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     

Passive integrated-optical waveguide structures by Ge-diffusion insilicon

The realization of low loss optical channel waveguides and passive waveguide structures by a germanium indiffusion process into silicon will be discussed. Employing relatively simple technological processing like standard lithography, e-beam evaporation and diffusion, single-mode waveguides could be produced exhibiting polarization independent losses of as low as 0.3 dB/cm at wavelengths of λ=1.3 μm and λ=1.55 μm. S-bends fabricated with the same technology offered an excess loss of 1 dB at a radius of around 5 mm without any optimization. For a Y-junction designed with S-bends the maximum opening angle was determined to be 1.8° if an excess loss of 1 dB is allowed. The examination of directional couplers with various coupling lengths and distances revealed an excellent agreement between measurement and theory     

Fused taper/filter hybrid single-mode wavelength divisionmulti/demultiplexer

A low loss and low crosstalk single-mode wavelength division multi/demultiplexer was successfully fabricated by embedding an interference filter in each output arm of a fused taper coupler. The insertion loss was around 1.5 dB at the wavelengths of 1.3 μm and 1.55 μm, and both near-end and far-end crosstalks were less than -50 dB     

Polarization- and wavelength-insensitive guided-wave optical switchwith semiconductor Y junction

A polarization- and wavelength-insensitive semiconductor guided-wave optical switch with a Y junction is proposed. The switch exhibits a digital response with respect to current, allowing its use as a wavelength-insensitive 1×2 optical switch. The switching characteristics are analyzed by using the beam propagation method, and a design example is given. The polarization- and wavelength-insensitive switching operation has been confirmed with a fabricated GaAs/GaAlAs switch at wavelengths of 1.3 and 1.55 μm, and the on/off ratio exceeded 20 dB at an injection current of 250 mA at these wavelengths     

Wavelength- and polarization-independent large angle InP/lnGaAsPdigital optical switches with extinction ratios exceeding 20 dB

Record polarization-independent extinction ratios are reported for ridge waveguide digital optical switches in InP/InGaAsP. Wavelength insensitivity is demonstrated for the first time, with extinction ratios that exceed 20 dB at both 1.3 and 1.5 μm for the same switch. The switch's total opening angle of 0.5° is more than a factor of two larger than other digital optical switches demonstrated at any wavelength     

Poly-Si/SiO2 laminated walk-off polarizer having abeam-splitting angle of more than 20

A spatial walk-off polarizer having a split angle of more than 20° in both the 1.3 and 1.5 μm wavelength regions has been fabricated for the first time. The polarizer consists of alternate laminated layers of poly-Si and silica. The new polarizer makes the best use of the characteristics of crystal Si, namely high refractive index, and low absorption coefficients in the longer wavelength regions. A rather simplified fabrication process that utilizes the RF sputtering method is also proposed, in which only the oxygen-intake valve is used to control the deposition of poly-Si and silica layers from a single-crystal Si target. The fabricated polarizer has beam splitting angles as large as 22 and 21° at wavelengths of 1.30 and 1.55 μm, respectively, being roughly four times larger than those of rutile or calcite     

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     

Monolithic integration of an ARROW-type demultiplexer andphotodetector in the shorter wavelength region

A monolithic integration of an antiresonant reflecting optical waveguide (ARROW)-type demultiplexer and photodetector is discussed. The isolation was theoretically calculated to be -21.6 dB between the wavelengths of 0.78 and 0.88 μm, with a maximum detecting efficiency of 58% in a short demultiplexing/photodetecting length of 100 μm. The fundamental characteristic was demonstrated experimentally. This type of device can be applied to a wavelength division multiplexing (WDM) system with comparatively wide wavelength separation, e.g. 1.3- and 1.55-μm wavelengths     

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     

Low-loss single-mode GaAs/AlGaAs miniature optical waveguides withstraight and bending structures

