Kupita patsogolo kwaukadaulo wowonjezera wa ultraviolet

Kuwonjezeka kwakukulu kwa ultravioletukadaulo wopangira magetsi

M'zaka zaposachedwa, magwero owopsa a ultraviolet high harmonic akopa chidwi chambiri m'magawo a ma elekitironi chifukwa chogwirizana kwambiri, nthawi yayitali ya kugunda kwamtima komanso mphamvu yayikulu ya photon, ndipo akhala akugwiritsidwa ntchito m'maphunziro osiyanasiyana owonera komanso oyerekeza. Ndi kupita patsogolo kwaukadaulo, izigwero lowalaikukula kupita ku ma frequency apamwamba, kuchuluka kwa ma photon, mphamvu ya photon yapamwamba komanso kufupikitsa kugunda kwa mtima. Kupita patsogolo kumeneku sikumangokwaniritsa kuyeza kwa magwero a kuwala kwa ultraviolet, komanso kumapereka mwayi watsopano wazomwe zikuchitika m'tsogolomu. Chifukwa chake, kuphunzira mozama ndikumvetsetsa kwa gwero la kuwala kwa ultraviolet kubwereza kubwereza kopitilira muyeso ndikofunikira kwambiri pakuzindikira komanso kugwiritsa ntchito ukadaulo wapamwamba kwambiri.

Pamiyezo ya ma electron spectroscopy pa sikelo ya nthawi ya femtosecond ndi attosecond, kuchuluka kwa zochitika zoyezedwa mu mtengo umodzi nthawi zambiri kumakhala kosakwanira, zomwe zimapangitsa kuti kuwala kocheperako kusakhale kokwanira kupeza ziwerengero zodalirika. Panthawi imodzimodziyo, gwero lowala lokhala ndi photon flux yochepa lidzachepetsa chiŵerengero cha chizindikiro ndi phokoso la kujambula kwa microscopic panthawi yochepa yowonekera. Kupyolera mu kufufuza kosalekeza ndi kuyesera, ochita kafukufuku apanga zosintha zambiri pakukhathamiritsa kwa zokolola ndi mapangidwe opatsirana obwerezabwereza pafupipafupi kwambiri kuwala kwa ultraviolet. Ukadaulo wotsogola waukadaulo wophatikizika ndi kubwereza kwanthawi yayitali kopitilira muyeso wa kuwala kwa ultraviolet kwagwiritsidwa ntchito kuti akwaniritse muyeso wolondola kwambiri wamapangidwe azinthu ndi njira zamagetsi zamagetsi.

Kugwiritsa ntchito magwero amphamvu kwambiri a kuwala kwa ultraviolet, monga miyezo ya ma electron spectroscopy (ARPES) yokhazikika, imafunikira kuwala kwa ultraviolet kowopsa kuti iwunikire chitsanzocho. The ma elekitironi pamwamba pa chitsanzo ndi okondwa kwa dziko mosalekeza ndi kwambiri ultraviolet kuwala, ndi mphamvu kinetic ndi umuna Angle wa photoelectrons muli gulu dongosolo zambiri chitsanzo. Ma electron analyzer okhala ndi Angle resolution ntchito amalandira ma photoelectrons oyaka ndikupeza mawonekedwe a bandi pafupi ndi gulu la valence lachitsanzo. Kwa otsika kubwereza pafupipafupi kwambiri gwero la kuwala kwa ultraviolet, chifukwa kugunda kwake kumodzi kumakhala ndi ma photon ambiri, kudzasangalatsa ma photoelectrons ambiri pachitsanzo munthawi yochepa, ndipo kulumikizana kwa Coulomb kudzabweretsa kufalikira kwakukulu kwa kugawa. mphamvu ya photoelectron kinetic, yomwe imatchedwa space charge effect. Kuti muchepetse mphamvu ya mlengalenga, ndikofunikira kuchepetsa ma photoelectrons omwe ali mumtundu uliwonse ndikusunga ma photon flux nthawi zonse, kotero ndikofunikira kuyendetsalaserndi kubwereza mobwerezabwereza kuti apange gwero la kuwala kwa ultraviolet kwambiri ndi kubwereza mobwerezabwereza.

Ukadaulo wowonjezera wa resonance umazindikira kubadwa kwa ma harmonics apamwamba kwambiri pafupipafupi kubwereza kwa MHz
Pofuna kupeza gwero lalikulu la kuwala kwa ultraviolet ndi kubwereza kwa 60 MHz, gulu la Jones ku yunivesite ya British Columbia ku United Kingdom linachita bwino kwambiri m'badwo wamtundu wa femtosecond resonance enhancement cavity (fsEC) kuti akwaniritse ntchito yabwino. gwero lalikulu la kuwala kwa ultraviolet ndikuligwiritsa ntchito pakuyesa kosinthika kwanthawi yayitali kwa ma electron spectroscopy (Tr-ARPES). Gwero la kuwala limatha kutulutsa photon flux yoposa manambala a photon a 1011 pamphindi imodzi ndi harmonic imodzi pa mlingo wobwerezabwereza wa 60 MHz mu mphamvu ya 8 mpaka 40 eV. Adagwiritsa ntchito makina a ytterbium-doped fiber laser system ngati gwero la mbewu za fsEC, ndikuwongolera mawonekedwe a pulse kudzera pamapangidwe amtundu wa laser kuti achepetse phokoso la carrier envelope offset frequency (fCEO) ndikusunga mawonekedwe abwino a pulse compression kumapeto kwa amplifier chain. Kuti akwaniritse kuwongolera kokhazikika mkati mwa fsEC, amagwiritsa ntchito malupu atatu owongolera ma servo pakuwongolera mayankho, zomwe zimapangitsa kuti pakhale kukhazikika kokhazikika pamadigiri awiri aufulu: nthawi yoyenda yozungulira ya pulse cycling mkati mwa fsEC imagwirizana ndi nthawi ya laser pulse, ndikusintha kwagawo. ya chonyamulira magetsi potengera kugunda kwa envelopu (ie, gawo la envelopu yonyamula, ϕCEO).

Pogwiritsa ntchito mpweya wa krypton monga gasi wogwira ntchito, gulu lofufuza lidakwanitsa kupanga ma harmonics apamwamba mu fsEC. Iwo anachita Tr-ARPES miyeso ya graphite ndipo anaona mofulumira thermiation ndi wotsatira pang'onopang'ono recombination sanali thermally okondwa elekitironi anthu, komanso mphamvu ya sanali thermally mwachindunji okondwa limati pafupi mlingo Fermi pamwamba 0,6 eV. Gwero lounikirali limapereka chida chofunikira chophunzirira mawonekedwe amagetsi azinthu zovuta. Komabe, kupangidwa kwa ma harmonics apamwamba mu fsEC kuli ndi zofunikira kwambiri zowonetsera, kubweza chipukuta misozi, kusintha kwabwino kwa utali wa patsekeke ndi kutsekeka kwamalumikizidwe, zomwe zingakhudze kwambiri kupititsa patsogolo kachulukidwe ka mkodzo wowonjezera. Panthawi imodzimodziyo, kuyankha kwa gawo lopanda malire la plasma pakatikati pa mtsempha ndizovuta. Chifukwa chake, pakali pano, kuwala kotereku sikunakhale mtundu waukulu wa ultravioletgwero lowala kwambiri la harmonic.