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Stimulated hyper Raman emission and super-fluorescent emission from sodium vapour
Volume
5 7, number
6
OPTICS COMMUNICATIONS
STIMULATED HYPER RAMAN EMISSION FROM SODIUM VAPOUR K. MORI ‘, Y. YASUDA,
N. SOKABE
Received
25 September
EMISSION
A. MURAI
and
Department of Applied Physics, Faculty of Engineering, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558, Japan
AND SUPER-FLUORESCENT
15 April 1986
Osaka City Uniuersity,
1985
Stimulated hyper Raman scattering at 2.3 pm due to the 4d-4p transition of Na atoms and super-fluorescent emission in the wavelength range from 7680 A to 7990 A due to the A’ZZ-X’Z: transition of Na, molecules were observed when sodium vapour was optically pumped by a N,-laser-pumped dye laser radiation with its frequency around the two-photon resonance of the 3s-4d transition of Na atoms. The former was as high as 64% in photon conversion efficiency and its frequency tunability was 26 cm-‘. The pump frequency increase to maximal Raman output was approximately 17276.6 cm-‘, which was higher than the 3s-4d two-photon resonance frequency (17274.4 cm-’ ). The latter was continuously observed over the pump wavelength range from 5740 A to 5840 A except the region in which Raman emission was produced. The pulse shape was composed of double peaks; each of them being 5 ns in FWHM and separated by 30 ns. Stimulated hyper Raman emission and super-fluorescent emission have shown different optimum temperatures of Na vapour.
1. Introduction The investigation of stimulated electronic Raman scattering (SERS) and stimulated hyper Raman scattering (SHRS) in metal vapour has attracted a considerable attention since the invention of a heat pipe oven in 1969 [ 11, A number of reports on SERS and SHRS have been devoted to alkali metal vapours [2-131. The major importance consists in its possibility to generate a coherent and tunable infrared emission. The first observation of SHRS in Na vapour was reported by Cotter et al. in 1977 [7]. They observed the infrared emission at a wavelength of 2.3 pm generated by the stimulated hyper Raman transition from the 3s to the 4p state via the intermediate 4d state of Na atoms. In their experiment, Na atoms were pumped with a dye laser which delivered an output energy of 8 mJ per pulse of 15 ns in width. The linewidth of the dye laser was 0.1 cm-l. They found that the infrared emission well generated over the pump frequency tuning range of 45 cm-l centered at ’ Present address: Hashiridani
418
Research Center, Sanyo Electric l-18-13, Hirakata, Osaka 573, Japan.
Co., Ltd.,
a wavelength of 5790 A and found that photon conversion efficiency was 2%. In this work, an experiment on Na vapour was carried out under somewhat different experimental condition from the previous one and an improved photon conversion efficiency was observed on the 3s-4p SHRS with much reduced input energies. The pump wavelength for maximum SHRS output was different from the previous observation. In addition to the SHRS, strong super-fluorescent emission (SFE), possibly from Na,, has been observed when the pump frequency is scanned over both lower and higher frequency regions than the SHRS resonance frequency. In this paper, experimental results on the SHRS and SFE are reported.
2. Experiments The experimental arrangement is shown in fig. 1. A nitrogen-laser-pumped dye laser which was built in our laboratory [ 141 delivered typically an output energy of 120 PJ per 5 ns pulse with Rhodamine 590 in 5 X lo-3 mol/l ethanol solution. The dye laser had 0 030-4018/86/$03.50 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
Volume 5 7, number 6
15 April 1986
OPTICS COMMUNICATIONS Stimulated hyper-Raman Super-fluorescent
em155’o”
em1551on
Super-fluore5cent eml*SlO”
a a
/m-l 5740
5760
Ii, I \A
a d%NA_,
5780 5800 PUMP DYE LASER WAVELENGTH h
5820
5840
Fig. 2. A survey excitation spectrum of sodium vapour as obtained with continuous scan of the dye laser wavelength. Buffer Ar gas pressure of 10 Torr and temperature of 45 1°C.
Fig. 1. Experimental setup.