Low-loss single-mode GaAs/AlGaAs miniature optical waveguides fabricated for use in monolithically integrated optical circuits are discussed. The propagation characteristics of these waveguides with straight and S-bending structures have been investigated at wavelengths of 1.30 and 1.55 μm. The lowest propagation losses are estimated to be 0.58 dB/cm and 0.69 dB/cm at wavelengths of 1.30 and 1.55 μm, respectively. The total loss of an S-bending waveguide with a curvature radius of 2 mm and with a lateral displacement of 200 μm was 0.61 dB and 0.46 dB at wavelengths of 1.30 and 1.55 μm. The fabricated single-mode strip-loaded waveguides proved to be suitable for application of the semiconductor waveguide into monolithically integrated optical circuits     

Novel micromirror for vertical optical path conversion formed insilica-based PLC using wettability control of resin

A novel technique has been developed for fabricating a micromirror in a single-mode silica-based planar lightwave circuit (PLC), in which the flat slope for the mirror is made of resin by utilizing wettability control and the surface tension effect. It was shown that the mirror could be designed by numerical calculation based on the equation of Young and Laplace for a liquid surface. A controllable mirror angle range from 30 to 60° was achieved experimentally by changing the position of the boundary line between high and low wettability regions using oblique evaporation. The characteristics of a fabricated 45° mirror installed in a silica-based PLC were evaluated by coupling it vertically to a single-mode fiber. The obtained coupling losses between waveguides and a fiber were 0.60-1.15 dB for mirrors with widths of more than 200 μm, and 0.92 1.62 dB for 190 μm wide mirrors, at a wavelength of 1.55 μm. The experimental minimum losses of 0.6 and 0.92 dB coincided with the calculated values     

Silicon thermooptical micromodulator with 700-kHz -3-dB bandwidth

A silicon Fabry-Perot waveguide modulator, operating at the fiber optic communication wavelengths of 1.3 and 1.55 μm, has been entirely fabricated using microelectronic techniques. The planar optical cavity has been defined by plasma etching and has a length of 100 μm. The device, based on the thermooptic effect, is electrically driven and exhibits a maximum modulation depths of 60%. The measured -3 dB bandwidth is 700 kHz, which is by far the best result ever reported, to our knowledge, for thermooptic effect based modulators     

Fabrication of variable bandwidth filters using arrayed-waveguidegratings

Variable bandwidth filters have been fabricated using silica-based N×N arrayed-waveguide gratings. The centre wavelengths are λ₀=1.55 μm for all channels. The 3 dB bandwidths are 40, 78, 116 and 154 GHz, for the filter with a path length difference ΔL=63 μm. In the filter with ΔL=8.6 μm, the 3 dB bandwidths are 414, 769, 1198 and 1608 GHz. The on-chip losses are 2.1-2.9 dB and sidemode suppression ratios are larger than 27 dB     

High-performance compact optical WDM transceiver module for passivedouble star subscriber systems

High-performance transceiver-type optical WDM interface modules with a volume of only 36 cc have been developed for PDS subscriber systems. The new module comprises an optical WDM sub-module, hybrid-integrated transmitter and receiver circuits. In the WDM sub-module, a planar lightwave circuit chip was hermetically sealed together with laser and photodiode chips in order to minimize the size of the transceiver module. The lightwave circuit was formed on an optical-waveguide chip by adopting a high-silica based optical-waveguide technology. The circuit has a 3-dB directional coupler for bi-directional transmission with a 1.3-μm wavelength through a single fiber and a wavelength division multiplexer between both 1.3-μm and 1.55-μm wavelengths. The overall characteristics of the fabricated WDM sub-module achieved were a responsitivity of 0.25±0.05 A/W, an insertion loss approximately 3 dB at 1.55 μm and an isolation of 35 dB between both wavelengths. Optical output power of the fabricated transceiver module was -3.8 dBm. Also, receiver sensitivity of less than -35 dBm with an overload of over -14 dBm were obtained by introducing high-speed automatic gain and threshold control techniques. Thus, an allowable span loss of over 30 dB and an optical dynamic range of over 20 dB were attained. The preamble bit length required to reach stable receiver operation was confirmed to be within three bits     

