Re: 1 dimensional photonic crstal
Frederic Brossard <[email protected]>
| Newsgroups | gmane.comp.science.photonic-bands |
|---|---|
| Message-ID | <[email protected]> |
Hi Hyma, It's been a long time since I did this but this should be very easily done if you choose each Bragg layer to have optimum optical thickness, that is a quarter of a wavelength. Normalise the result to the lattice spacing (as we pretty much always do in MPB) and you obtain d(high)=n(low)/(n(high)+n(low)) where d(high) corresponds to the thickness of the high index material normalised to the lattice. So the only input parameters are n(high) and n(low). Next, you just define a 1D unit cell of size 1 say in x with default material n(low) which you fill with d(high), hence automatically defining d(low). To "fill" with d(high) you can choose a cylinder with axis x, infinite radius and height d(high). The code should be in one of the examples downloaded with MPB I think... Just add d(high) as input parameter if you want to define each thickness, the rest is the same. You should get the result in no time. Frederic Hyma Yalamanchili wrote: > Hello > > Iam trying to find bandgap for a 1 dimensional photonic crystal.(bragg > reflector structure) > I have many doubts in simulating the structure.. > > 1.As Iam dealing with a 1 dimensional structure,how can I specify my > lattice vectors such that the structure repeats just in 1 > direction.(i.e if crystal strucutre is periodic in x has to repeat in x > but not in y and z).. > If I specify no-size in y or z direction it doesn't consider y at all > but I have to specify a length in that direction without the lattice > repeating... > Attached is the code that Iam using. > Please help me > > Thanks > Hyma Yalamanchili > > > > > ----- Original Message ----- > From: "F.S.F. Brossard" <[email protected]> > Date: Saturday, December 13, 2008 8:06 pm > Subject: Re: [MPB-discuss] > To: Hyma Yalamanchili <[email protected]> > > >> Hi Hyma, >> >> MPB does some internal dielectric averaging between boundaries so >> that your structure look more realistic. It also means you probably >> don't need such high resolution. For me, I rarely had to use a >> resolution beyond 16 in x and y for all bandgap calculations. I >> didn't see a significant difference with higher res (except a few >> %). Also, you can lower your supercell size in z to 8, even for low >> index material such as yours. >> Howevever, you should increase your k-interp to 8 at least to make >> sure you get a reasonably accurate bandgap. >> Last advice: there is no need to calculate all points of the >> reduced Brillouin zone to calculate the bandgap of a simple >> triangular lattice with circular air-holes, at least for TE-like >> modes (I have rarely looked at TM-like modes). In this last case, >> just look at the K and M points of your first and second bands and >> also at the intersection between the light cone and the G-K and G-M >> directions. >> Hope this helps, >> >> Frederic >> >> On Dec 12 2008, Hyma Yalamanchili wrote: >> >> >>> Hi Frederic >>> >>> Attached is the control file which Iam using.. >>> >>> Thank u so much for your reply. >>> I hope my problem gets resolved >>> >>> Hyma >>> >>> ----- Original Message ----- >>> From: Frederic Brossard <[email protected]> >>> Date: Friday, December 12, 2008 1:13 pm >>> Subject: Re: [MPB-discuss] efield vs. dpwr, field definition --> >>> >> follow>up on old thread >> >>> To: Hyma Yalamanchili <[email protected]> >>> Cc: [email protected] >>> >>> >>>> Hi Hyma, >>>> >>>> Could you please let us know your control file? otherwise, it is >>>> difficult to know why it takes so much time without asking you a >>>> lot of >>>> questions first. >>>> >>>> Thanks, >>>> >>>> Frederic >>>> >>>> Frederic Brossard >>>> Researcher >>>> Cavendish Laboratory >>>> J J Thomson Avenue >>>> Cambridge CB3 0HE >>>> >>>> >>>> >>>> Hyma Yalamanchili wrote: >>>> >>>>> Hii >>>>> >>>>> Iam in the initial stages of learning MPB tool. >>>>> My work is mainly focused on band gap tuning. >>>>> I tried to change the radius every time before I simulate and >>>>> >>>> find the >>>> >>>>> band gap but as Iam dealing with 3-D structures,its consuming >>>>> >> a >> >>>> lot of >>>> >>>>> time like 4 to 5 hrs for each simulation to run. >>>>> Can anybody suggest me a method to find the radius of the >>>>> >>>> triangular> lattice photonic crystal for a particular band gap >>>> using some kind of a >>>> >>>>> loop??? >>>>> >>>>> >>>>> Thanks, >>>>> hyma >>>>> >>>>> ----- Original Message ----- >>>>> From: "Steven G. Johnson" <[email protected]> >>>>> Date: Thursday, December 4, 2008 12:01 pm >>>>> Subject: Re: [MPB-discuss] efield vs. dpwr, field definition --> >>>>> follow up on old thread >>>>> To: [email protected] >>>>> >>>>> >>>>> >>>>>> Your k point is wrong, for one thing. Maybe you're not >>>>>> >> looking >> >>>> at >>>> >>>>>> a >>>>>> band underneath the light line. >>>>>> >>>>>> Look at the line-defect.ctl example file included with MPB. >>>>>> >>>>>> Alternatively, you may find it easier to rearrange things >>>>>> >> into >> >>>> an >>>> >>>>>> orthogonal supercell. See: >>>>>> >>>>>> http://article.gmane.org/gmane.comp.science.photonic-bands/1376 >>>>>> http://article.gmane.org/gmane.comp.science.photonic-bands/1213 >>>>>> >>>>>> Steven (with a v) >>>>>> >>>>>> On Dec 4, 2008, at 12:10 AM, Chad Husko wrote: >>>>>> >>>>>> >>>>>> >>>>>>> Stephen, >>>>>>> I spent a little more time with the fields and have some >>>>>>> >> follow >> >>>>>>> >>>>>>> >>>>>> up >>>>>> >>>>>> >>>>>>> questions (on the bottom). >>>>>>> >>>>>>> First, some answers to yours. I will be using the proper >>>>>>> >>>>>>> >>>>>> definition >>>>>> >>>>>> >>>>>>> of the effective area as you suggest. I am sure that there >>>>>>> >> is >> >>>> an >>>> >>>>>>> >>>>>>> >>>>>> Ex >>>>>> >>>>>> >>>>>>> field. The propagation direction is x of the PhCWG. z is the >>>>>>> >>>>>>> vertical super cell and y is the direction of sqrt(3)*a of >>>>>>> >> the >> >>>>>>> >>>>>>> >>>>>> air >>>>>> >>>>>> >>>>>>> holes. Attached is the CTL file. >>>>>>> >>>>>>> >>>>>> _______________________________________________ >>>>>> mpb-discuss mailing list >>>>>> [email protected] >>>>>> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss >>>>>> >>>>>> >>>>>> >>>>> _______________________________________________ >>>>> mpb-discuss mailing list >>>>> [email protected] >>>>> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss >>>>> >>>>> >> -- >> Dr Frederic Brossard >> Researcher >> Hitachi Cambridge Laboratory >> Cavendish Laboratory >> J J Thomson Avenue >> Cambridge CB3 0HE >> >> >> >> >> >> >> >> ------------------------------------------------------------------------ >>