Skip to main content

Photonic band gap materials as astronomical filters

Photonic band gaps are created when materials (at least 2) of different refractive index are stacked on top of one another. If the thickness of these alternating layers is exactly right, these materials act like optical band passes i.e allowing only a certain portion of the optical/electromagnetic spectrum to pass through them. I was taught this last year as part of a course on Optics & Photonics. And now, almost an year from when i was taught this, i realize how they can be applied in astronomy.

Astronomical filters, such as the Johnson UBVRI or the SDSS ugriz, are lenses which act like band passes. The band structures of UBVRI and the ugriz are shown.

source : http://www.vikdhillon.staff.shef.ac.uk/ultracam/filters.gif

Coming back, the idea is to look for a photonic band gap material which can be used as an astronomical filter. But before that, i needed to know what the actual composition of filters are! And this was harder than i thought. Google and wikipedia were of no help and i couldn't find anything on ads either. Then i realized that the companies that manufacture these filters probably patent them to be able to sell/profit from them. So i started searching google patents for filters and voila! I found two links here and here, referring to two types of filters that seem to vaguely resemble two component photonic band gaps.

A simple google search for "photonic band gap band pass" will show you the kind of band passes to expect - 

source : http://lts.fzu.cz/img/bsd_b.gif

I need to brush up on how to simulate the band pass i.e transmittance vs wavelength/frequency characteristics for various photonic band pass systems. And i need time. Some more time...

Popular posts from this blog

Animation using GNUPlot

Animation using GNUPlotI've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it.
I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet.
And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc.
In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana!

In the image, you see 5 static curves and one dynam…

on MOOCs.

For those of you who don't know, MOOC stands for Massively Open Online Course.

The internet is an awesome thing. It's making education free for all. Well, mostly free. But it's surprising at the width and depth of courses being offered online. And it looks like they are also having an impact on students, especially those from universities that are not top ranked. Students in all parts of the world can now get a first class education experience, thanks to courses offered by Stanford, MIT, Caltech, etc.

I'm talking about MOOCs because one of my new year resolutions is to take online courses, atleast 2 per semester (6 months). And I've chosen the following two courses on edX - Analyzing Big Data with Microsoft R Server and Data Science Essentials for now. I looked at courses on Coursera but I couldn't find any which was worthy and free. There are a lot more MOOC providers out there but let's start here. And I feel like the two courses are relevant to where I …

On programmers.

I just watched this brilliant keynote today. It's a commentary on Programmers and the software development industry/ecosystem as a whole.



I am not going to give you a tl;dr version of the talk because it is a talk that I believe everyone should watch, that everyone should learn from. Instead, I am going to give my own parallel-ish views on programmers and programming.
As pointed out in the talk, there are mythical creatures in the software development industry who are revered as gods. Guido Van Rossum, the creator of Python, was given the title Benevolent Dictator For Life (BDFL). People flock around the creators of popular languages or libraries. They are god-like to most programmers and are treated like gods. By which, I mean to say, we assume they don't have flaws. That they are infallible. That they are perfect.
And alongside this belief in the infallibility of these Gods, we believe that they were born programmers. That programming is something that people are born wit…