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A tunable infrared parametric oscillator in a CdSe crystal
Voh~me t), numlx'r 3
OPTICS COMMUNICATIONS
November 1973
A TUNABLE INFRARED PARAMETRIC OSCILLATOR IN A C d S e C R Y S T A L A.A. DAVYDOV, UA. KULEVSKII, A.M. PROKHOROV, A.D. SAVEL'EV, V.V. SMIRNOV and A.V. SHIRKOV t: N. !. ebedev Physica,! lnstitu te o f the Academy o f Sciences o f the USSR, Leninsky Prospect 53, Moscow, USSR Received 23 August 1973
~4e have demonstraled an infrared singly resonant parametric tunable oscillator in a CdSe crystal, l~le oscillator x~a, pumped at 2.36 u tCal- z :Dy ~'÷ laser) and has been operated with peak output power in the tens k¢,' range. Tuning from 2.8 u to 3.36 ~ and fre,m 7.88 , to 13.7 ~t with 1.5 c m - l bandwidth was obtained with a good temperature stabiht.~ of the parametric wavelengths.
Re~nfly we have reported a singly resonant pulsed optical parametric oscillator in CdSe using a CaF 2 :Dy 2+ laser as a pump [ 1]. The parametric wavelengths 3.37/a and 7.86/a were obtained without tuning. ~ i s paper is dealing with investigations of the optical parametric oscillator (OPO) in CdSe with temperature and ~gle tuning of the wavelengths. The OPOwas pumped with a Q-switched CaF 2:135'2+ laser with a p
mE density of 2.5 MW/cm 2. When the incident pump poa, er was 3 times above the threshold, a good stability from pulse to pulse oscillations has been observed. At 90 ° orientation when the operation of the oscillator was 4 times above the threshold, 15% of the energy converted into the idler wave. The parametric pulse duration was about 40 nsec. The energy' conversion decreased with the ,angle 0 and at 65 ° it was about 4~. We studied the temperature tuning of the parametric wavelengths for CdSe at q0 ° orientation. V,qhen the temperature of the crystal varied from ~50 K to 420 K the shift of the parametric frequency was only 29 crn- 1. The angle tuning of the parametric wavelengths with pump of 2.36 ~ was studied also. Fig. 1 shows the angle tuning curves for coUinear and non. collinear parametric iateraction which are calculated on the basis of refractive indexes presented in [3]. The solid lines are the theoretical tuning curves. The points show the measured wavelengths as a function of the angle 0 for collinear parametric interaction at room temperature. The parametric wavelengths were tuned from 2.8 t~ to 3.36/a for signal waves and from 7.88/a to 13.7/a for idler ones by changing the angle 0 between 90 ° and 65 °. The accuracy of the wave. length measurement was 0.03/~ and for 0 was 0.5 °. It should be noted that tterbst and Byer [2] have obtained tunable parametric oscillation in the 9.8/a to 10.4/a region pumped with the i.83/a line of an YAG:Nd laser.
Volume 9, number 3
OPTICS COMMUNICATIONS
, ,2 .\\
~ \
November 1973
CaSe 36
0 tO
28 -t
tO
1~
1'8
Fig. 2. a = stability factor; b = gain bandwidth; ! = 1 cm.
2
! -~
--------5
0"
ro
ao
Fig. i. Angle tuning curves for CdSe with h = 2.36 u. ! = collinear interaction @ = 0; 2,3 = noncollinear interaction ~ = 0,5 °, 1° ; kp, ks, k i = wave vectors of pump, signal, idler frequencies; 0 = angle between signal wavevector and CdSe optic axis; ff = angle between pumping wavevector and signal one.
All the~ investigations have demonstrated the possibility of obtaining powerful parametric oscillation in CdSe with convenient angle tuning of the parametric wavelength in a wide region with a good temperature stability. Fig. 2. shows the stability factor for the idler wave and the gain bandwidth which were found from the refractive indexes by the following formulas
0v i
_
{0%
Oks
{0k i
0k s
.
l
and i (0ks
At, lore-l] = ~ \ ~
bk i
I
the parametric wavelengths under 90 ° phase-matching conditions. The pump wavelengths which give the widest tuning range for parametric wavelengths in CdSe lie in the 2.3 p to 3.0/a region. The CaF 2 :Dy 2+ laser which we have used has wavelengths in this region, has low threshold and provides high repetition frequencies up to 103 pulse/sec [6]. However, the necessity to work with liquid nytrogen temperatures stimulates the search for pump sources for OPO in CdSe at room temperature. We have reported in [7] about the generation of laser t r a n s i t i o n 4111/2--+ 4113/2 o f Er 3+ in CaF2: ErF 3 crystals at room temperature. The laser wavelength was 2.73/a. The energy of a giant pulse in Q-switch for a 120 mm laser crystal was 0.3 J with 25 nsec pulse duration. Recently Keig and Deshazer [8] have informed about laser generation of the transition 3+.. Cr3+ 3F 4 ~ 3H 5 of Tn3+ (k = 2.35 ta) in YAIO3 • T m crystals at room temperature. One can hope that these lasers will be convenient as a pump source for CdSe OPO. In conclusion we should like to note that this power. ful tunable infrared source is probably to find wide applications.
