Research

In addition to teaching, the Faculty in the Department of Physics are actively engaged in the search for new knowledge and novel applications of physics. Researchers in the Department work in topics ranging from the very small (quantum systems) to the very large (space weather, astrophysics, and cosmology), from the highly theoretical (geometric algebra, many-body physics) to the very practical (photonics, vacuum physics technology, and instrumentation), and from pure hardcore physics (condensed matter physics, general relativity, and mathematical physics) to highly interdisciplinary topics (atmospheric physics, climate physics, and materials science). Listed below are the research groups in the Department:

Earth System Physics:
     •  Air Quality Group
               •  Cambaliza,  Simpas
     •  Physics of the Climate and Weather Group
               •   Narisma, Olaguera, Villarin
     •  Geophysics Group
               •  Maquiling
     •  Space Weather Group
               •  Bennett, McNamara, Sugon

Materials Science:
     •  Auxetic Materials Group
               •  Chan
     •  Materials Characterization Group
               •  Chan
     •  Thin Films and Plasma Processing Group
               •  Culaba, Delos Santos, Mahinay

Photonics:
     •  Photonics Group
               •  Guerrero, 

Physics Education:
     •  Physics Education Group
               •  Cambaliza, Chan, Culaba, Dailisan, Maquiling

Theoretical and Computational Physics:
     •  Geometric Algebra Group
               •  McNamara, Sugon
  
 
Some Selected Publications:

2015

Skew ray tracing in a step-index optical fiber using geometric algebra

By Sugon, Quirino Jr., McNamara, Daniel J., SJ

We used geometric algebra to compute the paths of skew rays in a cylindrical, step-index multimode optical fiber. To do this, we used the vector addition form for the law of propagation, the exponential of an imaginary vector form for the law of refraction, and the juxtaposed vector product form for the law of reflection. In particular, the exponential forms of the vector rotations enables us to take advantage of the addition or subtraction of exponential arguments of two rotated vectors in the derivation of the ray tracing invariants in cylindrical and spherical coordinates. We showed that the light rays inside the optical fiber trace a polygonal helical path characterized by three invariants that relate successive reflections inside the fiber: the ray path distance, the difference in axial distances, and the difference in the azimuthal angles. We also rederived the known generalized formula for the numerical aperture for skew rays, which simplifies to the standard form for meridional rays.

2012

Ray transfer matrix perturbation for an optical component with aberration

By

Jerry T. Barretto, Clark Kendrick C. Go, and Stein Alec C. Baluyot, "Ray transfer matrix perturbation for an optical component with aberration," Chin. Opt. Lett. 10, 080801- (2012)

The perturbation theory of matrices is applied to ray transfer matrices (RTMs) to describe an optical component with aberration. A quantitative description of the perturbation extent corresponding to aberration strength is provided using condition numbers and absolute errors for the perturbed RTM. An application to a single small aberration is presented, and the results are compared with those of the diffraction theory of aberrations.

OCIS codes: 080.0080, 080.2720, 080.2730.
doi: 10.3788/COL201210.080801.

Polarization ellipse and Stokes parameters in geometric algebra

By Sugon, Quirino Jr., McNamara, Daniel J., SJ

Adler G. Santos, Quirino M. Sugon, Jr., and Daniel J. McNamara, "Polarization ellipse and Stokes parameters in geometric algebra," J. Opt. Soc. Am. A 29, 89-98 (2012).

In this paper, we use geometric algebra to describe the polarization ellipse and Stokes parameters. We show that a solution to Maxwell’s equation is a product of a complex basis vector in Jackson and a linear combination of plane wave functions. We convert both the amplitudes and the wave function arguments from complex scalars to complex vectors. This conversion allows us to separate the electric field vector and the imaginary magnetic field vector, because exponentials of imaginary scalars convert vectors to imaginary vectors and vice versa, while exponentials of imaginary vectors only rotate the vector or imaginary vector they are multiplied to. We convert this expression for polarized light into two other representations: the Cartesian representation and the rotated ellipse representation. We compute the conversion relations among the representation parameters and their corresponding Stokes parameters. And finally, we propose a set of geometric relations between the electric and magnetic fields that satisfy an equation similar to the Poincaré sphere equation. © 2012 Optical Society of America

2011

An alternative approach for quantifying climate regulation by ecosystems

By Narisma, Gemma Teresa T.

