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Bulletin of the American Physical Society

Wavelength dependence near a degeneracy point of lasing and 4-wave mixing processes in Na vapor

Suzanne Yoakum, Leo Moorman

Published May 1, 1993• 0 citations
OpenAlex

Abstract

Accurate measurements were made of lasing and 4-wave mixing processes in Na-vapor inside a double heatpipe oven. Scanning Nd:YAG pumped pulsed dye laser through the two-photon resonance 3s{sup 2}S{sub 1/2} {yields} 5s{sup 2}S{sub 1/2}, and a high resolution double-monochromator near the 5s - 4p{sup 2}P{sub 1/2,3/2} single photon resonance, we easily distinguished the two lasing multiplets due to J = {1/2} and 3/2 populations emitting blue 330 nm light. We also observed two other components. By varying the laser polarization, intensity and Na density these were determined to be parametric 4-wave mixing lines with maximum intensity for slight phase mismatch. As the dye laser was scanned, the wavelengths of the lasing and 4-wave mixing peaks shifted, each pair with its own slope, and crossed - a process providing a spectroscopic pump mechanism to populate the {vert_bar}M{sub J} {>=}{vert_bar} + {1/2} > magnetic substate of the ground state. Similar experiments are underway for other 4 wave mixing processes.

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TWO-PHOTON RESONANT OPTICAL WAVE-MIXING AND PARAMETRIC PROCESSES USING POTASSIUM 5d 2DJ STATE

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The, output of a pulsed dye-laser pumped by a frequency-doubled Nd: YAG laser is focused into a heat-pipe oven. The optical wave-mixing processes and parametric oscillations from two-photon excitation of 5d2DJ state in potassium vapor are investigated. Twenty-eight coherent lines within the range of 302-421 nm are generated. Splits and frequency shifts of the parametric oscillations and wavelengths and relative intensities of spectral lines in the wave-mixing processes are explained with a theoretical analysis based on the wave equation, atomic polarization and phase-match condition. The theoretical values are found to be in agreement with the experimental results.

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Stanley J. Bajic, R. N. Compton, John A. D. Stockdale +1 more

Laser excitation and ionization processes in dense (1--10 Torr) sodium vapor have been studied for laser wavelengths near the two-photon allowed nd /sup 2/D(n = 3, 4, 5) and ns /sup 2/S(n = 4, 5, 6) states. In particular, the 1 /sup 3//Sigma//sup +//sub g//yields/1 /sup 3//Sigma//sup +//sub u/ excimer emission in Na/sub 2/, predicted in 1980 by Konowalow and Julienne and observed recently by Dinev et al, was studied here in greater detail. Strong excimer emission (/similar to/30 nm) was observed for two-photon pumping to both sides of the unresolved 4D states, and weak excimer emission was seen when pumping near the 5D levels. The excimer emission exhibits a complicated pump laser profile with a pronounced ''dip'' at the 4d /sup 2/D two-photon resonance. Similarly, (2+1) photon ionization via the 3d /sup 2/D and 4d /sup 2/D states shows a dramatic decrease as the sodium density increases. These results can be attributed either to depleted 3d /sup 2/D or 4d /sup 2/D population due to stimulated electronic Raman scattering (SERS) or to the interference effects recently reported by Malcuit et al. and Krasnikov et al. and treated theoretically by Manykin and Afanas'ev and by Agarwal. It is argued thatmore » both mechanisms are operative.« less

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STIMULATED EMISSION BASED ON TWO-STEP HYBRID RESONANCE $A^{1}\Sigma_{u}^{+}$ OR $B^{1}\Pi_{u}$ STATE OF $Na.^{*}$

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The first step of the hybrid excitation in the experiment was achieved by using a pulse broadband ($\\sim$200 {\\AA}) dye laser beam through a heat pipe oven. But the total covered pumping wavelength region from 4600 {\\AA} to 6800 {\\AA} the populated upper electronic state in $Na_{2}$ should be either $A^{\\prime}\\Sigma_{u}$ or $B^{\\prime}\\Pi_{u}$ state. The excited sodium dimers $Na_{2}^{\\ast}$ transfered their energy to sodium atoms Na by near resonace collisions and the Na then would populate up the 3P level from ground state 3s. The Na were consequentely pumped up to 4D, 5D, 5S or 6S level from 3P by using a narrowband dye laser pumped by the same $N_{2}$ laser. The infrared stimulated radiation corresponding to the transitions of 4D-4P(2.34 $\\mu$m). 5D-4P(5.02$\\mu$m), 5S-4P(3.42 $\\mu$m) and 6S-5P(7.52 $\\mu$m) with cascade stimulated emission from 4P to 4S (2.20 $\\mu$m) and from 5P to 5S (5.43 $\\mu$m) were then obtained, Furthermore the dependence of the output energy on the pumping wavelengthes was measured and discussed.