In the first place, we will present
the experimental
results of the SHRS generation.
a spectral linewidth of approximately 0.2 cm-1 as measured with a solid etalon of finesse 8. The pulse repetition frequency was 3 Hz. The pump beam was splitted into two directions, one beam was used to monitor the pump power and the other was focussed into a heat pipe oven containing Na vapour and Ar as a buffer gas (-13 Torr), through a CaF, window. The heat pipe oven of 53 cm in length was made of a stainless steel pipe of 27.3 mm i.d. and the vapour column was 30 cm in length. The heat pipe oven was maintained at temperatures around 410°C. The generated ir emission was detected by a pyroelectric detector with the transmitted pump beam being blocked by coloured glass filters. The output energy of SHRS and SFE varied with the location of the focal point of the pump beam in the vapour column. The optimum focal position was located at 2-3 cm behind the boundary layer of the vapour column. We could recognize by eye that the passage of the pump beam was emitting a deep red fluorescence. For spectral isolation of the SHRS and the SFE, a proper combination of coloured glass filters or a grating monochromator was used. A small grating spectrograph was also used to take spectra of the SFE with infrared films.
3. Results and discussion The observed total output signal is shown in fig. 2 as a function of the pump wavelength. The central peak corresponds to the SHRS (-2.3 pm) and the broad signal extending over both sides of the SHRS is due to SFE which will be discussed later in detail.
Conversion efficiency and tunability of the SHRS were measured under optimum conditions in this apparatus. An output energy of 10 PJ per pulse was obtained for a pump energy of 120 pJ. Thus, energy conversion efficiency is estimated as 8.3%, or equivalently, photon conversion efficiency is estimated as approximately 64%. The SHRS was observed for the pump frequency range from 17270 cm-l to 17283 cm-l. The SHRS has a frequency tunability of 26 cm-l if it is assumed that the SHRS tunability is twice the pump frequency range in which the SHRS generates. The tunability of 26 cm-l observed in this work is a reasonable one in comparison with that reported by Cotter et al. [7] if we take into account the small input power adopted in this work. The photon conversion efficiency, however is quite different from the previous observation. The low efficiency in ref. [7 ] may be ascribed to saturation. Furthermore, the pump wavelength giving maximum SHRS output power was different from the previous observation. In the present experiment, the pump frequency for maximum SHRS output was located in a higher frequency region (-17 276.6 cm-l) than the two photon resonance frequency of the 3s-4d transition (17 274.4 cm-l), while Cotter et al. found it in a lower (-17 270.4 cm-l). Thus, the asymmetry in the emission profile may change with input power. The SFE was observed for a pump wavelength range from 5740 A to 5840 A. In fig. 2, the SFE signals are seen on both sides of the SHRS, while they are missing in the pump frequency range in which SHRS generates. The SFE appeared merely discontinuously as pump wavelength was scanned with re419
Volume 57, number 6
OPTICS COMMUNICATIONS
15 April 1986
UMP WAVELENGTH
(A,
Fig. 4. Super-fluorescent emission and absorption intensities g
2
10°,W
as a function of pump wavelength. T = 440°C for emission and T = 45 1°C for absorption. 25
PUMP POWER (kW)
Fig. 3. Super-fluorescent intensity as a function of pump power. Pump wavelength: 5807 A, temperature:
450°C.
