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Adamovich IV, Li T, Lempert WR. Kinetic mechanism of molecular energy transfer and chemical reactions in low-temperature air-fuel plasmas. Philos Trans A Math Phys Eng Sci 2015; 373:rsta.2014.0336. [PMID: 26170427 DOI: 10.1098/rsta.2014.0336] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/12/2015] [Indexed: 06/04/2023]
Abstract
This work describes the kinetic mechanism of coupled molecular energy transfer and chemical reactions in low-temperature air, H2-air and hydrocarbon-air plasmas sustained by nanosecond pulse discharges (single-pulse or repetitive pulse burst). The model incorporates electron impact processes, state-specific N(2) vibrational energy transfer, reactions of excited electronic species of N(2), O(2), N and O, and 'conventional' chemical reactions (Konnov mechanism). Effects of diffusion and conduction heat transfer, energy coupled to the cathode layer and gasdynamic compression/expansion are incorporated as quasi-zero-dimensional corrections. The model is exercised using a combination of freeware (Bolsig+) and commercial software (ChemKin-Pro). The model predictions are validated using time-resolved measurements of temperature and N(2) vibrational level populations in nanosecond pulse discharges in air in plane-to-plane and sphere-to-sphere geometry; temperature and OH number density after nanosecond pulse burst discharges in lean H(2)-air, CH(4)-air and C(2)H(4)-air mixtures; and temperature after the nanosecond pulse discharge burst during plasma-assisted ignition of lean H2-mixtures, showing good agreement with the data. The model predictions for OH number density in lean C(3)H(8)-air mixtures differ from the experimental results, over-predicting its absolute value and failing to predict transient OH rise and decay after the discharge burst. The agreement with the data for C(3)H(8)-air is improved considerably if a different conventional hydrocarbon chemistry reaction set (LLNL methane-n-butane flame mechanism) is used. The results of mechanism validation demonstrate its applicability for analysis of plasma chemical oxidation and ignition of low-temperature H(2)-air, CH(4)-air and C(2)H(4)-air mixtures using nanosecond pulse discharges. Kinetic modelling of low-temperature plasma excited propane-air mixtures demonstrates the need for development of a more accurate 'conventional' chemistry mechanism.
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Affiliation(s)
- Igor V Adamovich
- Nonequilibrium Thermodynamics Laboratory, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Ting Li
- Nonequilibrium Thermodynamics Laboratory, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Walter R Lempert
- Nonequilibrium Thermodynamics Laboratory, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
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Loccisano F, Joshi S, Franka IS, Yin Z, Lempert WR, Yalin AP. Fiber-coupled ultraviolet planar laser-induced fluorescence for combustion diagnostics. Appl Opt 2012; 51:6691-6699. [PMID: 23033042 DOI: 10.1364/ao.51.006691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/31/2012] [Indexed: 06/01/2023]
Abstract
Multimode silica step-index optical fibers are examined for use in planar laser-induced fluorescence (PLIF) for combustion diagnostics using ultraviolet (UV) laser sources. The multimode step-index fibers are characterized at UV wavelengths by examining their energy damage thresholds and solarization performance. The beam quality achievable with large clad step-index multimode fibers is also studied. Emphasis is placed on simultaneously achieving high output energy and beam quality (low output M(2)). The use of multimode fibers to deliver UV pulses at 283 nm for PLIF measurements of OH radicals in a Hencken burner is demonstrated. The fiber delivery capability of UV light will benefit combustion diagnostics in hostile environments, such as augmentor and combustor rigs.
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Abstract
This Letter presents results from a new master-oscillator, power-amplifier pulse-burst laser system demonstrating ultrahigh pulse energies greater than 2.0 J/pulse at 1064 nm with interpulse separations of 100 μs (10 kHz) for burst durations of 100 pulses. Each pulse generates peak powers exceeding 130 MW and an average power of approximately 20 kW is generated over a 100-pulse-burst. Pulse energies decrease by less than 10% over a 100 sequential pulses, demonstrating negligible "droop" over long-duration pulse trains. Second-harmonic generation of 532 nm with conversion efficiency greater than 50% is demonstrated for 100-pulse-burst durations.
