The Experts below are selected from a list of 48411 Experts worldwide ranked by ideXlab platform
M Mahjoei - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis of spectral hole burning and relaxation oscillation in all optical gain stabilized multichannel erbium doped fiber amplifier edfa
Journal of Lightwave Technology, 2001Co-Authors: A R Bahrampour, M MahjoeiAbstract:The spectral hole burning effects and gain dynamics of all-optical gain clamped multichannel erbium-doped fiber amplifiers (EDFAs) are modeled. The two-level Laser model is used to write the propagation and rate equations of the inhomogeneous Laser Medium. The governing equations are an uncountable system of partial differential equations (PDEs). After some mathematical manipulations, averaging over the fiber length and introducing an approximation method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The gain dynamics and hole burning of an all-optical stabilized multiwavelength EDFA and the transient response of an optical fiber inverter are analyzed by the solution of the system of ODEs. Theoretical results are in good agreement with the published experimental result.
Yu M Kantor - One of the best experts on this subject based on the ideXlab platform.
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thomson scattering system on the textor tokamak using a multi pass Laser beam configuration
Plasma Physics and Controlled Fusion, 2009Co-Authors: Yu M Kantor, A J H Donne, R Jaspers, H J Van Der Meiden, Textor TeamAbstract:The main challenge for the Thomson scattering (TS) diagnostic on the TEXTOR tokamak is the detailed study of fast plasma events at a high spatial resolution and a high repetition rate of the measurements. The diagnostic uses intra-cavity probing of the plasma with a repetitively pulsed ruby Laser and a fast CMOS camera as detectors. Since 2004, the TS system on TEXTOR has been gradually and systematically enhanced for the measurements of fast plasma events. For that it has recently been upgraded to obtain a multi-pass configuration. Two spherical mirrors have been installed that force the Laser beam to probe the plasma a specified number of times before it is directed back into the Laser Medium. The diagnostics with the upgraded probing system have achieved the measurement accuracy of 3% for the electron temperature and 1.5% for the electron density at <1 cm spatial resolution and 3 × 1019 m−3 plasma density and can measure at 5 kHz during an interval up to 8 ms. This makes it possible to detect, amongst others, fine structures of magnetic islands and variations of the edge pedestal in the ELMy limiter H-mode.
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thomson scattering system on the textor tokamak using a multi pass Laser beam configuration
Plasma Physics and Controlled Fusion, 2009Co-Authors: Yu M Kantor, A J H Donne, R Jaspers, H J Van Der Meiden, Textor TeamAbstract:The main challenge for the Thomson scattering (TS) diagnostic on the TEXTOR tokamak is the detailed study of fast plasma events at a high spatial resolution and a high repetition rate of the measurements. The diagnostic uses intra-cavity probing of the plasma with a repetitively pulsed ruby Laser and a fast CMOS camera as detectors. Since 2004, the TS system on TEXTOR has been gradually and systematically enhanced for the measurements of fast plasma events. For that it has recently been upgraded to obtain a multi-pass configuration. Two spherical mirrors have been installed that force the Laser beam to probe the plasma a specified number of times before it is directed back into the Laser Medium. The diagnostics with the upgraded probing system have achieved the measurement accuracy of 3% for the electron temperature and 1.5% for the electron density at <1 cm spatial resolution and 3 × 1019 m−3 plasma density and can measure at 5 kHz during an interval up to 8 ms. This makes it possible to detect, amongst others, fine structures of magnetic islands and variations of the edge pedestal in the ELMy limiter H-mode.
A R Bahrampour - One of the best experts on this subject based on the ideXlab platform.
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an inhomogeneous theory for the analysis of an all optical gain stabilized multichannel erbium doped fiber amplifier in the presence of ion pairs
Optical Fiber Technology, 2008Co-Authors: A R Bahrampour, Shahram Keyvaninia, Masoumeh KarvarAbstract:Abstract In this paper the gain dynamics of an all-optical gain-clamped multichannel erbium-doped fiber amplifier (EDFA) with an inhomogeneous active Medium in the presence of ion pairs is modeled. A two-level model for single ions and a three-level model for ion pairs are used to drive the propagation and rate equations of inhomogeneous Laser Medium. The governing equations are an uncountable system of partial differential equations (PDEs). Using the moment method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The solution of the system of ODEs is used to analyze the gain dynamics of all-optical gain-stabilized multi-wavelength heavy doped EDFA. Theoretical results are in good agreement with the published experimental results.
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theoretical analysis of spectral hole burning and relaxation oscillation in all optical gain stabilized multichannel erbium doped fiber amplifier edfa
Journal of Lightwave Technology, 2001Co-Authors: A R Bahrampour, M MahjoeiAbstract:The spectral hole burning effects and gain dynamics of all-optical gain clamped multichannel erbium-doped fiber amplifiers (EDFAs) are modeled. The two-level Laser model is used to write the propagation and rate equations of the inhomogeneous Laser Medium. The governing equations are an uncountable system of partial differential equations (PDEs). After some mathematical manipulations, averaging over the fiber length and introducing an approximation method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The gain dynamics and hole burning of an all-optical stabilized multiwavelength EDFA and the transient response of an optical fiber inverter are analyzed by the solution of the system of ODEs. Theoretical results are in good agreement with the published experimental result.
