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Wu W, Li X, Yan R, Chen D, Tang S. Cavity-dumped burst-mode Nd:YAG laser master-oscillator power-amplifier system with a flat-top beam output realized by gain profile-controlled side pumping. OPTICS EXPRESS 2022; 30:20401-20414. [PMID: 36224786 DOI: 10.1364/oe.460305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 05/12/2022] [Indexed: 06/16/2023]
Abstract
We report a compact cavity-dumped burst-mode Nd:YAG laser master-oscillator power-amplifier system with a flat-top intensity distribution across the output-beam section. Custom-designed gain profile-controlled diode side pumping modules providing flat-top and concave gain profiles were utilized to generate a uniform beam profile and suppress thermal lensing during amplification, respectively. Bursts with an energy of 2.0 J and duration of 1.6 ms were operated at 10 Hz. Within the bursts, single pulses with an energy of 12.7 mJ and pulse width of 3.3 ns were achieved at 100 kHz.
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Lester L, Gragston M. 10 kHz laser-induced schliere anemometry for velocity, Mach number, and static temperature measurements in supersonic flows. APPLIED OPTICS 2021; 60:8644-8650. [PMID: 34613089 DOI: 10.1364/ao.433085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 08/30/2021] [Indexed: 06/13/2023]
Abstract
A new, to the best of our knowledge, technique for measuring velocity and Mach number in freestream flow is discussed and demonstrated. The technique, laser-induced schliere anemometry, uses a laser to write a laser-induced schliere in the flow, which can then be imaged using high-speed schlieren imaging. Here, we use a laser-induced plasma from the focusing of nanosecond-duration laser pulses from a pulse burst laser to write the disturbance. The resulting localized index of refraction gradient left from the plasma is tracked well beyond the plasma emission lifetime using schlieren imaging, and velocity is found from tracking or through a simple correlation analysis. The blast wave is also used to independently determine the Mach number via the Mach cone effect, which provides information about the mean static temperature. This technique shows great potential for use in characterizing freestream flow in supersonic facilities and is demonstrated here in a Mach 2 blowdown facility and a Mach 4 Ludwieg tube.
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Felver J, Slipchenko MN, Braun EL, Meyer TR, Roy S. High-energy laser pulses for extended duration megahertz-rate flow diagnostics. OPTICS LETTERS 2020; 45:4583-4586. [PMID: 32797015 DOI: 10.1364/ol.400831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 07/18/2020] [Indexed: 06/11/2023]
Abstract
Optical diagnostics of highly dynamic supersonic and hypersonic flows requires laser sources with a combination of high pulse intensities and fast repetition rates. A burst-mode Nd:YAG laser system is presented for increasing the overall energy of 532 nm pulse trains by ∼100× and the number of high-energy pulses by 30× for extended duration megahertz-rate flow diagnostics. At a lower repetition rate of 100 kHz, unprecedented energies near 1 J/pulse are achieved at 532 nm over a 1.1 ms burst. The laser performance is characterized and demonstrated for megahertz-rate laser-induced breakdown spectroscopy in a Mach 2 turbulent jet.
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Time-Resolved Measurements of Turbulent Mixing in Shock-Driven Variable-Density Flows. Sci Rep 2019; 9:20315. [PMID: 31889164 PMCID: PMC6937284 DOI: 10.1038/s41598-019-56736-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 12/17/2019] [Indexed: 11/27/2022] Open
Abstract
Recent developments of burst-mode lasers and imaging systems have opened new realms of simultaneous diagnostics for velocity and density fields at a rate of 1 kHz–1 MHz. These enable the exploration of previously unimaginable shock-driven turbulent flow fields that are of significant importance to problems in high-energy density physics. The current work presents novel measurements using simultaneous measurements of velocity and scalar fields at 60 kHz to investigate Richtmyer-Meshkov instability (RMI) in a spatio-temporal approach. The evolution of scalar fields and the vorticity dynamics responsible for the same are shown, including the interaction of shock with the interface. This temporal information is used to validate two vorticity-deposition models commonly used for initiation of large scale simulations, and have been previously validated only via simulations or integral measures of circulation. Additionally, these measurements also enable tracking the evolution and mode merging of individual flow structures that were previously not possible owing to inherently random variations in the interface at the smallest scales. A temporal evolution of symmetric vortex merging and the induced mixing prevalent in these problems is presented, with implications for the vortex paradigms in accelerated inhomogenous flows.