Laminated polarizers exhibiting high performance over a wide rangeof wavelength

A laminated polarizer exhibiting high performance over a wide range of wavelengths has been fabricated for the first time. The polarizer consists of alternate layers of laminated silica film and metal-included semiconductor ultra-thin film as the transparent and absorptive layers, respectively. Extinction ratios of greater than 50 dB with insertion losses of less than 0.4 dB have been obtained over the wavelength range of 0.8-1.55 μm. At the wavelength 0.98 μm where previously no viable laminated polarizer had been available, the extinction ratio is as high as greater than 60 dB and the insertion loss less than 0.3 dB     

Low dispersion penalty and wide temperature range operation over120 K with 1.55 μm strained MQW-DFB laser module

STM 16 (2.488 Gbit/s) system operation over a wide DFB chip temperature range of more than 120 K (from -25°C to +95°C) is presented with dispersion penalty below 1 dB after transmission across 100 km standard fibre. DFB operation at 1.55 μm with a high sidemode suppression ratio of 40 dB is achieved within -40°C to +95°C. The lasers were realised using a BRS lateral structure and a quaternary InGaAsP MQW stack with six compressively strained quantum wells and a highly detuned DFB grating     

Polarization-insensitive InP-based MQW digital optical switch

A polarization-insensitive InP-based p-i-n multiple-quantum-well switch is demonstrated for the first time. Polarization-insensitive switching and loss are achieved. Crosstalk and loss measurements across a wavelength range of 20 nm centered at 1.55 μm are reported. A crosstalk of better than -13 dB is achieved for both TE and TM polarizations across the 1.54-1.56-μm wavelength range with a switching voltage of -7 V. A low on-chip loss of less than 3 dB is achieved for both TE and TM across the above wavelength range, with a compact switch structure which is 3 mm long     

4×4 polymer thermo-optic directional coupler switch at 1.55μm

An integrated 4×4 polymer thermo-optic switch at 1.55 μm is demonstrated for the first time. A fibre to fibre insertion loss of 10 dB, and extinction ratios of 17.5-19.5 dB were measured. The polarisation sensitivity was typically less then 0.5 dB and the response time was less then 1 ms. The electrical power consumption was found to be 70 mW per single switch     

InGaAs microwave switch transistors for phase shifter circuits

A new InGaAs insulated-gate FET (IGFET) with 1 μm gate length and three different gate widths has been designed, fabricated and characterized as switch devices for microwave control applications in phase shifter circuits. The devices employed a plasma deposited silicon dioxide gate insulator and had multiple air bridged source regions. The details of the DC current-voltage (I-V) characteristics and small signal S-parameter measurements up to 20 GHz are presented. The switch IGFET's had a drain saturation current density of 300 mA/mm gate width with breakdown voltages of higher than 35 V. An insertion loss of 1.0, 0.6, and 0.4 dB at 10 GHz and 1.4, 0.8, and 0.4 dB at 20 GHz have been measured for the 300, 600, and 1200 μm gate width IGFET's, respectively. Equivalent circuit models fitted to the measured S-parameters for IGFET's yielded on-state resistances from 10.7 to 3.3 Ω, off-state resistances from 734.4 to 186.8 R and off-state capacitances from 0.084 to 0.3 pF as the gate width is increased from 300 to 1200 μm The simulation results using IGFET models for the phase shifter circuits indicated a maximum phase error of 0.11°, 0.26°, and 0.479 with 0.74, 0.96, and 1.49 dB maximum insertion loss and greater than 33, 26, and 19 dB return loss for the 11.25°, 22.5°, and 45° phase bits, respectively, over the 9.5-10.5 GHz frequency band     

High-power semiconductor edge-emitting light-emitting diodes foroptical low coherence reflectometry

A new semiconductor source was designed for optical low coherence reflectometry, increasing the sidelobe-free dynamic range by three to five orders of magnitude compared to conventional EELED's. Reflectivities internal to an optical fiber circuit separated by as much as eight orders of magnitude can now be detected at wavelengths of 1.3 and 1.55 μm, using compact semiconductor sources. For applications not requiring sidelobe-free operation, the same devices can be operated at high current (200 mA) and low temperatures (near 0°C) to produce nearly 1 mW of 1.5 μm emission coupled into single-mode fiber. The resulting wavelength spectrum is smooth, enabling fiber-based absorption spectral measurements