Takehiro Oishi - One of the best experts on this subject based on the ideXlab platform.
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solar pumped 80 w Laser irradiated by a fresnel lens
Optics Letters, 2009Co-Authors: Tomomasa Ohkubo, Takashi Yabe, Kunio Yoshida, Shigeaki Uchida, Takayuki Funatsu, Behgol Bagheri, Takehiro Oishi, Kazuya Daito, Manabu Ishioka, Yuichirou NakayamaAbstract:A solar-pumped 100 W class Laser that features high efficiency and low cost owing to the use of a Fresnel lens and a chromium codoped neodymium YAG ceramic Laser Medium was developed. A Laser output of about 80 W was achieved with combination of a 4 m2 Fresnel lens and a pumping cavity as a secondary power concentrator. This output corresponds to 4.3% of conversion efficiency from solar power into Laser, and the maximum output from a unit area of Fresnel lens was 20 W/m2, which is 2.8 times larger than previous results with mirror-type concentrator.
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high efficiency and economical solar energy pumped Laser with fresnel lens and chromium codoped Laser Medium
Applied Physics Letters, 2007Co-Authors: Takashi Yabe, Masahiro Nakatsuka, Tomomasa Ohkubo, Kunio Yoshida, Shigeaki Uchida, Takayuki Funatsu, A Mabuti, A Oyama, K Nakagawa, Takehiro OishiAbstract:The authors achieved 11%–14% slope efficiency of solar-pumped Laser by Cr-codoped Nd:yttrium aluminum garnet ceramic and Fresnel lens focusing from natural sunlight. The Laser output of 24.4W was achieved with 1.3m2 Fresnel lens. The maximum output for unit area of sunlight was 18.7W∕m2, which is 2.8 times larger than previous results with mirror collector. The utilization of Cr3+ ion enabled efficient absorption and energy transfer to Nd3+ ion of solar spectrum. The fluorescence yield at 1064nm for various pumping wavelengths was measured both for Crcodoped and nondoped Laser media, and 1.8 times enhancement of Laser output from sunlight is predicted.
Fedor Jelezko - One of the best experts on this subject based on the ideXlab platform.
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absorptive Laser threshold magnetometry combining visible diamond raman Lasers and nitrogen vacancy centres
arXiv: Quantum Physics, 2021Co-Authors: Sarath Raman Nair, Fedor Jelezko, Lachlan J Rogers, D J Spence, Andrew D Greentree, Thomas Volz, Jan JeskeAbstract:We propose a high-sensitivity magnetometry scheme based on a diamond Raman Laser with visible pump absorption by an ensemble of coherently microwave driven negatively charged nitrogen-vacancy centres (NV) in the same diamond crystal. The NV centres' absorption and emission are spin-dependent. We show how the varying absorption of the NV centres changes the Raman Laser output. A shift in the diamond Raman Laser threshold and output occurs with the external magnetic-field and microwave driving. We develop a theoretical framework including steady-state solutions to describe the effects of coherently driven NV centres in a diamond Raman Laser. We discuss that such a Laser working at the threshold can be employed for magnetic-field sensing. In contrast to previous studies on NV magnetometry with visible Laser absorption, the Laser threshold magnetometry method is expected to have low technical noise, due to low background light in the measurement signal. For magnetic-field sensing, we project a shot-noise limited DC sensitivity of a few $\mathrm{pT}/\sqrt{\mathrm{Hz}}$ in a well-calibrated cavity with realistic parameters. This sensor employs the broad visible absorption of NV centres and unlike previous Laser threshold magnetometry proposals it does not rely on active NV centre lasing or an infrared Laser Medium at the specific wavelength of the NV centre's infrared absorption line.
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stimulated emission from nitrogen vacancy centres in diamond
Nature Communications, 2017Co-Authors: Jan Jeske, Desmond W M Lau, Xavier Vidal, Liam P Mcguinness, Philipp Reineck, B C Johnson, Marcus W Doherty, J C Mccallum, Shinobu Onoda, Fedor JelezkoAbstract:Stimulated emission is the process fundamental to Laser operation, thereby producing coherent photon output. Despite negatively charged nitrogen-vacancy (NV−) centres being discussed as a potential Laser Medium since the 1980s, there have been no definitive observations of stimulated emission from ensembles of NV− to date. Here we show both theoretical and experimental evidence for stimulated emission from NV− using light in the phonon sidebands around 700 nm. Furthermore, we show the transition from stimulated emission to photoionization as the stimulating Laser wavelength is reduced from 700 to 620 nm. While lasing at the zero-phonon line is suppressed by ionization, our results open the possibility of diamond Lasers based on NV− centres, tuneable over the phonon sideband. This broadens the applications of NV− magnetometers from single centre nanoscale sensors to a new generation of ultra-precise ensemble Laser sensors, which exploit the contrast and signal amplification of a lasing system. Here Jeskeet al. show both theoretical and experimental evidence for stimulated emission from negatively charged nitrogen vacancy centres using light in the phonon sidebands around 700 nm, demonstrating its suitability as a Laser Medium.