duced intensities. Those signals had obviously different wavelengths from the SHRS signal and they could be well detected with a Si PIN photo-diode which had a spectral sensitivity for wavelengths not longer than 900 nm. Their origin can be attributed to molecules because the range of pump wavelength producing them extends over almost 100 A. The candidates may be NaZ, NaOH and Na20 which are oxidation impurities of Na [ 151. However, the vapour pressures of Na,O and NaOH at the temperatures of interest are much lower than that of Na2. Moreover, it may be expected that the Na sample has been purified to a certain degree due to the characteristic of the heat pipe oven [ 11. It is the most reasonable to conclude that the SFE signals are emitted by Na, molecules. It is known that Na, molecules have a partial vapour pressure of 2.8% in sodium vapour at a temperature of 410°C [16]. The change in the fluorescent intensity with dye laser pump power was examined to confirm the stimulation in emission. The experimental result is shown in fig. 3. It demonstrates the existence of a threshold pump power. A comparison between the absorption of the incident radiation and the SFE output energy in the pump wavelength range from 5812 A to 5820 A is shown in fig. 4. Good correlation between the two as seen in fig. 4 was also observed in the other range of pump wavelength wherein the SFE was produced. 420
The spectra of the SFE obtained for the pump wavelengths of 5823.1,5813.0,5806.6,5775.3 and 5756.8 A are shown in fig. 5. The SFE spectral lines distribute in the wavelength range from about 7680 a to 7990 A, while its spectrum is considerably different from each other for different pump frequencies. A similar spectrum of a stimulated emission from Na2 for the pump wavelength of 6040 A was reported by Itoh et al. [ 171. The output energy of the SFE and SHRS as a function of vapour temperature is shown in fig. 6. The optimum temperature for the SFE was 460°C which was different from that for the SHRS (410°C) [ 181. From those experimental results, it is reasonable to consider that the SFE originates in the transition between the A 1~: and X 1Ci states * of Na,. Precise molecular constants for the X lC+ and A ‘Zt states were reported by Kush et al. [ 19f and Kaminsky [20], respectively. However, owing to the perturbation by the a 3II state in the highly lying rotational levels of the A 1x: state [21], the assignment of the observed SFE lines are difficult even if the wavelengths are measured to high accuracy. By use of a PIN photo-diode, the SFE pulse was observed to be composed of double peaks (fig. 7). The FWHM of the two peaks was approximately 5 ns which was almost the same as that of the pump pulse. The time lag between the two peaks was approximately 30 ns and the pulse height of the second peak was one part of sixth of that of the first. A similar double peaked emission has been reported on the XC-BII * This band has the simplest rotational structure.
and 5756.8 A (e).
band of Na, excited by a dye laser [22], and it has been explained in terms of BII-AZ collisional excitation transfer followed by an AZ-XX optical transi-
tion. Such an explanation may not apply to the present case because the energy of the incident photons is not enough to excite Na2 molecules to the BfI state. In conclusion, sodium vapour has been optically pumped by a N2-laser-pumped dye laser radiation with
-3
FIRST
.% 3 T
4
TEMPERATURE (“C)
Fig. 6. Intensities of total super-fluorescent emission (closed circles) and stimulated hyper Raman emission (open circles) as a function of vapour temperature. The pump wavelength for SFE and SHRS were 5814 R and 5788 A, respectively, and the pump power was approximately 25 kW in both cases.
4
b
20 nsecldiv
Fig. 7. Pulse shape of Naa (A ‘C:--X ‘xi) super-fluorescent emission. Pump power: 25 kW (at 5815 A), temperature: 448°C.
421
Volume 5 7, number 6
OPTICS COMMUNICATIONS
its wavelength around the two-photon resonance of the 3s-4d transition of Na atoms. Stimulated hyper Raman emission at 2.3 pm due to the 4d-4p transition of Na atoms and super-fluorescent emission in the wavelength range from about 7680 A to 7990 A due to the A lC:-X 1~‘; transition of Na, molecule have been observed. The SHRS was as high as 64% in photon conversion efficiency and frequency tunability was 26 cm-l. The pump frequency for the maximum SHRS output was located in a higher frequency region than the 3s-4d two photon resonance frequency. Strong super-fluorescent emission originating in the A lZi-X 1X; of Na2 was observed over the pump frequency range from 5740 A to 5840 A, but it was missing for the pump frequencies that produced the SHRS. The SFE pulse composed of double peaks: each of them being 5 ns in FWHM and separated by 30 ns.
References [l] C.R.Vidaland J.Cooper,J.Appl.Phys.40(1969) 3370. 121 PP. Sorokin, J.J. Wynne and J.R. Lankard, Appl. Phys. Lett. 22 (1973) 342. [3] J.J. Wynne and P.P. Sorokin, J. Phys. B: Atom. Molec. Phys. 8 (1975) L37.