~v i ) obtained from refs. [4] and [5]. Here I = the CdSe crystal length, kp, ks, k i and Up, Vs, vi are the wavevectors and the frequencies for the pumping, the signal and the idler wave, respectively. The bandwidth of die parametric oscillation measured by means of a scan interferometer was 1.5 cm- I Olalf-width). The mode structure was not observed due to insufficient resolution of the interferome ter. One can believe that use of CdSxSel_ x mixed crystals of variable x concentration will provide tuning of
We wish to thank V.G. Koloshnikov and V.A. Ageikin for placing their scan interferometer at our disposal and for the help in measuring the spectral bandwidth of the parametric radiation.
References I 1] A.A. Davydov, L.A. Kulevskii, A.M. Prokhorov, A.D. Savel'ev and V.V. Smirnov, Z t I E T F P ~ u a 15 (1972) 12. [2] R.L. Herbst and R.L. Byer, Appl. Phys. Lett. 21 11972) 189.
235
Vohmlc 9. numt.x'r 3
OPTICS COMMUNICATIONS
131 NI. Vltrikhov~y, L.F. Gudymenko, A.F. Maznichenko, V N. Malinko, [.V. Podlisnyi and S.F. Terekhova, Ukr. tt~ J. 12~1967)726; M,t'. Llslt,,,a, L.I . Gud) mcnko, V.N. Malmko and SAC Terekhtwa, Phys. Star. Sol. 31 f19"59) 389. 141 A.I. Kovri~n and R.L. Byer, IEEE J. of QE-5 (1969) 7. 15] R.L Byer and S.1t. Itarris, Phys. Rev. 168 (1968) 1064. [el V,V. Kostm, L.A. Kulevskii, T.M. Murina, A.M. Prokhorov and A.A. Tikhonov, II".EE ]. of QE-2 (1966) 611 ; Zh.
236
November 1973
Prikladnoy Spectros., 6 (1967) 33. V.I. Zhekhov, L.A. Kulevskii, TM. Murina, M. Prokhorov and V.V. Smimov, Radiotecknika i electronika l 5 ( | 970) 2130. 17] Report of the Intern. Conf. "Lasers und ihre Anwendungen" (Juni 1973), Dresden, Germany. 181 G.A. Keig and L.G. Deshazer, Laser + Electronics 3 (1972) 45.
OPTICS COMMUNICATIONS
November 1973
A TUNABLE INFRARED PARAMETRIC OSCILLATOR IN A C d S e C R Y S T A L A.A. DAVYDOV, UA. KULEVSKII, A.M. PROKHOROV, A.D. SAVEL'EV, V.V. SMIRNOV and A.V. SHIRKOV t: N. !. ebedev Physica,! lnstitu te o f the Academy o f Sciences o f the USSR, Leninsky Prospect 53, Moscow, USSR Received 23 August 1973
~4e have demonstraled an infrared singly resonant parametric tunable oscillator in a CdSe crystal, l~le oscillator x~a, pumped at 2.36 u tCal- z :Dy ~'÷ laser) and has been operated with peak output power in the tens k¢,' range. Tuning from 2.8 u to 3.36 ~ and fre,m 7.88 , to 13.7 ~t with 1.5 c m - l bandwidth was obtained with a good temperature stabiht.~ of the parametric wavelengths.
Re~nfly we have reported a singly resonant pulsed optical parametric oscillator in CdSe using a CaF 2 :Dy 2+ laser as a pump [ 1]. The parametric wavelengths 3.37/a and 7.86/a were obtained without tuning. ~ i s paper is dealing with investigations of the optical parametric oscillator (OPO) in CdSe with temperature and ~gle tuning of the wavelengths. The OPOwas pumped with a Q-switched CaF 2:135'2+ laser with a p
mE density of 2.5 MW/cm 2. When the incident pump poa, er was 3 times above the threshold, a good stability from pulse to pulse oscillations has been observed. At 90 ° orientation when the operation of the oscillator was 4 times above the threshold, 15% of the energy converted into the idler wave. The parametric pulse duration was about 40 nsec. The energy' conversion decreased with the ,angle 0 and at 65 ° it was about 4~. We studied the temperature tuning of the parametric wavelengths for CdSe at q0 ° orientation. V,qhen the temperature of the crystal varied from ~50 K to 420 K the shift of the parametric frequency was only 29 crn- 1. The angle tuning of the parametric wavelengths with pump of 2.36 ~ was studied also. Fig. 1 shows the angle tuning curves for coUinear and non. collinear parametric iateraction which are calculated on the basis of refractive indexes presented in [3]. The solid lines are the theoretical tuning curves. The points show the measured wavelengths as a function of the angle 0 for collinear parametric interaction at room temperature. The parametric wavelengths were tuned from 2.8 t~ to 3.36/a for signal waves and from 7.88/a to 13.7/a for idler ones by changing the angle 0 between 90 ° and 65 °. The accuracy of the wave. length measurement was 0.03/~ and for 0 was 0.5 °. It should be noted that tterbst and Byer [2] have obtained tunable parametric oscillation in the 9.8/a to 10.4/a region pumped with the i.83/a line of an YAG:Nd laser.
