Chun-Sheng Ma

Optical gain at 1535nm in LaF3:Er,Yb nanoparticle-doped organic-inorganic hybrid material waveguide

LaF3:Er,Yb nanoparticle-doped organic-inorganic hybrid material waveguides were demonstrated using reactive ion etching technology. The absorption and photoluminescence spectra were observed on a 140μm thick film of the nanoparticle-doped hybrid material. Under excitation at 976nm, the fluorescence was obtained at 1535nm, and its full width at half maximum was about 83nm. A relative optical gain of about 5dB was measured at 1535nm in a 22-mm-long waveguide.

Parameter optimization and structural design of polymer arrayed waveguide grating multiplexer

Abstract First some important parameters are optimized for the structural design of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, mode effective refractive indices and group refractive index, diffraction order, pitch of adjacent waveguides, length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range (FSR), the number of input/output (I/O) channels, and that of arrayed waveguides. Then the bent angles, radii and lengths of all the input/output channels and arrayed waveguides are determined. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 11 input channels, 11 output channels, and 91 arrayed waveguides.

Design and analysis of a polymer Mach-Zehnder interferometer electro-optic switch over a wide spectrum of 110 nm

A dual-driving polymer Mach-Zehnder interferometer (MZI) electro-optic switch is designed and optimized, which consists of a phase-generating coupler (PGC) and a 3-dB directional coupler. Structural schematics and principles of the PGC and the switch are described. Novel formulas of the switching time are presented. Under the central operation wavelength of 1550 nm, simulation for the designed device shows that the push-pull switching voltage is 2.445 V, the switching time is 18.1 ps, and the cross talk is less than −30 dB. By optimizing the PGC structure, the phase error resulting from the wavelength shift can be compensated effectively, and a wide spectrum about 110 nm can be achieved. The proposed analytical technique on waveguides and electrodes proves to be accurate and computationally efficient when compared with the beam propagation method (BPM) and the experimental results.

Design of integrated 1×2, 1×4 low driving voltage polymer electro-optic switches based on Y-fed directional couplers

Two integrated 1 × 2 and 1 × 4 polymer electro-optic switches based on Y-fed directional couplers are designed and optimized in terms of the coupled mode theory, electro-optic modulation theory, conformal transforming method and image method. The principle of the 1 × 2 electro-optic switch is described. Parameters including the core size, buffer layer thickness, electrode thickness, electrode width and electrode gap are optimized. Simulation results show that the length of the designed 1 × 2 switch is about 3.126 mm, the driving voltages of the two branches are as low as 0.891 and −0.891 V, respectively, the crosstalk and insertion loss are less than −30 and 1.42 dB, respectively, within the operation wavelength from 1527 to 1574 nm. Under the same driving voltages, the 1 × 4 optical switch with a total length of less than 7 mm can be switched by altering the voltages applied on the electrodes of the three Y-fed directional couplers. Simulation results from the beam propagation method (BPM) indicate that the two designed devices exhibit favorable switching functions.

An Efficient Technique for Analyzing Transmission Characteristics of Arrayed Waveguide Grating Multiplexers

An efficient technique is presented for analyzing transmission characteristics of arrayed waveguide grating (AWG) multiplexers. As an example, calculations using this technique are performed for a polymer 33 × 33 AWG multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 0.8 nm. Computed results show that this technique possesses high accuracy for analyzing the power profile, diffraction efficiency, transmission spectrum, free spectral range and crosstalk of the AWG multiplexer.

Low-power and high-speed thermo-optic switch using hybrid silica/polymer waveguide structure: design, fabrication and measurement

Response speed and power consumption are improved for a Mach–Zehnder interferometer (MZI) thermo-optic (TO) switch, by using a hybrid silica/polymer waveguide structure and optimizing both the thickness of the silica under cladding and that of the PMMA-GMA upper cladding. Fabrication techniques, including chemical vapor deposition (CVD), spin-coating and wet-etching, are adopted to develop the switch sample. Under 1550 nm wavelength, the driving powers under ON and OFF states are measured to be 0 and 13 mW, respectively, indicating a switching power of 13 mW. The fiber-to-fiber insertion loss under the ON state is 15 dB, the extinction ratio between the ON state and the OFF state is 18.3 dB, and the rise time and fall time are 73.5 and 96.5 µs, respectively. Compared with the TO switches based on Si/SiO2 or all-polymer waveguide structure, the proposed device possesses both low power consumption and fast response speed, by virtue of the large TO coefficient of the polymer core, thin upper/under claddings and the large thermal conductivity of silica.

