Birefringence control of silica waveguides on Si and itsapplication to a polarization-beam splitter/switch

A novel polarization-beam splitter/switch with a Mach-Zehnder interferometer configuration was fabricated using a silica-based planar lightwave circuit (PLC) on a silicon substrate. The polarization-beam splitter/switch was realized by accurately controlling the waveguide birefringence and the phase state by laser trimming two kinds of stress-applying amorphous silicon film with widths of 50 μm and 95 μm. Fiber-waveguide-fiber insertion loss of 0.5 dB and crosstalk attenuations of over 25.6 dB were attained     

2×2 optical waveguide switch with bow-tie electrode based oncarrier-injection total internal reflection in SiGe alloy

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, a 2×2 intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for the wavelength of 1.3-μm operation. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The on-state crosstalk is -19.6 dB, the off-state extinction ratio is 38.5 dB and the off-state insertion loss is less than 1.70 dB. The switching time is about 180 ns     

An InGaAs/GaAs MQW optical switch based on field-induced waveguides

A novel optical waveguide switch containing InGaAs/GaAs multiple-quantum wells (MQW) is proposed. In this structure, a large field-induced refractive index increase (0.1%) due to the quantum-confined Stark effect (QCSE) is utilized to generate electrically controllable waveguides. Switching operation of a first fabricated device has been investigated at wavelengths of about 1 μm. A crosstalk ratio of -18.8 dB and an extinction ratio of 20.9 dB was achieved at a reverse voltage of -7 V. Within an operational wavelength region of 9 nm, crosstalk was found to be less than -13 dB for both switching conditions. Further, the proposed switch structure seems to be well suited for monolithic integration with laser diodes and exhibits the potential for high-speed operation     

Broad-band array multiplexers made with silica waveguides onsilicon

A waveguide array multiplexer design that is particularly suitable for making broadband low-order devices is presented. Two-channel multiplexers at 1.0-1.55 μm, 1.31-1.53 μm, and 1.47-1.55 μm are demonstrated. Compared to conventional waveguide multiplexers, these devices have wide spectral ranges of low crosstalk. The devices are polarization independent. The crosstalk and fiber-to-fiber insertion loss for the 1.31-1.53 μm multiplexer were about -35 and -2 dB, respectively     

Compensation of Raman-induced crosstalk using a lumpedgermanosilicate fiber Raman amplifier in the 1.571-1.591-μm region

A new method to equalize power imbalance caused by Raman-induced crosstalk among optical channels is proposed using a lumped germanosilicate fiber Raman amplifier. Evolution of optical channels through the Raman amplifier was simulated using Raman frequency modeling, which theoretically predicted simultaneous amplification and power equalization. Experimentally, a gain band with negative slope in the range of 1.571-1.591 μm was achieved in a lumped Raman amplifier pumped by a broad-band laser diode centered at 1.467 μm. We demonstrated compensation of the Raman-induced crosstalk of 5 dB accumulated along 330 km of conventional single-mode fiber     

Film-level hybrid integration of AlGaAs laser diode with glasswaveguide on Si substrate

A ridge-waveguide AlGaAs laser diode (LD) was integrated with a SiO₂-Ta₂O₅ embedded waveguide on a Si substrate by using a film-level hybrid integration technique of semiconductor epitaxial film. CW operation of the LD was achieved at room temperature. The LD-waveguide butt-coupling loss was 9 dB, and the loss due to misalignment was estimated at 3 dB, which corresponds to a displacement of about 1 μm in both the vertical and lateral directions     

An ultra-compact cross/bar optical routing switch using two polymer electro-optic microrings

A 2×2 cross/bar polymer electro-optic(EO) routing switch is proposed,which is composed of two passive channel waveguides and two active EO polymer microrings with bending radius of only 13.76 μm.Detailed structure,theory and formulation are provided to characterize the output power of the switch.For obtaining fundamental mode propagation,small bending loss and phase-matching between channel waveguide and microring resonator(MRR) waveguide,the structural parameters are optimized under the wavelength of 1550 nm.Analyses and simulations on output power and output spectra indicate that a switching voltage of 5 V is desired to realize the exchange between cross state and bar state,the crosstalk under cross state and that under bar state are about 28.8 dB and 39.9 dB,respectively,and the insertion losses under these two states are about 2.42 dB and 0.13 dB,respectively.Compared with our four EO switches reported before,this device possesses ultra-compact size of 0.233 mm×0.233 mm as well as low crosstalk and insertion loss,and therefore it can serve as a good candidate for constructing large-scale optical routers or switching arrays in photonic network-on-chip(NoC).     