Volume 9, number 3
OPTICS COMMUNICATIONS
, ,2 .\\
~ \
November 1973
CaSe 36
0 tO
28 -t
tO
1~
1'8
Fig. 2. a = stability factor; b = gain bandwidth; ! = 1 cm.
2
! -~
--------5
0"
ro
ao
Fig. i. Angle tuning curves for CdSe with h = 2.36 u. ! = collinear interaction @ = 0; 2,3 = noncollinear interaction ~ = 0,5 °, 1° ; kp, ks, k i = wave vectors of pump, signal, idler frequencies; 0 = angle between signal wavevector and CdSe optic axis; ff = angle between pumping wavevector and signal one.
All the~ investigations have demonstrated the possibility of obtaining powerful parametric oscillation in CdSe with convenient angle tuning of the parametric wavelength in a wide region with a good temperature stability. Fig. 2. shows the stability factor for the idler wave and the gain bandwidth which were found from the refractive indexes by the following formulas
0v i
_
{0%
Oks
{0k i
0k s
.
l
and i (0ks
At, lore-l] = ~ \ ~
bk i
I
the parametric wavelengths under 90 ° phase-matching conditions. The pump wavelengths which give the widest tuning range for parametric wavelengths in CdSe lie in the 2.3 p to 3.0/a region. The CaF 2 :Dy 2+ laser which we have used has wavelengths in this region, has low threshold and provides high repetition frequencies up to 103 pulse/sec [6]. However, the necessity to work with liquid nytrogen temperatures stimulates the search for pump sources for OPO in CdSe at room temperature. We have reported in [7] about the generation of laser t r a n s i t i o n 4111/2--+ 4113/2 o f Er 3+ in CaF2: ErF 3 crystals at room temperature. The laser wavelength was 2.73/a. The energy of a giant pulse in Q-switch for a 120 mm laser crystal was 0.3 J with 25 nsec pulse duration. Recently Keig and Deshazer [8] have informed about laser generation of the transition 3+.. Cr3+ 3F 4 ~ 3H 5 of Tn3+ (k = 2.35 ta) in YAIO3 • T m crystals at room temperature. One can hope that these lasers will be convenient as a pump source for CdSe OPO. In conclusion we should like to note that this power. ful tunable infrared source is probably to find wide applications.
~v i ) obtained from refs. [4] and [5]. Here I = the CdSe crystal length, kp, ks, k i and Up, Vs, vi are the wavevectors and the frequencies for the pumping, the signal and the idler wave, respectively. The bandwidth of die parametric oscillation measured by means of a scan interferometer was 1.5 cm- I Olalf-width). The mode structure was not observed due to insufficient resolution of the interferome ter. One can believe that use of CdSxSel_ x mixed crystals of variable x concentration will provide tuning of
We wish to thank V.G. Koloshnikov and V.A. Ageikin for placing their scan interferometer at our disposal and for the help in measuring the spectral bandwidth of the parametric radiation.
References I 1] A.A. Davydov, L.A. Kulevskii, A.M. Prokhorov, A.D. Savel'ev and V.V. Smirnov, Z t I E T F P ~ u a 15 (1972) 12. [2] R.L. Herbst and R.L. Byer, Appl. Phys. Lett. 21 11972) 189.
235
Vohmlc 9. numt.x'r 3
OPTICS COMMUNICATIONS
131 NI. Vltrikhov~y, L.F. Gudymenko, A.F. Maznichenko, V N. Malinko, [.V. Podlisnyi and S.F. Terekhova, Ukr. tt~ J. 12~1967)726; M,t'. Llslt,,,a, L.I . Gud) mcnko, V.N. Malmko and SAC Terekhtwa, Phys. Star. Sol. 31 f19"59) 389. 141 A.I. Kovri~n and R.L. Byer, IEEE J. of QE-5 (1969) 7. 15] R.L Byer and S.1t. Itarris, Phys. Rev. 168 (1968) 1064. [el V,V. Kostm, L.A. Kulevskii, T.M. Murina, A.M. Prokhorov and A.A. Tikhonov, II".EE ]. of QE-2 (1966) 611 ; Zh.
236
November 1973
Prikladnoy Spectros., 6 (1967) 33. V.I. Zhekhov, L.A. Kulevskii, TM. Murina, M. Prokhorov and V.V. Smimov, Radiotecknika i electronika l 5 ( | 970) 2130. 17] Report of the Intern. Conf. "Lasers und ihre Anwendungen" (Juni 1973), Dresden, Germany. 181 G.A. Keig and L.G. Deshazer, Laser + Electronics 3 (1972) 45.