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Affiliation(s)
- Frederik Fuest
- Department of Mechanical and Aerospace Engineering, Ohio State University, Columbus, Ohio, USA
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Lempert WR, Kearney SP, Barnat EV. Diagnostic study of four-wave-mixing-based electric-field measurements in high-pressure nitrogen plasmas. Appl Opt 2011; 50:5688-5694. [PMID: 22015362 DOI: 10.1364/ao.50.005688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present the results of a diagnostic study of the use of coherent four wave mixing for in situ measurement of an electric field in air or in nitrogen-containing plasmas. Static electric fields in air at a nominal pressure of 625 Torr and temperature of 300 K are detected using vibrational CARS of nitrogen. It is shown that the ratio of the infrared signal to the vibrational N(2) CARS signal is equal to approximately 10(-8) at 8.33 kV/cm, a factor of approximately 50 less than that predicted assuming equal third-order nonlinear susceptibilities. It is also shown that the spatial resolution of a typical collinear geometry measurement is approximately 1 cm. Finally, it is shown that achieving sensitivities of the order of 1 kV/cm requires that the coherent Raman pumping be performed in the highly saturated and Stark broadened regime.
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Affiliation(s)
- Walter R Lempert
- Department of Mechanical & Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210, USA.
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Jiang N, Webster M, Lempert WR, Miller JD, Meyer TR, Ivey CB, Danehy PM. MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel. Appl Opt 2011; 50:A20-A28. [PMID: 21283217 DOI: 10.1364/ao.50.000a20] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Nitric oxide planar laser-induced fluorescence (NO PLIF) imaging at repetition rates as high as 1 MHz is demonstrated in the NASA Langley 31 in. Mach 10 hypersonic wind tunnel. Approximately 200 time-correlated image sequences of between 10 and 20 individual frames were obtained over eight days of wind tunnel testing spanning two entries in March and September of 2009. The image sequences presented were obtained from the boundary layer of a 20° flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transitional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified.
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Affiliation(s)
- Naibo Jiang
- Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio 43201, USA
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Miller JD, Slipchenko M, Meyer TR, Jiang N, Lempert WR, Gord JR. Ultrahigh-frame-rate OH fluorescence imaging in turbulent flames using a burst-mode optical parametric oscillator. Opt Lett 2009; 34:1309-1311. [PMID: 19412255 DOI: 10.1364/ol.34.001309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Burst-mode planar laser-induced fluorescence (PLIF) imaging of the OH radical is demonstrated in laminar and turbulent hydrogen-air diffusion flames with pulse repetition rates up to 50 kHz. Nearly 1 mJ/pulse at 313.526 nm is used to probe the OH P(2)(10) rotational transition in the (0,0) band of the A-X system. The UV radiation is generated by a high-speed-tunable, injection-seeded optical parametric oscillator pumped by a frequency-doubled megahertz-rate burst-mode Nd:YAG laser. Preliminary kilohertz-rate wavelength scanning of the temperature-broadened OH transition during PLIF imaging is also presented for the first time (to our knowledge), and possible strategies for spatiotemporally resolved planar OH spectroscopy are discussed.
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Affiliation(s)
- Joseph D Miller
- Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA
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Jiang N, Webster MC, Lempert WR. Advances in generation of high-repetition-rate burst mode laser output. Appl Opt 2009; 48:B23-B31. [PMID: 19183578 DOI: 10.1364/ao.48.000b23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
It is demonstrated that the incorporation of variable pulse duration flashlamp power supplies into an Nd:YAG burst mode laser system results in very substantial increases in the realizable energy per pulse, the total pulse train length, and uniformity of the intensity envelope. As an example, trains of 20 pulses at burst frequencies of 50 and 20 kHz are demonstrated with individual pulse energy at 1064 nm of 220 and 400 mJ, respectively. Conversion efficiency to the second- (532 nm) and third- (355 nm) harmonic wavelengths of approximately 50% and 35-40%, respectively, is also achieved. Use of the third-harmonic output of the burst mode laser as a pump source for a simple, home built optical parametric oscillator (OPO) produces pulse trains of broadly wavelength tunable output. Sum-frequency mixing of OPO signal output at 622 nm with residual output from the 355 nm pump beam is shown to produce uniform bursts of tunable output at approximately 226 nm, with individual pulse energy of approximately 0.5 mJ. Time-correlated NO planar laser induced fluorescence (PLIF) image sequences are obtained in a Mach 3 wind tunnel at 500 kHz, representing, to our knowledge, the first demonstration of NO PLIF imaging at repetition rates exceeding tens of hertz.
