, 2017Co-Authors: Robert J Williams, David J Spence, Oliver Lux, Richard P MildrenAbstract:We report continuous-wave beam conversion from 1.06 to 1.49 µm in a diamond Raman laser operating on the second Stokes shift. High power (114 W) and high conversion efficiency (44%) is achieved using a single cavity that is highly resonant at the first Stokes wavelength but has high output coupling at the second Stokes wavelength (89%). An analytical model was developed for external-cavity Raman Lasers operating in steady-state, revealing that optimization of second Stokes output is markedly different to first Stokes and that there is a direct and proportional relationship between the second Stokes output coupling and the pump depletion in the diamond, which we have confirmed by experiment. This technology shows promise for power scaling beyond the capabilities of current fiber Lasers operating in the applications-rich 1.5–1.6 µm wavelength range.
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spectral effects of stimulated Raman scattering in crystals
Progress in Quantum Electronics, 2017Co-Authors: David J SpenceAbstract:Abstract This paper will review the coupling by stimulated Raman scattering between two laser fields and its dependence on the spectral properties of those fields. We describe the coupling in terms of an effective Raman gain that depends on the fields’ linewidths, the material dispersion, and specific experimental conditions. The aim is to provide an intuitive understanding of this behaviour, by presenting analytic and numerical results in both the time- and frequency-domains. We review some recent experimental results using crystalline Raman materials, to highlight why spectral effects must be taken into consideration to push crystalline Raman Lasers to new extremes of performance.
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modelling and optimization of continuous wave external cavity Raman Lasers
Optics Express, 2015Co-Authors: Ondrej Kitzler, David J Spence, Aaron Mckay, Richard P MildrenAbstract:We report an analytical model describing power and efficiency of a 23 W quasi-continuous-wave diamond Raman laser. The model guides the optimization of the first Stokes output power as a function of resonator and crystal parameters. We show that, in the limit of a weak thermal lens, efficient operation requires strong focussing, low output coupling and low-absorption crystals. Efficient damage-free operation at higher pump powers is predicted to benefit greatly from increased optimum output couplings that act to limit the intracavity Stokes field.
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spatial and spectral effects in continuous wave intracavity Raman Lasers
IEEE Journal of Selected Topics in Quantum Electronics, 2015Co-Authors: David J SpenceAbstract:We develop an analytic model to explore spatial and spectral effects in intracavity Raman Lasers. The effects of deterioration of the spatial and spectral properties of the fundamental and Stokes fields on the laser performance are derived. We quantify how the fundamental field strength can be used to diagnose the behavior of the system, and apply this tool to key prior experimental results.
Helen M Pask - One of the best experts on this subject based on the ideXlab platform.
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spectral broadening in continuous wave intracavity Raman Lasers
Optics Express, 2014Co-Authors: Gerald M Bonner, A J Kemp, David J Spence, Jipeng Lin, Jiyang Wang, Huaijin Zhang, Helen M PaskAbstract:Spectral broadening of the fundamental field in intracavity Raman Lasers is investigated. The mechanism for the spectral broadening is discussed and the effect is compared in two Lasers using Raman crystals with different Raman linewidths. The impact of the spectral broadening on the effective Raman gain is analyzed, and the use of etalons to limit the fundamental spectral width is explored. It was found that an improvement in output power could be obtained by using etalons to limit the fundamental spectrum to a single narrow peak.
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control of cascading in multiple order Raman Lasers
Optics Letters, 2012Co-Authors: Andrew J Lee, Helen M Pask, David J SpenceAbstract:In this work we explore a method for controlling Raman cascade within an intracavity Raman laser, with a view to maximizing output power at desired visible wavelengths. Sum-frequency generation is used to suppress unwanted Stokes orders, and prevent their build up. Using this method to control the Raman cascade, we demonstrate increases in output power of 40% at 532 nm, 42% at 559 nm, and 67% at 586 nm.
