Zhang Da-ming

High Cost Performance Organic–Inorganic Hybrid Material for Electro-optic Devices

We report a low-cost electro-optic (EO) sol-gel material with large EO coefficient and excellent poling stability for EO devices. Disperse red 1 (DR1) chromophore is doped in the three-dimensional silicon dioxide/titanium dioxide network possessing a high γ33 (88 pm/V at 1300nm wavelength and 71 pm/V at 1550 nm wavelength). Favourable poled stability (less than 5% relaxed after 2500 hours at 80°C) and low absorption are demonstrated. Strip-loaded waveguide Mach–Zehnder (M-Z) modulators are implemented based on this synthesized EO material, showing 7 V half-wave voltage and less than 9 dB insertion loss at 1550 nm wavelength.

Optimized design and fabrication of nanosecond response electro–optic switch based on ultraviolet-curable polymers*

A nanosecond response waveguide electro-optic (EO) switch based on ultraviolet (UV) sensitive polymers of Norland optical adhesive (NOA73) and Dispersed Red 1 (DR1) doped SU-8 (DR1/SU-8) is designed and fabricated. The absorption properties, refractive indexes, and surface morphologies of NOA73 film are characterized. The single-mode transmission condition is computed by the effective index method, and the percentage of optical field distributed in EO layer is optimized to be 93.78 %. By means of spin-coating, thermal evaporation, photolithography, and inductively coupled plasma etching, a Mach–Zehnder inverted-rib waveguide EO switch with micro-strip line electrode is fabricated on a silicon substrate. Scanning electron microscope characterization proves the physic-chemical compatibility between NOA73 cladding and DR1/SU-8 core material. The optical transmission loss of the fabricated switch is measured to be 2.5 dB/cm. The rise time and fall time of switching are 3.199 ns and 2.559 ns, respectively. These results indicate that the inverted-rib wave-guide based on UV-curable polymers can effectively reduce the optical transmission loss and improve the time response performance of an EO switch.

Polymer Electro-optic Modulator Linear Bias Using the Thermo-optic Effect

A quasi-rectangular waveguide polymer Mach?Zehnder (M-Z) electro-optic (EO) modulator based on an organic/inorganic hybrid material with thermal bias control is fabricated and demonstrated. Linear bias for the modulator is obtained through thermo-optic effect. The optical output is adjusted by changing phase difference between the two arms of the M-Z interferometer. A power consumption of 16.1 mW for ? phase change is observed owing to the application of silica cladding. This approach is proved to be effective to suppress direct current drift in polymer EO modulators.

Poled Silica/DR1 Films with Thermally Stability and Large Electro-Optic Coefficient Applying in External Probe Tip

Sol-gel-processed silica films doped with Disperse Red 1(DR1) were prepared at 80°C aging temperature and 120°C baking temperature with corona poling to obtain stable and large electro-optic (EO) coefficient and film strength. A large EO coefficient of γ33 = 56 pm/V was measured for the film of 0.5-μm thickness at the wavelength of 1300 nm, and the value was unvaried at room temperature. Moreover, an external EO probe tip using the film was fabricated for the first time, and a signal voltage level corresponding to the EO signal was calibrated successfully.

A Strip-Loading Optical Waveguide Using Well Poled Stability Organic/Inorganic Hybrid Materials

An optical waveguide for a polymer modulator based on organic/inorganic hybrid electro-optic (EO) materials is designed and fabricated by utilizing a strip-loading structure. This hybrid material has a controllable refractive index, high EO coefficient and good poled stability, which are suitable for the EO modulators and switches. The embedded waveguide made of the above EO material can reduce the coupling loss. The light is coupled into the guided-core layer and then undergoes a transition from the buried waveguide into the EO material. Obvious modulation is observed by application of ac voltage to the EO material. The measured Vπ of co-planar waveguide (CPW) is 5 V for the Mach–Zehnder (MZ) modulator in length of 3.5 cm.

Box-like spectral response of a series-coupled microring resonant filter in a parallel channel

Formulas of the transfer functions are presented for a series-coupled microring resonant filter and the filtering characteristics of this device are investigated around the central wavelength of 1.55 μm. The simulation results show that when the number of the microring is 4, the amplitude coupling ratio between the channel and the microring is 0.25, that between two microrings is 0.022, and the flat box-like spectral response can be formed. The 3-dB bandwidth is about 0.2 nm, the insertion loss is about 1.5 dB, and the minimum of non-resonant light is close to −150 dB.

Fabrication of 32×32 Arrayed Waveguide Grating Using Fluorinated Polymers

We investigate the optical properties of ZIP49 and ZIP51. The thickness and the refractive index of the polymer film are measured using an ellipsometer to be from 2 μm to 10 μm and from 1.49 to 1.51, respectively. A 32×32 arrayed waveguide grating is fabricated using the reactive ion etching technique. The curing temperature is increased to 270 degrees C in nitrogen atmosphere. The etching rate is about 0.067 μm/min. Using re-solution technique, the surface roughness of polymer film was reduced to less than 0.4 nm after spin coating. The insertion loss of the arrayed waveguide grating is about 10 dB and the crosstalk is about -20 dB.

Parameter Optimization of a 9 × 9 Polymer Arrayed Waveguide Grating Multiplexer

Some important parameters are optimized for a 9?9 polymer arrayed waveguide grating multiplexer around the central wavelength of 1.55??m with the wavelength spacing of 1.6?nm. These parameters include the thickness and width of the guide core, diffraction order, pitch of adjacent waveguides, path length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range, the number of input/output channels and the number of arrayed waveguides. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 9 input and 9 output channels, and 91 arrayed waveguides.

The analysis and measurement of electric field crosstalk on the GaAs IC's microstrip electrodes utilizing internal electro-optic sampling method

The electric field crosstalk of microstrips on a GaAs integrated circuit was calculated by static state finite difference method. The crosstalk was also measured by a practical internal electro-optic sampler. The principles of electro-optic sampling and finite difference method were introduced. When the width of active electrode was 5 /spl mu/m and the distance between the two electrodes was 10 /spl mu/m, the practical measured and theory crosstalk value was about 40% and 46%, respectively.

External Electro-optic Sampling Utilizing an Asymmetric Fabry-Pérot Film of Poled Electro-optical Polymer

External electro-optic sampling has been first demonstrated using a poled electro-optical polymer asymmetric Fabry-Perot film, placed freely on the indium-tin oxide coplanar waveguide transmission line and used as an electro-optic probe tip. Only one laser beam is required due to the fact that the asymmetric Fabry-Perot film is utilized to convert the phase modulation to amplitude modulation. A 1.2 GHz microwave signal is sampled, and the voltage sensitivity of about 2 mV/(Hz)1/2 is obtained. The results are promising for technical applications in high-speed electronic devices and monolithic microwave integrated circuits research.