Fluorinated polyimide waveguides with low polarization-dependentloss and their applications to thermooptic switches

Fluorinated polyimide waveguides with low polarization dependent loss (PDL) and thermooptic (TO) switches made from them were demonstrated. The waveguides showed loss of less than 0.3 dB/cm at the wavelength of 1.3 μm and 0.6 dB/cm at 1.55 μm for both TE and TM polarizations. The PDL's were less than 0.1 dB/cm. Extinction ratios of Y-branching-type TO switches fabricated from these waveguides were larger than 20 dB when over 160 mW of electric power was applied at 1.3 μm, and over 150 mW at 1.55 μm. The switching speed was faster than 8 ms     

A wide-angle X-junction polymeric thermooptic digital switch with low crosstalk

We present our recent design of a wide-angle asymmetric X-junction for the implementation of a digital-optical switch. The simulated crosstalk in the OFF and ON states are -28 and -26 dB, respectively, at an X-branching angle of 1/spl deg/. Polymeric material benzocyclobutene was used to fabricate our design and its switching property was demonstrated using the thermooptic effect. The measured crosstalk is approximately -24 dB in both states with rise-time and fall-time 140 and 210 /spl mu/s, respectively.     

Polarization-independent thermooptic phase shifters in silicon-oxynitride waveguides

The effective refractive index of dielectric waveguides can be tuned using the thermooptic effect. In general, the tuning efficiency is polarization-dependent owing to temperature-induced stress in the layers, which causes polarization-dependent loss in optical devices. These stress issues are analyzed and tested for a high-index-contrast waveguide structure based on a silicon-oxynitride core. Experimental results are in agreement with simulations. The relative difference in tuning efficiency for transverse electric and transverse magnetic polarized light can be tuned from -3% to +3% by appropriate waveguide technology control. The optimized thermooptic phase shifters show tuning efficiency differences below 0.25%, which are reproducible from wafer to wafer.     

Optical TIR switches using PLZT thin-film waveguides on sapphire

Light beam switching in a four-port channel waveguide has been achieved using electrooptic modulation of epitaxially grown PLZT thin film on sapphire. The switches exhibited a low drive voltage of 4.7 V with a switching speed of higher than 1 GHz.     

Asymmetric dark modes in symmetric nonlinear waveguides

We show that symmetric nonlinear waveguides can support the asymmetric dark modes. The existence of a novel class of bright nonlinear guided wave with nonzero-intensity background is also demonstrated     

Gigahertz-bandwidth InGaAsP/InP optical modulators/switches with double-hetero waveguides

A new kind of InGaAsP/InP electro-optic directional coupler modulator/switch with double-hetero plano-convex waveguides, which is suitable for monolithic integrated optics, has been proposed and demonstrated. The fabricated devices have shown low optical loss (4 dB/cm) and high modulation bandwidth of 1 GHz at 1.3 ?m wavelength.     

Molecular photochromic switches based on dihydropyridine

Photochromic behaviour of l-methyl-2,4,4,6-tetraphenyI-l,4-dihydropyridine and the mechanism of the photochromism based on phenyl transfer is described. Formation of polar colour species, changes in optical absorption and in the pi-electron character of the molecular skeleton allow the fabrication of molecular optical memories and switches     

Asymmetric dilation of multiwavelength cross-connect switches forlow-crosstalk WDM optical networks

We predict that, for wavelength division multiplexing optical-network applications, an asymmetrically dilated configuration of a 2×2 cross-connect is significantly better in terms of overall crosstalk when the levels of the bar-port crosstalk and the cross-port crosstalk are significantly different from each other, as is the case with optical-frequency filters which utilize grating-assisted coupling. As a verification, we present a simulation study with 2×2 polarization-diversified acousto-optic tunable filters. We present a recursive method to extend the principle of asymmetric dilation to larger-size cross-connect switches, and make a recommendation for an asymmetrically dilated 4×4 cross-connect configuration     

Semiconductor space switches based on multimode interferencecouplers

It is shown theoretically that selective perturbation by electrorefractive effect of the even-order modes in III-V semiconductor multimode interference couplers gives rise to high-performance optical switching. The calculated performance of the proposed switch is 3.4 GHz/Vmm, compared to 0.85 GHz/Vmm for an equivalent Mach-Zehnder interferometer (MZI) switch. The effects of electroabsorption and dimension variations are analyzed to demonstrate the feasibility of the proposed device     

Optical directional coupler based on Si-wire waveguides

We fabricated optical directional couplers with Si-wire waveguides and demonstrated their fundamental characteristics. Their coupling-length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. Wavelength demultiplexing functions were also demonstrated for devices with a long coupled waveguide. Optical output from a device 800 /spl mu/m long changed reciprocally with 2.5-nm wavelength spacing between the parallel and cross ports.     

Integrated optical switches in silicon based on SiGe-waveguides

The realization of switches in silicon base on monomode Ge-indiffused SiGe waveguides is reported. At a wavelength of 1.3 μm a Mach-Zehnder interferometer switch with a modulation depth of -10 dB at a current of 150 mA is obtained. This is the lowest value reported so far for single-mode optical switches in silicon     

Gain optimization in switches based on semiconductor opticalamplifiers

The distribution of unsaturated gains that minimizes the noise figure of a three-stage optical switch based on semiconductor-optical-amplifier (SOA) gates is found. Gain saturation under both unidirectional (isolators inserted) and bidirectional (no isolators) propagation of spontaneous emission noise is analyzed, and a noise figure penalty associated with the absence of isolators is determined. Determination of the optimal set of pump currents is a nonlinear optimization problem, while determination of the optimum set of saturated gains is a linear optimization problem. The latter solution is found analytically, while the former solution requires a nonlinear optimization approach. The results are extended to the case of a sequence of N SOA's     

