Surface emitting characteristics of silicon waveguides

This paper concerns the surface emitting characteristics of silicon waveguides in the millimeter-wave frequency band. The waveguides used in the experiment are rectangular slabs of high resistivity silicon (30,000 ohm-cm). A series of periodic perturbations on the waveguide surface provide a radiating antenna. A rectangular grating with a period of Λ=1.8 mm, a height of 0.35 mm, and a duty cycle of 0.46 was sawn into the top surface of a silicon waveguide with a width of 3 mm and a height of 1.41 mm. Experiments were performed to measure the attenuation, dispersion and the radiation characteristics of the waveguides. The test setup was used to monitor the frequency, radiation angle, and the radiated power. Measurements are made over a band of frequencies around the second Bragg frequency. The detector was scanned from 88–95 GHz and changes were observed in the attenuation constant, dispersion relation and the far field radiation pattern. From these results we were able to verify the grating theory.     

Thermally tunable integrated optical ring resonator with poly-Sithermistor

Doped polysilicon is applied as a thermo-optic heating element to temperature tune the ring resonator based on silicon nitride rib waveguides on silicon. The ring diameter is 2 mm allowing a large free spectral range of 26 GHz. For the first time, a poly-Si resistor is used as a thermistor to measure waveguide temperature. The temperature coefficient of the poly-Si thermistor is 9.5×10^-4/°C. The reproducibility of the temperature measurement is 0.3°C. The finesse of the ring resonator is 77. The propagation loss of silicon nitride rib waveguide is 0.5 dB/cm at the wavelength of 1.312 μm. The temperature tuning of the ring resonator and the in situ supervision of the temperature on chip based on the same poly-Si fabrication process may find use especially in optical sensor applications     

Glass waveguides on silicon for hybrid optical packaging

Work on deposited glass waveguides on silicon to form waveguides and filters is reviewed. The choice of these particular waveguides makes sense only as part of a consistent approach to optoelectronic packaging. Hybrid optical packaging on silicon (HOPS) is described and briefly compared with other techniques. For these packages, two waveguides were developed: a tight mode waveguide with a silicon nitride rib core for matching a semiconductor laser and a loose mode waveguide with a phosphosilicate glass core for matching an optical fiber     

Reflective arrayed waveguide grating multiplexer

A high-performance reflective arrayed waveguide grating multiplexer/demultiplexer designed for compatibility with silicon integrated circuit processing is described. The grating, folded by a flat reflecting surface, can be printed in a single-exposure field of a photolithographic stepper. Advanced plasma assisted deposition is used to prepare waveguides with very low loss and minimum birefringence. Multiplexers with 40 channels separated by 100 GHz show intrinsic insertion losses of -2.4 dB, channel uniformity less than 0.6 dB, and very low polarization dependent wavelength shift of 0.012 nm.     

硅基光波导结构与器件

简要评述硅基光波导的结构，工艺及其器件，包括低损耗的硅基光波导，电光波导器件，红外波导探测器，氧化硅光回路等。     

60 GHz multi-chip-module receiver with substrate integrated waveguide antenna and filter

A compact 60 GHz MCM receiver has been demonstrated by integrating millimetre-wave substrate-integrated waveguides and GaAs MMICs for the first time. The module includes a waveguide antenna and filter, MMIC LNA and mixer, and lumped elements for IF filtering embedded into the multilayer photo-imageable thick-film substrate. Cavities for MMIC attachment are photo-imaged as part of the standard process.     

Design of a Silicon Based High Speed Plasmonic Modulator

In this paper, we propose a silicon-based high-speed plasmonic modulator. The modulator has a double-layer structure with a 16 μm long metal-dielectric-metal plasmonic waveguide at the upper layer and two silicon single-mode waveguides at the bottom layer. The upper-layer plasmonic waveguide acts as a phase shifter and has a dielectric slot that is 30 nm wide. Two taper structures that have gradually varied widths are introduced at the bottom layer to convert the photonic mode into plasmonic-slot mode with improved coupling efficiency. For a modulator with two 1 μm-long mode couplers, simulation shows that there is an insertion loss of less than 11 dB and a half-wave voltage of 3.65 V. The modulation bandwidth of the proposed modulator can be more than 100 GHz without the carrier effect being a limiting factor in silicon. The fabrication process is also discussed, and the proposed design is shown to be feasible with a hybrid of CMOS and polymer technology.     

