S. Motakef

Organic-inorganic optical materials

We describe the use of an intriguing class of materials, termed polycerams, for applications in integrated optics. Polycerams are ceramic-polymer hybrid materials that are synthesized by wet-chemical methods. As films they can be deposited in single-step operations with thicknesses from <100 nm to >5 microm, and their refractive indices and Abbe numbers can be varied over a wide range. Polycerams synthesized as planar waveguides exhibit optical attenuations as low as <0.15 dB/cm, and they can be patterned by embossing. These materials exhibit exceptional optical properties that are due to combination of organic and inorganic constituents at the molecular level.

Optical properties of sol-gel-derived PZT thin films

A series of sol-gel derived PT-based films, including PT, PZ, PZT, PLT, PLZ and PLZT, was prepared on platinized Si, fused SiO2 and Corning 7059 substrates. These films were fired at 400 - 700 C for 30 mins. The phase assembly and development were dependent on the precursor chemistries, processing and choice of substrates. The presence of Zr impacted significantly on the crystallization behavior, PbO loss and cracking behavior of the films. Crystallization was severely retarded, especially in Zr-containing PZT films when deposited on amorphous substrates compared to crystalline Pt substrates. Amorphous and crystalline PZT films can be utilized for passive and active optical applications. Waveguiding was achieved in an amorphous PZT 53/47 and a crystalline PLT 28 films and gave attenuation losses of 1.0 and 1.4 dB/cm respectively which represent the lowest values reported to date. The optical properties of the films were investigated using ellipsometry, UV-VIS transmission spectroscopy and waveguide loss measurements. Depending on composition and processing conditions, PZT films (2500 A thick) with refractive indices of 1.60 to 2.33 and absorption edges of 2900 - 3100 A can be obtained. It was ascertained that the resulting interfacial reaction layers between the films and substrates affected considerably the optical properties of thinner films (< 2000 A).

Ceramic Films for Optical Applications Code: D7

Recent progress is reviewed on the wet chemical synthesis of films for optical applications. Specific attention is directed to planar waveguides and to electrooptic, non-linear optical and electrochromic films, including recent results obtained in our laboratories.

Polyceram planar waveguides and optical properties of polyceram films

Low loss sol-gel derived polyceram optical waveguides have been prepared for the first time. Polyceram films were obtained by reacting (N-triethoxysilyl propyl) o-polyethylene oxide urethane with silicon and titanium alkoxides. The optical properties of the films were investigated using ellipsometry, UV-VIS transmission spectroscopy and waveguide loss measurements. Refractive index and attenuation loss measurements were carried out as a function of organic/inorganic content, different processing conditions and aging of solutions. Refractive indices as high as 1.685 and attenuation losses as low as 1.4 dB/cm were obtained. In addition, surface morphology, mechanical properties and thermal stability of the polyceram films were studied.

Optical waveguide losses of PZT thin films with various Zr/Ti stoichiometries

Abstract Sol-gel derived PZT thin films were spincoated on Corning 7059 glass substrates and fired to temperatures ranging from 500C to 600C for 30 min. The PZT compositions consisted of PZT x/y where x/y = 0/100, 20/80, 35/65, 53/47, 65/35, 80/20 and 100/0. Only single coated films were used since multiple coatings led to higher losses. XRD was used to characterize the phase assembly of the fired films and indicated that films with higher Zr contents contained proportionally more pyrochlore; while films with higher Ti contents have higher perovskite contents. UV-VIS spectroscopy was utilized to obtain the transmission and optical properties(refractive index and extinction coefficient) via the envelope method. Waveguide losses were measured using prism coupling at the 633 nm HeNe laser wavelength. The waveguide losses in the PZT films ranged from 1.3 to 2.0 dB/cm. The surface texture or morphology of the films significantly affected the optical losses as striated films gave losses of 2.7 to 3.3 dB/cm. The...

