A proposed design for ultralow-loss waveguide grating routers

We propose a design for a dense wavelength-division multiplexing (WDM) demultiplexer whose total fiber-to-fiber insertion loss can be as low as 0.3881 dB. Our three dimensional (3-D) models-beam propagation and mode solver-show that waveguide bending losses and fiber coupling losses are almost insignificant. Most of the loss comes from the star couplers and from material losses     

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     

Low loss GaAs optical waveguides

To realize an optical integrated circuit, various losses in the semiconductor waveguide such as absorption loss, waveguide loss, bending loss, and coupling loss, have to be minimized. Theoretical and experimental considerations for the reduction of these losses have been presented. A propagation loss of less than 0.5 dB/cm has been observed for a well-designed GaAs ridge waveguide. Moreover its coupling loss with a polarization-maintaining optical fiber decreased below 1.5 dB.     

Low loss GaAs optical waveguides

To realize an optical integrated circuit, various losses in the semiconductor waveguide such as absorption loss, waveguide loss, bending loss, and coupling loss, have to be minimized. Theoretical and experimental considerations for the reduction of these losses have been presented. A propagation loss of less than 0.5 dB/cm has been observed for a well-designed GaAs ridge waveguide. Moreover its coupling loss with a polarization-maintaining optical fiber decreased below 1.5 dB.     

Efficient single-mode fiber to titanium diffused lithium niobate waveguide coupling for λ = 1.32 µm

We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide atlambda = 1.32 mum. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.     

Polymer waveguide thermooptic switch with low electric powerconsumption at 1.3 μm

A polymer waveguide thermooptic 2×2 switch with low electric power consumption is demonstrated. The switch consists of a Mach-Zehnder interferometer with Cr thin-film heaters. The waveguides are fabricated using acrylic polymers synthesized from deuterated methacrylate and deuterated fluoromethacrylate monomers. The total insertion loss of the switch is 0.6 dB at a wavelength of 1.3 μm, including fiber coupling losses and waveguide losses. The switching power is as low as 4.8 mW, and the rise and fall times are both 9 ms     

A study of fiber-to-fiber losses in waveguide grating routers

Most of the waveguide grating router's loss comes from fiber coupling and star coupler. Our three-dimensional (3-D) models quantifies both losses. In addition, we study how various waveguide parameters affect the value and nonuniformity of this loss. Our optimization yields a design where the total fiber-to-fiber insertion loss can be reduced to 0.535 dB     

Millimetre-wave wideband reflection-type CPW MMIC phase shifter

A reflection-type coplanar waveguide (CPW) phase shifter fabricated using a standard monolithic microwave integrated circuit (MMIC) process is presented. Air-gap overlay CPW couplers were employed for wideband 3 dB coupling and low loss at millimetre wave. The two-stage cascaded analogue phase shifter showed insertion losses of 6.9 ± 1.6 dB, return losses > 10 dB, and maximum rms phase error of +5.5° for the relative phase shift from -20° to 135°, over a wideband 27 to 47 GHz     

Influence of temperature and initial titanium dimensions of fiber-Ti:LiNbO3waveguide insertion loss at λ = 1.3 µm

This paper describes the influence of fabrication parameters on fiber-Ti:LiNbO3waveguide-fiber insertion loss measured atlambda = 1.32 mum inc-cut LiNbO3. We present a systematic study of the influence of titanium thickness on insertion loss. Within the range examined, diffusion of 950 Å thick 6 μm wide strip of Ti at 1050°C for 6 h produced the minimum loss of 2.0 dB in a 2 cm long waveguide for both TE and TM modes. An analysis of fiber-waveguide coupling for the particular case of an asymmetric diffused waveguide is presented. In general, we find that coupling loss due to modal mismatch between the fiber and waveguide and propagation loss in the waveguide contribute approximately equally to total insertion loss.     

Low-loss 1.5%-Δ arrayed waveguide grating with narrowlaterally tapered spotsize converter

A low coupling loss of 0.5 dB/point between 1.5%-Δ silica-based waveguides and a singlemode fibre has been achieved by employing a simple laterally tapered waveguide with a narrow core width. By applying this structure to an arrayed waveguide grating multiplexer, the insertion loss was decreased from 4.9 to 2.6 dB     

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     

High performance dual directional couplers for near-mm wavelengths

A low loss, high directivity dual directional coupler has been developed suitable for fabrication in waveguide bands up to WR3 (220-325 GHz). The design uses waveguide split on the E plane centerline with three waveguides running side by side and coupling holes made by drilling through all three guides. Construction is relatively simple and the resulting structure is very robust mechanically. Typical coupling is 15 dB, directivity is 25-30 dB, and the insertion loss of the WR3 coupler is 0.5 dB     

5/spl times/9 integrated optical star coupler in silicon-on-insulator technology

We describe fabrication of the first optical star coupler in silicon-on-insulator (SOI) technology. The 5/spl times/9 coupler consists of two silicon rib waveguide arrays with a radiative slab waveguide region. The star geometry was analyzed and designed using the beam propagation method. The coupler exhibits low loss (average excess insertion loss /spl alpha//spl sim/1.3 dB) and good coupling uniformity (standard deviation /spl sigma//spl sim/1.4 dB) at /spl lambda/=1.55 /spl mu/m. It represents a key component for realization of photonic circuits in a silicon integrated circuit technology.     

