Ying-Hao Kuo

Ring resonator-based electrooptic polymer traveling-wave modulator

The authors report the bandpass-modulation characteristics of a ring resonator-based traveling-wave modulator using an electrooptic polymer AJL8/APC. The use of the traveling-wave electrode makes it possible to achieve an efficient modulation around 28 GHz, which is the free spectral range of the resonator, with a 3-dB bandwidth of 7 GHz. The modulation sensitivity is evaluated by defining an equivalent half-wave voltage of ring modulators. It is shown that the modulator has a potential in the microwave and millimeter-wave photonics applications

High-speed AJL8/APC polymer modulator

High-speed polymer modulators were fabricated using low-Vpi AJL8 chromophore in amorphous polycarbonate, and highly calibrated frequency response measurements were obtained using convenient coplanar-microstrip transitions. These Mach-Zehnder modulators show good frequency response to 50 GHz, with a loss and velocity mismatch-limited Vpi at 50 GHz <12 V. The measurements establish AJL8 as an excellent candidate for future military analog optical links

Enhanced thermal stability of electrooptic polymer Modulators using the diels-alder crosslinkable polymer

A thermally stable modulator using a novel Diels-Alder crosslinkable electrooptic (EO) polymer was fabricated. This new material system presents a smartly controlled process to overcome the EO coefficient-thermal stability tradeoff of conventional thermosetting EO polymers and obtains poling efficiency and thermal stability simultaneously. The modulator showed long-term stability at 85/spl deg/C, which shows potential for industrial applications.

Analysis and demonstration of coupling control in polymer microring resonators using photobleaching

We describe postfabrication trimming of coupling in both laterally and vertically coupled polymer microring resonators (MRRs), using photobleaching. For both cases, a tapered directional-coupler-based simple analytical model is developed to simulate the change in coupling due to a bleaching-induced decrease in refractive index. A tightly focused laser beam spot (a few kilowatts per square centimeter) is used to precisely bleach the coupling region alone. Coupling control is achieved for (1) high-Q passive rings by bleaching the vertically coupled chromophore-doped bus waveguide, and for (2) laterally coupled electro-optic ring modulators, by bleaching both the ring and the waveguide in the coupling region. The power coupling ratio (PCR) of an undercoupled high-Q MRR filter is reduced by 0.54 percentage points for the TE mode, causing the MRR finesse to increase from a value of 72 to 108. For a ring modulator, the PCR was increased by 3.5 percentage points for the TM mode, causing a 6 dB increase in extinction ratio, to achieve a final value of nearly 25 dB. Phase/group-delay characterization confirmed that the ring was trimmed toward critical coupling.

Organic electro-optic materials: some unique opportunities

Recent use of quantum mechanics to guide the improvement of molecular hyperpolarizability and the use of statistical mechanical analysis of the effects of intermolecular electrostatic interactions to improve the acentric ordering of organic chromophores has led to the realization of electro-optic coefficients, r33, greater than 100 pm/V (at telecommunication wavelengths). This material design and development paradigm is likely to lead to further improvement in electro-optic activity, which will in turn facilitate the development of a variety of electro-optic devices with drive (Vπ) voltage requirements of less than one volt. The utility of organic electro-optic materials for development of high bandwidth devices is now well documented. What is less obvious is the utility of organic electro-optic materials for the fabrication of complex (including conformal, flexible, and three-dimensional) device structures. In this communication, we review recent improvements in electro-optic activity; thermal and photochemical stability; and processability of organic electro-optic materials and the use of these materials to fabricate conformal and flexible electro-optic devices and devices based upon single and multiple coupled ring microresonators.

High speed polymer electro-optic modulators

We have used this polymer technology to fabricate modulators with balanced outputs by including a 3 dB coupler on the output and incorporated them in a digital time delay array. Arrays of RF photonic phase shifter operating at 20 GHz has also been demonstrated. For more complex integrated optical circuits, it will be important to use low loss passive polymers to interconnect the active polymer devices.

Advances in polymer waveguide devices

Material and fabrication advances have brought polymer high speed, low voltage EO modulators close to commercial development. The technology is now being applied to more complex photonic switches and circuits and we will review some of the latest applications of polymers in photonics. We will briefly review the state of the art for high band-width, low voltage optical modulators for applications in fiber communication systems and in RF photonics. Using an EO polymer, APC/CLD, we have demonstrated a waveguide Mach Zehnder modulator operating in a push-pull mode with low frequency V/sub /spl pi// of 1.2 V at 1300 nm and 1.8 V at 1550 nm. EO and passive polymers also hold promise in the field of micro-photonics. We will present our results on polymer micro-ring resonators integrated with polymer waveguides. Coupled micro-resonators can be used for wide-band tuning of lasers based on the vernier effect. These coupled resonators have been both voltage and thermally tuned. The measurements on a tunable laser based on the coupled resonators and EDFA that tunes over 35 nm will be presented.

Demonstration of wavelength-insensitive biasing using an electrooptic polymer modulator

Wavelength-insensitive biasing (WIB) of an optical intensity modulator was demonstrated using the photobleaching technique to control the initial phase difference of the electrooptic polymer modulator. The WIB technique reduced the wavelength sensitivity of the bias point at 1550 nm by a factor of 17.

Demonstration of 28 GHz ring resonator based electro-optic polymer modulator

We demonstrate a ring resonator based traveling wave electro-optic polymer modulator. Efficient modulation at 28 GHz (FSR of the resonator) with 3 dBe bandwidth of 7 GHz is achieved.

Coupling Control in Polymer Microring Based High-Q Filters and Electro-Optic Modulators Using Photobleaching

Precise and fast post-fabrication trimming of coupling has been demonstrated using high-intensity laser photobleaching of the coupling region in high-Q passive polymer microrings vertically coupled to chromophore-doped waveguides, and in laterally coupled electro-optic ring modulators.