Astronomical research at VMI is focused on measuring the polarization of starlight.  Recently, a polarimeter was designed and constructed for use with the 0.5 meter, f/13.05 Cassegrain telescope at the VMI observatory.¹  The polarimeter is based on the common dual-beam design and utilizes a rotatable half-wave plate and Wollaston prism to image starlight onto a CCD detector after passing through a broadband (or narrowband) filter.  The usable field of view is approximately 10 arcminutes and the operational range of the instrument is 400 nm - 700 nm.

Measuring the polarization state of starlight can yield information about the interstellar medium, the nature and environment around certain stars, and the magnetic field in our local region of the galaxy.  Students have the opportunity to utilize the observatory and its equipment by engaging in undergraduate research and work with Lt. Col. G. A. Topasna.

¹G. A. Topasna, D. M. Topasna, G. B. Popko, "An Easily Designed and Constructed Optical Polarimeter for Small Telescopes", Publications of the Astronomical Society of the Pacific, 125, 1056 (2013)

The Thin Films Lab contains some of the latest scientific instruments, to which physics majors at other schools may not be exposed at the undergraduate level. Students who choose to do undergraduate research in the department's thin films lab will have the opportunity to work with an atomic force microscope (AFM), scanning tunneling microscope (STM), UV/VIS/NIR spectrophotometer, materials microscope, vacuum evaporation system, and an array of recently purchased electronic instrumentation. Students will have direct, hands-on experience with the type of equipment they will be working with once they graduate from VMI.

Microscopy

The ability to measure the topology (surface characteristics) of thin films is very important in understanding the fundamental nature of a particular material and how that material may play a role in the creation of certain thin film devices. Optical microscopy is one way of seeing details in the surface of materials. Other methods include scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy. Each method has its advantages and disadvantages, and not all methods are suitable in certain circumstances.

The department's thin films lab contains a Zeiss Axioskop 2 materials microscope. This microscope allows us to visually image films in brightfield, darkfield, and polarized light from 50x to 1000x.  With the Total Interference Contrast attachment we are capable of measuring step heights with 20 nm precision.

The department's thin films lab contains an Atomic Force Microscope (AFM) capable of imaging the surface of materials from 80 (m to less than 1 (m with a resolution of less than 2 nanometers at the lower end. One nanometer (nm) is 10-9 meters.  Atomic force microscopy can be used on all types of solid materials and produces a three-dimensional image of the surface. The AFM can operate in either contact or intermittent contact mode (including phase imaging) and can be expanded to include magnetic force microscopy.

The scanning tunneling microscope (STM) works by the principle of quantum tunneling and can image the surface of conductors or semiconductors. 

Spectroscopy

The department's thin film lab has a Perkin-Elmer Lambda 900 UV/VIS/NIR spectrophotometer with a 150 mm integrating sphere, 6( incident specular reflectance attachment, and slide holder for transmission measurements. The instrument is capable of measuring transmitted and specular reflected light from 175 to 3300 nm.

Vacuum Evaporator

To deposit thin films in a vacuum environment, the thin films lab has a Ladd 30000 vacuum evaporator. The system uses a diffusion pump with liquid nitrogen and can reach 10-7 Torr (1 Torr = 1 mmHg) inside a 12-inch diameter bell jar. Shielded electrodes allow us to deposit solid material either by tungsten boats or filaments.

Electrical Characterization

To characterize the electrical properties of thin films, the lab is equipped with electronic equipment. These include such instruments as a source measure unit, picoammeter, digital multimeters, power supplies, digital phosphor oscilloscope, and RCL meter. These are new instruments from Keithly, Agilent, and Tektronix and are like the ones graduates will find throughout industry or in graduate school.

Miscellaneous Equipment

The lab is outfitted with other equipment typically found in a laboratory setting. A fume hood, nanopure water system, spin coater, computers, and data analysis and programming software are but some of the other equipment that students will find available while pursuing undergraduate research at VMI.

Dr. Thompson’s primary areas of research are the physics of pulsed lasers and the interaction of these pulses with glass optical fiber. Much of this work requires the precise control of various properties of the laser pulses. As a result, we work with lasers that we build rather than off-the-shelf laser systems.

Most applications require that these sources of light be very stable. From a fundamental perspective, nature is replete with events or processes that depend in some way on random fluctuations; consequently, what we learn from these experiments may help us think more clearly about natural processes involving randomness.

Molecular Spectroscopy

We perform research projects which entail studying rare earth and transition metal ions doped into crystal host materials using optical and laser spectroscopy. These materials are of interest because of potential applications such as new laser materials and because of some fundamental physical properties.

The lab is equipped with a Q-switched Nd:YAG laser (Spectra Physics GCR 150) with a 10 Hz repetition rate and 650 mJ of energy at the fundamental (1064nm). The laser also has frequency doubling (532nm) and tripling (355nm) capabilities. In addition, we have a continuous wave, air-cooled Argon Ion laser and a 30-watt deuterium lamp. We have constructed a pulsed dye laser that is pumped by the Nd:YAG laser. We also have KDP frequency doubling crystal for additional wavelength options.

We use photomultiplier tubes for detection. We have a Standford Research multichannel scalar average (SR430) for photon counting. We also have a computer-controlled monochromator (Acton Research Corp).

Cadet Research Projects  

• Energy Transfer Between Gd3+ and Cr3+ in GGG:Cr3+, D. Dunn (98)
• Holographic Interferometry, D. Hendrix (99)
• Constructing a Pulsed-Dye Laser, K. Russell (01)
• Latent Fingerprinting, C. Tyree (01)
• Holography, N. Wahlgren (02)
• Using a CCD to Image Latent Fingerprints, C. Chat (03)
• Aligning and Operating a Pulsed-Dye Laser System, M. Guberovic (03)