Observation of a train of attosecond pulses from high. Osa extended phase matching of high harmonic generation. High harmonic generation physics 208a presentation october 11, 2004 tom allison uc berkeley. Corkum, theory of high harmonic generation by lowfrequency laser fields. Abstract we study the highharmonic spectrum emitted by a singlelayer graphene, irradiated by an ultrashort intense infrared laser pulse. We find that the harmonic spectra are fairly robust against elastic and inelastic scattering. High harmonic generation in bulk solids is a new research topic while the atomic hhg has been studied for about 30 years now. Generation of excessive free electrons in the medium at high peak intensity results in a phase mismatch 9. The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet xuv. Theory of highorder harmonic generation from molecules by. High harmonic generation hhg is a technique for producing spatially and. Highorder harmonic generation provides a new method for generating coherent, xuv radiation.
Fully quantum treatment explicitly presents the high harmonic generation as a threestep process. Harmonic generation is a nonlinear optical proc ess in which the frequency of laser light is. We show the emergence of the typical nonperturbative spectral features, harmonic plateau and cutoff, for midinfrared driving fields, at fluences below the damage threshold. High harmonics generation is a process in which an atom absorbs q photons of energy. Fully quantum treatment explicitly presents the high harmonic generation as a threestage process.
High harmonic generation hhg is a nonlinear process during which a target gas, plasma, or solid sample is illuminated by an intense laser pulse. The paper semiglobal approach for propagation of the timedependent schr odinger. The phenomenon of hhg in solids is not yet well understood and has triggered a wide range of theoretical studies. We illustrate the high oam harmonics generation in a plasma using several examples including the. Highharmonic generation hhg of femtosecond lasers produces unique shortwavelength light pulses with femtosecond to attosecond duration. We show with theory and particleincell simulations that the orders of the oam harmonics can be tuned according to a selection rule that depends on the initial oam of the interacting waves. Introduction in traditional electromagnetism textbooks, polarization in the dielectric material is linearly proportional to the applied electric field. Its possible implications for numerical calculations of the high harmonic signal are discussed. A highgain harmonicgeneration freeelectron laser is demonstrated. The papers optimal control theory of harmonic generation and optimization of high harmonic generation by optimal control theoryclimbing a mountain in extreme conditions represent the work of ido schaefer under the supervision of prof. A microscopic theory is presented to describe highharmonic generation in solids with the semiconductorbloch equations. The frequency of the generated radiation extends into the xuv region. Using timedependent density functional theory, highharmonic generation hhg is studied in onedimensional structures of sizes from a single nucleus up to hundreds of nuclei. Observation of highorder harmonics from bulk crystals was, however, reported much more recently, in 2010.
High order harmonic generation in rare gases thesis. We reproduce many observed characteristics of high harmonic generation experiments in solids including the formation of only odd harmonics in inversionsymmetric materials, and the nonlinear formation of high harmonics with increasing field. The generation of highorder harmonics from atomic and molecular gases enables the production of highenergy photons and ultrashort isolated pulses. At these intensities we can start to look for nonlinear optics in the xray regime. Introduction the generation of high order harmonics hhg of intense. Rp photonics encyclopedia high harmonic generation, hhg. The quantitative rescattering theory qrs for highorder harmonic generation hhg by intense laser pulses is presented. We demonstrate highharmonic spectroscopy in manyelectron molecules using timedependent densityfunctional theory. High harmonic spectroscopy utilizes the extremely nonlinear optical process of highorder harmonic generation hhg to measure complex attosecondscale dynamics within the emitting atom or molecule subject to a strong laser field.
Highorder harmonic generation due to the interaction of a short ultrarelativistic laser pulse with overdense plasma is studied analytically and numerically. Intesities as high as 1014 wcm2 have been observed. However, free electrons in the partially ionized gas medium are known to prevent phase matching and limit upconversion to lowenergy harmonics only. Second harmonic generation in nonlinear optical crystal diana jeong 1. Highharmonic generation hhg is a signature optical phenomenon of strongly driven, nonlinear optical systems. Highgain harmonicgeneration freeelectron laser science.