422
15 April 1986
[4] D. Cotter, D.C. Hanna and R. Wyatt, Optics Comm. 16 (1976) 256. [S] D. Cotter and D.C. Hanna, J. Phys. B: Atom. Molec. Phys. 9 (1976) 2165. [6] R.T.V. Kung and I. ltzkan, IEEE J. Quantum Electron. QE-13 (1977) 73. [7] D. Cotter, D.C. Hanna, W.H.W. Tuttlebee and M.A. Yuratich, OpticsComm. 22 (1977) 190. [S] D. Cotter and DC. Hanna, IEEE J. Quantum Electron. QE-14 (1978) 184. [9] W, Hartig, Appl. Phys. 15 (1978) 427. [lo] R.T. Hodgson, Appl. Phys. Lett. 34 (1979) 58. [ 111 P. Niay, P. Bernage and H. Bocquet, Optics Comm. 29 (1979) 369. [12] R. Wyatt and D.Cotter, OpticsComm. 32 (1980) 481. 1131 R. Wyatt and D. Cotter, Optics Comm. 37 (1981) 421. [14] Y, Yasuda, K. Mori, N. Sokabe and A. Murai, Memoirs of the Faculty of Engineering, Osaka University 23 (1982) 219. [ 15 ] C .C . Addison, The chemistry of the liquid alkali metals (Wiley-Interscience, 1985) p. 1288135. [16] M. Lapp and L.P. Harris, J. Quant. Spectrosc. Radiat. Transfer 6 (1966) 169. [17] H. ltoh, H. Uchiki and M. Matsuoka, Optics Comm. 18 (1976) 271. [18] V.G. Arkhipkin, A.K. Popov and V.P. Thnofeev, Optics Comm. 25 (1978) 111. [19] P. Kush and MM. Hessel, J. Chem. Phys. 68 (1978) 2591. [20] M.E. Kaminsky, J. Chem. Phys. 66 (1977) 4951. [Zl] P. Kusch and MM. Hessel, J. Chem. Phys. 63 (1975) 4087. [22] M.A. Henesian, R.L. Herbst and R.L. Byer, J. Appl. Phys. 47 (1976) 1515.
5 7, number
6
OPTICS COMMUNICATIONS
STIMULATED HYPER RAMAN EMISSION FROM SODIUM VAPOUR K. MORI ‘, Y. YASUDA,
N. SOKABE
Received
25 September
EMISSION
A. MURAI
and
Department of Applied Physics, Faculty of Engineering, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558, Japan
AND SUPER-FLUORESCENT
15 April 1986
Osaka City Uniuersity,
1985
Stimulated hyper Raman scattering at 2.3 pm due to the 4d-4p transition of Na atoms and super-fluorescent emission in the wavelength range from 7680 A to 7990 A due to the A’ZZ-X’Z: transition of Na, molecules were observed when sodium vapour was optically pumped by a N,-laser-pumped dye laser radiation with its frequency around the two-photon resonance of the 3s-4d transition of Na atoms. The former was as high as 64% in photon conversion efficiency and its frequency tunability was 26 cm-‘. The pump frequency increase to maximal Raman output was approximately 17276.6 cm-‘, which was higher than the 3s-4d two-photon resonance frequency (17274.4 cm-’ ). The latter was continuously observed over the pump wavelength range from 5740 A to 5840 A except the region in which Raman emission was produced. The pulse shape was composed of double peaks; each of them being 5 ns in FWHM and separated by 30 ns. Stimulated hyper Raman emission and super-fluorescent emission have shown different optimum temperatures of Na vapour.
1. Introduction The investigation of stimulated electronic Raman scattering (SERS) and stimulated hyper Raman scattering (SHRS) in metal vapour has attracted a considerable attention since the invention of a heat pipe oven in 1969 [ 11, A number of reports on SERS and SHRS have been devoted to alkali metal vapours [2-131. The major importance consists in its possibility to generate a coherent and tunable infrared emission. The first observation of SHRS in Na vapour was reported by Cotter et al. in 1977 [7]. They observed the infrared emission at a wavelength of 2.3 pm generated by the stimulated hyper Raman transition from the 3s to the 4p state via the intermediate 4d state of Na atoms. In their experiment, Na atoms were pumped with a dye laser which delivered an output energy of 8 mJ per pulse of 15 ns in width. The linewidth of the dye laser was 0.1 cm-l. They found that the infrared emission well generated over the pump frequency tuning range of 45 cm-l centered at ’ Present address: Hashiridani
418
Research Center, Sanyo Electric l-18-13, Hirakata, Osaka 573, Japan.