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P. L. Zhang, Y. C. Wang, ARTHUR L. SCHAWLOW

A pulsed dye-laser beam (ωL) pumped by a frequency-doubled Nd:YAG laser is focused into a heat-pipe oven containing potassium vapor (nk ≈ 1016 cm−3). Two-photon resonant four-wave and six-wave mixing processes using the potassium 8s 2S1/2 state are investigated. Thirty-two coherent UV radiation lines are generated within the range of 300–400 nm through the processes ωUV = 2ωL ± ωIR and ωUV = 2ωL − ω′IR − ω″IR ± ω‴IR, where ωIR are frequencies of laser-induced IR waves generated in the vapor near the transitions 8S–7P, 7P–7S, 7P–5D, 8S–6P, 7S–6P, 5D–6P, etc. The influence of resonant enhancement on the UV line intensities and the phase-matching condition are analyzed.

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Degenerate four-wave mixing line shapes in sodium vapor under pulsed excitation

Prem Kumar

Degenerate four-wave mixing (DFWM) line shapes are investigated in sodium vapor near the D(2) resonance line using nearly Fourier-transform-limited pulses. At low pump intensities sub-Doppler resolution is obtained. When the Rabi frequency associated with the pump intensity becomes comparable with the ground-state hyperfine frequency separation of sodium, each component of the double-peaked DFWM spectrum splits further into two components. An adiabatic-following model explains the near-resonant intensity dependence of the DFWM signal. A qualitative explanation of the observed splitting is also given.