Sapphire lasers as well as many other wavelength ranges, covering second harmonic generation shg, third harmonic generation thg and fourth harmonic generation fhg. Presented next are selected experimental results related to optimizing the. High harmonic generation hhg is an extremely nonlinear effect, where a medium is driven by a strong laser field, generating coherent broadband radiation with photon energies ranging up to the xray and pulse durations reaching attosecond timescales. Both methods have, in theory, a tendency to produce a train of closely spaced pulses rather than a single pulse.
First, we describe an analytical estimate using the hghg parameters in the duvfel project at bnl as an example. Ishikawa photon science center, graduate school of engineering, university of tokyo japan 1. We present a simple, analytic, and fully quantum theory of highharmonic generation by lowfrequency laser fields. We show the emergence of the typical nonperturbative spectral features, harmonic plateau and cutoff, for midinfrared driving fields. Specifically, the understanding of the hhg process in rare gases has played a. Chapter high harmonic generation ultrafast optics and xrays. Our approach uses a laserseeded freeelectron laser to produce amplified, longitudinally coherent, fourier transformlimited output at a harmonic of the seed laser. C r mcdonald, g vampa1, g orlando1, p b corkum1 and t brabec1. Subsequently iii stimulated or laser assisted recombination brings the electron back into the initial state. A nonperturbative floquetbloch theory of the interacting system crystal plus laser field is developed and applied to obtain the fieldmodified band structure of the system. On the basis of the ultrarelativistic similarity theory we show that the highorder harmonic spectrum is universal, i. We show that highharmonic generation can produce higher photon energies and flux by using higher laser intensities than are typical, strongly ionizing the medium and creating plasma that. Theory of highorder harmonic generation for gapless graphene. Theory of highorder harmonic generation from molecules by intense laser pulses 2 highorder harmonic generation hhg is one of the most studied nonlinear phenomena in intense lasermatter interaction 1.
Theory of high harmonic generation by low frequency laser. Recollision dynamics analysis of highorder harmonic. Theoretical description of highorder harmonic generation in solids a. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent xuv radiation. It is commonly assumed that a complete theory for selection rules in optical nonlinear harmonic generation was developed previously. High harmonic generation from surface states of solids arxiv. Devereaux1,2 1stanford institute for materials and energy science, slac national accelerator laboratory, menlo park, ca 94025, usa 2geballe laboratory for advanced materials, stanford university, stanford, ca 94305, usa. High harmonic generation hhg is a nonlinear process during which a target is illuminated by. They have a great potential to overcome the limitations of current laser sources and to extend attosecond pulses towards the xray regime. Citeseerx document details isaac councill, lee giles, pradeep teregowda.
We have computed nonlinear susceptibilities for harmonic generation in hydrogenic ions, as described by lowestand nextlowestorder perturbation theory. Highharmonic generation in solids university of arizona. Theory of highharmonic generation chapter 1 theory of highharmonic generation in considering the generation of high harmonic radiation with high intensities, two main aspects can be distinguished. We address theoretically and numerically the possibility of observing ellipticity in highorder harmonic generation hhg from aligned molecules driven by linearly polarized fieldsa subject of controversy in the recent literature with significant implications. The harmonixx product line is a series of frequency converters for ultrafast lasers. Multiple harmonic plateaus up to very high harmonic orders are observed already. Quantum theory of a high harmonic generation as a three. Harmonic generation is a nonlinear optical process in which the frequency of. According to the qrs, hhg spectra can be expressed as a product of a returning electron wave packet and the photorecombination differential cross section of the laserfree continuum electron back to the initial bound state. Laserdriven highharmonic generation provides the only demonstrated route to generating stable, tabletop attosecond xray pulses but has low flux compared to other xray technologies. Therefore it would be desirable to compare the generation process in solid and gas phase same atomic constituents. We study the highharmonic spectrum emitted by a singlelayer graphene, irradiated by an ultrashort intense infrared laser pulse.