Co., Ltd.,
a wavelength of 5790 A and found that photon conversion efficiency was 2%. In this work, an experiment on Na vapour was carried out under somewhat different experimental condition from the previous one and an improved photon conversion efficiency was observed on the 3s-4p SHRS with much reduced input energies. The pump wavelength for maximum SHRS output was different from the previous observation. In addition to the SHRS, strong super-fluorescent emission (SFE), possibly from Na,, has been observed when the pump frequency is scanned over both lower and higher frequency regions than the SHRS resonance frequency. In this paper, experimental results on the SHRS and SFE are reported.
2. Experiments The experimental arrangement is shown in fig. 1. A nitrogen-laser-pumped dye laser which was built in our laboratory [ 141 delivered typically an output energy of 120 PJ per 5 ns pulse with Rhodamine 590 in 5 X lo-3 mol/l ethanol solution. The dye laser had 0 030-4018/86/$03.50 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
Volume 5 7, number 6
15 April 1986
OPTICS COMMUNICATIONS Stimulated hyper-Raman Super-fluorescent
em155’o”
em1551on
Super-fluore5cent eml*SlO”
a a
/m-l 5740
5760
Ii, I \A
a d%NA_,
5780 5800 PUMP DYE LASER WAVELENGTH h
5820
5840
Fig. 2. A survey excitation spectrum of sodium vapour as obtained with continuous scan of the dye laser wavelength. Buffer Ar gas pressure of 10 Torr and temperature of 45 1°C.
Fig. 1. Experimental setup.
In the first place, we will present
the experimental
results of the SHRS generation.
a spectral linewidth of approximately 0.2 cm-1 as measured with a solid etalon of finesse 8. The pulse repetition frequency was 3 Hz. The pump beam was splitted into two directions, one beam was used to monitor the pump power and the other was focussed into a heat pipe oven containing Na vapour and Ar as a buffer gas (-13 Torr), through a CaF, window. The heat pipe oven of 53 cm in length was made of a stainless steel pipe of 27.3 mm i.d. and the vapour column was 30 cm in length. The heat pipe oven was maintained at temperatures around 410°C. The generated ir emission was detected by a pyroelectric detector with the transmitted pump beam being blocked by coloured glass filters. The output energy of SHRS and SFE varied with the location of the focal point of the pump beam in the vapour column. The optimum focal position was located at 2-3 cm behind the boundary layer of the vapour column. We could recognize by eye that the passage of the pump beam was emitting a deep red fluorescence. For spectral isolation of the SHRS and the SFE, a proper combination of coloured glass filters or a grating monochromator was used. A small grating spectrograph was also used to take spectra of the SFE with infrared films.
3. Results and discussion The observed total output signal is shown in fig. 2 as a function of the pump wavelength. The central peak corresponds to the SHRS (-2.3 pm) and the broad signal extending over both sides of the SHRS is due to SFE which will be discussed later in detail.
