Platinum diselenide(PtSe_(2))is a promising two-dimensional(2D)material for the terahertz(THz)range as,unlike other transition metal dichalcogenides(TMDs),its bandgap can be uniquely tuned from a semiconductor in the ...Platinum diselenide(PtSe_(2))is a promising two-dimensional(2D)material for the terahertz(THz)range as,unlike other transition metal dichalcogenides(TMDs),its bandgap can be uniquely tuned from a semiconductor in the nearinfrared to a semimetal with the number of atomic layers.This gives the material unique THz photonic properties that can be layer-engineered.Here,we demonstrate that a controlled THz nonlinearity—tuned from monolayer to bulk PtSe_(2)—can be realized in wafer size polycrystalline PtSe_(2)through the generation of ultrafast photocurrents and the engineering of the bandstructure valleys.This is combined with the PtSe_(2)layer interaction with the substrate for a broken material centrosymmetry,permitting a second order nonlinearity.Further,we show layer dependent circular dichroism,where the sign of the ultrafast currents and hence the phase of the emitted THz pulse can be controlled through the excitation of different bandstructure valleys.In particular,we show that a semimetal has a strong dichroism that is absent in the monolayer and few layer semiconducting limit.The microscopic origins of this TMD bandstructure engineering are highlighted through detailed DFT simulations,and shows the circular dichroism can be controlled when PtSe_(2)becomes a semimetal and when the K-valleys can be excited.As well as showing that PtSe_(2)is a promising material for THz generation through layer controlled optical nonlinearities,this work opens up a new class of circular dichroism materials beyond the monolayer limit that has been the case of traditional TMDs,and impacting a range of domains from THz valleytronics,THz spintronics to harmonic generation.展开更多
The control of light–matter coupling at the single electron level is currently a subject of growing interest for the development of novel quantum devices and for studies and applications of quantum electrodynamics.In...The control of light–matter coupling at the single electron level is currently a subject of growing interest for the development of novel quantum devices and for studies and applications of quantum electrodynamics.In the terahertz(THz)spectral range,this raises the particular and difficult challenge of building electromagnetic resonators that can conciliate low mode volume and high quality factor.Here,we report on hybrid THz cavities based on ultrastrong coupling between a Tamm cavity and an LC circuit metamaterial and show that they can combine high quality factors of up to Q=37 with a deep-subwavelength mode volume of V=3.2×10^(-4)λ^(3).Our theoretical and experimental analysis of the coupled mode properties reveals that,in general,the ultrastrong coupling between a metamaterial and a Fabry–Perot cavity is an effective tool to almost completely suppress radiative losses and,thus,ultimately limit the total losses to the losses in the metallic layer.These Tamm cavity-LC metamaterial coupled resonators open a route toward the development of single photon THz emitters and detectors and to the exploration of ultrastrong THz light–matter coupling with a high degree of coherence in the few to single electron limit.展开更多
The use of fundamental modelocking to generate short terahertz(THz)pulses and THz frequency combs from semiconductor lasers has become a routine affair,using quantum cascade lasers(QCLs)as a gain medium.However,unlike...The use of fundamental modelocking to generate short terahertz(THz)pulses and THz frequency combs from semiconductor lasers has become a routine affair,using quantum cascade lasers(QCLs)as a gain medium.However,unlike classic laser diodes,no demonstrations of harmonic modelocking,active or passive,have been shown in THz QCLs,where multiple pulses per round trip are generated when the laser is modulated at the harmonics of the cavity’s fundamental round-trip frequency.Here,using time-resolved THz techniques,we show for the first time harmonic injection and mode-locking in which THz QCLs are modulated at the harmonics of the round-trip frequency.We demonstrate the generation of the harmonic electrical beatnote within a QCL,its injection locking to an active modulation and its direct translation to harmonic pulse generation using the unique ultrafast nature of our approach.Finally,we show indications of self-starting harmonic emission,i.e.,without external modulation,where the QCL operates exclusively on a harmonic(up to its 15th harmonic)of the round-trip frequency.This behaviour is supported by time-resolved simulations of induced gain and loss in the system and shows the importance of the electronic,as well as photonic,nature of QCLs.These results open up the prospect of passive harmonic modelocking and THz pulse generation,as well as the generation of low-noise microwave generation in the hundreds of GHz region.展开更多
