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Fun with 'WHISPERING GALLERY' MICROLASERS with COMSOL
Posted 16.12.2010, 15:11 GMT-5 RF & Microwave Engineering Version 4.1 7 Replies
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Hello
I wanted to share a simple and rapidly built model, inspired (but in no way claiming to be a thourough study of the main subject) by the article I found this morning in the Photnics news, and later in NTB:
www.seas.harvard.edu/news-events/press-releases/harvard-scientists-demonstrate-highly-unidirectional-201cwhispering-gallery201d-microlasers
So I built rapidly a small elliptic disc, set an arbitrary size, index of refraction and wavelength etc, made a notch and run a few modal and frequency sweep studies.
The most impressive one is to scan over a large frequency range, using the notch as source, with a small frequency step and see how rapidly the boundary whixper modes appear and disapear. I find it inspirating to look at such images, you get a feeling of how modes build up.
One can further set an eletric conductor on one half side of the ellipse as reflector and get surface modes and buildup two symmetric sources at the end of the conduction region that again shapes differently the modes
you need RF but a 2Gb computer should do I modelled just one half to make it lighter
the png image is the total electric energy inside the cavity versus wavelength, some of the whisper modes show up, one in particular around 1.65 (with reflector)
Note that there is far mor to be done to get to a full laser cavity mode, with gain and losses, that I leave to you out there, with COMSOL one can really do advanced physics today, in an easy and ludique way
--
Have fun Comsoling
Ivar
I wanted to share a simple and rapidly built model, inspired (but in no way claiming to be a thourough study of the main subject) by the article I found this morning in the Photnics news, and later in NTB:
www.seas.harvard.edu/news-events/press-releases/harvard-scientists-demonstrate-highly-unidirectional-201cwhispering-gallery201d-microlasers
So I built rapidly a small elliptic disc, set an arbitrary size, index of refraction and wavelength etc, made a notch and run a few modal and frequency sweep studies.
The most impressive one is to scan over a large frequency range, using the notch as source, with a small frequency step and see how rapidly the boundary whixper modes appear and disapear. I find it inspirating to look at such images, you get a feeling of how modes build up.
One can further set an eletric conductor on one half side of the ellipse as reflector and get surface modes and buildup two symmetric sources at the end of the conduction region that again shapes differently the modes
you need RF but a 2Gb computer should do I modelled just one half to make it lighter
the png image is the total electric energy inside the cavity versus wavelength, some of the whisper modes show up, one in particular around 1.65 (with reflector)
Note that there is far mor to be done to get to a full laser cavity mode, with gain and losses, that I leave to you out there, with COMSOL one can really do advanced physics today, in an easy and ludique way
--
Have fun Comsoling
Ivar
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7 Replies Last Post 27.03.2011, 22:36 GMT-4
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Posted:
1 decade ago
Thanks Ivar for sharing the model as well as actual news. Sounds very interesting!
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Posted:
1 decade ago
Hi
I can not open your mph file since I am using COMSOL 3.5a,
is it possible to convert your file to be compatable with COMSOL 3.5a? I really want to see your file.Many thanks!
I can not open your mph file since I am using COMSOL 3.5a,
is it possible to convert your file to be compatable with COMSOL 3.5a? I really want to see your file.Many thanks!
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Posted:
1 decade ago
Hi
No I do not think there is any way to convert it backwards tp 3.5. The 2D model is a simple ellipse (2-3 um radius) of material index n=2 surounded by a circle somewhat bigger of index n=1 (air) and a ring around for a PML layer (k=0). Then I have cut a small ellispoidal notch (1:20) of the ellipse on one edge along the small axis of the ellipse (copying the shape of the article but not respecting any dimensions). I defined the small slot part as a field source Ez =1V/m simulating very roughly a scatter source
I then selected a wavelength of My_lambda=1um in air and did a frequency scan in freq=c_const/My_lambda and run a scan towards the UV over >1 octave with fine step around 1:1000
I looked at the energy (surface intetgration of the total field in the highindex region) and notice that it has a few narrow peaks, that corresponds to nice whisper mode patterns linig up along the ellipseedge
to make the model ligheter I cut the lower half part and applied a magnetic symemtry condition on the x (y=0) axis
--
Good luck
Ivar
No I do not think there is any way to convert it backwards tp 3.5. The 2D model is a simple ellipse (2-3 um radius) of material index n=2 surounded by a circle somewhat bigger of index n=1 (air) and a ring around for a PML layer (k=0). Then I have cut a small ellispoidal notch (1:20) of the ellipse on one edge along the small axis of the ellipse (copying the shape of the article but not respecting any dimensions). I defined the small slot part as a field source Ez =1V/m simulating very roughly a scatter source
I then selected a wavelength of My_lambda=1um in air and did a frequency scan in freq=c_const/My_lambda and run a scan towards the UV over >1 octave with fine step around 1:1000
I looked at the energy (surface intetgration of the total field in the highindex region) and notice that it has a few narrow peaks, that corresponds to nice whisper mode patterns linig up along the ellipseedge
to make the model ligheter I cut the lower half part and applied a magnetic symemtry condition on the x (y=0) axis
--
Good luck
Ivar
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Posted:
1 decade ago
Sir
Could you build a V3.5 file for me? I am hoping to learn this example.
Thank you.
Could you build a V3.5 file for me? I am hoping to learn this example.
Thank you.
Hi
No I do not think there is any way to convert it backwards tp 3.5. The 2D model is a simple ellipse (2-3 um radius) of material index n=2 surounded by a circle somewhat bigger of index n=1 (air) and a ring around for a PML layer (k=0). Then I have cut a small ellispoidal notch (1:20) of the ellipse on one edge along the small axis of the ellipse (copying the shape of the article but not respecting any dimensions). I defined the small slot part as a field source Ez =1V/m simulating very roughly a scatter source
I then selected a wavelength of My_lambda=1um in air and did a frequency scan in freq=c_const/My_lambda and run a scan towards the UV over >1 octave with fine step around 1:1000
I looked at the energy (surface intetgration of the total field in the highindex region) and notice that it has a few narrow peaks, that corresponds to nice whisper mode patterns linig up along the ellipseedge
to make the model ligheter I cut the lower half part and applied a magnetic symemtry condition on the x (y=0) axis
--
Good luck
Ivar
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Posted:
1 decade ago
Hi dear Ivar,
I also severely need to 3.5 version of your file.Big help!!!!!!!!!
You are a lifesavers.
Very thanks.
Regards,
Mohamad
I also severely need to 3.5 version of your file.Big help!!!!!!!!!
You are a lifesavers.
Very thanks.
Regards,
Mohamad
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Posted:
1 decade ago
Hi, Ivar:
How did you add the notch as source in ComSol? Can I just join a line, add set it as both port1 for excitation, and port 2 for exit?
Also, how do I export at one time all simulated E-field plot over scan frequency, and set color bar range in 2-D plot of E-field?
Thanks
How did you add the notch as source in ComSol? Can I just join a line, add set it as both port1 for excitation, and port 2 for exit?
Also, how do I export at one time all simulated E-field plot over scan frequency, and set color bar range in 2-D plot of E-field?
Thanks
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Posted:
1 decade ago
you can set the boundary condition of the notch to be "port", select the "excitation from this port", set port to be "analysis". I think for this model, you do not need port 2.
for frequency sweep. In the "solve", choose parameter sweep, than youcan scan the frequency
for frequency sweep. In the "solve", choose parameter sweep, than youcan scan the frequency