Shortwavelength V: Physics with Intense Laser Pulses最新文献

{"title":"Super-Dressed Two-Level Atom: Very High Harmonic Generation and Multi-Resonances","authors":"A. Kaplan, P. Shkolnikov","doi":"10.1364/swv.1993.h156","DOIUrl":"https://doi.org/10.1364/swv.1993.h156","url":null,"abstract":"We show that a simple nonperturbative two-level model of an atom driven\u0000 by a very strong periodic field, results in a rich picture of very\u0000 high harmonic generation and related phenomena. It reproduces\u0000 experimentally observed plateau, yields for the first time simple\u0000 analytic formulas for the plateau cutoff frequency, critical driving\u0000 intensity, and saturation, and predicts intensity-induced\u0000 multi-resonances. One of the most fascinating phenomenon discovered\u0000 recently in nonlinear interaction of light with atoms and ions, is\u0000 very high-order (up to 135) odd harmonic generation (HHG) by intense\u0000 (∼ 1013 W/cm2 and higher) optical laser\u0000 radiation in rare gasses and some ions [1], The spectra of generated\u0000 harmonics drasticly deviate from the perturbation theory predictions\u0000 [2], In particular, intensity of harmonics, falling monotonically with\u0000 their orders only up to a certain point, levels off forming a\u0000 so-called “plateau\", and falls monotonically again beyond it.\u0000 Generally, harmonte generation depends on phase-matching conditions\u0000 and nonlinear response of individual atoms. It has recently become\u0000 clear however [3,4] that the major features of HHG, in particular the\u0000 plateau, result mainly from general properties of atomic nonlinear\u0000 response. The most direct and apparently successful way so far to\u0000 approach the problem theoretically has been numerical simulation of\u0000 the Schrödinger [2,5-7] (including an empiric rule [6]) for\u0000 many-electron atoms using Hartry-Slater approximation. This approach\u0000 requires, however, tremendous amount of calculations and involves many\u0000 processes, making it difficult to gain simple insights. An interesting\u0000 simplified model [8] based on 3-D delta-potential with a single\u0000 (ground) level [9] produces results in integration form. The idea of\u0000 retaining a single energy scale (ionization energy) brings one close\u0000 to an even simpler system: a two-level model atom. A two-level model\u0000 of HHG [10], however, due to various complications introduced into it,\u0000 failed to generate simple results, whereas an analytic solution [11]\u0000 holds for a virtually degenerate two-level model only (see below)\u0000 which is unapplicable to the experimental conditions [1-4,7,9];\u0000 besides, no relaxation was considered in [10,11].","PeriodicalId":140696,"journal":{"name":"Shortwavelength V: Physics with Intense Laser Pulses","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122396084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Resonant Frequency Transformations of Shortwavelength Coherent Radiation in Plasma","authors":"P. Shkolnikov, A. Kaplan","doi":"10.1364/swv.1993.xrlaxr239","DOIUrl":"https://doi.org/10.1364/swv.1993.xrlaxr239","url":null,"abstract":"We have found and evaluated plasma media for efficient multiple-resonant nonlinear frequency transformations of X-ray and XUV laser radiation. Realized experimentally, these nonlinear transformations may result in new short-wavelength coherent sources and in both \"line-by-line\" and continuously tunable short-wavelength lasing.","PeriodicalId":140696,"journal":{"name":"Shortwavelength V: Physics with Intense Laser Pulses","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132268204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}