If you are in San Francisco, and attending the conference, and have found this page, I’d like to invite you to attend my talk on Thursday at 11:20 in room 234 (Mezzanine). My talk is entitled “Photonic Crystal Switching by the electrophoretic movement of dye ions” and is part of the session on “Novel effects and Applications in Photonic Crystal Structures” within the “Photonic and Phononic Crystal Materials and Devices IX“. Relevant information is on pages 238-240 of the Technical Program.

Now that I’ve located all this spatially, temporally, and categorically I’d probably be wise to briefly outline the paper:

ABSTRACT: Glancing angle deposition (GLAD) facilitates the fabrication of nanostructured thin films with varying density, using a motion control algorithm governing substrate movements during film growth, which engineerings the film structure. Film architectures for specific optical applications including photonic crystals are easily produced with GLAD. A challenge in the photonic crystal field has been the realization of in-situ control of optical characteristics. We have demonstrated partial control of stopband optical characteristics using an electric field in a GLAD 1D photonic crystal by the electrophoretic movement of absorbing dye ions.

Authors: Joshua D. Krabbe, Univ. of Alberta (Canada); Michael J. Brett, Univ. of Alberta (Canada) and National Institute for Nanotechnology (Canada)

With a bit more elaboration:

The basic premise of this work is that the movement of absorbing dye ions into and out of a porous photonic crystal yields a means by which the optical properties of the stopband of the photonic crystal may be modified. The device structure (shown below) is probed for reflectance optical properties from the top surface within the operating region (delimited by dashed lines). The photonic crystal is deposited on a transparent conducting oxide film and when the sandwich structure is completed with an identical counter electrode the device becomes electrically addressable. A dissociating dye (Methylene Blue) is used and when a positive voltage (top with respect to bottom) is applied the cations of the dye (absorbing species) are driven out of the photonic crystal. Reversal of the voltage attracts these cations and absorbing dye species accumulate in the photonic crystal.

Note: this image is (very!) not to scale.

As you likely have already anticipated, the presence of absorbing species within the photonic crystal has an inhibiting effect on the reflectance. Changing the dye concentration affects the probability of photon-dye interaction. The response of reflectance properties with addressing voltage, and an examination of the time response of optical properties to electrical switching of the device will be presented; along with an elaboration of the GLAD technique used to fabricate the porous photonic crystal that forms the basis of the device.

If you can’t attend, the proceedings will be published in 2-4 weeks.

I have to say that I thought the speeches were a ton better than expected, I wondered sometimes as an undergrad how out of touch the administration was with what actually went on on campus. While I’m probably still justified in thinking that to a certain extent what everyone had to say was particularly relevant to the occasion and as a whole rather well presented.

So as Dr. Zemp would say “I’m running out of things to say so let’s look at some pictures”

]]> http://krabbe.ca/blog/2008/219/feed 0 http://krabbe.ca/blog/2008/223 http://krabbe.ca/blog/2008/223#comments Mon, 21 Apr 2008 19:17:56 +0000 admin http://krabbe.ca/blog/?p=223

Quotes from PHYS 481 Electrodynamics number four, Fall Semester 2007

• This is where mathematics can take control of you if you don’t pay attention to what’s going on.
• That is the general case which includes both plucked and hammered types.
• I am not discovering a powder, you have all seen this before.
• This is really easy, you just add it and then bend your mind.
• kx – wt is my favorite way.
• That’s kind of tricky when there is a war going on.
• Sorry, I’m feeling slightly disorganized today.
• The assignment that was due yesterday is now going to be due on Friday at 4:00pm

]]> http://krabbe.ca/blog/2008/223/feed 0 http://krabbe.ca/blog/2008/224 http://krabbe.ca/blog/2008/224#comments Mon, 21 Apr 2008 19:04:28 +0000 admin http://krabbe.ca/blog/?p=224

Quotes from PHYS 472 Quantum Mechanics II, Fall Semester 2007

• Watch out: log-log scales always tend to fool you.
• You are all eligible to make a mistake with a delta function, I have been making mistakes my whole life.
• I can’t prove Bloch’s theorem so I will tell you a story instead.
• Those guys cannot appreciate physics, therefore we’re better than them.
• It’s just an integral! well I guess it’s two integrals, in three dimensions, so I guess really it’s just six integrals, but it’s still just an integral.
• If there were no h-bar we’d just have classical mechanics
• Sines and Cosines have a greater impact on your life than Airy functions.
• The reason you’ve not heard of Airy functions is just because they’re not a button on your calculator
• I’m treating this isotropically so the mass is the same in all directions.
• All the even ones are odd
• This notation is a disaster, don’t try this at home
• So, if anyone ever asks you how to make a hermite polynomial out of sine functions remember you only need about 25 of them.
• The Zeno paradox is actually kinda cute.
• My comments last class about keeping the final exam to two hours are probably a bit false.
• Could someone please look up the word cumulative in the dictionary for him
• Bonus points for Devon
  
  < Ross’s response > Dammit
  
  Bonus points are worth zero
  
  < Ross’s re-response > Yeah! Integrate that!

]]> http://krabbe.ca/blog/2008/224/feed 0 http://krabbe.ca/blog/2007/228 http://krabbe.ca/blog/2007/228#comments Tue, 18 Dec 2007 20:12:07 +0000 admin http://krabbe.ca/blog/?p=228 So I squeezed my way through semester 7. My Quantum Mechanics final exam today came blasting right down the calendar and arrived all too soon. Any time I’ve had to write more than 2 exams back to back one of them often suffers. I think that’s mostly due to the fact that any time you select 3 of my courses at random from the past years your bound to get at least one stickler. I don’t think I really suffered this time though as a matter of preparation or skills with the course. The final was just too long! I probably could have made my way through all the questions in a full 12 hour day of work with some help from a good calculator and a textbook, but to do it in 3 hours with no discussion or help was a bit much.

