بررسي نوع جديدي از تشديدهاي چند فوتوني با استفاده از ميدان هاي ليزري متقارن

Studying a new kind of multiphoton resonances by using symmetric laser fields

ر اﯾﻦ ﻣﻘﺎﻟﻪ، ﺑﺎ اﺳﺘﻔﺎده از ﻣﯿﺪانﻫﺎي ﻟﯿﺰري ﻣﺘﻘﺎرن ﮐﻪ ﺑﻪ ﻃﻮر ﻗﻮي ﺑﺎ دو ﺗﺎ از ﺗﺮازﻫﺎي اﻧﺮژي ﯾﮏ ﺳﯿﺴﺘﻢ ﭼﻬﺎرﺗﺮازي ﺟﻔﺖ ﺷﺪهاﻧﺪ، وﻗﻮع ﺗﺸﺪﯾﺪﻫﺎي ﺗﺪاﺧﻠﯽ و ﺗﻔﺎوت رﻓﺘﺎر آﻧﻬﺎ در ﻣﻀﺎرب زوج ﯾﺎ ﻓﺮد ﻓﻮﺗﻮنﻫﺎ ﺑﺮرﺳﯽ ﻣﯽﺷﻮد. ﺑﺮاي اﻧﺠﺎم اﯾﻦ ﮐﺎر، ﻣﺪﻟﯽ ﺑﺮ ﭘﺎﯾﮥ ﻧﻘﺎط ﺗﻘﺎﻃﻊ ﺗﺮازﻫﺎ ﯾﻌﻨﯽ ﻣﺤﻞ رﺧﺪاد ﮔﺬارﻫﺎي ﭼﻨﺪ ﻓﻮﺗﻮﻧﯽ اراﺋﻪ ﻣﯽﺷﻮد. اﺑﺘﺪا ﺑﺎ ارزﯾﺎﺑﯽ ﻓﺎز ﺗﺪاﺧﻞ، ﺗﺸﺪﯾﺪﻫﺎي ﭼﻨﺪ ﻓﻮﺗﻮﻧﯽ در ﺳﯿﺴﺘﻢﻫﺎي دوﺗﺮازي و ﺳﻪﺗﺮازي ﺑﻪﺻﻮرت ﻣﺨﺘﺼﺮ ﺑﺮرﺳﯽ و ﺑﺎ ﻫﻢ ﻣﻘﺎﯾﺴﻪ ﻣﯽﺷﻮﻧﺪ ﺳﭙﺲ در ﯾﮏ ﺳﯿﺴﺘﻢ ﭼﻬﺎرﺗﺮازي، رژﯾﻢ واﻓﺎزي ﻗﻮي ﻣﻌﺮﻓﯽ و ﺗﺮازﻫﺎ ﺑﻪ زﻣﺎن واﺑﺴﺘﻪ ﻣﯽﺷﻮﻧﺪ و آﻫﻨﮓﻫﺎي ﮔﺬار ﻣﺮﺗﺒﮥ دوم و ﻣﺮﺗﺒﮥ ﭼﻬﺎرم ﮐﻪ ﺧﺼﻮﺻﯿﺎت ﺗﺸﺪﯾﺪداري در n ﻫﺎي ﺻﺤﯿﺢ )ﺗﻌﺪاد ﻓﻮﺗﻮنﻫﺎ( دارﻧﺪ ﺣﺴﺎب ﻣﯽﺷﻮﻧﺪ. ﻣﺤﺎﺳﺒﺎت ﻧﺸﺎن ﻣﯽدﻫﻨﺪ ﮐﻪ ﻧﺎﻣﺘﻘﺎرﻧﯽ ﺗﺸﺪﯾﺪﻫﺎ در ﻣﻀﺎرب زوج ﯾﺎ ﻓﺮد، ﻧﺴﺒﺖ ﺑﻪ ﻧﻮﺳﺎﻧﺎت ﺗﺮازﻫﺎي ﺑﻪ ﺷﺪت ﺗﺤﺮﯾﮏ ﺷﺪه ﻏﯿﺮﺣﺴﺎس ﺑﻮده و در رژﯾﻢ ﻣﺬﮐﻮر ﺑﺎﻗﯽ ﻣﯽﻣﺎﻧﺪ. از ﻃﺮﯾﻖ ﻣﺪلﺳﺎزي ﺗﺮازﻫﺎي ﯾﮏ ﻧﻘﻄﮥ ﮐﻮاﻧﺘﻮﻣﯽ دوﮔﺎﻧﻪ و اﺳﺘﻔﺎده از ﺷﺒﯿﻪﺳﺎزي ﻋﺪدي، ﺑﻪ ﺑﺮرﺳﯽ واﺑﺴﺘﮕﯽ ﻧﺎﻣﯿﺰاﻧﯽ ﺟﺮﯾﺎن ﺣﺎﻟﺖ ﻣﺎﻧﺎ و ﺗﻮاﻓﻖ ﮐﺎﻣﻞ آن ﺑﺎ آزﻣﺎﯾﺸﺎﺗﯽ ﻣﺒﺘﻨﯽ ﺑﺮ ﻣﺤﺎﺳﺒﮥ ﺟﺮﯾﺎن در ﺷﺮاﯾﻂ ﺳﺪﺷﺪﮔﯽ اﺳﭙﯿﻦ ﻣﯽﭘﺮدازﯾﻢ. ﺳﺮاﻧﺠﺎم ﻧﺸﺎن ﻣﯽدﻫﯿﻢ ﮐﻪ ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ، ﺗﻤﺎم ﺧﺼﻮﺻﯿﺎت اﺳﺎﺳﯽ دادهﻫﺎي ﺗﺠﺮﺑﯽ را دارا اﺳﺖ.

In this paper the occurrence of interference resonances and their different behavior at even or odd multiples of photon are studied by using symmetric laser fields that are strongly coupled with two energy levels of a four-level system. For doing this work, a model is presented based on crossing points of levels where transitions are created. At first multiphoton resonances in the two-level and three-level systems are investigeted briefly and compared with each other through calculating of interference phase, then the strong dephasing regime for a four-level system is introduced and the levels are become time-dependent, in this way, the transition rates of second order and fourth order that have resonant features for integer n (photon number) are calculated. The calculations display asymmetry of resonances at multiples of even or odd is insensitive to fluctuations of the strongly driven levels, and survives into the strong dephasing regime. We investigate the detuning dependence of current steady-state and its complete agreement with the experiments which are done based on calculating current in spin-blockaded conditions via the levels modeling a double quantum dot and by using numerical simulation. Finally, we show the obtained results have the main features of the experimental data.