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Wu W, Li X, Mei F, Chen D, Yan R. 30 mJ, 1 kHz sub-nanosecond burst-mode Nd:YAG laser MOPA system. OPTICS EXPRESS 2019; 27:36129-36136. [PMID: 31873398 DOI: 10.1364/oe.27.036129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 11/19/2019] [Indexed: 06/10/2023]
Abstract
We demonstrated a sub-nanosecond burst-mode MOPA Nd:YAG laser at 1.06 µm that consists of a cavity-dumped Q-switched master oscillator and a double-pass side-pumped amplification system. During the 1 kHz burst-mode operation, outputs with the single pulse energy of 29.8 mJ were obtained within the burst duration of 100 ms. The pulse width was 900 ps, which resulted in a peak power of 33.1 MW. During the 10 Hz operation, the single pulse energy reached 81 mJ with a pulse width of 900 ps, which resulted in a peak power of 90 MW.
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Yang X, Fu C, Wang G, Li Z, Li T, Gao Y. Simultaneous high-speed SO 2 PLIF imaging and stereo-PIV measurements in premixed swirling flame at 20 kHz. APPLIED OPTICS 2019; 58:C121-C129. [PMID: 31045082 DOI: 10.1364/ao.58.00c121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 03/20/2019] [Indexed: 06/09/2023]
Abstract
Interactions between flow structures and premixed swirling flame were investigated using simultaneous sulfur dioxide (SO2) planar laser induced fluorescence (PLIF) and stereoscopic particle imaging velocimetry (PIV) with high temporal resolution at 20 kHz. In this work, a premixed swirling flame was operated with methane and air doped with 0.5% (volume fraction) SO2 at ambient pressure under different equivalence ratios (ϕ=0.7-1.2). The results show that global SO2 PLIF signal shows a consistent response to the density ratio with the change of equivalence ratio, making it a good indicator for the high temperature zone and a very useful tool to study the global effect of equivalence ratio. In addition, the three-component flow structure is affected by the varying equivalence ratio and the structure of the inner recirculation zone changes accordingly. The transient results show that the circumferential velocity of some vortices outside the flame zone is inconsistent with that of the main flow and these vortices cause local flame contour curling and shedding. The high temporal resolution measurements provide more details for the study of the evolution of some isolated flame isles.
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Retzer U, Pan R, Werblinski T, Huber FJT, Slipchenko MN, Meyer TR, Zigan L, Will S. Burst-mode OH/CH 2O planar laser-induced fluorescence imaging of the heat release zone in an unsteady flame. OPTICS EXPRESS 2018; 26:18105-18114. [PMID: 30114090 DOI: 10.1364/oe.26.018105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 05/29/2018] [Indexed: 06/08/2023]
Abstract
The paper presents simultaneous high-speed (7.5 kHz) planar laser-induced fluorescence (PLIF) of formaldehyde (CH2O) and the hydroxyl-radical (OH) for visualization of the flame structure and heat release zone in a non-premixed unsteady CH4/O2/N2 flame. For this purpose, a dye laser designed for high-speed operation is pumped by the second-harmonic 532 nm output of a Nd:YAG burst-mode laser to produce a tunable, 566 nm beam. After frequency doubling a high-energy kHz-rate narrowband pulse train of approximately 2.2 mJ/pulse at 283 nm is used for excitation of the OH radical. Simultaneously, CH2O is excited by the frequency-tripled output of the same Nd:YAG laser, providing a high-frequency pulse train over 10 ms in duration at high pulse energies (>100 mJ/pulse). The excitation energies enable signal-to-noise ratios (SNRs) of ~10 and ~60 for CH2O and OH PLIF, respectively, using a single high-speed intensified CMOS camera equipped with an image doubler. This allows sufficient SNR for investigation of the temporal evolution of the primary heat release zone and the local flame structure at kHz rates from the spatial overlap of the OH- and CH2O-PLIF signals.
