Low (Sub-1-volt) halfwave voltage polymeric electro-optic modulators achieved by controlling chromophore shape

Theoretical study of nonlinear optical properties of "parallel connection" chromophores containing parallel nonconjugated D-pi-A units

Chromophores containing two parallel nonconjugated D-pi-A units are effective chromophores with high hyperpolarizability and good optical transparency. It provides a method for the design and synthesis of effective chromophores. The semiempirical method ZINDO was employed to study the relationship between enhancement of the static first hyperpolarizabilities (beta0) per D-pi-A unit and the number of parallel nonconjugated D-pi-A units in a chromophore. The results show that the chromophores containing two parallel nonconjugated D-pi-A units would exhibit higher beta0 values than two times the beta0 value of the corresponding reference chromophore containing a D-pi-A unit. The chromophore containing three parallel nonconjugated D-pi-A units exhibits the highest enhancement of beta0 per D-pi-A unit, which is 10.1 times the beta0 value of the corresponding reference chromophore. However, the beta0 value of the chromophore containing four parallel nonconjugated D-pi-A units is very small, and the enhancement of beta0 value per D-pi-A unit decreases sharply, from 10.1 to 0.3, with increasing the number of parallel D-pi-A units in a chromophore from 3 to 4. It could give a useful suggestion for designing chromophores containing parallel nonconjugated D-pi-A units.

Dendronlike main-chain nonlinear optical (NLO) polyurethanes constructed from "H"-type chromophores: synthesis and NLO properties

For the first time, a series of dendronlike main-chain polyurethanes have been successfully designed and synthesized, in which different isolation groups with different sizes were introduced to modify the subtle structure of the used "H"-type chromophores, according the concept of "suitable isolation groups". Thanks to the advantages of "H"-type chromophores and the introduced suitable isolation group, all of the polymers demonstrated large NLO effects, good processability, improved optical transparency, and thermal stability. The obtained experimental results indicated that the utilization of "H"-type chromophores might be a promising choice to efficiently translate the large beta values of the organic chromophores into high macroscopic NLO activities of polymers.

Flexible compact microdisk lasers on a polydimethylsiloxane (PDMS) substrate

Compact microdisk cavities were fabricated on a polydimethylsiloxane substrate. The lasing of the flexible compact cavity was achieved with a low threshold power. The whispering-gallery mode of the microdisk was also characterized with three-dimensional finite-difference time-domain simulation. The curvature dependence in output power and threshold was also demonstrated by bending the microdisk cavity.

Fabrication and phase modulation in organic single-crystalline configurationally locked, phenolic polyene OH1 waveguides

A novel and promising technique for the fabrication of electro-optically active single crystalline organic waveguides from 2-{3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene}malononitrile (OH1) is presented. OH1 is an interesting material for photonic applications due to the large electro-optic coefficients (r333 = 109+/-4 pm/V at 632.8 nm) combined with a relatively high crystal symmetry (orthorhombic with point group mm2). Due to the very favorable growth characteristics, large-area (> 150 mm(2)) single crystalline thin films with very good optical quality and thickness between 0.05-10 microm have been grown on amorphous glass substrates. We have developed and optimized optical lithography and reactive ion etching processes for the fabrication of wire optical waveguides with dimensions of w x h = 3.4 x 3.5 microm(2) and above. The technique is capable of producing low loss integrated optical waveguides having propagation losses of 2 dB/cm with a high refractive index contrast between core-cladding and core-substrate of delta n = 1.23 and 0.72, respectively at 980 nm. Electro-optic phase modulation in these waveguides has been demonstrated at 632.8 nm and 852 nm. Calculations show that with an optimized electrode configuration the half-wave voltage x length product V(pi) x L can be reduced from 8.4 Vcm, as obtained in our device, to 0.3 Vcm in the optimized case. This allows for the fabrication of sub-1 V half-wave voltage, organic electro-optic modulators with highly stable chromophore orientation.

Electro-optic single-crystalline organic waveguides and nanowires grown from the melt

Organic nonlinear optical materials have proven to possess high and extremely fast nonlinearities compared to conventional inorganic crystals, allowing for sub-1-V driving voltages and modulation bandwidths of over 100 GHz. Compared to more widely studied poled electro-optic polymers, organic electro-optic crystals exhibit orders of magnitude better thermal and photochemical stability. The lack of available structuring techniques for organic crystals has been the major drawback for exploring their potential for photonic structures. Here we present a new approach to fabricate high-quality electro-optic single crystal waveguides and nanowires of configurationally locked polyene DAT2 (2-(3-(2-(4-dimethylaminophenyl)vinyl)-5,5-dimethylcyclohex-2-enylidene)malononitrile). The high-index-contrast waveguides (delta(n) = 0.54 +/- 0.04) are grown from the melt between two anodically bonded borosilicate glass wafers, which are structured and equipped with electrodes prior to bonding. Electro-optic phase modulation is demonstrated for the first time in the non-centrosymmetric DAT2 single crystalline channel waveguides at a wavelength of 1.55 microm. We also show that this technique in combination with DAT2 material allows for the fabrication of single-crystalline nanostructures inside large-area devices with crystal thicknesses below 30 nm and lengths of above 7 mm.

Phase modulation of an electro-optic polymer cladded polarization-maintaining optic fiber

We present, for the first time based on our knowledge, a novel in-fiber optical phase modulator that is inherently broadband, efficient, and polarization-maintaining (PM). The modulator is a 25 mm long section of a D-shaped cladding PM fiber with half of its silica cladding replaced with an electro-optic (EO) silicone gel. A phase modulation of more than pi rad has been demonstrated. We describe techniques that enable the long-distance exposure of the fiber core, microfabrication of on-fiber electrodes, a low refractive index EO cladding material for replacing silica fiber cladding, and accurate phase measurement utilizing a Sagnac interferometer.

Phase-perturbation-free measurement of electro-optic effect based on Mach-Zehnder interferometer

A novel method of evaluating the electro-optic (EO) effect is proposed based on a Mach-Zehnder interferometer, where the interference fringes are perturbed by air turbulence and/or other mechanical vibrations of an optical bench. The method enables the practical and industrial measurement of the EO coefficient in any environment. It also provides the continuous or repetitive measurement, leading to evaluation of temporal change of an EO coefficient or orientation relaxation of an EO-chromophore containing polymer poled by an electric field.