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cascaded self Raman Lasers based on 382 cm 1 shift in nd gdvo4
Optics Express, 2012Co-Authors: Jipeng Lin, Helen M PaskAbstract:We report quasi-continuous-wave, cascaded Nd:GdVO4 self-Raman Lasers based on a secondary Raman transition at 382 cm−1 for which the Raman gain was estimated to be 0.7cm/GW. Laser output was obtained in the near-infrared at 1108 nm, 1156 nm and 1227 nm. By incorporating intracavity sum-frequency generation (SFG) or second-harmonic generation (SHG), high power output at four discrete visible wavelengths could be selected, specifically 3.4 W at 542 nm, 2.8 W at 554 nm, 1.4 W at 566 nm and 0.8 W at 577 nm, with corresponding diode-to-visible optical conversion efficiencies of 11.7%, 9.7%, 4.8% and 2.7% respectively.
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wavelength versatile visible and uv sources based on crystalline Raman Lasers
Progress in Quantum Electronics, 2008Co-Authors: Helen M Pask, David J Spence, Peter Dekker, Richard P Mildren, James A PiperAbstract:Abstract By combining stimulated Raman scattering and sum-frequency generation within a single laser system, indeed often within a single resonator, it is possible to achieve frequency conversion over a wide range of output wavelengths, that are useful for a number of applications. This paper reviews the concepts, principles of operation and performance characteristics of visible and ultraviolet (UV) laser systems based on these two nonlinear processes. The systems we review include fixed-wavelength operation in the yellow–orange spectral region (pulsed and continuous wave—CW), discretely tunable pulsed sources operating across the green–red spectral region and discretely tunable UV sources spanning the entire UV-B region.
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crystalline Raman Lasers
IEEE Journal of Selected Topics in Quantum Electronics, 2007Co-Authors: James A Piper, Helen M PaskAbstract:In this paper, we review the developments of crystalline Raman Lasers over the past five years. Average powers exceeding 5 W and pulse energies above 1 J in the near infrared have been demonstrated for larger scale devices. There has been a rapid development of all-solid-state sources based on the standard diode-pumped Lasers, especially intracavity crystalline Raman Lasers, which offer wavelength versatility at high conversion efficiencies (overall diode Stokes optical conversion efficiencies up to 17%) in the near infrared, including the 1.5- mum eye-safe band. Passively Q-switched intracavity Raman Lasers based on self-Raman laser materials offer many advantages for miniaturization of short-pulse (1 ns) sources. Intracavity frequency-doubled crystalline Raman Lasers have also emerged as practical and versatile sources in the yellow orange region at 1-W power levels with diode-visible efficiencies near 10%. Recent developments of all-solid-state continuous-wave (CW) intracavity crystalline Raman Lasers offer many possibilities for the future: intracavity frequency doubling has already resulted in the demonstration of CW visible sources with powers approaching 1 W at 5% diode-visible efficiency.
A J Kemp - One of the best experts on this subject based on the ideXlab platform.
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spectral broadening in continuous wave intracavity Raman Lasers
Optics Express, 2014Co-Authors: Gerald M Bonner, A J Kemp, David J Spence, Jipeng Lin, Jiyang Wang, Huaijin Zhang, Helen M PaskAbstract:Spectral broadening of the fundamental field in intracavity Raman Lasers is investigated. The mechanism for the spectral broadening is discussed and the effect is compared in two Lasers using Raman crystals with different Raman linewidths. The impact of the spectral broadening on the effective Raman gain is analyzed, and the use of etalons to limit the fundamental spectral width is explored. It was found that an improvement in output power could be obtained by using etalons to limit the fundamental spectrum to a single narrow peak.
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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.
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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
Richard P Mildren - One of the best experts on this subject based on the ideXlab platform.
