Joshua Petrus

Thermo-spectral study of all-polymer multilayer lasers

We investigate the temperature dependence of the emission wavelength and reflection band of polymer Distributed Bragg Reflector (DBR) and defect Distributed FeedBack (DFB) lasers fabricated using a coextrusion melt-process. We show the measured spectral shifts are a direct consequence of the optical path modifications associated with layer expansion and thermo-optic coefficients. By varying the choice of polymer bilayers and sandwiching the DBR laser films between glass coverslips, we fabricated DBR lasers that are either readily tunable up to 0.36nm/°C or made thermally stable at 0.035nm/°C.

Chromatic control in coextruded layered polymer microlenses

We describe the formation, characterization and theoretical understanding of microlenses comprised of alternating polystyrene and polymethylmethacrylate layers produced by multilayer coextrusion. These lenses are fabricated by photolithography, using a grayscale mask followed by plasma etching, so that the refractive index alternation of the bilayer stack appears across the radius of the microlens. The alternating quarter-wave thick layers form a one-dimensional photonic crystal whose dispersion augments the material dispersion, allowing one to sculpt the chromatic dispersion of the lens by adjusting the layered structure. Using Huygens principle, we model our experimental measurements of the focal length of these lenses across the reflection band of the multilayer polymer film from which the microlens is fashioned. For a 56 μm diameter multilayered lens of focal length 300 μm, we measured a ∼ 25% variation in the focal length across a shallow, 50 nm-wide reflection band.

Thermo-spectral properties of plastic lasers

We study the effects of temperature changes on the operating wavelength of all-polymer microresonator lasers, particularly on multilayered defect distributed feedback and distributed Bragg reflector lasers. The parameters that change the operating wavelength are discussed with comparisons between experiments and simulations.