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nnp:optics:optical_absorption_simple [2019/03/11 13:21]
stefan.birner [Structure]
nnp:optics:optical_absorption_simple [2021/07/22 17:38] (current)
stefan.birner [Optics tutorial (Simple)]
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 ====== Optics tutorial (Simple) ====== ====== Optics tutorial (Simple) ======
 This simple tutorial shows a simple simulation studies for absorption of semiconductor devices. This simple tutorial shows a simple simulation studies for absorption of semiconductor devices.
 +(It seems that this tutorial is based on the file AlGaAs_QW_Frankenberger_nnp.in which has been documented here: [[https://​www.nextnano.com/​dokuwiki/​doku.php?​id=nnp:​optics#​part_3frankenberger|Optics tutorial]])
  
 ===== Structure ===== ===== Structure =====
-The structure is a simple AlGaAs ​Quantum ​wellwhich can be seen on the following figure.  +The structure is a simple AlGaAs ​quantum ​well which can be seen in the following figure.  
-{{:​nnp:​optics:​optics_simple_material_image_simple.png?​500|The structure of the simulated device}}+{{:​nnp:​optics:​optics_simple_material_image_simple.png?​500|}} 
 + 
 +<​caption>​The structure of the simulated device</​caption>​
  
 The barriers are made from AlGaAs, and the well is GaAs. The barriers are made from AlGaAs, and the well is GaAs.
Line 41: Line 44:
 </​code>​ </​code>​
  
-  * ''​interband'',​ ''​intraband''​ Initalizes, should it calculates the intra/​interband transitions or not.+  * ''​interband'',​ ''​intraband''​ Initalizes ​if intra/​interband transitions ​should be calculated ​or not.
   * ''​polarization''​ describes the polarization direction of the electric field. (When there is an '​i'​ it means it is circulary polarized)   * ''​polarization''​ describes the polarization direction of the electric field. (When there is an '​i'​ it means it is circulary polarized)
-  * ''​output_transitions''​ Calculation of the transition matrix elements(yes/​no) +  * ''​output_transitions''​ Calculation of the transition matrix elements (''​yes''​/''​no''​
-  * ''​occupation_threshold'',​ ''​energy_threshold'' ​t, ''​transition_threshold''​ The minimum value of the (energy, ​ +  * ''​occupation_threshold'',​ ''​energy_threshold'',​ ''​transition_threshold''​ The minimum value of the energy, ​ occupation ​and transition intensity of the transition which should be calculated. 
-  * ''​occupation'',​ ''​transition intensity''​) ​of the transition which should be calculated. +  * ''​energy_min'',​ ''​energy_max'' ​Boundaries ​of the calculated energy spectra. 
-  * ''​energy_min'',​ ''​energy_max'' ​Borders ​of the calculated energy spectra. +  * ''​energy_resolution''​ The energy grid spacing of the calculated points in the energy space.
-  * ''​energy_resolution''​ The spacing of the calculated points in the energy space.+
   * ''​k_integration''​ defines the points for integrating in the k space   * ''​k_integration''​ defines the points for integrating in the k space
  
 ===== The output ===== ===== The output =====
 ==== Bandedges in the sample ==== ==== Bandedges in the sample ====
-After it has calculated ​the strainit calculates the the bandedges of the structure which can be seen on the figure: +After the strain ​has been calculated, the bandedges of the structure ​are determined ​which can be seen in the figure: 
-{{ :​nnp:​optics:​optics_simple_bandedges.png?​600 |The bandedges in the sample Conduction band HH, and LH bands SO band}} +{{ :​nnp:​optics:​optics_simple_bandedges.png?​600 |}} 
-In the quantum well region it can be seen that the bandedge smaller, and the valence band edge is close to the fermi level. That is the reasonwhy the valence band is populatedand interband transition could happen. ​+ 
 +<​caption>​ 
 +The bandedges in the sampleConduction band, heavy hole, light hole and split-off hole band edges 
 +</​caption>​ 
 + 
 +In the quantum well region it can be seen that the bandedge ​is smaller, and the valence band edge is close to the Fermi level. 
 +That is the reason why the valence band is populated and interband transition could happen. ​
 ==== Quantum Mechanics ==== ==== Quantum Mechanics ====
-From the bandedges the program calculates the wavefunctionsin each band which is definied ​in the line: +From the bandedges the program calculates the wavefunctions in each band which is defined ​in the line: 
 <​code>​ <​code>​
 num_electrons=$NumE num_electrons=$NumE
 num_holes=$NumH ​ num_holes=$NumH ​
 </​code>​ </​code>​
-It means how many electron and hole states should be calculated.+Here you can specify ​how many electron and hole states should be calculated.
 The wavefunctons are plotted on the following figure: ​ The wavefunctons are plotted on the following figure: ​
 +{{ :​nnp:​optics:​optics_simple_wf_simple.png?​600 |}}
  
 +<​caption>​The wavefunction probabilities for each band</​caption>​
 ==== Optics ==== ==== Optics ====
 === Absorption === === Absorption ===
-For each definied ​polarization ​it calculates the transition matrix ​element ​between the states(Integrationing ​the wavefunctions in k space). ​Than it calculates the absorption coefficient (1/mucm) per one transition (it should consider the population of the states). For example one absorption coefficient can be seen in the function of the energy of the incoming field: ​+For each defined ​polarization ​the program ​calculates the transition matrix ​elements ​between the states (integration of the wavefunctions in k space). 
 +Then it calculates the absorption coefficient (1/mucm) per one transition (it should consider the population of the states). 
 +For example one absorption coefficient can be seen as a function of the energy of the incoming field: ​
  
-The overall absorption coefficient of the system is the sum of the partial ​absoprtion ​coefficients of each transition. ​+{{ :​nnp:​optics:​optics_simple_absorption1-11.png |}} 
 + 
 +<​caption>​The absorption coefficient between the 1st and the 11th eigenstate of the system as a function of energy</​caption>​ 
 + 
 + 
 +The overall absorption coefficient of the system is the sum of the partial ​absorption ​coefficients of each transition. 
 + 
 +{{ :​nnp:​optics:​optics_simple_absorptionall.png |}} 
 + 
 +<​caption>​The overall absorption coefficient as a function of energy</​caption>​
  
 === Im($\epsilon$) === === Im($\epsilon$) ===
-It imaginary part of the permittivity (related to the conductivity)could be calculated from the the absorption coefficientwith the following formulaif the absoprtion ​is small.+Its imaginary part of the permittivity (related to the conductivity) could be calculated from the absorption coefficient with the following formula if the absorption ​is small.
  
 $\alpha= \frac{\omega}{n_r c} \cdot \frac{\epsilon_2}{\epsilon_0}$ $\alpha= \frac{\omega}{n_r c} \cdot \frac{\epsilon_2}{\epsilon_0}$
  
-The values of the imaginary part of the permittivity function is in files ''​imepsilon''​.+The values of the imaginary part of the permittivity function is in the files ''​imepsilon*.dat''​. 
 === Transitions === === Transitions ===
-The summary of the transitions have been saved in the "​transitions_all"​ files. With the intensity, and the rate of the transition. ​+The summary of the transitions have been saved in the "​transitions_all.dat" files, together with the intensity, and the rate of the transition. ​
  
nnp/optics/optical_absorption_simple.1552310492.txt.gz · Last modified: 2019/03/11 13:21 by stefan.birner