Using polyimide as host in a guest-host thin film we demonstrate the first poled-polymer electro-optic response stable at temperatures up to 150 °C (samples poled and cured at 250 °C). A coplanar-electrode poling geometry is used so that the molecular alignment of the guest dye between the electrodes is coincident with the free volume of the host. We hypothesize that ‘‘high’’ temperature poling during the imidization process, when the polyimide forms rings and densifies, accounts for the excellent poled response stability.

The gain-feedback approach to lasing and optical instabilities has been applied to sodium vapor driven by a nearly resonant intense field. The observed lasing frequencies agree with the two-beam-coupling gain curve calculated for a Doppler-broadened two-level medium. Rayleigh-gain lasing is seen for no external cavity with use of counterpropagating beams, and Raman-gain lasing is seen in a ring cavity. PACS numbers: 42.65.Ma, 32.80.Wr, 42.50. Tj, 42.65.Ky Silberberg and Bar-Joseph' have analyzed the onset of an optical instability as the simultaneous occurrence of sufficient gain and feedback to permit lasing at a new frequency.The instability observed on the transmitted light is then merely the beat between the pump field and the newly generated "lasing. " We have used this gainfeedback approach in sodium vapor using the Rayleigh gain to generate sideband lasing displaced from the driving laser field by 8 to 14 MHz. Raman-gain lasing is also seen, but it is displaced by the on-resonance Rabi frequency, typically 4 6Hz or less here, rather than by the effective Rabi frequency which is larger because of the detuning. The new observations are Rayleigh-gain lasing with no external mirrors with use of counterpropagating pump beams, ' Rayleigh-gain lasing without a foreign gas, and Raman-gain lasing in a ring cavity.The pump-probe or two-beam-coupling gain curve for a stationary Na atom has already been derived and verified.Here we adopt the nomenclature of Haroche and Hartman and refer to the dispersion-shaped resonance at the laser frequency vL, as "Rayleigh" (called 1/T~in Ref. 4) and the gain peak at vL, -vttE as "Raman" (sometimes called Rabi or three-photon ' gain).Here the effective Rabi frequency is vaE (~BvL+ va) ', where va is the on-resonance Rabi frequency, pvL =vLvo, and vo is the two-level-atom frequency.For moving atoms, one must integrate this curve over the velocity distribution; this has been expressed as easily calculable sums of plasma dispersion functions. " ' Figure 1 compares the detuned stationary-atom curve in Fig. 1(a) with the Doppler-broadened curve in Fig. 1(b) showing the ac Stark shift of the absorption peak and the shift and broadening of the Raman gain. The peak of the Raman gain occurs at a frequency v given by v=-vL~v&E for a stationary atom, where~is given by &vL/I&vL~. For moving atoms and when the Doppler broadening is roughly equal to b'vL, as in Fig. 1(b), the Raman gain is much broader and its peak shifts to almost vL -vR. In contrast, the Rayleigh gain is Doppler free and hardly affected. Lasing will be described on the basis of these two gain mechanisms with use of two different feedback configurations.The experimental apparatus consists of a cw ring dye laser and sodium cell. The =-900-mW single-mode output power of the dye laser is diffracted from an acoustooptic Bragg cell so that any feedback is shifted by 80 MHz and has no effect on the dye-laser frequency. The beam is then spatially filtered, collimated, and focused by a 30or 45-cm focal-length lens into the sodium wit...

We report development of the first all-polyimide system (cladding/core/cladding) suitable for fabrication of electro-optic waveguide devices on silicon substrates. The cladding layers are spun from a low optical loss, commercially available polyimide that is suitable for multilayer stacks. The electro-optic material consists of this same polyimide as host to a commercially available guest chromophore and is based upon our prior work on thermoplastic polyimides [J. F. Valley, J. W. Wu, S. Ermer, M. Stiller, E. S. Binkley, J. T. Kenney, G. F. Lipscomb, and R. Lytel, Appl. Phys. Lett. 60, 160 (1992)]. We present the materials and process development methodology with the results for this polymer system and demonstrate it by fabrication of an all-polyimide Mach–Zehnder modulator operating at 830 nm.

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We demonstrate the first polyimide guest/host system which exhibits stable electro-optic response after parallel-plate poling. Such systems are based on a class of polyimides which, once cured, possess a clear glass transition in their dielectric relaxation spectra, characteristic of thermoplasticity. After doping with compatible nonlinear optical molecules the polyimide host system can first be thermally imidized (cured) and then poled with an electric field. High glass transition temperatures are achieved leading to excellent thermal stability of the poled electro-optic response.

The cell-exit transverse profile for one-way propagation through sodium vapor forms a pattern of spots with complexity and beauty rivaling that of a kaleidoscope. These patterns are stationary in time, reproduce completely when the power or frequency is scanned, and agree well with one-way computations that show that the patterns change very little after one-fifth of the propagation distance, i.e., they exhibit the properties of bifurcations of transverse solitary waves.

As the demand for planarity increases with advanced IC technologies, nanotopography has arisen as an important concern in shallow trench isolation (STI) chemical mechanical polishing (CMP) processes. Previous work has shown that nanotopography, or small surface height variations on raw wafers 20 to 50 nm in amplitude extending across millimeter scale lateral distances, can result in substantial CMP-induced localized thinning of surface films such as oxides or nitrides used in STI [1]. This interaction with CMP depends both on characteristics of the wafer such as heights and spatial wavelengths of the nanotopography, and characteristics of the CMP process including the planarization length or pad stiffness.

We examine the linear electro-optic response of a polymer thin film to an applied step function poling electric field. Time-resolved measurement of the electro-optic response is compared to theory. The electro-optic response measurement uses a heterodyne interferometric technique not previously reported. Response rise and fall times of the order of milliseconds are resolvable and the temperature dependence of those times reported. Good qualitative agreement between theory and data is presented.