Henry O. Marcy

Second-harmonic generation in zinc tris(thiourea) sulfate

The linear and second-order nonlinear optical properties of single-crystal zinc tris(thiourea) sulfate, or ZTS, are determined. The deduced nonlinear coefficients are |d(31)| = 0.31, |d(32)| = 0.35, and |d(33)| = 0.23 pm/V compared with a |d(14)| value of 0.39 pm/V for potassium dihydrogen phosphate. Because it exhibits a low angular sensitivity (deltaDeltak/deltatheta), ZTS may prove useful for type-II second-harmonic generation from 1.06 to 1.027 microm. We present the phase-matching measurement data for ZTS and compare the calculated frequency conversion efficiency for ZTS with that of several other well-characterized materials.

Long-term redox switching stability of polypyrrole

Abstract Polypyrrole (PP) films, including poly(pyrrole chloride) (PP-Cl), polypyrrole/poly(styrenesulfonate) (PP/PSS) and poly(pyrrole p -toluenesulfonate) (PP-TOS), were synthesized from various electrolyte/solvent systems. The films were subjected to potential cycling to equilibrate the electroactivity in various switching media. In most cases, the use of a different solvent from the synthesis medium strongly decreased the electroactivity of the PP. The effect of this solvent exchange was strongest in PP-Cl and relatively small in PP/PSS and PP-TOS. After equilibration, the films were subjected to multiple potential steps between the reduced and oxidized states while monitoring the charge passed. The electroactivity changes, measured as the amount of switching charge passed relative to the initial switching charge, were monitored with the number of double potential steps as a probe of the long-term stability. In general, the order of long-term switching stability of PP was determined to be PP-TOS>PP/PSS>PP-Cl, with each system exhibiting unique responses based on its electrochemical history.

Salt-based approach for frequency conversion materials

A salt-based approach for the development of frequency conversion materials is presented. Salts are generally rugged materials due to their strong ionic bonding. A high degree of chemical substitution (both of anion and cation) is possible, including highly nonlinear organic ions. This flexibility is consistent with the use of empirical survey techniques to identify promising candidate materials. We describe in detail our experimental approach and present examples of nonlinear optical crystals we have identified in our materials surveys.

Development of micro-electro-mechanical optical scanner

Rockwell is working on the development of a micro-electromechanical optical scanner based on bimorph microactuators. This scanner is lightweight, is small, and has superior scanning performance. The scanner is a low-power (<1 W) device that has large scan angles (?20 deg) and scan rates in the range of 100 to 2000 Hz. It works for all wavelengths and offers the potential for monolithic integration with both electronics and optics for on-chip signal processing and control. The optical scanner consists of two main components—actuator and mirror— which are fabricated on a silicon cantilever beam. The actuator is comprised of a bimorph layer covered with two metal layers, which function as top and bottom electrodes. The mirror can be as large as 12 mm2 in area, is placed at the end of the cantilever beam, and is designed for maximum optical flatness. The optical efficiency of the device is very high and can exceed 90% on proper metallization of the mirror area. The scan angle is a function of beam thickness, power efficiency of the bimorph, and many other design criteria. Through many improvements in these design parameters, a scan angle greater than 20 deg is expected to be achieved with high yield.

Time‐resolved degenerate four‐wave mixing studies of solid‐state poly(p‐phenylene) oligomers

We have measured χ(3) for a series of solid‐state samples of polyphenylene oligomers, (Ph)n, where n=4–8 is the number of phenyl ring units, using optical pulses of 140 fs duration and 650 nm wavelength. A degenerate four‐wave mixing (DFWM) signal was only observable for n≥6, and thereafter the measured values of χ(3) increased monotonically with n. Measurements of the linear absorption are also reported. Although the DFWM measurements were performed at wavelengths far from resonance, the figure of merit χ(3)/α was essentially flat beyond n≥6. In contrast to previous studies of oligomers in solution, the principal nonlinear responses were instantaneous within the 140 fs temporal resolution.

Second and third order nonlinear optical properties of crystalline inorganic/organic complexes

Properties for members of a new class of nonlinear optical (NLO) materials which stoichiometrically incorporate organic and inorganic constituents into a single crystalline lattice are reported. Recent results for our synthetic, crystal growth, and optical studies suggest that a number of these relatively transparent ``semiorganic`` compounds have significant second and/or third order NLO responses and often display favorable crystal growth morphologies. The prototype material of this class zinc tris(thiourea) sulfate, or ZTS, has a UV cutoff at about 325 nm, can be readily grown to cm{sup 3} sizes, and has been shown to be a highly efficient Type II frequency doubler for 1064 nm Nd:Yag laser radiation. ZTS also processes a moderate third order nonlinear optical response (ca. 0.1{times}CS{sub 2}) which occurs on at least a picosecond time scale as determined by degenerate four-wave mixing (DFWM) experiments at 532 nm. Refractive index, second harmonic generation, and DFWM data for a number of these new compounds are presented.

Solid state electroactive devices based on redox switching polymers

The redox switching of some conducting polymers was investigated. Poly(3,4- ethylenedioxythiophene) and two of its alkyl derivatives were investigated in a liquid electrolyte to probe its usefulness as a visible electrochromic device. The other type of device is based upon actively changing the surface conductivity of one active layer of the device using conducting polymer: in one state the surface conductivity is high, in the other state the surface conductivity is low. Switching speed, contrast ratio, and overall lifetime for both devices were determined and discussed.