Optics Letters•Feb 1, 1985•13 citations
Accurate measurements were made of lasing and 4-wave mixing processes in Na-vapor inside a double heatpipe oven. Scanning Nd:YAG pumped pulsed dye laser through the two-photon resonance 3s{sup 2}S{sub 1/2} {yields} 5s{sup 2}S{sub 1/2}, and a high resolution double-monochromator near the 5s - 4p{sup 2}P{sub 1/2,3/2} single photon resonance, we easily distinguished the two lasing multiplets due to J = {1/2} and 3/2 populations emitting blue 330 nm light. We also observed two other components. By varying the laser polarization, intensity and Na density these were determined to be parametric 4-wave mixing lines with maximum intensity for slight phase mismatch. As the dye laser was scanned, the wavelengths of the lasing and 4-wave mixing peaks shifted, each pair with its own slope, and crossed - a process providing a spectroscopic pump mechanism to populate the {vert_bar}M{sub J} {>=}{vert_bar} + {1/2} > magnetic substate of the ground state. Similar experiments are underway for other 4 wave mixing processes.
The, output of a pulsed dye-laser pumped by a frequency-doubled Nd: YAG laser is focused into a heat-pipe oven. The optical wave-mixing processes and parametric oscillations from two-photon excitation of 5d2DJ state in potassium vapor are investigated. Twenty-eight coherent lines within the range of 302-421 nm are generated. Splits and frequency shifts of the parametric oscillations and wavelengths and relative intensities of spectral lines in the wave-mixing processes are explained with a theoretical analysis based on the wave equation, atomic polarization and phase-match condition. The theoretical values are found to be in agreement with the experimental results.
Laser excitation and ionization processes in dense (1--10 Torr) sodium vapor have been studied for laser wavelengths near the two-photon allowed nd /sup 2/D(n = 3, 4, 5) and ns /sup 2/S(n = 4, 5, 6) states. In particular, the 1 /sup 3//Sigma//sup +//sub g//yields/1 /sup 3//Sigma//sup +//sub u/ excimer emission in Na/sub 2/, predicted in 1980 by Konowalow and Julienne and observed recently by Dinev et al, was studied here in greater detail. Strong excimer emission (/similar to/30 nm) was observed for two-photon pumping to both sides of the unresolved 4D states, and weak excimer emission was seen when pumping near the 5D levels. The excimer emission exhibits a complicated pump laser profile with a pronounced ''dip'' at the 4d /sup 2/D two-photon resonance. Similarly, (2+1) photon ionization via the 3d /sup 2/D and 4d /sup 2/D states shows a dramatic decrease as the sodium density increases. These results can be attributed either to depleted 3d /sup 2/D or 4d /sup 2/D population due to stimulated electronic Raman scattering (SERS) or to the interference effects recently reported by Malcuit et al. and Krasnikov et al. and treated theoretically by Manykin and Afanas'ev and by Agarwal. It is argued thatmore » both mechanisms are operative.« less
Experimental studies have been made of conjugate wave generation in a Na metal vapor heat pipe. Detailed measurements of gain profiles, pump beam absorption, and parametric wave generation at infrared frequencies for phase conjugation near the two-photon resonance with the Na 4d2D5/2 state, yield details of the effects of parasitic processes on degenerate four-wave mixing. Studies are conducted with an excimer-pumped dye laser system with ~4 ns pulses of < 10mJ/pulse, traversing Na vapor heat pipe. Included in the measurements are pump beam depletion, probe and conjugate beam intensities, and infrared light which is generated by the strong pump beams through stimulated Raman (SR) and amplified spontaneous emission processes. The role of ac Stark shifting in degenerate four-wave mixing near the 4d level is studied. We find a new effect involving a large contribution to the ac Stark effect from the internally generated SR photons. We observe a rapid onset with pressure of stimulated Raman emission accompanied by a dramatic increase in the ac Stark profile of the 4d level, and the sharp onset of gain saturation for the phase conjugate signal, due to the competition of these two processes. This effect results in an ac Stark coefficient which can be very nonlinear in laser power and Na pressure.
STIMULATED EMISSION BASED ON TWO-STEP HYBRID RESONANCE A1Σu+A^{1}\Sigma_{u}^{+}A1Σu+​ OR B1ΠuB^{1}\Pi_{u}B1Πu​ STATE OF Na.∗Na.^{*}Na.∗
The first step of the hybrid excitation in the experiment was achieved by using a pulse broadband ($\\sim$200 {\\AA}) dye laser beam through a heat pipe oven. But the total covered pumping wavelength region from 4600 {\\AA} to 6800 {\\AA} the populated upper electronic state in Na2Na_{2}Na2​ should be either AprimeSigmauA^{\\prime}\\Sigma_{u}AprimeSigmau​ or BprimePiuB^{\\prime}\\Pi_{u}BprimePiu​ state. The excited sodium dimers Na2astNa_{2}^{\\ast}Na2ast​ transfered their energy to sodium atoms Na by near resonace collisions and the Na then would populate up the 3P level from ground state 3s. The Na were consequentely pumped up to 4D, 5D, 5S or 6S level from 3P by using a narrowband dye laser pumped by the same N2N_{2}N2​ laser. The infrared stimulated radiation corresponding to the transitions of 4D-4P(2.34 mu\\mumum). 5D-4P(5.02mu\\mumum), 5S-4P(3.42 mu\\mumum) and 6S-5P(7.52 mu\\mumum) with cascade stimulated emission from 4P to 4S (2.20 mu\\mumum) and from 5P to 5S (5.43 mu\\mumum) were then obtained, Furthermore the dependence of the output energy on the pumping wavelengthes was measured and discussed.
A pulsed dye-laser beam (ωL) pumped by a frequency-doubled Nd:YAG laser is focused into a heat-pipe oven containing potassium vapor (nk ≈ 1016 cm−3). Two-photon resonant four-wave and six-wave mixing processes using the potassium 8s 2S1/2 state are investigated. Thirty-two coherent UV radiation lines are generated within the range of 300–400 nm through the processes ωUV = 2ωL ± ωIR and ωUV = 2ωL − ω′IR − ω″IR ± ω‴IR, where ωIR are frequencies of laser-induced IR waves generated in the vapor near the transitions 8S–7P, 7P–7S, 7P–5D, 8S–6P, 7S–6P, 5D–6P, etc. The influence of resonant enhancement on the UV line intensities and the phase-matching condition are analyzed.
Degenerate four-wave mixing (DFWM) line shapes are investigated in sodium vapor near the D(2) resonance line using nearly Fourier-transform-limited pulses. At low pump intensities sub-Doppler resolution is obtained. When the Rabi frequency associated with the pump intensity becomes comparable with the ground-state hyperfine frequency separation of sodium, each component of the double-peaked DFWM spectrum splits further into two components. An adiabatic-following model explains the near-resonant intensity dependence of the DFWM signal. A qualitative explanation of the observed splitting is also given.