基金H2020 Future and Emerging Technologies,Grant/Award Number:964735H2020 Excellent Science,Grant/Award Number:881603+3 种基金Agence Nationale de la Recherche,Grant/Award Numbers:ANR-16-CE24-0023,ANR-2018-CE08-018-05National Research Foundation Singapore,Grant/Award Number:NRF-CRP26-2021-0004Region Ile de FranceEquipMeso,Grant/Award Number:ANR-10-EQPX-29-01。
文摘Platinum diselenide(PtSe_(2))is a promising two-dimensional(2D)material for the terahertz(THz)range as,unlike other transition metal dichalcogenides(TMDs),its bandgap can be uniquely tuned from a semiconductor in the nearinfrared to a semimetal with the number of atomic layers.This gives the material unique THz photonic properties that can be layer-engineered.Here,we demonstrate that a controlled THz nonlinearity—tuned from monolayer to bulk PtSe_(2)—can be realized in wafer size polycrystalline PtSe_(2)through the generation of ultrafast photocurrents and the engineering of the bandstructure valleys.This is combined with the PtSe_(2)layer interaction with the substrate for a broken material centrosymmetry,permitting a second order nonlinearity.Further,we show layer dependent circular dichroism,where the sign of the ultrafast currents and hence the phase of the emitted THz pulse can be controlled through the excitation of different bandstructure valleys.In particular,we show that a semimetal has a strong dichroism that is absent in the monolayer and few layer semiconducting limit.The microscopic origins of this TMD bandstructure engineering are highlighted through detailed DFT simulations,and shows the circular dichroism can be controlled when PtSe_(2)becomes a semimetal and when the K-valleys can be excited.As well as showing that PtSe_(2)is a promising material for THz generation through layer controlled optical nonlinearities,this work opens up a new class of circular dichroism materials beyond the monolayer limit that has been the case of traditional TMDs,and impacting a range of domains from THz valleytronics,THz spintronics to harmonic generation.
基金Agence Nationale de la Recherche (ANR-19-CE24-0015,ANR-22-CE09-0018)European Research Council (820133)。
文摘The control of light–matter coupling at the single electron level is currently a subject of growing interest for the development of novel quantum devices and for studies and applications of quantum electrodynamics.In the terahertz(THz)spectral range,this raises the particular and difficult challenge of building electromagnetic resonators that can conciliate low mode volume and high quality factor.Here,we report on hybrid THz cavities based on ultrastrong coupling between a Tamm cavity and an LC circuit metamaterial and show that they can combine high quality factors of up to Q=37 with a deep-subwavelength mode volume of V=3.2×10^(-4)λ^(3).Our theoretical and experimental analysis of the coupled mode properties reveals that,in general,the ultrastrong coupling between a metamaterial and a Fabry–Perot cavity is an effective tool to almost completely suppress radiative losses and,thus,ultimately limit the total losses to the losses in the metallic layer.These Tamm cavity-LC metamaterial coupled resonators open a route toward the development of single photon THz emitters and detectors and to the exploration of ultrastrong THz light–matter coupling with a high degree of coherence in the few to single electron limit.
基金funding from the European Union FET-Open grant ULTRAQCL 665158the German Research Foundation(DFG)within the Heisenberg program(JI 115/4-2).
文摘The use of fundamental modelocking to generate short terahertz(THz)pulses and THz frequency combs from semiconductor lasers has become a routine affair,using quantum cascade lasers(QCLs)as a gain medium.However,unlike classic laser diodes,no demonstrations of harmonic modelocking,active or passive,have been shown in THz QCLs,where multiple pulses per round trip are generated when the laser is modulated at the harmonics of the cavity’s fundamental round-trip frequency.Here,using time-resolved THz techniques,we show for the first time harmonic injection and mode-locking in which THz QCLs are modulated at the harmonics of the round-trip frequency.We demonstrate the generation of the harmonic electrical beatnote within a QCL,its injection locking to an active modulation and its direct translation to harmonic pulse generation using the unique ultrafast nature of our approach.Finally,we show indications of self-starting harmonic emission,i.e.,without external modulation,where the QCL operates exclusively on a harmonic(up to its 15th harmonic)of the round-trip frequency.This behaviour is supported by time-resolved simulations of induced gain and loss in the system and shows the importance of the electronic,as well as photonic,nature of QCLs.These results open up the prospect of passive harmonic modelocking and THz pulse generation,as well as the generation of low-noise microwave generation in the hundreds of GHz region.