Conversion efficiency and tunability of the SHRS were measured under optimum conditions in this apparatus. An output energy of 10 PJ per pulse was obtained for a pump energy of 120 pJ. Thus, energy conversion efficiency is estimated as 8.3%, or equivalently, photon conversion efficiency is estimated as approximately 64%. The SHRS was observed for the pump frequency range from 17270 cm-l to 17283 cm-l. The SHRS has a frequency tunability of 26 cm-l if it is assumed that the SHRS tunability is twice the pump frequency range in which the SHRS generates. The tunability of 26 cm-l observed in this work is a reasonable one in comparison with that reported by Cotter et al. [7] if we take into account the small input power adopted in this work. The photon conversion efficiency, however is quite different from the previous observation. The low efficiency in ref. [7 ] may be ascribed to saturation. Furthermore, the pump wavelength giving maximum SHRS output power was different from the previous observation. In the present experiment, the pump frequency for maximum SHRS output was located in a higher frequency region (-17 276.6 cm-l) than the two photon resonance frequency of the 3s-4d transition (17 274.4 cm-l), while Cotter et al. found it in a lower (-17 270.4 cm-l). Thus, the asymmetry in the emission profile may change with input power. The SFE was observed for a pump wavelength range from 5740 A to 5840 A. In fig. 2, the SFE signals are seen on both sides of the SHRS, while they are missing in the pump frequency range in which SHRS generates. The SFE appeared merely discontinuously as pump wavelength was scanned with re419
Volume 57, number 6
OPTICS COMMUNICATIONS
15 April 1986
UMP WAVELENGTH
(A,
Fig. 4. Super-fluorescent emission and absorption intensities g
2
10°,W
as a function of pump wavelength. T = 440°C for emission and T = 45 1°C for absorption. 25
PUMP POWER (kW)
Fig. 3. Super-fluorescent intensity as a function of pump power. Pump wavelength: 5807 A, temperature:
450°C.
duced intensities. Those signals had obviously different wavelengths from the SHRS signal and they could be well detected with a Si PIN photo-diode which had a spectral sensitivity for wavelengths not longer than 900 nm. Their origin can be attributed to molecules because the range of pump wavelength producing them extends over almost 100 A. The candidates may be NaZ, NaOH and Na20 which are oxidation impurities of Na [ 151. However, the vapour pressures of Na,O and NaOH at the temperatures of interest are much lower than that of Na2. Moreover, it may be expected that the Na sample has been purified to a certain degree due to the characteristic of the heat pipe oven [ 11. It is the most reasonable to conclude that the SFE signals are emitted by Na, molecules. It is known that Na, molecules have a partial vapour pressure of 2.8% in sodium vapour at a temperature of 410°C [16]. The change in the fluorescent intensity with dye laser pump power was examined to confirm the stimulation in emission. The experimental result is shown in fig. 3. It demonstrates the existence of a threshold pump power. A comparison between the absorption of the incident radiation and the SFE output energy in the pump wavelength range from 5812 A to 5820 A is shown in fig. 4. Good correlation between the two as seen in fig. 4 was also observed in the other range of pump wavelength wherein the SFE was produced. 420
The spectra of the SFE obtained for the pump wavelengths of 5823.1,5813.0,5806.6,5775.3 and 5756.8 A are shown in fig. 5. The SFE spectral lines distribute in the wavelength range from about 7680 a to 7990 A, while its spectrum is considerably different from each other for different pump frequencies. A similar spectrum of a stimulated emission from Na2 for the pump wavelength of 6040 A was reported by Itoh et al. [ 171. The output energy of the SFE and SHRS as a function of vapour temperature is shown in fig. 6. The optimum temperature for the SFE was 460°C which was different from that for the SHRS (410°C) [ 181. From those experimental results, it is reasonable to consider that the SFE originates in the transition between the A 1~: and X 1Ci states * of Na,. Precise molecular constants for the X lC+ and A ‘Zt states were reported by Kush et al. [ 19f and Kaminsky [20], respectively. However, owing to the perturbation by the a 3II state in the highly lying rotational levels of the A 1x: state [21], the assignment of the observed SFE lines are difficult even if the wavelengths are measured to high accuracy. By use of a PIN photo-diode, the SFE pulse was observed to be composed of double peaks (fig. 7). The FWHM of the two peaks was approximately 5 ns which was almost the same as that of the pump pulse. The time lag between the two peaks was approximately 30 ns and the pulse height of the second peak was one part of sixth of that of the first. A similar double peaked emission has been reported on the XC-BII * This band has the simplest rotational structure.
and 5756.8 A (e).
band of Na, excited by a dye laser [22], and it has been explained in terms of BII-AZ collisional excitation transfer followed by an AZ-XX optical transi-
tion. Such an explanation may not apply to the present case because the energy of the incident photons is not enough to excite Na2 molecules to the BfI state. In conclusion, sodium vapour has been optically pumped by a N2-laser-pumped dye laser radiation with
-3
FIRST
.% 3 T
4
TEMPERATURE (“C)
Fig. 6. Intensities of total super-fluorescent emission (closed circles) and stimulated hyper Raman emission (open circles) as a function of vapour temperature. The pump wavelength for SFE and SHRS were 5814 R and 5788 A, respectively, and the pump power was approximately 25 kW in both cases.