On Surface Losses in Direct Metal Laser Sintering Printed Millimeter and Submillimeter Waveguides

Different lengths of WR3 (220–330 GHz) and WR10 (75–110 GHz) waveguides are fabricated through direct metal laser sintering (DMLS). The losses in these waveguides are measured and modelled using the Huray surface roughness model. The losses in WR3 are around 0.3 dB/mm and in WR10 0.05 dB/mm. The Huray equation model is accounting relatively good for the attenuation in the WR10 waveguide but deviates more in the WR3 waveguide. The model is compared to finite element simulations of the losses assuming an approximate surface structure similar to the resulting one from the DMLS process.     

Recent Progress in High-Speed Silicon-Based Optical Modulators

The evolution of silicon optical modulators is recalled, from the first effect demonstrations to the characterization of high-performance devices integrated in optical waveguides. Among possibilities to achieve optical modulation in silicon-based materials, the carrier depletion effect has demonstrated good capacities. Carrier depletion in Si and SiGe/Si structures has been theoretically and experimentally investigated. Large phase modulation efficiency, low optical loss, and large cutoff frequency are obtained by considering simultaneously optical and electrical structure performances. Integrated Mach-Zehnder interferometers and resonators are compared to convert phase modulation into intensity modulation. Finally, recent results on high-speed and low-loss silicon optical modulator using an asymmetric Mach-Zehnder interferometer are presented. It is based on a p-doped slit embedded in the intrinsic region of a lateral pin diode integrated in a silicon-on-insulator waveguide. This design allows a good overlap between the optical mode and carrier density variations. An insertion loss of 5 dB has been measured with a -3 dB bandwidth of 15 GHz.     

Partially Dielectric-Slab-Filled Waveguide Phase Shifter

An equivalent circuit of a waveguide junction between two asymmetrically filled waveguides is obtained. This equivalent circuit is applied to the design of single-section impedance-matching transformers for a dielectric-slab-filled waveguide phase shifter. Calculation and measurement indicated that when a thin alumina slab is employed, a 360/spl deg/ phase shift can be accomplished in a section approximately 1.1 times the unloaded waveguide wavelength at 2.7 GHz, and that the VSWR between 2.7 and 3.0 GHz is kept to less than 1.15.     

Experimental investigation of millimeter wave Gunn oscillator circuits in circular waveguides

Millimeter wave Gunn oscillator circuits using circular waveguides for 33–50 GHz and 75–110 GHz frequency bands are described. These oscillators are simpler to construct at millimeter wavelengths compared to the conventional rectangular waveguide circuits. The effect of various circuit parameters on the oscillator frequency and output power has been experimentally studied. The CW power and mechanical tuning range obtained from the circular waveguide Gunn oscillators are found to be comparable and sometimes even better than those obtained with conventional rectangular waveguide circuits using the same Gunn device.     

Dielectric waveguides for millimetre-wavelength transmission

The letter describes the salient features of a parametric study of dielectric waveguides intended for millimetre-wavelength microwave transmission. The waveguide is an analogue of the monomode optical waveguide, and, if core and cladding are made from foam materials, with loss tangents of order 10?5, the HE11 mode attenuation is about 40 dB/km, and the group delay change is 0.35 ns/km over 1 GHz bandwidth centred at 40 GHz.     

Birefringence control and dispersion characteristics of silicon oxynitride optical waveguides

The design, fabrication and characterisation of birefringent silicon oxynitride planar optical waveguides are described for applications at the wavelength of 1.54 mu m. Form birefringence is attained by interposing a thin silicon nitride film in the waveguide stack, and can be controlled by adjusting the nitride layer thickness. Dispersion characteristics of the oxynitride waveguides have been measured and compared with theory.<>     

Photoimageable thick-film millimetre-wave metal-pipe rectangularwaveguides

A novel dielectric-filled metal-pipe rectangular waveguide has been fabricated using photoimageable thick-film materials. The waveguides incorporate a new transition from CPW-to-TFMS-to-MPRWG. Standard on-wafer measurement techniques, waveguide STD calibration standards, demonstrated low attenuation across the 60 to 90 GHz frequency range     

Optical study of porous silicon buried waveguides fabricated from p-type silicon

The realisation of optical buried waveguides fabricated from porous silicon layers is presented. The refractive index of porous silicon layer varies according to its porosity and its oxidisation process conditions. So either step or graded index waveguides are achieved. These waveguides are formed by a localised anodisation of heavily doped p-type silicon wafers. Measurements at a wavelength of 1.3 μm yield waveguide losses below 4 dB/cm. The waveguides are also characterised by the near-field-guided mode profile at 1.3 μm. This study deals with the modulation of the waveguiding-layer refractive index and the losses on waveguides fabricated from p⁺.     