Theory of high harmonic generation by low frequency laser fields. Quantitative rescattering theory for highorder harmonic. High harmonic generation hhg of an intense laser pulse is a highly nonlinear optical phenomenon that provides the only proven source of tabletop attosecond pulses, and. The appearance of even harmonic orders is shown to require at least three electronic bands and a mutual interband coupling between them. High harmonic generation is the phenomenon that very high harmonics of an intense input laser beam are generated in a gas. Quantumorbit theory of highorder harmonic generation hhg by bicircular laser field is presented. We compared high harmonic generation in the solid and gas phases of argon and krypton. Theory of highorder harmonic generation in relativistic. We present a simple, analytic, and fully quantum theory of high harmonic generation by lowfrequency laser fields. Quantumorbit analysis of highorder harmonic generation. Harmonic generation is a nonlinear optical process in which photons of intense incoming laser radiation interact with a nonlinear material and radiation with corresponding harmonics frequencies is generated.
However, it can be difficult to compare theory and experiment, since the dynamics under investigation are often very sensitive to the laser intensity, which. Sources operating with long interaction lengths produce soft xrays with a high degree of spatial coherence, allowing focusing to high intensity. Perturbation theory study of highharmonic generation osa. An overview the nonlinear interaction of an ultrashort laser pulse with matter generates coherent radiation at multiples harmonics of the laser frequency. Hhg is most easily understood using the threestep model 2, 3, 4. High order harmonic generation in rare gases unt digital. Theoretical description of highorder harmonic generation. High harmonic generation an overview sciencedirect topics. In this picture the process is treated in two steps. The harmonic generation topology adopts an oscillator operating at a subharmonic of the rf carrier frequency i. Phase matching of high harmonic generation in the soft and. The approach includes the relevant interband polarizations and intraband currents. Theory of highharmonic generation in solids iopscience.
This typically occurs at optical intensities of the order of 1014 wcm 2 or higher. Second harmonic generation in nonlinear optical crystal. Highharmonic generation hhg in bulk crystals exposed to intense midinfrared lasers with photon energies below the bandgap is investigated theoretically. We show that a weak attosecondpulsetrain ionization seed that is properly synchronized with the strong driving midinfrared laser field can produce experimentally relevant highharmonic generation hhg signals, from which we extract both the spectral amplitude and the target. The theory recovers the classical interpretation of kulander et al. Harmonic generation is a nonlinear optical process in which the frequency of laser light is converted into its integer multiples. We discuss the theory of the high gain harmonic generation hghg.
We have demonstrated experimentally and theoretically an unconventional phasematching scheme. Highharmonic generation by a laserdriven solid slab is simulated using timedependent density functional theory. Theory of highharmonic generation by lowfrequency laser. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. We demonstrate from ab initio simulations that it is possible to generate highorder. Introduction we present theoretical aspects of highharmonic generation hhg in this chapter. Citeseerx quantum theory of high harmonic generation via. Origin and implication of ellipticity in high harmonic. Generation of high harmonics by the interaction of intense laser fields with periodic crystal structures is investigated theoretically. Highflux soft xray harmonic generation from ionization. Highharmonic generation from solids nature physics. On the quantumoptical nature of high harmonic generation.
This phenomenon is known as high order harmonic generation hhg 1. Quantum optimal control theory of high harmonic generation. Harmonic generation an overview sciencedirect topics. Rather than by the perturbation theory found in standard textbooks of. We present theoretical aspects of highharmonic generation hhg in this chapter. Obtaining efficiently similar photon energy from solidstate systems could lead, for instance, to more compact extreme ultraviolet and soft xray sources. Phase matching and coherence of highorder harmonic. A very intense laser pulse i approximately10sup 10sup 14 wcmsup 2 is focused into a dense approximately10sup l7 particlescmsup 3 atomic. Atomiclike highharmonic generation from twodimensional. Hhg is a strong laserfieldinduced process in which the energy absorbed from the laser field is emitted in the form of a highenergy photon. Under such conditions, the sample will emit the high harmonics of the generation beam above the fifth harmonics.