Using off-the-shelf optical components a simple, compact optical polarimeter is designed for use with portable telescopes. The polarimeter is optimized for telescopes with an aperture of 10 inches and an f/10 focal ratio, which are typically used in introductory observational astronomy courses. The polarimeter can be used to measure bright standard stars that have published polarization values for the degree of polarization and position angle in the V band. Aperture photometry is used to measure the stellar fluxes on CCD images, which in turn is used to determine the Stokes parameters that are used to calculate the polarization state of a star. In using the polarimeter, students gain insight into how stellar polarization is accurately measured and they become familiar with how Stokes parameters are used in practice.
Simple, reliable, lightweight, and inexpensive thin films based sensors are still in intense development and high demand in many applications such as biomedical, industrial, environmental, military, and consumer products. One important class of sensors is the optical pH sensor. In addition, conformal thin film based sensors extend the range of application for pH optical sensors. We present the results on the fabrication and characterization of optical pH sensing coatings made through ionic self-assembled technique. These thin films are based on the combination of a polyelectrolyte and water-soluble organic dye molecule Direct Yellow 4. A series of films was fabricated and characterized in order to determine the optimized parameters of the polymer and of the organic dye solutions. The optical pH responses of these films were also studied. The transparent films were immersed in solutions at various temperature and pH values. The films are stable when immersed in solutions with pH below 9.0 and temperatures below 90 °C and they maintain their performance after longer immersion times. We also demonstrate the functionality of these coatings as conformal films.
Students experience the entire process of designing, fabricating and testing thin films during their capstone course. The films are fabricated by the ionic-self assembled monolayer (ISAM) technique, which is suited to a short class and is relatively rapid, inexpensive and environmentally friendly. The materials used are polymers, nanoparticles, and small organic molecules that, in various combinations, can create films with nanometer thickness and with specific properties. These films have various potential applications such as pH optical sensors or antibacterial coatings. This type of project offers students an opportunity to go beyond the standard lecture and labs and to experience firsthand the design and fabrication processes. They learn new techniques and procedures, as well as familiarize themselves with new instruments and optical equipment. For example, students learn how to characterize the films by using UV-Vis-NIR spectrophotometry and in the process learn how the instruments operate. This work compliments a previous exercise that we introduced where students use MATHCAD to numerically model the transmission and reflection of light from thin films.
We present a comprehensive student exercise in partial polarization. Students are first introduced to the concept of partial polarization using Fresnel Equations. Next, MATHCAD is used to compute and graph the reflectance for dielectrics materials. The students then design and construct a simple, easy to use collimated light source for their experiment, which is performed on an optical breadboard using optical components typically found in an optics lab above the introductory level. The students obtain reflection data that is compared with their model by a nonlinear least square fit using EXCEL. Sources of error and uncertainty are discussed and students present a final written report. In this one exercise students learn how an experiment is constructed “from the ground up”. They gain practical experience on data modeling and analysis, working with optical equipment, machining and construction, and preparing a final presentation.
Thin films are an important and sometimes essential component in many optical and electrical devices. As part of their studies in optics, students receive a basic grounding in the propagation of light through thin films of various configurations. Knowing how to calculate the transmission and reflection of light of various wavelengths through thin film layers is essential training that students should have. We present exercises where students use Mathcad to numerically model the transmission and reflection of light from various thin film configurations. By varying the number of layers and their optical parameters, students learn how to adjust the transmission curves in order to tune particular filters to suit needed applications.
Polarization is a concept most students readily understand in terms of the preferential direction of electric field vectors. The visualization of the electric field component of an electromagnetic wave facilitates the understanding of a large body of knowledge concerning propagation and measurement of completely and partially polarized light. Little known to undergraduate students, however, is the Stokes parameters and students typically receive a cursory treatment regarding their usefulness in describing and measuring polarized light in a laboratory or astronomical setting. We present laboratory exercises where students use Stokes parameters when measuring and describing the polarization of electromagnetic radiation and in the statistical analysis of polarized light.
An educational experience in numerical modeling for physics majors at Virginia Military Institute has been created as part of the undergraduate research learning paradigm. As part of the independent project course required of all physics majors at VMI, those joining the thin films research group are taught the various stages of numerical modeling applied to complex problems (such as optical limiting) as a precursor to experimental work. Students are introduced to a realistic method of research involving open-ended experiments by this exercise. By teaching students how to design, create, and test a complex numerical model, they gain insight into how an experiment is set up and executed as well as what results can be anticipated. We present an exercise in which undergraduate students use Mathcad in their modeling and calculations.
An educational experience in numerical modeling for physics majors at Virginia Military Institute has been created as part of the undergraduate research learning paradigm. As part of the independent project course required of all physics majors at VMI, those joining the thin films research group are taught the various stages of numerical modeling applied to complex problems (such as optical limiting) as a precursor to experimental work. Students are introduced to a realistic method of research involving open-ended experiments by this exercise. By teaching students how to design, create, and test a complex numerical model, they gain insight into how an experiment is set up and executed as well as what results can be anticipated. We present an exercise in which undergraduate students use MATHCAD in their modeling and calculations.