介质金属膜波导在G波段和4.3THz的传输特性

制作了具有不同介质膜厚度的大口径柔性介质金属膜波导,测试了金属膜波导和介质金属膜波导在G波段、4. 3 THz和中远红外等频段的传输特性.结果表明,波导的传输损耗在G波段随介质膜厚的增加而增加,孔径2. 6mm的金属膜波导在160 GHz传输损耗为2. 1 d B/m且在G波段波导的传输损耗对弯曲不敏感.在4. 3 THZ频点波导的传输损耗随介质膜厚的增加而减小,镀制介质膜可以大幅减小波导的传输损耗以及弯曲附加损耗,孔径3. 6mm介质膜厚为1. 2μm的介质金属膜波导的传输损耗为2. 84 d B/m.光斑能量则随介质膜厚的增加更加集中于低阶传输模式.     

Integrated-optic 1×128 power splitter with multifunnelwaveguide

An integrated-optic 1×128 power splitter is demonstrated. It is composed of a slab waveguide, funnel-shaped waveguides, and output waveguides. Input light from a fiber is diffracted in the slab waveguide and received by funnel waveguides. To achieve uniform power splitting, the width of the funnel waveguides is designed based on the Gaussian diffraction pattern; that is the funnel widths increase progressively away from the center. The splitter is fabricated with GeO₂-doped silica waveguides on silicon. The 1×128 splitting is achieved with a low excess loss of 2.3 dB and a small standard deviation of 0.63 dB     

CMOS-Compatible All-Si High-Speed Waveguide Photodiodes With High Responsivity in Near-Infrared Communication Band

Submicrometer silicon photodiode waveguides, fabricated on silicon-on-insulator substrates, have photoresponse from <1270 to 1740 nm (0.8 AW^-1 at 1550 nm) and a 3-dB bandwidth of 10 to 20 GHz. The p-i-n photodiode waveguide consists of an intrinsic waveguide 500times250 nm where the optical mode is confined and two thin, 50-nm-thick, doped Si wings that extend 5 mum out from either side of the waveguide. The Si wings, which are doped one p-type and the other n-type, make electric contact to the waveguide with minimal effect on the optical mode. The edges of the wings are metalized to increase electrical conductivity. Ion implantation of Si⁺ 1times10 ¹³ cm^-2 at 190 keV into the waveguide increases the optical absorption from 2-3 dBmiddotcm^-1 to 200-100 dBmiddotcm^-1 and causes the generation of a photocurrent when the waveguide is illuminated with subbandgap radiation. The diodes are not damaged by annealing to 450 degC for 15 s or 300 degC for 15 min. The photoresponse and thermal stability is believed due to an oxygen stabilized divacancy complex formed during ion implantation     

Radiation method for the measurement of mode-conversion levels

A novel method for the determination of mode-conversion levels in overmoded waveguides is described. It relies on a swept-frequency measurement of the perturbation of the dominant-mode radiation pattern of the open-ended waveguide, owing to the presence of higher-order modes. Results are reported for mode-conversion effects in corrugated waveguides at frequencies near 9 GHz. Excellent agreement with the trapped-resonance method is demonstrated, although the present technique has advantages over this method when the mode excitation level is high or the waveguide length is imprecisely known.     

A dielectric rod waveguide coupled with metal rectangular waveguide

Measurements have been done in the millimeter wave region on a composite waveguide which comprises a dielectric rod waveguide connecting two metal rectangular waveguides. Such a waveguide has been used by us in a Josephson harmonic mixer installed in a small metal cryostat, to prevent the thermal invasion from outside environment and to transmit both signal and LO waves with small losses. The measured transmission loss, that is caused mainly by the coupling loss between metal rectangular waveguides (TE₁₀ mode) and a dielectric rod waveguide (HE₁₁ mode), has been less than 2dB in the frequency range of 52–104 GHz.