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Pan R, Retzer U, Werblinski T, Slipchenko MN, Meyer TR, Zigan L, Will S. Generation of high-energy, kilohertz-rate narrowband tunable ultraviolet pulses using a burst-mode dye laser system. OPTICS LETTERS 2018; 43:1191-1194. [PMID: 29489813 DOI: 10.1364/ol.43.001191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/08/2018] [Indexed: 06/08/2023]
Abstract
Typical commercial pulsed dye laser systems used in the generation of narrowband, tunable ultraviolet radiation for planar laser-induced fluorescence (PLIF) imaging are optimized for either high (∼5-10 kHz) repetition rates at comparatively low ultraviolet pulse energies (hundreds of microjoules) or high-output pulse energies (>10 mJ) at comparatively low repetition rates (∼10 Hz). In this work we use a frequency-doubled Nd:YAG burst-mode laser to pump a custom dye laser system for high pulse energies and repetition rates of 7.5, 10, and 20 kHz at 566 nm. The frequency-doubled output of over 2.2 mJ/pulse at 283 nm, which can be used for PLIF imaging of combustion radicals, is an order of magnitude higher per pulse energy as compared with continuously pulsed dye laser systems and is ∼3× higher in overall efficiency than a burst-mode optical parametric oscillator at similar wavelengths. The influence of repetition rate, pump energy, and dye concentration on the output conversion efficiency and pulse-to-pulse stability of the current system is discussed.
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Wu W, Li X, Yan R, Zhou Y, Ma Y, Fan R, Dong Z, Chen D. 100 kHz, 3.1 ns, 1.89 J cavity-dumped burst-mode Nd:YAG MOPA laser. OPTICS EXPRESS 2017; 25:26875-26884. [PMID: 29092171 DOI: 10.1364/oe.25.026875] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 10/16/2017] [Indexed: 06/07/2023]
Abstract
We demonstrated a cavity-dumped burst-mode 1.06 μm side-pumped Nd:YAG laser and its dual-stage dual-pass amplified laser performance. The cavity dumping process has been theoretically studied and the output performance has been experimentally investigated. At the pumping duration of 2 ms and pumping frequency of 10 Hz, burst energy, peak power and pulse width of the amplified laser reached 1.89 J, 2.87 MW and 3.1 ± 0.3 ns, respectively, at the Q-switch repetition rate of 100 kHz. The maximum energy extraction efficiency reaches to 30%.
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Jiang N, Hsu PS, Mance JG, Wu Y, Gragston M, Zhang Z, Miller JD, Gord JR, Roy S. High-speed 2D Raman imaging at elevated pressures. OPTICS LETTERS 2017; 42:3678-3681. [PMID: 28914931 DOI: 10.1364/ol.42.003678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 08/27/2017] [Indexed: 06/07/2023]
Abstract
Two-dimensional (2D) Raman scattering at 10 kHz in non-reacting flow mixtures is demonstrated by employing a burst-mode laser with a long-duration pulse of about 70 ns and pulse energy of about 750 mJ at 532 nm. To avoid optical breakdown, the pulse width of the laser was varied in the range of 10-1000 ns. The effects of pulse shape, pulse energy, and harmonic conversion on 2D measurements are also studied. The applications of high-speed, single-shot, 2D imaging of CH4 and H2 jets in N2 at elevated pressures are demonstrated. In addition, the scalar dissipation rate of CH4 in N2 at 20 bar is determined, and multi-dimensional, multi-species, high-speed imaging of flows at elevated pressures is demonstrated.