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Affiliation(s)
- Naibo Jiang
- Department of Mechanical Engineering, The Ohio State University, 201 West 19th Avenue, Columbus, Ohio 43210, USA
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Jiang N, Lempert WR. Ultrahigh-frame-rate nitric oxide planar laser-induced fluorescence imaging. Opt Lett 2008; 33:2236-2238. [PMID: 18830363 DOI: 10.1364/ol.33.002236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We demonstrate the ability to generate ultrahigh frequency burst sequences of deep UV at 226 nm by mixing the optical parametric oscillator signal output at 622 nm with third harmonic at 355 nm from a pulse burst laser system. We obtained 226 nm burst sequences with uniform burst envelopes, and the average pulse energy is approximately 0.5 mJ. Nitric oxide planar laser-induced fluorescence image sequences at ultrahigh (100 kHz) frame rates have been obtained.
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Affiliation(s)
- Naibo Jiang
- Department of Mechanical Engineering, The Ohio State University, Columbus, OH 43202, USA
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Den Hartog DJ, Jiang N, Lempert WR. A pulse-burst laser system for a high-repetition-rate Thomson scattering diagnostic. Rev Sci Instrum 2008; 79:10E736. [PMID: 19044552 DOI: 10.1063/1.2965733] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A "pulse-burst" laser system is being constructed for addition to the Thomson scattering diagnostic on the Madison Symmetric Torus (MST) reversed-field pinch. This laser is designed to produce a burst of up to 200 approximately 1 J Q-switched pulses at repetition frequencies 5-250 kHz. This laser system will operate at 1064 nm and is a master oscillator, power amplifier. The master oscillator is a compact diode-pumped Nd:YVO(4) laser, intermediate amplifier stages are flashlamp-pumped Nd:YAG, and final stages will be flashlamp-pumped Nd:glass (silicate). Variable pulse width drive (0.3-20 ms) of the flashlamps is accomplished by insulated-gate bipolar transistor switching of large electrolytic capacitor banks. The burst train of laser pulses will enable the study of electron temperature (T(e)) and electron density (n(e)) dynamics in a single MST shot, and with ensembling, will enable correlation of T(e) and n(e) fluctuations with other fluctuating quantities.
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Affiliation(s)
- D J Den Hartog
- Department of Physics and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Jiang N, Lempert WR, Switzer GL, Meyer TR, Gord JR. Narrow-linewidth megahertz-repetition-rate optical parametric oscillator for high-speed flow and combustion diagnostics. Appl Opt 2008; 47:64-71. [PMID: 18157278 DOI: 10.1364/ao.47.000064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We demonstrate the ability to generate ultra-high-frequency sequences of broadly wavelength-tunable, high-intensity laser pulses using a custom-built optical parametric oscillator pumped by the third-harmonic output of a "burst-mode" Nd:YAG laser. Burst sequences consisting of 6-10 pulses separated in time by 6-10 mus are obtained, with average total conversion efficiency from the 355 nm pump to the near-IR signal and idler wavelengths of approximately 33%. Typical individual pulse output energy for the signal and idler beams is in the range of 4-6 mJ, limited by the available pump energy. Line narrowing is demonstrated by means of injection seeding the idler wave using a low-power external-cavity diode laser at 827 nm. It is shown that seeding reduces the time-averaged linewidth of both the signal and idler outputs to approximately 300 MHz, which is near the 220 MHz Fourier transform limit. Line narrowing is achieved without recourse to active cavity stabilization.