Elimination of polarization sensitivity in silica-based wavelengthdivision multiplexer using a polyimide half waveplate

This paper proposes a low-loss technique for eliminating polarization sensitivity in a silica-based planar lightwave circuit (PLC) which uses a polarization mode converter formed at the center of the circuit. This converter consists of a waveguide gap housing a polyimide half waveplate. The excess loss of the converter was drastically reduced to 0.26 dB with a Δ=0.75% waveguide by employing an 18 μm-wide waveguide gap and a 14.5 μm-thick polyimide half waveplate. A polarization mode conversion crosstalk of -37 dB was achieved at 1.55 μm. Using this converter, we successfully eliminated the polarization sensitivity in some silica-based PLC-type wavelength division multiplexers. The converter is also insensitive to temperature and offers long term stability     

Suppressed modal interference switches with integrated curvedamplifiers for scaleable photonic crossconnects

A novel, compact optical switch that incorporates two 1×2 suppressed modal interference (SMI) switches with an integrated curved amplifier is demonstrated as a basic component for scaleable, lossless photonic crossconnects. The basic operation of the switch is described and measured on/off ratios of 22 dB (16 dB) are reported for the cross (bar) state with switching currents of less than 25 mA per section. Lossless switching was attained in the amplified cross state, while only 0.5 dB of excess loss was measured in the unamplified bar state. Cascading of these elements should lead to N×N lossless, optical crossconnects with crosstalk levels near 40 dB     

Reflection-type optical waveguide switch with bow-tie electrode

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, an intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for operating wavelengths of 1.3 and 1.55 μm. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The crosstalks are -19.6 dB for 1.3 μm and -21.8 dB for 1.55 μm. At both wavelengths, the extinction ratio is larger than 38.5 dB and the insertion loss is less than 1.70 dB. The switching time is about 180 ns     

A 1×8 InP/InGaAsP optical matrix switch with low insertionloss and high crosstalk suppression

We present a current controlled passive 1×8 InP/InGaAsP optical matrix switch for routing applications at wavelength 1.55 μm. It is realized in a tree architecture and has integrated tapers for efficient fiber butt coupling. An AR coated device has average fiber-chip-fiber insertion losses of 6.8 and 6.3 dB for TE and TM polarizations, respectively. The homogeneity of the eight outputs is better than 0.3 dB in each polarization state. The crosstalk suppression is better than 19 dB. The performance of the device indicates that large InP-based switching matrices can be realized     

1.55μm SiGe 2×3光开关

利用多模干涉效应和自由载流子等离子体色散效应设计和模拟了基于1.55μm波长的2×3 SiGe光开关.该光开关由两个单模输入端口、一个多模干涉区和三个单模输出端口构成.在多模干涉区,设有两个折射率调制区,可以利用来把从两个输入端口输入的光信号分别从三个输出端口输出.束传播法分析结果表明,该光开关的传输损耗小于1.43dB,串扰在-18～-32.8dB之间.     

Four-channel wavelength division multiplexers and bandpass filtersbased on elliptical Bragg reflectors

Four-channel multiplexers and four-wavelength bandpass filters based on elliptical Bragg reflectors (EBRs) are discussed. The channel spacing is 50 Å near 1.56 μm. The EBRs are narrowband elliptical mirrors that can refocus light from an input waveguide to any one of a number of output waveguides. Spectrally, they perform similarly to Bragg reflectors. The devices were fabricated on silicon using silica-based waveguide technology. The elliptical gratings with 0.53-μm periods were patterned using deep UV spatial frequency doubling photolithography. Multiplexers with single filtering and double filtering were demonstrated. With single filtering, the fiber-to-fiber insertion loss was 3.0±0.5 dB, and the crosstalk was -20 dB; with double filtering, the insertion loss was 4.0±0.5 dB, and the crosstalk was -30 dB. About 2 dB of this loss was due to coupling between the fibers and the waveguide. The additive loss associated with the EBR, including propagation, Bragg reflection, and coupling between input and output waveguides, was about 1 dB     

Gain characteristics of an Er3+-doped multicomponentglass single-mode optical fiber

