We have investigated a select group of amorphous aromatic polyimides to determine their potential suitability in fabricating thermally stable optical components, intended for use at high temperatures. Compared to current commercial polymers, these polyimides have much higher glass transition and decomposition temperatures, and also have much lower thermo-optic and thermal expansion coefficients. This combination of characteristics makes them potentially useful in a wide range of commercial and military applications. To better understand the optical properties of these polyimides, we have investigated correlations between several aspects of their chemical structures and their thermo-optical properties. Our study consisted of synthesizing variations of these polyimides, which incorporated targeted structural modifications, and then correlating these structures with trends observed in their optical properties. The modifications studied included the substitution of a variety of side groups that affect the low-frequency vibrational modes, the substitution of structural isomers with distinct symmetries, and the introduction of functional groups that alter the monomer-level anisotropy. Furthermore, we also investigated copolymerization in compatible pairs of monomers as a means of fine-tuning the thermo-optical properties.
Vendor-supplied calibration curves for fixed-grating, fixed-detector-array portable spectrometers typically provide wavelength accuracies of about ±1 pixel on the array. Independent calibration using atomic lamp spectra is hampered by the sparsity of available lines: interpolation between atomic lines typically leads, again, to pixel-width errors or greater. We provide a technique that combines information from sparse atomic line spectra with densely populated peaks from the transmission spectrum of an air-spaced etalon to generate calibration curves capable of ~1/10th pixel accuracies across entire detector arrays. Subsequent transmission spectra through solid etalons of well-characterized glass samples validate the calibration procedure.
We are investigating materials for direct blue solid-state lasers assuming UV excitation with GaN based laser diodes.
Room temperature spectroscopy is reported relevant to a proposed quasi-three level laser from the 4F9/2 level in trivalent
dysprosium. Modeling based on these measurements suggests this is a promising new laser transition.
The design, fabrication, and properties of one of a new class of gradient-index lenses are reported. The lens is an f/2.25 GRIN singlet based on a nanolayered polymer composite material, designed to correct for spherical aberration. The light
gathering and focusing properties of the polymer lens are compared to a homogeneous BK7 glass singlet with a similar
f-number. The modulation transfer function of the polymer GRIN lens exceeded that of the homogeneous glass lens at
all spatial frequencies and was as much as 3 times better at 5 cyc/mm. The weight of the polymer lens was
approximately an order of magnitude less than the homogeneous glass lens.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.