Free-space fiber-optic switches based on MEMS vertical torsionmirrors

This paper reports on the design, fabrication, and performance of a novel MEMS (micro-electro-mechanical-system) fiber-optic switch based on surface-micromachined vertical torsion mirrors. The vertical torsion mirror itself can be used as a 1×2 or an ON-OFF switch. A 2×2 MEMS fiber-optic switch with four vertical torsion mirrors has also been fabricated. The switching voltage is measured to be 80 V for switching angles of 45°. We have achieved a switching time of less than 400 μs (fall time) and an optical insertion loss of 1.25 dB for single-mode fibers. In addition, a bulk-micromachined silicon submount has been developed to package the switch with microball lenses and multimode fibers with passive alignment. With the micromachined switch chip and the hybrid-packaging scheme, the size, weight, and potentially the cost of the fiber-optic switches can be dramatically reduced     

Colorless tunable optical dispersion compensator based on a silica arrayed-waveguide grating and a polymer thermooptic lens

We present a colorless tunable optical dispersion compensator (TODC) comprised of a silica arrayed-waveguide grating (AWG) directly coupled to a polymer thermooptic lens. Using silica for the AWG allows it to be low loss and manufactured by a standard process, and using polymer for the thermooptic lens allows it to have a large tuning range and low electrical power consumption. This hybrid TODC is fully solid-state and scales to a large figure-of-merit (dispersion range times bandwidth squared). We demonstrate a version with 100-GHz free-spectral range and 1300-ps/nm tuning range with a 3-dB bandwidth >39 GHz and a lens power consumption <74 mW.     

Fast and low-power thermooptic switch on thin silicon-on-insulator

We have designed and fabricated Mach-Zehnder interferometer thermooptic switches using a wafer-bonded thin-silicon-on-insulator materials system. The thermally switched devices use single-mode strip waveguides with dimensions 0.26/spl times/0.6 /spl mu/m/sup 2/, operating at a wavelength of /spl lambda/=1.55 /spl mu/m. Useful device characteristics include a low switching power, 50 mW, and a fast rise time of <3.5 /spl mu/s. These results demonstrate the potential of this high-index-contrast materials system for the design of fast and low-power thermooptic switches and as an active element in photonic integrated circuits.     

Design and demonstration of weighted-coupling digital Y-branchoptical switches in InGaAs/InGaAlAs electron transfer waveguides

We have designed and demonstrated the first semiconductor digital optical switches that use weighted-coupling Y-branches. Using the beam propagation method we model both conventional Y-branches as well as weighted-coupling, shaped Y-branches with two angles. Theoretically we find that optimal shaping of the branch can provide, for the same device length, enhanced crosstalk performance and voltage efficiency. These features are confirmed by our experimental results on switches fabricated in InGaAs/InGaAlAs chopped quantum well electron transfer waveguides. In the shaped Y-branch switch, we measure a voltage-length product of 4 V-mm with single-arm drive, while that for the conventional Y-branch is 8 V-mm, With dual arm drive in the push-pull configuration, the shaped switch only requires 3.7 V for a 550 μm active length. This switch also has polarization and wavelength insensitive switching characteristics, with less than 1.0 dB variation in crosstalk over a wide operating range from 1.52 to 1.58 μm wavelength     

钛扩散LiNbO_3晶体光波导长周期光栅

设计了一种钛扩散铌酸锂(LiNbO_3)晶体光波导结构,并在该基础上制作了长周期光栅.使用两步钛扩散方法在Z切LiNbO_3基片上制造了波导,它包括一个单模芯层和一个平面包层,之后用光刻胶光栅置于波导表面.实验证明用这种结构设计长周期波导光栅是可行的.对光波导制造工艺和波导结构的深入研究,为制作高速电光调制型光栅提供技术基础.     

Microwave p-i-n diodes and switches based on 4H-SiC

The 4H-SiC p-i-n diodes were designed, fabricated, and characterized for use in microwave applications. The diodes with mesa structure diameters between 80 and 150 /spl mu/m, exhibited a blocking voltage of 1100 V, a 100-mA differential resistance of 1-2 /spl Omega/, a capacitance below 0.5 pF at a punchthrough voltage of 100 V and a carrier effective lifetime between 15-27 ns. X-band microwave switches based on 4H-SiC p-i-n diodes are demonstrated for the first time. The switches exhibited insertion loss as low as 0.7 dB, isolation up to 25 dB and were able to handle microwave power up to 2.2 kW in isolation mode and up to 0.4 kW in insertion mode.     

Micromechanical optical switches based on thermocapillaryintegrated in waveguide substrate

This paper proposes micromechanical optical switches which are suitable for integration in an optical waveguide substrate. The switching mechanism is based on the capillary effect induced by a temperature gradient. The switch has a simple structure which consists of a oil filled slit and a pair of microheaters. We designed two types of thermocapillary optical switches. One was a bubble-driven type, the other was an oil-column-driven type. We fabricated both types of 1×3 micro-switches and demonstrated excellent optical switching and self-latching performance     

A temperature-stable semiconductor laser based on coupled waveguides

The design of a stripe semiconductor laser with a composite waveguide formed of two tunneling-coupled waveguides, one of which is narrow and contains the active medium and the other of which is wide and forms the optical mode is considered. It is shown that temperature stabilization of the lasing wavelength can be attained with such a semiconductor laser design. Stabilization of the wavelength can be brought about by lasing in antiresonance conditions of coupling of two waveguides; these conditions arise in a narrow range of wavelengths that depends on temperature only slightly. Calculations performed at the parameters characteristic of the InAlGaAsP laser system show that it is possible to reduce the temperature dependence of the lasing wavelength by a factor of 3 in the temperature range with the width of 60 K.