Nonlinear optical spectroscopies are powerful tools for investigating both static material properties and light-induced dynamics.Terahertz(THz)emission spectroscopy has emerged in the past several decades as a versati...Nonlinear optical spectroscopies are powerful tools for investigating both static material properties and light-induced dynamics.Terahertz(THz)emission spectroscopy has emerged in the past several decades as a versatile method for directly tracking the ultrafast evolution of physical properties,quasiparticle distributions,and order parameters within bulk materials and nanoscale interfaces.Ultrafast optically-induced THz radiation is often analyzed mechanistically in terms of relative contributions from nonlinear polarization,magnetization,and various transient free charge currents.While this offers material-specific insights,more fundamental symmetry considerations enable the generalization of measured nonlinear tensors to much broader classes of systems.We thus frame the present discussion in terms of underlying broken symmetries,which enable THz emission by defining a system directionality in space and/or time,as well as more detailed point group symmetries that determine the nonlinear response tensors.Within this framework,we survey a selection of recent studies that utilize THz emission spectroscopy to uncover basic properties and complex behaviors of emerging materials,including strongly correlated,magnetic,multiferroic,and topological systems.We then turn to low-dimensional systems to explore the role of designer nanoscale structuring and corresponding symmetries that enable or enhance THz emission.This serves as a promising route for probing nanoscale physics and ultrafast light-matter interactions,as well as facilitating advances in integrated THz systems.Furthermore,the interplay between intrinsic and extrinsic material symmetries,in addition to hybrid structuring,may stimulate the discovery of exotic properties and phenomena beyond existing material paradigms.展开更多
Vigorous research efforts during the past several decades have successfully closed the"terahertz gap"between microwaves and infrared lig ht,offering new and increasingly efficient ways to produce,detect,and ...Vigorous research efforts during the past several decades have successfully closed the"terahertz gap"between microwaves and infrared lig ht,offering new and increasingly efficient ways to produce,detect,and manipulate radiation fields in the terahertz(THz)frequency range.In our laboratory,THz time he itspy IDS)and optical-pumрTHz-its have been routinely utilized as ulltrafast spectrosopy tools to investigate a variety of emerg ing quantum materinls pulses are produced by femtosecond laser excitation of photo-and metamaterials!.The ultrafast THz conductive antennas,semiconductor surfaces(InAs),and non-linear crystals(ZnTe,GaSe.and LiNbO,).Photoconductive an tennas and nonlinear crystals also al low for the coherent de-tection of these pulses in the time domain,with amplitude and phase spectra obtained in the frequency domain via fast Fourier transform.Although such solid-state schemes are highly desirable in many aspects and thus also commonly utilized in many research laboratories and industrial applications,they typically sufer from limited bandwidths due to the absorption and frequency dispersion induced primarily by pho-non resonances,limiting THz applications such as spectroscopрy of emerging materinl,l,imaging ansd detection4.5 and biomedi-cal chuacterization.展开更多
基金support of the Los Alamos National Laboratory Laboratory-Directed Research and Development(LDRD)program via projects 20230124ER and 20210845PRD1.
文摘Nonlinear optical spectroscopies are powerful tools for investigating both static material properties and light-induced dynamics.Terahertz(THz)emission spectroscopy has emerged in the past several decades as a versatile method for directly tracking the ultrafast evolution of physical properties,quasiparticle distributions,and order parameters within bulk materials and nanoscale interfaces.Ultrafast optically-induced THz radiation is often analyzed mechanistically in terms of relative contributions from nonlinear polarization,magnetization,and various transient free charge currents.While this offers material-specific insights,more fundamental symmetry considerations enable the generalization of measured nonlinear tensors to much broader classes of systems.We thus frame the present discussion in terms of underlying broken symmetries,which enable THz emission by defining a system directionality in space and/or time,as well as more detailed point group symmetries that determine the nonlinear response tensors.Within this framework,we survey a selection of recent studies that utilize THz emission spectroscopy to uncover basic properties and complex behaviors of emerging materials,including strongly correlated,magnetic,multiferroic,and topological systems.We then turn to low-dimensional systems to explore the role of designer nanoscale structuring and corresponding symmetries that enable or enhance THz emission.This serves as a promising route for probing nanoscale physics and ultrafast light-matter interactions,as well as facilitating advances in integrated THz systems.Furthermore,the interplay between intrinsic and extrinsic material symmetries,in addition to hybrid structuring,may stimulate the discovery of exotic properties and phenomena beyond existing material paradigms.
文摘Vigorous research efforts during the past several decades have successfully closed the"terahertz gap"between microwaves and infrared lig ht,offering new and increasingly efficient ways to produce,detect,and manipulate radiation fields in the terahertz(THz)frequency range.In our laboratory,THz time he itspy IDS)and optical-pumрTHz-its have been routinely utilized as ulltrafast spectrosopy tools to investigate a variety of emerg ing quantum materinls pulses are produced by femtosecond laser excitation of photo-and metamaterials!.The ultrafast THz conductive antennas,semiconductor surfaces(InAs),and non-linear crystals(ZnTe,GaSe.and LiNbO,).Photoconductive an tennas and nonlinear crystals also al low for the coherent de-tection of these pulses in the time domain,with amplitude and phase spectra obtained in the frequency domain via fast Fourier transform.Although such solid-state schemes are highly desirable in many aspects and thus also commonly utilized in many research laboratories and industrial applications,they typically sufer from limited bandwidths due to the absorption and frequency dispersion induced primarily by pho-non resonances,limiting THz applications such as spectroscopрy of emerging materinl,l,imaging ansd detection4.5 and biomedi-cal chuacterization.