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Comprehensive Thermal Analysis of Diamond in a High-Power Raman Cavity Based on FVM-FEM Coupled Method
'MDPI AG', 2021Co-Authors: Zhenxu Bai, Zhanpeng Zhang, Kun Wang, Jia Gao, Zhendong Zhang, Xuezong Yang, Yulei Wang, Richard P MildrenAbstract:Despite their extremely high thermal conductivity and low thermal expansion coefficients, thermal effects in diamond are still observed in high-power diamond Raman Lasers, which proposes a challenge to their power scaling. Here, the dynamics of temperature gradient and stress distribution in the diamond are numerically simulated under different pump conditions. With a pump radius of 100 μm and an absorption power of up to 200 W (corresponding to the output power in kilowatt level), the establishment period of thermal steady-state in a millimeter diamond is only 50 μs, with the overall thermal-induced deformation of the diamond being less than 2.5 μm. The relationship between the deformation of diamond and the stability of the Raman cavity is also studied. These results provide a method to better optimize the diamond Raman laser performance at output powers up to kilowatt-level
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spectral and polarization effects in cascaded narrow linewidth diamond Raman Lasers
Laser Congress 2020 (ASSL LAC) (2020) paper ATu2A.5, 2020Co-Authors: E Granados, Richard P Mildren, Daniel T Echarri, K Chrysalidis, Valentin Fedosseev, Vaila A Leask, B A Marsh, S G Wilkins, S M Olaizola, David J SpenceAbstract:We study theoretically and experimentally the spectral and polarization effects occurring when cascading stimulated Raman scattering processes in diamond. We demonstrate an efficient, few-GHz linewidth, broadly tunable, multi-Stokes comb for spectroscopic applications.
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high power continuous wave Raman frequency conversion from 1 06 µm to 1 49 µm in diamond
Optics Express, 2017Co-Authors: Robert J Williams, David J Spence, Oliver Lux, Richard P MildrenAbstract:We report continuous-wave beam conversion from 1.06 to 1.49 µm in a diamond Raman laser operating on the second Stokes shift. High power (114 W) and high conversion efficiency (44%) is achieved using a single cavity that is highly resonant at the first Stokes wavelength but has high output coupling at the second Stokes wavelength (89%). An analytical model was developed for external-cavity Raman Lasers operating in steady-state, revealing that optimization of second Stokes output is markedly different to first Stokes and that there is a direct and proportional relationship between the second Stokes output coupling and the pump depletion in the diamond, which we have confirmed by experiment. This technology shows promise for power scaling beyond the capabilities of current fiber Lasers operating in the applications-rich 1.5–1.6 µm wavelength range.
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modelling and optimization of continuous wave external cavity Raman Lasers
Optics Express, 2015Co-Authors: Ondrej Kitzler, David J Spence, Aaron Mckay, Richard P MildrenAbstract:We report an analytical model describing power and efficiency of a 23 W quasi-continuous-wave diamond Raman laser. The model guides the optimization of the first Stokes output power as a function of resonator and crystal parameters. We show that, in the limit of a weak thermal lens, efficient operation requires strong focussing, low output coupling and low-absorption crystals. Efficient damage-free operation at higher pump powers is predicted to benefit greatly from increased optimum output couplings that act to limit the intracavity Stokes field.
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investigating diamond Raman Lasers at the 100 w level using quasi continuous wave pumping
Optics Letters, 2014Co-Authors: Robert J Williams, Ondrej Kitzler, Aaron Mckay, Richard P MildrenAbstract:Quasi-cw pumping is used to investigate the high-power characteristics of cw beam conversion in diamond Raman Lasers (DRLs). We show that thermal gradients establish in DRLs at approximately 50 μs for a 100 μm pump beam diameter, and thus that the steady state for cw operation can be reached within the 100–300 μs pulse duration of conventional quasi-cw pump laser technology. Using this approach, a steady-state on-time output power of 108 W was obtained from an external-cavity DRL during 250 μs pulses with 34% conversion efficiency. No thermal lens in the diamond was evident, showing excellent prospects for further power scaling.