4
b
20 nsecldiv
Fig. 7. Pulse shape of Naa (A ‘C:--X ‘xi) super-fluorescent emission. Pump power: 25 kW (at 5815 A), temperature: 448°C.
421
Volume 5 7, number 6
OPTICS COMMUNICATIONS
its wavelength around the two-photon resonance of the 3s-4d transition of Na atoms. Stimulated hyper Raman emission at 2.3 pm due to the 4d-4p transition of Na atoms and super-fluorescent emission in the wavelength range from about 7680 A to 7990 A due to the A lC:-X 1~‘; transition of Na, molecule have been observed. The SHRS was as high as 64% in photon conversion efficiency and frequency tunability was 26 cm-l. The pump frequency for the maximum SHRS output was located in a higher frequency region than the 3s-4d two photon resonance frequency. Strong super-fluorescent emission originating in the A lZi-X 1X; of Na2 was observed over the pump frequency range from 5740 A to 5840 A, but it was missing for the pump frequencies that produced the SHRS. The SFE pulse composed of double peaks: each of them being 5 ns in FWHM and separated by 30 ns.
References [l] C.R.Vidaland J.Cooper,J.Appl.Phys.40(1969) 3370. 121 PP. Sorokin, J.J. Wynne and J.R. Lankard, Appl. Phys. Lett. 22 (1973) 342. [3] J.J. Wynne and P.P. Sorokin, J. Phys. B: Atom. Molec. Phys. 8 (1975) L37.
422
15 April 1986
[4] D. Cotter, D.C. Hanna and R. Wyatt, Optics Comm. 16 (1976) 256. [S] D. Cotter and D.C. Hanna, J. Phys. B: Atom. Molec. Phys. 9 (1976) 2165. [6] R.T.V. Kung and I. ltzkan, IEEE J. Quantum Electron. QE-13 (1977) 73. [7] D. Cotter, D.C. Hanna, W.H.W. Tuttlebee and M.A. Yuratich, OpticsComm. 22 (1977) 190. [S] D. Cotter and DC. Hanna, IEEE J. Quantum Electron. QE-14 (1978) 184. [9] W, Hartig, Appl. Phys. 15 (1978) 427. [lo] R.T. Hodgson, Appl. Phys. Lett. 34 (1979) 58. [ 111 P. Niay, P. Bernage and H. Bocquet, Optics Comm. 29 (1979) 369. [12] R. Wyatt and D.Cotter, OpticsComm. 32 (1980) 481. 1131 R. Wyatt and D. Cotter, Optics Comm. 37 (1981) 421. [14] Y, Yasuda, K. Mori, N. Sokabe and A. Murai, Memoirs of the Faculty of Engineering, Osaka University 23 (1982) 219. [ 15 ] C .C . Addison, The chemistry of the liquid alkali metals (Wiley-Interscience, 1985) p. 1288135. [16] M. Lapp and L.P. Harris, J. Quant. Spectrosc. Radiat. Transfer 6 (1966) 169. [17] H. ltoh, H. Uchiki and M. Matsuoka, Optics Comm. 18 (1976) 271. [18] V.G. Arkhipkin, A.K. Popov and V.P. Thnofeev, Optics Comm. 25 (1978) 111. [19] P. Kush and MM. Hessel, J. Chem. Phys. 68 (1978) 2591. [20] M.E. Kaminsky, J. Chem. Phys. 66 (1977) 4951. [Zl] P. Kusch and MM. Hessel, J. Chem. Phys. 63 (1975) 4087. [22] M.A. Henesian, R.L. Herbst and R.L. Byer, J. Appl. Phys. 47 (1976) 1515.