Generation of Coherent Radiation at 53.2 nm by Fifth-Harmonic Conversion

Abstract

PHYSICAL REVIEW LETTERS 6 DECEMBER 1976 sponding nd amplitudes and coherent addition of the pure Coulomb amplitude. 11 This amounts to neglecting the Coulomb modifications of the strong nd amplitudes which, in the present formalism, means neglect of all shorter-range Coulomb effects in V ,(M) and G 0 (/J) . However, we are now in the position to check the reliability of such a procedure. For this purpose we have included in Fig. 2 the cross sections obtained in such a way. It appears that at low energies this approximate treatment is rather unsatisfactory, whereas it may become more reliable at higher energies.In conclusion we emphasize once more that our approach to the Coulomb corrections in pd scattering is not only mathematically correct but also well suited for practical applications with no need for drastic approximations. (This is in contrast to the use of the formalism of Ref. 2 made in Ref. 4. Indeed, the results obtained there bear only a faint resemblance to ours or to the experimental data.) Apart from employing separable nuclear potentials, only one approximation has been made in the present calculations. Namely, the effective potentials and Green's functions which determine, via Eq. (7), the Coulomb-modified strong amplitude Tsc (ll) 9 are evaluated to lowest order in e 2 only. However, the neglect of higher-order terms can and will be checked. Furthermore, the difficult question which is bound to plague most other approaches of how many partial waves in the pp subsystem should be taken into account never does arise in our method where, characteristically, Frequency upconversion using third-harmonic generation and four-wave mixing has received attention in recent years for the generation of coherent radiation in the vacuum ultraviolet (VUV) region of the spectrum. 1 " 3 Such processes have been used to produce coherent radiation at wavelengths as short as 57.0 nm. 4 The generation of coherent light in the extreme ultraviolet region by third-order processes becomes increasingly difficult because of the scarcity of intense coherent sources at the required pumping wavelengths. the full three-dimensional Coulomb potential is built in.The development of frequency conversion techniques utilizing higher-order nonlinearities offers an attractive alternative to this approach, since it would allow larger steps along the frequency scale to be made in a single conversion process.Several of these processes have been suggested in the literature. 5 * 6 Although reasonable conversion efficiencies have been predicted for some of these interactions, the only published experimental evidence of such processes has been the fifth-The generation of coherent radiation of 53.2 nm by fifth-harmonic conversion of laser pulses at 266.1 nm in both Ne and He is reported.1540

Higher-Order Processes

“…(1) and (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). (1) and (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13).…”

“…The corresponding fifth-harmonic intensity is = 8.2944 χ 1 0^1 2 i V 4 l Z i 3 ) Z i 3 ) , | L 2 /^s i n 2 ( A / c 1 3 L / 2 ) n 5 nln\c*X\Ak\, 5 (A/c 1 3 L/2) ' K }…”

Asymptotic behaviour and general properties of harmonic generation susceptibilities

“…Since the pioneering work on second harmonic generation by Franken [3], a continuous development in this field has produced experimental and theoretical studies of harmonic generation in solids [4][5][6][7], molecules [8] and atoms [9,10], up to very high orders [11,12] in the last case.…”

“…This component is by definition proportional to e inωt and is given by the contribution to the term A j1 (t − τ 1 )...A j k (t − τ n ) in (7) obtained by the product of the only positive frequency components (∝ e −iωt ) of every factor A ji (t − τ i ). It can be written as: (9) where the nth order harmonic generation susceptibility is:…”

Resonant third harmonic generation of KrF laser in Ar gas

“…[1][2][3][4][5][6] The generation of a specific harmonic can be greatly enhanced if there is a real bound state to which the multiphoton resonance can occur. 1 That is the case in argon with a three-photon near-resonance of KrF laser at 248.5 nm.…”