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Mance JG, Slipchenko MN, Roy S. Regenerative amplification and bifurcations in a burst-mode Nd:YAG laser. OPTICS LETTERS 2015; 40:5093-5096. [PMID: 26512527 DOI: 10.1364/ol.40.005093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
An Nd:YAG-based burst-mode regenerative amplifier laser was developed that offers high extraction efficiency at high repetition rates with low seed energies. The regenerative amplification technique, combined with the burst-mode laser technology, shows promise as an efficient method for amplification of femtojoule-nanojoule pulses up to millijoule energies at repetition rates exceeding 100 kHz. Output energies at repetition rates near the inverse upper state lifetime are limited by bifurcations in the pulse energies of the burst. A model is developed and advantages and limitations are discussed.
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Slipchenko MN, Miller JD, Roy S, Meyer TR, Mance JG, Gord JR. 100 kHz, 100 ms, 400 J burst-mode laser with dual-wavelength diode-pumped amplifiers. OPTICS LETTERS 2014; 39:4735-4738. [PMID: 25121861 DOI: 10.1364/ol.39.004735] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The burst duration of an all-diode-pumped burst-mode laser is extended to 100 ms and 100 kHz (10,000 pulses) by utilizing dual-wavelength diode pumping. Total energies of 225 J at 10 kHz and 400 J at 100 kHz are achieved during the 100 ms burst period at 1064 nm. This represents an order-of-magnitude increase in the number of pulses compared with prior work, while maintaining similar or higher pulse energies. Amplitude tailoring of each pulse is used to flatten the burst profile, reducing the standard deviation in pulse energy over the 100 ms burst from 3.7% to 2.1% with a burst-to-burst standard deviation of 0.8%.
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Michael JB, Venkateswaran P, Miller JD, Slipchenko MN, Gord JR, Roy S, Meyer TR. 100 kHz thousand-frame burst-mode planar imaging in turbulent flames. OPTICS LETTERS 2014; 39:739-742. [PMID: 24562194 DOI: 10.1364/ol.39.000739] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
High-repetition-rate, burst-mode lasers can achieve higher energies per pulse compared with continuously pulsed systems, but the relatively few number of laser pulses in each burst has limited the temporal dynamic range of measurements in unsteady flames. A fivefold increase in the range of timescales that can be resolved by burst-mode laser-based imaging systems is reported in this work by extending a hybrid diode- and flashlamp-pumped Nd:YAG-based amplifier system to nearly 1000 pulses at 100 kHz during a 10 ms burst. This enables an unprecedented burst-mode temporal dynamic range to capture turbulent fluctuations from 0.1 to 50 kHz in flames of practical interest. High pulse intensity enables efficient conversion to the ultraviolet for planar laser-induced fluorescence imaging of nascent formaldehyde and other potential flame radicals.
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Hsu PS, Kulatilaka WD, Roy S, Gord JR. Investigation of optical fibers for high-repetition-rate, ultraviolet planar laser-induced fluorescence of OH. APPLIED OPTICS 2013; 52:3108-15. [PMID: 23669781 DOI: 10.1364/ao.52.003108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 04/05/2013] [Indexed: 05/20/2023]
Abstract
We investigate the fundamental transmission characteristics of nanosecond-duration, 10 kHz repetition rate, ultraviolet (UV) laser pulses through state-of-the-art, UV-grade fused-silica fibers being used for hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) imaging. Studied in particular are laser-induced damage thresholds (LIDTs), nonlinear absorption, and optical transmission stability during long-term UV irradiation. Solarization (photodegradation) effects are significantly enhanced when the fiber is exposed to high-repetition-rate, 283 nm UV irradiation. For 10 kHz laser pulses, two-photon absorption is strong and LIDTs are low, as compared to those of laser pulses propagating at 10 Hz. The fiber characterization results are utilized to perform single-laser-shot, OH-PLIF imaging in pulsating turbulent flames with a laser that operates at 10 kHz. The nearly spatially uniform output beam that exits a long multimode fiber becomes ideal for PLIF measurements. The proof-of-concept measurements show significant promise for extending the application of a fiber-coupled, high-speed OH-PLIF system to harsh environments such as combustor test beds, and potential system improvements are suggested.
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Affiliation(s)
- Paul S Hsu
- Spectral Energies, LLC, 5100 Springfield Street, Suite 301, Dayton, Ohio 45431, USA
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