E-Plane Integrated Circuit Filters with Improved Stopband Attenuation (Short Papers)

Improved stopband attenuation is achieved by thick strips, by reduced waveguide sidewall dimensions, and by double planar integrated circuits. In contrast to thick strips which may cause high passband insertion losses and filters with reduced waveguide dimensions which require additional tapers, double planar E-plane integrated circuit filters combine the advantages of low costs, high stopband, and low passband insertion losses. Computer-aided design of a four-resonator Ka -band double metal insert filter achieves a calculated stopband attenuation between 40 and 60 GHz of more than 50 dB, the calculated minimum passband insertion loss is 0.43 dB (measured 1.8 dB). Higher order mode excitation and finite thicknesses of the inserts are included in the calculations.     

Low-loss GaAs/GaAlAs strip-loaded waveguides with high coupling efficiency to single-mode fibres

We report measurements of low-loss MOVPE-grown GaAlAs/GaAs strip-loaded waveguides with high coupling efficiency to single-mode fibres. A propagation loss of 2 dB/cm and a coupling efficiency of 70% has been achieved for a p+-i-n+-structure waveguide. A propagation loss of 0.7 dB/cm and a coupling efficiency of 61% has also been achieved for an n?-i-n?-structure waveguide.     

A manufacturable technique for implementing low-loss self-imagingwaveguide beamsplitters

A manufacturable technique to implement self-imaging waveguide beamsplitters is proposed and demonstrated. This technique offers low insertion loss and polarization crosstalk, uniform splitting ratios, ease in manufacture, and most importantly application to diverse waveguide material systems. Beamsplitters with splitting ratios that range from 1×2 through 1×17 were fabricated in GaAs-AlGaAs waveguides. For 1×16 splitters integrated with an output ridge waveguide array, the insertion losses in many devices were less than the insertion losses in adjacent straight-through ridge waveguides. The best uniformity spread among the 16 channels was 17.8% and the TE-to-TM and TM-to-TE polarization crosstalks were lower than -25 dB     

A Fully Embedded 60-GHz Novel BPF for LTCC System-in-Package Applications

In this paper, a novel LTCC stripline (SL) 60-GHz band-pass filter (BPF) composed of transitions to coplanar waveguide (CPW) pads for monolithic microwave integrated circuit integration is presented. For low-loss interconnection with active devices, a CPW-to-SL vertical via transition integrating air cavities and a CPW-to-CPW planar transition using internal ground planes are proposed and implemented. The fabricated transition shows an insertion loss of 1.6 dB and a reflection loss below -20 dB at the passband of the filter. The implemented SL BPF using dual-mode patch resonators shows a center frequency of 60.4 GHz, 3.5 % bandwidth, and reflection losses below -15 dB at the passband. Excluding the insertion loss of the transitions, the filter insertion loss reveals 4.0 dB     

PLZT film waveguide Mach-Zehnder electrooptic modulator

We report the numerical analysis and the fabrication of a reversed-ridge PLZT film waveguide. It is single-mode, has low transmission loss, and has large transverse cross-section suitable for efficient coupling to single-mode optical fibers. We used this structure to fabricate Mach-Zehnder (MZ) waveguide modulators. The field distribution in the channel and Y branch waveguides was calculated using a beam propagation method to analyze the modal profiles and the propagation loss. The reversed-ridge waveguides and the MZ structures were fabricated on r-sapphire substrates with a patterned ITO spacer film by sol-gel deposition. At 1.55 μm the propagation loss was 2.7 dB/cm. In the MZ, the half-wave modulation voltage was 8.5 V using 1.55 μm light and electrode length of 3.5 mm     

High-gain array of semiconductor optical amplifier integrated withbent spot-size converter (BEND SS-SOA)

We propose a high-gain semiconductor optical amplifier with an integrated bent spot-size converter (BEND SS-SOA). A straight active waveguide enables us to use a pn-buried heterostructure (pn-BH) with a high current-blocking effect and uniform characteristics. We can optimize a bent spot-size converter waveguide to provide low optical feedback from the facets and high-coupling efficiency to a flat-end optical fiber with low radiation loss due to the bend. The devices we fabricated achieve a high fiber-to-fiber gain of 18 dB with a coupling efficiency of -3.5 dB, and we have demonstrated a four-channel array with uniform characteristics     

A new type of demountable optical device for coupling single-mode planar waveguides to a multifiber array using passive alignment

A novel demountable optical device is developed for coupling single-mode waveguides to a multifiber array using passive alignment. This device is fabricated by forming V-grooves on a waveguide chip and precisely molding both end portions of the chip. The 1/spl times/8 coupling device exhibits a low insertion loss of 10.7 dB and a small loss change of /spl plusmn/0.2 dB for 100 reconnections.