Dong Hun Park

Analysis of multiple reflection effects in reflective measurements of electro-optic coefficients of poled polymers in multilayer structures

We present new closed-form expressions for analysis of Teng-Man measurements of the electro-optic coefficients of poled polymer thin films. These expressions account for multiple reflection effects using a rigorous analysis of the multilayered structure for varying angles of incidence. The analysis based on plane waves is applicable to both transparent and absorptive films and takes into account the properties of the transparent conducting electrode layer. Methods for fitting data are presented and the error introduced by ignoring the transparent conducting layer and multiple reflections is discussed.

Broadband and mid-infrared absorber based on dielectric-thin metal film multilayers

We propose a periodic multilayer structure of dielectric and metal interlayers to achieve a near-perfect broadband absorber of mid-infrared radiation. We examine the influence of four factors on its performance: (1) the interlayer metal conductance, (2) the number of dielectric layers, (3) a nanopatterned antireflective layer, and (4) a reflective metallic bottom layer for backreflection. Absorption characteristics greater than 99% of the 300 K and 500 K blackbody spectra are found for the optimized structures. Incident angle and polarization dependence of the absorption spectra are examined. We also investigate the possibility of fabricating a nanopatterned antireflective layer to maximize absorption.

Closed-form Maker fringe formulas for poled polymer thin films in multilayer structures.

We report new closed-form expressions for Maker fringes of anisotropic and absorbing poled polymer thin films in multilayer structures that include back reflections of both fundamental and second-harmonic waves. The expressions, based on boundary conditions at each interface, can be applied to multilayer structures containing a buffer and a transparent conducting oxide layer, which might enhance multiple reflections of fundamental and second-harmonic waves inside a nonlinear thin film layer. This formulation facilitates Maker fringe analysis for a sample containing additional multilayer structures on either side of a poled polymer thin film. Experimental data and numerical simulations are given to indicate the importance of inclusion of such a reflective layer in analyses for reliable characterization of second-harmonic tensor elements.

High speed electro-optic polymer phase modulator using an in-plane slotline RF waveguide

In this paper, we report on progress in the fabrication of a high speed optical phase modulator based on a nonlinear electro-optic (EO) polymer with an in-plane slotline radio frequency (RF) electrode structure. Compared to microstrip, a slotline RF electrode design has several potential advantages such as easy fabrication, high poling efficiency, low Vπ, and suppression of current drift. The guest-host nonlinear polymer system AJL49/APC was used in the device. Design, fabrication, and characterization are presented.

Impact of interface roughness on the performance of broadband blackbody absorber based on dielectric-metal film multilayers

We report on factors affecting the performance of a broadband, mid-IR absorber based on multiple, alternating dielectric / metal layers. In particular, we investigate the effect of interface roughness. Atomic layer deposition produces both a dramatic suppression of the interface roughness and a significant increase in the optical absorption as compared to devices fabricated using a conventional thermal evaporation source. Absorption characteristics greater than 80% across a 300 K black body spectrum are achieved. We demonstrate a further increase in this absorption via the inclusion of a patterned, porous anti-reflection layer.

MAP-fabricated acrylic double ring resonators (DRRs) with expanded free spectral range (FSR)

MAP was used to fabricate polymer DRRs as its high resolution allows precise control on the coupling/transmission coefficients. Pedestal acrylic DRRs with 33nm FSR and -15dB isolation were fabricated and showed qualitative agreement with simulation results.

Efficient wafer-scale poling of electro-optic polymer thin films on soda-lime glass substrates: large second-order nonlinear coefficients and exceptional homogeneity of optical birefringence

Air Force Research Laboratory (AFRL); Air Force Office of Scientific Research (AFOSR) [FA8650-14-C-5005]; Small Business Technology Transfer Research program (STTR)

Probing limits on spatial resolution using nonlinear optical effects and nonclassical light.

Resolution of an optical system for grating detection was improved by a factor of two beyond the Abbe diffraction limit using nonlinear optics. Use of non-classical illumination did not provide any improvement.

Analysis of reflective Mach-Zehnder interferometry for electro-optic characterization of poled polymer films in multilayer structures

We consider the Mach-Zehnder interferometer (MZI) method that specifically uses a poled organic thin film as one of the reflective mirrors in order to characterize the two independent electro-optic tensor elements r(13) and r(33). We discuss both a simple analysis based on a three-layer structure and a rigorous method including multiple reflection effects in a multilayer structure. In doing so, we find that the simple analysis of the reflective MZI method yields identical results to the reflection ellipsometric method (simple Teng-Man method), first introduced by Teng and Man as well as Shildkraut in 1990, when the ratio of r(13) to r(33) obtained from the MZI method is used in the analysis of the simple Teng-Man method. Error introduced by ignoring the multilayer nature of the sample structures in the MZI method is discussed and corrections are given for previous expressions in the literature for the simple analysis.

Improvement in resolution using four-wave mixing in nonlinear confocal microscopy

Improvement of resolution beyond the Rayleigh limit is obtained by monitoring non-resonant four wave mixing generated by the target in a confocal scanning microscope configuration.