Paul C West, Gemma T Narisma, Carol C Barford, Christopher J Kucharik, and Jonathan A Foley. 2011. An alternative approach for quantifying climate regulation by ecosystems. Frontiers in Ecology and the Environment 9: 126–133. doi:10.1890/090015 Concepts and Questions An alternative approach for quantifying climate regulation by ecosystems Paul C West1,2*, Gemma T Narisma1,3, Carol C Barford1, Christopher J Kucharik1,4, and Jonathan A Foley5

Ecosystems provide multiple benefits to people, including climate regulation. Previous efforts to quantify this ecosystem service have been either largely conceptual or based on complex atmospheric models. Here, we review previous research on this topic and propose a new and simple analytical approach for estimating the physical regulation of climate by ecosystems. The proposed metric estimates how land-cover change affects the loading of heat and moisture into the atmosphere, while also accounting for the relative contribution of wind-transported heat and moisture. Although feedback dynamics between land, atmosphere, and oceans are not modeled, the metric compares well with previous studies for several regions. We find that ecosystems have the strongest influence on surface climatic conditions in the boreal and tropical regions, where temperature and moisture changes could substantially offset or magnify greenhouse-forced changes. This approach can be extended to estimate the effects of changing land cover on local, physical climate processes that are relevant to society.

1Center for Sustainability and the Global Environment (SAGE), University of Wisconsin-Madison, Madison, WI; current address: Institute on the Environment, University of Minnesota, St Paul, MN

2The Nature Conservancy, Madison, WI

3Ateneo de Manila University, Loyola Heights, Quezon City, Philippines

4Department of Agronomy, University of Wisconsin-Madison, Madison, WI

5Institute on the Environment, University of Minnesota, St Paul, MN

Dynamic angular dispersion of a tunable plane grating

By Culaba, Ivan B., Guerrero, Raphael A.

Jerry T. Barretto, M. Louise P. Jamero, Ivan B. Culaba, Raphael A. Guerrero, “Dynamic angular dispersion of a tunable plane grating,” SPP 2011-145.

We present the fabrication of a reflective elastic plane diffraction grating actuated by asymmetric elongation and investigate the reciprocal angular dispersion. Using a white light source, increasing the grating pitch allows variable wavelength output. A dynamic dispersion relation in terms of the applied strain, parameterized by a single angle of incidence, is presented. Such an element may find use in inexpensive monochromators and spectrometers.

(national conference)

A liquid lens based on Electrowetting of a water droplet on an Alumina ITO glass substrate

By Guerrero, Raphael A.

Juan Paolo S. Bermundo* and Raphael A. Guerrero, “A liquid lens based on Electrowetting of a water droplet on an Alumina ITO glass substrate,” SPP 2011-023.

A liquid lens system is devised by actuating the contact angle of a 3 μL liquid droplet over an Alumina ITO-coated glass substrate via electrowetting. Introduction of a voltage potential of up to 31 V across the coating changes the hydrophobicity of that layer. This causes a change in the shape of the liquid droplet. Because the shape of the liquid droplet is dictated by the amount of voltage potential, the focal length of the liquid lens system will also depend on the applied voltage. This study has potential applications in miniaturized systems like miniaturized cameras and lab-on-a-chip systems.

(national conference)

Characterization of the historical southwest monsoon rainfall in the Philippines

By Narisma, Gemma Teresa T.

Faye T. Cruz, Marcelino Q. Villafuerte II,  and Gemma T. Narisma, “Characterization of the historical southwest monsoon rainfall in the Philippines,” SPP 2011-130.

The historical behavior of the southwest monsoon (SWM) rainfall is examined, particularly over western Philippines, using observed data and model results. A rainfall anomaly index shows a potential seasonal reversal in the SWM rainfall in response to the El Niño Southern Oscillation. A drying trend in the SWM rainfall is also found in the recent decades over selected stations. The regional climate model used is able to capture the spatial distribution of SWM rainfall and direction of prevailing winds.

(national conference)

Near- Surface Atmospheric Dynamics of Changing Crops to Forests in the Philippines

By Narisma, Gemma Teresa T.

Julie Mae B. Dado, Faye Abigail T. Cruz, and Gemma Teresa T. Narisma, “Near- Surface Atmospheric Dynamics of Changing Crops to Forests in the Philippines,” SPP 2011-171.

We explore the effects of changing cropland into forests on the energy and water balances and the consequent changes in near surface atmospheric conditions. We used two regional climate models, RegCM3 and MM5, to simulate a 10-year period using two land-cover scenarios. The first scenario represents current land cover while the second scenario replaces this current land cover with broadleaf trees. Results from both models show that changing cropland areas to forests results in an increase in temperature. This warming is due mainly to increased sensible heat flux with the change in albedo being the dominant factor.

(national conference)