In this paper, we present a novel device structure for organic electro-optic modulators using transparent conducting oxides (TCOs) as electrodes to substantially reduce the switching voltage, and describe their fabrication. We report two different types of device geometry, a top conducting and a side conducting geometry, and discuss their strengths and weaknesses. We discuss how the voltage and speed performance of such modulators are dependant on the conductivity/optical loss ratio of the TCO electrodes. Our device simulation shows that by appropriately engineering the high TCO conductivity/optical loss ratio, 4-6x lower switching voltage can be achieved while still maintaining high modulation frequencies and low optical loss. We show that certain new TCO materials are capable of achieving the high conductivity/optical loss required for efficient modulation in the 1300-1550 nm wavelength range. We summarize the optical loss characteristics at 1300 nm of different types of thin-film TCO materials grown using different deposition techniques. TCO electrodes based on different types of materials, such as In2O3, ZnO, and ITO have been investigated for our device structures. Fabrication issues associated with the deposition of TCO electrodes directly on organic EO materials and our approach to addressing them are discussed. Initial results for organic EO modulators fabricated with TCOs as electrodes are presented, and the performance of these modulators are compared with theoretical modeling results. The new device structures presented here will enable next generation low-voltage organic EO modulators targeting RF photonics applications.
Self-assembled superlattices (SASs) are intrinsically acentric and highly cross-linked structures. For organic electro-optics, they offer great advantages such as not requiring electric field poling for creating an acentric, EO-active microstructure and having excellent chemical, thermal, and orientational stabilities. In this paper, a greatly improved two-step all "wet-chemical" self-assembly (SA) approach is reported. Excellent radiation hardness of the SAS films is demonstrated by high-energy proton irradiation experiments. By introducing metal oxide nanolayers during SA, we show that the refractive indices of SAS films can be tuned over a wide range. Through special chromophore design, the optical absorption maxima of SAS films can also be greatly blue-shifted. Prototype waveguiding electro-optic modulators have been fabricated using the SAS films integrated with low-loss polymeric materials functioning as partial guiding and cladding layers. EO parameters such as the half-wave voltage and the effective electro-optic coefficient are reported.
We describe here the fabrication and characterization of novel organic electro-optic materials composed of self-assembled superlattices. The SAS structures are intrinsically acentric and exhibit large second harmonic generation and electro-optic responses. This approach using SAS electro-optic materials has advantages such as not requiring poling for creating nonlinearity in the films and efficient film growth on a variety of substrates over large areas. Prototype waveguide electro-optic modulators have been fabricated using SAS films integrated wtih low-loss polymeric materials functioning as partial guiding and cladding layers. The waveguide EO modulators are fabricated using a multistep process including e-beam deposition, plasma-enhanced chemical vapor deposition, photolithogrpahy, and reactive ion etching. Electro-optic parameters such as thehalf-wave voltage and the effective electro-optic coefficient, and the velocity mismatch between the optical and radio frequency waves have been evaluated.
In this paper we describe methods of fabricating and characterizing organic electro-optic modulators based on intrinsically polar self-assembled superlattices. These structures are intrinsically acentric, and exhibit large second harmonic generation and electro-optic responses without the requirement of poling by an external electric field. A novel wet chemical protection-deprotection approach for the growth of self-assembled superlattices have been developed, and the refractive indices of self-assembled organic electro-optic superlattices may be tuned during the self-assembly process. Prototype electro-optic modulators based on chromophoric self-assembled superlattices have been designed and fabricated. The effective electro-optic coefficient of the self-assembled superlattice film in a phase modulator is estimated as about 20 pm/V at a wavelength of 1064 nm.
As a kind of nonlinear optical materials, polydiacetylenes (PDAs) have attracted great attention because of their large third-order susceptibilities, ultrafast responsibilities, and high damage threshold, etc. 5-(2-methylthio-4-methyl)- pyrimidinyl-2,4-pentadiyne-1-ol (PDAA) and its derivatives were synthesized. The optical limiting characteristics of these compounds were demonstrated with nanosecond and picosecond pulses at 532 nm. With linear transmittance as high as 87%, the limiting threshold and limited amplitude of PDATS(PDAA tosylate) were observed to be 200 mJ/cm2 and 150 mJ/cm2 respectively, which are lower than that of C60 with the same high transmittance for visible light. A five-level model describing reverse saturable absorption (RSA) of PDATS was proposed to explain its optical limiting effect. The excited-state absorption cross section and the excited-state lifetime were estimated to be 4.0 multiplied by 10-19 cm2 and 0.6 microseconds respectively.
In the paper, 4-n-butoxy carboyl-methyl-urethane was synthesized by the reaction of 5,7- dodecadiyn-1, 12-diol-bis-chloro-formate with buthylaminoacetate hydrochloride. High conversion of monomer in solid state into polymer was obtained by (lambda) -irradiation. We fabricated high optical quality waveguiding film and measured the optical limiting effect of poly-4BCMU in chloride and nonlinear response time of poly-4BCMU.