Anyhow, Christmas vacation has arrived and I’m quite happy to get out of classes for two weeks and do everything other than work hard on school.

• Anyone remember the pythagorean theorem?
  
• Trigonometry from Grade 8 with a mistake in it?? A was supposed to be a unit vector.
  
• Scientific notation from Elementary school??
  

I’ll admit there might be evidence in the last photo that there is some tricky stuff going on, but consider how long it takes to write a partial derivative and how long it takes to draw a picture. The time investment isn’t where the “tricky stuff” is.

Luckily last semester carried a few more labs that boosted the total credit earned up by 0.8 engineering course units over the second semester of third year. That combined with last semester’s almost spotless set of numbers… well let’s just say it keeps me just above that beautiful threshold they call 0.05 which allows me to round up instead of down when calculating the GPA. I’ll admit it’s a pretty sad tale when I’m figuring out those kinds of things but you need something to try and calculate when you’re biking in the rain. What else did I calculate you might ask? Well… I’m still above a 4.0 if I do the calculations factoring all the “+” marks as a bonus 0.3 grade points.

I was well pleased by the stellar lab report mark I sucked out of the last 397 project. While the system is designed to wreak havoc on the self esteem of everyone in engineering physics and honors physics programs, I feel like I won a tiny battle with the last project. Isn’t that what it’s about? I won the battle even though they won the war?? Oh well, so it isn’t quite that way but when you deal with “a personality” such as the one we all had to deal with it’s enough to leave me feeling alright about it.

Electric Field Properties of Asymmetric Capacitances

Properties of the electric field produced between two parallel charged conducting wires are described and analyzed. A DC high voltage supply is used to charge a capacitive configuration of narrow gauge wire which produces a strong electric field. An electrostatic model of the apparatus is developed and used to describe the observed phenomenon of ionization of atmospheric gasses in this electric field. Measurement of the forces caused by the acceleration of these ions provided a means of ascertaining an approximate threshold for the electric field to cause ionization of atmospheric gasses of 2.8 ± 0.4 MV·m−1 in excellent agreement with the accepted value of 3 MV·m−1. Forces on the order of tens of milliNewtons are observed, sufficient to support the entire weight of the apparatus generating the field.

The magnitude of the propulsion force depends on how much air is being ionized and the electric field that it is going to be accelerated across (remember that the mean free path in air (SATP) is on the order of microns, not meters). Generating an electric field strong enough to strip electrons from air molecules isn’t all that simple when you imagine how strong it needs to be, but there is a relatively simply way of doing it. A very simple application of Gauss’s Law to an infinite line charge shows that the field goes like (lambda)/(2*pi*eo*r) where lambda is the linear charge density eo is the permittivity of free space, and r is the distance from the axis of the line charge. That means that the electric field gets arbitrarily large as you approach a theoretical line charge.

To charge a very thin wire (good approx of line charge) we just need to include it in a capacitor and put a large voltage across it. We’re just suspending the thin wire (42 gauge magnet wire) above a large radius of curvature conductor (piece of Al foil).

To measure the force generated (as the obvious manifestation of the phenomenon) we’re suspending the apparatus on a pendulum and measuring the angle of deflection from vertical.

Prelimiary tests have shown that we’re not completely out to lunch, we’re deflecting our “flyer” by close to 10⁰ with a mass of many tens of grams if not hundred (haven’t yet measured).

• EE 380: Microprocessors Microcomputer architecture, assembly language programming, sub-routine handling, memory and input/output system and interrupt concepts.
• EE 470: Waveguides Distributed circuits, propagation and radiation of energy. Transient and time harmonic signals in transmission lines, including impedance matching. Microwave and optical waveguides.
• PHYS 472: Quantum Mechanics B Review of the postulates of quantum mechanics; quantization of angular momentum; matrix representations, spin and parity; approximation methods; perturbation theory; variational and other methods; applications; scattering theory; systems of identical particles.
• EE 456: Nanoelectronics Fundamental concepts related to current flow in nanoelectronic devices. Energy level diagram and the Fermi function. Single-energy-level model for current flow and associated effects, such as the quantum of conductance, Coulomb blockade, and single electron charging. The Schroedinger equation and quantum mechanics for applications in nanoelectronics. Matrix-equation approach for numerical band structure calculations of transistor channel materials. k-space, Brillouin zones, and density of states. Subbands for quantum wells, wires, dots, and carbon nanotubes. Current flow in nanowires and ballistic nanotransistors, including minimum possible channel resistance, quantum capacitance, and the transistor equivalent circuit under ballistic operation.
• EE 351: Digital Electronics MOS digital circuits, logic gates, threshold voltages. MOS logic families: design and simulation. CMOS timing: propagation delay, rise and fall times. Storage elements, memory, I/O and interfacing.

I’m not choosing the easiest way to get through fourth year, Quantum is going to be a decent time investment, and picking EE351 and EE 470 require having labs when I could get away with choosing one of those courses to have no lab. I think it’s important to keep my feet wet in as many areas as I can so I’m pursuing a range of tech electives rather than aiming at taking all the photonics courses I can, or doing something like hitting all the courses in the IC design series. It’s also worth noting that I’m not registering for EE457, microfabrication. I have some experience on that topic and will get a bit more this coming summer, for that reason I’ll direct my focus elsewhere. If I want to pursue it in grad school I’m not getting all that far behind anyways.