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Affiliation(s)
- Naibo Jiang
- Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio 43202, USA
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Lee W, Lempert WR. Enhancement of spectral purity of injection-seeded titanium:sapphire laser by cavity locking and stimulated Brillouin scattering. Appl Opt 2003; 42:4320-4326. [PMID: 12921280 DOI: 10.1364/ao.42.004320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report improvements to and better characterization of the spectral purity of a diode laser injection-seeded, cavity-locked titanium sapphire laser that serves as the source for a previously reported rubidium vapor spectrally filtered Thomson scattering apparatus at 780.24 nm. In a detailed set of measurements the spectral purity P of the laser, defined as the ratio ofthe narrowband component of the laser output to the total output, has been studied as a function of frequency mismatch between the seed laser frequency and the central frequency of the unseeded cavity. It is found that spectral purity exceeding 0.999 can be obtained for a seed-cavity mismatch as high as +/- 0.25 nm, corresponding to approximately 950 cavity longitudinal-mode spacings and as high as approximately 0.9999 for a cavity-seed mismatch in the range +/- 0.10 nm (380 mode spacings). It is also shown that the addition of an external-cavity stimulated Brillouin-scattering phase-conjugate mirror increases both the spectral purity, to a minimum of 0.99999, and the cavity-seed mismatch range, to +/- 0.25 nm, for which this maximum effective purity is obtained.
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Affiliation(s)
- Wonchul Lee
- Department of Mechanical Engineering, Ohio State University, 206 West 18th Avenue, Columbus, Ohio 43210-1337, USA
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Plönjes E, Palm P, Babu Viswanathan G, Subramaniam VV, Adamovich IV, Lempert WR, Fraser HL, William Rich J. Synthesis of single-walled carbon nanotubes in vibrationally non-equilibrium carbon monoxide. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(01)01473-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Lee W, Adamovich IV, Lempert WR. Optical pumping studies of vibrational energy transfer in high-pressure diatomic gases. J Chem Phys 2001. [DOI: 10.1063/1.1332400] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Plönjes E, Palm P, Lee W, D. Chidley M, Adamovich IV, R. Lempert W, Rich J. Vibrational energy storage in high pressure mixtures of diatomic molecules. Chem Phys 2000. [DOI: 10.1016/s0301-0104(00)00257-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Finkelstein ND, Yalin AP, Lempert WR, Miles RB. Dispersion filter for spectral and spatial resolution of pure rotational Raman scattering. Opt Lett 1998; 23:1615-1617. [PMID: 18091862 DOI: 10.1364/ol.23.001615] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A new filtering technique for Raman spectroscopy utilizes atomic vapor to suppress strong elastic and Rayleigh scattering while simultaneously resolving individual rotational Raman lines. Filtered images capture high-resolution spectral information in one dimension and spatial resolution in the other dimension. The filter is based on resonance enhanced dispersion, where the index of refraction varies dramatically. In a simple prism geometry the vapor disperses incident radiation according to frequency. A mercury-vapor-based dispersion filter has been fabricated, modeled, and demonstrated to capture pure rotational Raman scattering from CO(2).
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Grinstead JH, Finkelstein ND, Lempert WR. Frequency-locked light scattering: real-time Doppler velocimetry with closed-loop feedback control. Appl Opt 1998; 37:1617-1625. [PMID: 18268756 DOI: 10.1364/ao.37.001617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Real-time measurement capability of a frequency-modulated filtered light-scattering- (FM FLS) Doppler velocimeter has been demonstrated. Doppler-shifted light from a frequency-modulated Ti:sapphire laser scattered from a supersonic flow is imaged through a potassium vapor cell and is detected by FM spectroscopy. The FM signal is used in closed-loop feedback control of the laser frequency to lock the Doppler-shifted scattered light to the resonance frequency of the filter. The difference between the filter resonance frequency and the laser frequency when the scattered light is frequency locked to the filter resonance is the flow-induced Doppler shift. Changes in flow velocity are tracked by changes in laser frequency, which is subsequently measured to obtain the Doppler shift. The frequency-locking capability of the technique was achieved with use of a simple analog controller. The random Doppler shift measurement errors (2varsigma) were approximately 20 MHz, which correspond to velocity measurement errors for the real-time measurement of less than 3% in a 10-Hz bandwidth.