Fourier Modeling and Numerical Characterization on a High-Linear Bias-Free Polymer Push-Pull Poled Y-Fed Coupler Electro-Optic Modulator

A high-linear bias-free polymer Y-fed coupler electro-optic (EO) modulator with push-pull poled two section waveguides is proposed. Using Fourier transformation, a novel formulation technique is presented to numerically model and characterize the device performances. As an EO modulator, the half-wave voltage is 2.6852 V, and the 3-dB modulation bandwidth is ~ 143 GHz. As an EO switch, the insertion loss and crosstalk are <; 3.548 and <; -30 dB, respectively, and the 10%-90% rise time and fall time are both ~ 3.90 ps, indicating a cutoff switching frequency up to 128.2 GHz. As the modulation coefficient is within the range of 1%-10%, the distortion suppression on the third-order intermodulation distortion signals is as high as 60-90 dB, suggesting favorable linearity. This analytical technique is also efficient to theoretically predict the performances of a device with Y-fed coupler structure.

Analysis and optimum design of a polymer Y-fed coupler electro-optic switch using double-section reversed electrodes

A packaged polymer electro-optic switch using double-section reversed electrodes based on the Y-fed coupler structure is investigated in terms of the conformal transforming method, image method, coupled mode theory and electro-optic modulation theory. The structure and principle are described, and unique formulations are proposed for simulating the device, including the amplitude transfer matrix, propagation powers and output powers. Design and optimization are performed, and characteristics are analyzed. Under the central operation wavelength of 1550 nm, the coupling region length is 4391.5 µm, the driving voltages of the upper and lower branches are as low as +0.633 and −0.633 V, respectively; the insertion loss and crosstalk are less than 2.04 and −30 dB, respectively, within the relative large ranges of fabrication error and wavelength shift. The proposed analysis and formulations are proved to be sufficiently accurate by comparison with the beam propagation method (BPM). The designed switch with the above waveguide and electrode structure shows lower switching voltage compared to our previous reported switches.

Analytical modeling of loss characteristics of a polymer arrayed waveguide grating multiplexer

Abstract Theoretical analysis is performed for the loss characteristics of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm . The total loss of the device includes the diffraction loss in the input and output (I/O) slab waveguides, bent loss caused by the AWG and I/O channels, leakage loss resulted from the high refractive index substrate, and propagation loss due to the absorption and scattering of the materials of the device. The effects of some structural parameters on the loss characteristics are investigated and discussed. The computed results show that when we select the core thickness as 4 μm , core width as 6 μm , pitch of adjacent waveguides as 15.5 μm , diffraction order as 50, the number of the arrayed waveguides as 91, that of the I/O channels as 17, confined layer thickness between the core and the substrate as 10 μm , distance between the focal point and the origin as 5500 μm , and central angle between the central waveguide and the x-axis (i.e. the vertical of the symmetrical line of the device) as 60°, the total loss of the device can be dropped to the range 3.79– 7.93 dB .

Analysis of coupling effect on valence band structures of strained multiple quantum wells

The multi-well energy representation technique is presented for the analysis of the valence band structures of multiple quantum well (MQW) lasers. In terms of this technique and its relative formulae, calculations are performed for InGaAs/InGaAsP strained MQW structures. It is found that the coupling exists between the wells, and causes the energy split. So, on the basis of the computed results, the coupling between the wells is analysed, and the split of both the quantized energy levels at the Γ point and the quantized energy bands at the non-Γ points is described. It is also found that the structural parameters of the MQW system strongly influence the coupling property and the energy split, and hence these effects are also discussed in relation to the periodic length, the well width, the distance between the wells, and the ratio of the well width to the periodic length.