Dielectric properties of organic-inorganic hybrids: PDMS-based systems

Organic-inorganic hybrids, with tailorable properties via control of their chemistries, offer great potential for many optical, electrical and mechanical applications. PDMS-based materials have been fabricated, having low optical losses of < 0.15 dB/cm but the dielectric properties of these hybrids have rarely been explored or reported. In the present study, the dielectric properties of PDMS:SiO{sub 2}:TiO{sub 2} films are explored as a function of composition and curing temperature using an impedance analyzer. Dielectric spectroscopy was also performed to investigate the dielectric relaxation and dispersion behaviors. Results indicate that {var_epsilon}{sub r} at 1 MHz ranges from 3 to 5. Residual hydroxyl and alkoxy species in the films contribute to the overall polarizabilities especially at low frequencies (< 100 kHz).

Optical loss study of MPEOU-based polyceram planar waveguides.

Sol-gel-derived polyceram materials based on organically modified silicon and titanium alkoxides have been synthesized in planar waveguide forms. They exhibit optical losses as low as <0.25 dB/cm and refractive indices as high as 1.685, coupled with exceptional ease of processing. The optical properties of the films (index of refraction, loss, and dispersion) are studied as functions of processing and composition, and the influence of chemistry on volume homogeneities and surface roughness of the films is investigated.

Optical losses in sol-gel derived lead lanthanum titanate waveguides

Abstract A series of solgel derived lead lanthanum titanate films were prepared on Corning 7059 glass substrates. Waveguiding properties of these films were studied as a function of La content and film thickness. 0.5M precursor solutions based on lead acetate, La nitrate and Ti Zr alkoxides were refluxed for 1 hour and later spincoated at various speeds on the substrates under clean room condition. Films were fired to 400C for 1 hr to burn off the organics and to consolidate the coatings. They were then fired at temperatures ranging from 500C to 600C. XRD was used to determine the phase assembly present in these films; the presence of La seemed to aid in the formation of the perovskite phase. Transmission spectra were gathered using a UV-Vis spectrometer; and the spectra were then used to calculate the refractive indices based on the envelope method. The waveguiding properties and optical attenuation were studied via prism coupling using a rutile prism. The optical losses in these films decrease with La content and also in thicker single-coated films. On the other hand, thicker films achieved by multiple coating appeared to exhibit higher losses. Crystalline PLZT 28/0/100 yielded loss of

Sol-gel derived La-doped PbTiO3 waveguides

Abstract PbTiO3-based ferroelectric films are attractive materials for passive and active waveguides due to their high refractive indices (> 2·0), small attenuation losses (1–6 dB/cm) and low processing temperatures (< 600C). A series of sol-gel derived La-doped PbTiO3 waveguides was prepared on Corning 7059 glasses. 0·5M precursor solutions of Pb1−x/100Lax/100Ti1−x/400O3 with × = 0, 5, 10, 15, 20, 25, 28, 30 and 32 were spincoated on the substrates and fired to 400C, 500C and 600C for 30 mins. XRD was used to determine the phase assembly present in the films as a funcion of La stoichiometry and firing temperature. The presence of La seemed to aid in achieving the formation of single-phase perovskite films. Transmission spectra obtained using a UV-Vis spectrometer provided information on band gap energies; and the spectra were used to calculate the refarctive indices and extinction coefficients based on the envelope method. The refractive index decreased and band gap increased with increasing La content i...

Optical properties of sol-gel derived La-doped PbTiO3 thin films

A series of sol-gel derived, La-doped PbTiO3 films, with compositions Pb1-x/100 Lax/100 Ti1-x/400 O3 (PLTX) with La content, x equals 0, 5, 10, 15, 20, 25, 28, 30, and 32 were prepared on Corning 7059 substrates. These films were fired at 400 - 600 degree(s)C for 30 mins. The phase assembly and phase development were dependent on the precursor chemistries (La content) and processing (firing temperature). The grain size of the crystallized PLT films decreased with higher La content, and PLT films with higher La contents appeared denser. The optical properties of the films were investigated using UV - VIS transmission spectroscopy. Depending on composition and processing conditions, PZT films (2500 A thick) with refractive indices of 2.00 - 2.56, sufficient for waveguiding on Corning 7059 glasses with refractive index of 1.53, and band gaps of 3.11 - 3.55 eV can be obtained. Exhibiting high refractive indices, these amorphous and crystalline PLT films can be utilized for both passive and active optical applications.