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Affiliation(s)
- Walter D. Gillespie
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544
| | - Christoph J. Meinrenken
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544
| | - Walter R. Lempert
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544
| | - Richard B. Miles
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544
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Forkey JN, Lempert WR, Miles RB. Corrected and calibrated I2 absorption model at frequency-doubled Nd:YAG laser wavelengths. Appl Opt 1997; 36:6729-6738. [PMID: 18259537 DOI: 10.1364/ao.36.006729] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We present a computer model for accurately predicting absorption profiles for molecular iodine cells over the tuning range of frequency-doubled Nd:YAG lasers. The model is compared with experimental data for a number of different cell conditions. This model is intended for use in the design and optimization of absorption filters and for data analysis in applications in which the accuracy of the measurement is related closely to the accuracy with which the filter profile is known.
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Affiliation(s)
- J N Forkey
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
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Meinrenken CJ, Gillespie WD, Macheret S, Lempert WR, Miles RB. Time domain modeling of spectral collapse in high density molecular gases. J Chem Phys 1997. [DOI: 10.1063/1.473893] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Finkelstein ND, Lempert WR, Miles RB. Narrow-linewidth passband filter for ultraviolet rotational Raman imaging. Opt Lett 1997; 22:537-539. [PMID: 18183259 DOI: 10.1364/ol.22.000537] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We present a narrow-passband spectral filter capable of frequency-resolved imaging of rotational Raman light scattering with strong spectral rejection of out-of-band Raman, Rayleigh, and Mie scattering. The filter is based on mercury-vapor absorption, and subsequent resonant fluorescence and has a passband of less than 1 cm(-1). It is paired with an injection-seeded, cavity-locked, frequency-tripled Ti:sapphire laser that produces >30 mJ/pulse of single-mode, tunable light in the vicinity of 253.7 nm. The laser and filter are combined to spectrally resolve scattering from individual rotational Raman lines of nitrogen and oxygen.
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Grinstead JH, Finkelstein ND, Lempert WR. Doppler velocimetry in a supersonic jet by use of frequency-modulated filtered light scattering. Opt Lett 1997; 22:331-333. [PMID: 18183192 DOI: 10.1364/ol.22.000331] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A new nonintrusive velocimetry diagnostic that combines the sensitivity of frequency-modulated (FM) absorption spectroscopy techniques and the spectral discrimination afforded by atomic-vapor absorption filters is presented. Doppler-shifted light from a FM Ti:sapphire laser scattered from a supersonic flow is imaged through a potassium-vapor cell and is detected by FM spectroscopy. The difference between the potassium resonance frequency and the laser frequency when the scattered light is in resonance is the flow-induced Doppler shift.
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Forkey JN, Lempert WR, Miles RB. Observation of a 100-MHz frequency variation across the output of a frequency-doubled injection-seeded unstable-resonator Q-switched Nd:YAG laser. Opt Lett 1997; 22:230-232. [PMID: 18183159 DOI: 10.1364/ol.22.000230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report high-resolution measurements of the spatial variation of the optical frequency of an injection-seeded unstable-resonator Q-switched Nd:YAG laser. Images of the second harmonic taken through a molecular-iodine notch filter show frequency variations of as much as 100 MHz (second harmonic) between the center and the edge of the beam.
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Zhang B, Lempert WR, Miles RB, Diskin G. Efficient vibrational Raman conversion in O2 and N2 cells by use of superfluorescence seeding. Opt Lett 1993; 18:1132. [PMID: 19823311 DOI: 10.1364/ol.18.001132] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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