1286 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. QE-21, NO. 8, AUGUST 1985 z Optical Parametric Interactions in 3-Methyl-4- Nitropyridine-I-Oxide (POM) Single Crystals JOSEPH zyxwvut NMLKJ ZYSS, ISABELLE LEDOUX, ROLLAND B. HIERLE, RAMA K. RAJ, AND JEAN-LOUIS OUDAR Abstract-Various configurations of three-wave parametric interac- bilities measured [52], [56]-[59]. However, to our h o w l - tions are reported at the picosecond time scale, in 3-methyl-4-nitropyr- edge, the investigation of parametric effects was limited idine-1-oxide (POM) single crystals. Wavelength dispersion of phase- matched second-harmonic generation orientation is experimentally so far to MAP [60] (fluorescence and amplification) and established within the 0.8-2 zyxwvutsr GFEDCBA pm range using as fundamental input the urea (sum-frequency mixing [591 and parametric Oscilla idler and signal emissions of a picosecond LiI03 parametric emitter. tion [61]); in particular, no parametric effects Were e Efficient parametric amplification is demonstrated: at degeneracy a gain reported, to our knowledge, in an organic crystal at the of lo3 is measured for a pump intensity of 130 MW . cm-' at 0.53 pm p~cosecon~ tirne scale, leading to single-pass pico and an input signal of zyxwvuts FEDCBA 5 kW . cm-' at 1.06 pm. Single pass parametric emission is achieved, for the first time in an parametric emission. organic crystal, yielding 200 kW . em-' at 1.06 pm, using the fre- In this paper we successively report the experimen- quency-doubled output of a passively mode-locked YAG system. Both tal determination of phase-matching conditions for fre- dispersion and interaction length dependence of the experimental gain quency doubling and parametric emission (crystal orien are accounted for. tation versus wavelength) within the transparen range of POM crystals, and the demonstration of efficient para- I. INTRODUCTION metric amplification and single-pass parametric em number of applications of three-wave interactions , such as second-harmonic generation [14]- 11. EXPERIMENTAL SETUP [18], frequency up- or down-conversion [4], [SI-[ 131 , A. Optical Picosecond Source [191-[2119 parametric amp1ification 14i, 3 l 2 l 1 9 In the experiments further described, a home-made, ac- emission [211-[251 , or [111, [261-[301 zyxwv NMLKJ 9 require tively mode-locked picosecond Nd:YAG laser at 1.0 LLm materials of increased quadratic nonlinear efficiency, high was used. The hig., peak-power pulses lead to nonlinear In addition, the short pulses, duration consider- ably raises the damage threshold of the illuminated crys- with 15 ns to a damage thresh- old higher than 270 MW cmP2 with 25 ps laser pulses. Such parametric effects were already obtained in a num- The picosecond Nd:YAG laser emits a 35 ps pulsed beam, Optical damage and Optical quality. conversion rates higher than allowed by nanosecond Parametric emission is of special interest, enabling the efficient emission of short tunable pulses in the near in- range is not readily and continuously available through tained at o.532 LLm by POM is zyx ML 50 MW . cm-2 classical sources and is of great relevance toward spectro- laser pulse duration, to be scopic studies in semiconductors [31]-[34]. frared [221-[251, from to pm. This tals. As an example, the maximum power density sus- ber of inorganic materia1s (KDP [351, LiN03 [36i , [371, at 3 Hz repetition rate, with 150 MW maximum peak LiIo3 1381 7 1391 9 Ba2NaNb5015 [40i). The search for new power and a 5 mm diameter beam after amplification. The and possibly more efficient nonlinear materials has evi- horizontal polarization of the 1.064 LLm laser beam is ro- cases, demonstrate efficiencies at least one order of mag- to satisfy type-II index matching conditions for second- nitude above that of classical inorganic materials [41]-[55] harmonic generation in a 25 mm KDP crystal. The con- ing feature of this class of materials jointly results from 0.532 LLm pulse duration is 25 ps, its diameter is mm, the virtually unlimited number of structures available and the power density available for subsequent pumping of through organic synthesis and the existence of a now well- a LiIo3 parametric generator ranges from zy H 70 270 proved set of rules allowing for the prediction of both MW . cm-2. The remaining infrared light at the output structures. Highly efficient second-harmonic generation oriented at zyxw KJIH 450 with respect to the incident beam and re- organic crystals and second-order macroscopic suscepti- gering photodiode. The o.532 LLm laser beam pumps a 25 Manuscript received March 22, 1985. mm long LiI03 single-pass parametric emitter cut The authors are with the CNET Laboratoire de Bagneux, 92220 Bag- mal incidence for degenerate phase-matched emission. neux, France. This crystal acts as a tunable infrared source, the pump the interest of Organic compounds~ which, in Some tated to 45" after passage through a half-wavelength plate and higher damage The most version rate in the KDP crystal is close to 30 percent. !bear and nonlinear optical properties in view Of these of the KDP doubler is eliminated by a BG 18 Schott filter were PreviouslY Performed in a number Of flecting about 5 percent of the harmonic light onto a trig- 0018-9197/80/0800-1286$01.00 zyxw JIHG 0 1985 IEEE