First Pizza Lunch Meeting

Wednesday 2 July 2014


Presentations by LTC Students and Mentors

Alex Kelser, Simons Fellow
Characterizing IR Transmission of Materials Using a Novel Thermo-Mechanical Detector

Bimetallic strips convert a temperature change into a mechanical displacement. I sought to investigate the possibility of using a bimetallic strip as a practical means of detecting heat from infrared light. To optically characterize the deflection of a bimetallic strip, I glued a small mirror onto the end of the strip and directed a laser off of the mirror into a position sensitive detector (PSD). Thus, the position of the laser varied as a function of the deflection angle of the bimetallic strip. The data recorded by the PSD was DC coupled and fed into an oscilloscope. After analyzing the sensitivity of this configuration, I discovered that fluctuations in room temperature were causing baseline thermal drift. To correct for this problem, I chopped the radiation from the infrared source to match the natural frequency of the bimetallic strip. This caused the bimetallic strip to go into thermally induced resonance. The Q-Factor for this resonance was 300. I then AC-coupled the signal from the PSD, and set the oscilloscope to trigger off of a signal from the optical chopper. The result was an apparatus capable of measuring heat from an infrared source, but which filtered out external fluctuations in temperature. This device has proved capable of detecting 0.5 mw/cm2, comparable to the sensitivity of commercially available thermopiles.

Jon Gill, Simons Fellow
An Interference Lithography Technique for Creating Ultra-high Resolution Patterns

Thomas Young demonstrated the wave nature of light by creating interference patterns with light coming from two slits. A recent application of this idea is nonlinear interference lithography.  Last fall, I participated in research with Dr. Sean Bentley at Adelphi University whose goal is to use interference lithography to create arbitrary ultra-high resolution patterns.  The technique depends on the interaction of intense laser pulses with a substrate activated by three photon absorption. By slightly shifting the fringe pattern between multiple exposures narrow bands of unactivated material can be created.  My work last year involved a simplified apparatus in which an interference pattern ablates a conventional substrate such as dark nail polish. It took considerable trial-and-error effort to properly overlap the focussed beams and position the substrate at their common focal point. With a properly aligned setup I was able to observe periodic fringe patterns recorded into the substrate under a microscope.

Andrea O'Brisky, Commack High School
Single Bubble Sonoluminescence: The Star in a Jar

This past school year I have been investigating Single Bubble Sonoluminescence (SBSL) under the guidance of my dedicated science research teacher at Commack High School, Mr. Kurtz.   Sonoluminescence is the process in which intense high frequency sound waves are used to induce cavitation in tiny bubbles trapped in a degassed liquid medium. Under just the right conditions, the temperature of the gas inside the cavitating bubble exceeds 10,000 K and the bubble to become a tiny point of light.  The standard setup for SBSL is a 100 mL spherical flask with piezo-electric transducers (PZTs) attached on opposite sides.   Another smaller PZT on the bottom of the flask acts as a microphone to monitor the response of the flask and the sound of the collapsing trapped bubble, which contains many high harmonics of the driving frequency.  In my setup the fundamental resonant mode of the flask (largest microphone signal) was found at 24.5 kHz. Unfortunately as yet I have not been able to achieve SL or even trap a single bubble with my setup.  In retrospect this was because the home audio amplifier I used could not provide enough voltage to the PZT, which was then unable to create a sufficiently intense sound pressure wave.

Ikaasa Suri, Simons Fellow
Examining the Behavior of Non-Newtonian Fluids Under Stress

It is important to understand how raw materials flow, especially for industrial applications.  Last summer I conducted research at UC Santa Barbara on the behavior of polymer solutions under stress to better understand the physical phenomenon known as spurt. Spurt is the sudden increase in flow rate through a pipe or channel when the pressure is increased beyond a certain value.  I simulated fluid flow in a pipe or channel by using two parallel plates and found that at random times there were reductions in resistance, similar to increases in flow rate.

Elizabeth (Libby) Sutton, SB WISE program, sophomore physics major
My First Research Experience in the Laser Teaching Center

This past semester I had the opportunity to work in the LTC alongside several other undergraduates; this was my first research experience of any kind. One thing I learned is that finding a suitable project topic can be harder than it sounds.  I found many possible topics, but most would have been unrealistic given the amount of time and resources available.  One of these was optical cloaking with metamaterials. Optical cloaking refers to the cloaking or hiding of an object by manipulating the electromagnetic waves around said object. Over the past decade there have been many advances in this field of research. I later learned that it's possible to create simple optical cloaking devices without specialized metamaterials ( John Howell, University of Rochester).  Howell used mirrors, tanks filled with water, and lenses to create cloaked areas.  I lacked time and materials to make my own cloaking tank, but this idea of using everyday objects inspired my final project of demonstrating optical properties of some optics toys we have in the lab.

Melia Bonomo, LTC Mentor
My Personal Path to a Third Summer in the LTC

For the past couple of summers I’ve had the opportunity to work in the Laser Teaching Center alongside some very talented students and mentors.  My initial exposure to the LTC’s unique educational environment as an NSF-REU Fellow during summer 2012 created a solid foundation that has served me well during a variety of subsequent research and teaching experiences.  I carried out a project on creating Bessel beams with a 4-f spatial filter that gave me my first experience with the methodology and presentation of physics research. The following academic year I completed an honors senior thesis at Dickinson College, analyzing the singularities that form at the tip of freezing water droplets.  Then, with a firsthand understanding of how the LTC operates, I returned to the lab for the summer to take on a new role as mentor.  This past academic year I was a high school teaching assistant in Italy, where I  tackled the challenge of designing and executing physics and math lessons for non-native English speakers. Now I’m back in the LTC, looking forward to being a mentor once again.