Experimental results on gain characteristics of an Er³⁺-doped multicomponent glass single-mode optical-fiber amplifier are reported. This amplifier shows a gain spectrum with twin gain peaks of 1.535 and 1.543 μm, providing a broadened gain bandwidth. The apparent 6-dB gain bandwidth is 12 nm. Furthermore, the signal gain of 17 dB and 15-mW pump power is realized at a signal wavelength of 1.536 μm, and a signal gain coefficient of 1.4 dB/mW is achieved     

A dual wavelength (1.32-1.56 μm) directional couplerdemultiplexer by ion exchange in glass

A 1.32-1.56-μm demultiplexer using a symmetrical directional coupler consisting of Ag⁺-Na⁺ exchanged channel waveguides in BK7 glass with a total insertion loss of 1.25 dB for a 14.5-mm-long device and a propagation loss of 0.15 dB/cm is demonstrated. The crosstalk at 1.315 and 1.561 μm and the cross power ratio at 1.315 μm were measured to be less than -40 dB for the TE mode     

Eight-channel p-i-n/HBT monolithic receiver array at 2.5 Gb/s perchannel for WDM applications

We report a monolithic chip incorporating an eight channel p-i-n/HBT photoreceiver array designed for multichannel WDM applications. The p-i-n photodetectors are edge illuminated and centered at a 250 μm pitch for mating with either ribbon fiber connectors or waveguide demultiplexers. Each channel operates at 2.5 Gb/s with an electrical crosstalk of -20 dB between adjacent channels. The average sensitivity of each receiver in the array was measured to be (-20±1) dBm for a bit error rate of 10^-9 at a wavelength of 1.5 μm     

Weighted-coupling Y-branch optical switch in InGaAs/InGaAlAsquantum well electron transfer waveguides

We demonstrate the first weighted-coupling Y-branch switch in semiconductors. The active waveguide core contains an InGaAs/InGaAlAs chopped quantum well electron transfer structure which provides large voltage-controlled refractive index changes near 1.55 μm with high speed capability. We obtain polarization-independent switching over a wide operating range, from 1.52 to 1.58 μm wavelength. We show that shaping the Y-branch results in significant improvements in voltage-length product and crosstalk performance over conventional, non-shaped Y-branches. In push-pull configuration, the drive voltage requirement is only 3.5 V for a 550 μm active length switch     

8×8 symmetric nonblocking integrated acoustooptic spaceswitch module on LiNbO3

An 8×8 symmetric nonblocking integrated acoustooptic space switch module has been realized on a Y-cut LiNbO₃ substrate, 1.0×10.0×37.0 mm in size. The switch module consists of a new hybrid beam expanding-collimating lens, a large aperture focusing lens, and a pair of four-element tilted surface acoustic wave (SAW) transducer arrays in a titanium-in-diffused channel-planar-channel composite waveguide. Experimental results of point-to-point nonblocking switching at the optical wavelength of 0.6328 μm, including an average crosstalk of -12.2 dB, optical switching efficiency of 25% at 125 mW RF drive power, carrier frequency increment of 13.5 MHz for switching between adjacent output channels and reconfiguration time of 0.4 μs have been obtained     

High-drive CMOS current amplifier

A high-performance current amplifier is proposed which is based on a folded-cascode transresistance amplifier and a low-distortion class AB current output stage. The loop gain of the transresistance amplifier exhibits a gain bandwidth product of 10 MHz and a DC gain as high as 100 dB which allows accurate closed-loop operations to be achieved. Despite the intrinsic low-linearity performance of current amplifiers with respect to their voltage amplifier counterpart, the proposed circuit provides an output current of 7 mA with a total harmonic distortion (THD) better than -55 dB while requiring only 200 μA of quiescent current for the output transistors. The circuit was fabricated in a 1.2 μm CMOS process, uses a 5 V power supply, and dissipates 4 mW     

Fully packaged polymeric four arrayed 2×2 digital opticalswitch

A fully packaged polymeric four arrayed 2×2 digital optical switch is fabricated. Crosslinkable fluorinated polymers with a large thermooptic coefficient and a low loss are used for a low electrical power consumption and a low insertion loss. We improve the uniformity, crosstalk, and insertion loss with introducing a rib waveguide, a channel waveguide, and a tapered waveguide in the polymeric four arrayed 2×2 digital optical switch. The deviation of crosstalks is ±2 dB at 250 mW. The crosstalks are less than -30 dB for all four 2×2 digital optical switch elements with each total electrical power of 250 mW. The fall and rise times are less than 5 ms. The polarization-dependent losses are in the range of 0.2-0.7 dB. The total insertion losses range from 3.5 to 4.0 dB