Si Photonic Wire Waveguides Research Articles

Mirror-based polarization-insensitive broadband vertical optical coupling for Si waveguide

To achieve an efficient, broadband, and polarization-insensitive vertical optical input/output for Si photonics, we demonstrated vertical optical coupling for a Si photonic wire waveguide with an integrated 45° mirror and a spot size converter. The output beam from the fabricated mirror was evaluated and a high-quality single mode beam was obtained. On the basis of coupling loss measurements, the coupling losses for the Si photonic wire waveguide were estimated to be 0.85 and 0.55 dB in TE and TM polarizations, respectively. The wavelength-dependent loss was ±0.1 dB over a wavelength range of 1500–1600 nm.

Long external cavity Si photonic wavelength tunable laser diode

We fabricated wavelength-tunable laser diodes with external cavity consist of Si photonic wire waveguide ring resonators. About 51.5 nm wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. The cavity length dependence of the spectral line width was verified to obtain narrower spectral linewidth. The observed spectral linewidth of 3.78 mm long cavity and 8.19 mm long cavity are 131.0 and 64.8 kHz, respectively. The advantage of long external cavity to design the narrow spectral linewidth Si photonic wavelength tunable laser diode was confirmed.

Practical fabrication and analysis of an optimized compact eight-channel silicon arrayed-waveguide grating

We have designed, fabricated, and characterized a 1×8 ultra-small compact arrayed-waveguide grating (AWG) on silicon-on-insulator (SOI) in a fiber grating demodulation integration microsystem. The miniature AWG, consisting of Si photonic wire waveguides, was designed using the complete modeling simulation in the beam propagation method. The device was fabricated on an SOI substrate and evaluated in the wavelength range around 1.55 μm, with an effective area of 230×160 μm . Clear demultiplexing characteristics were observed with a channel spacing of 1.91 nm. The influence of the waveguide widths on crosstalk defined by adjacent channel crosstalk and phase error is discussed. Insertion loss, crosstalk, and nonuniformity of loss were measured to be −3.18 , −23.1 , and −1.35 dB , respectively. Thus, the AWG design is the best choice for a fiber Bragg grating demodulation microsystem.

Basic Study of Coupling on Three-Dimensional Crossing of Si Photonic Wire Waveguide for Optical Interconnection on Inter or Inner Chip

For speeding up of transmission and energy saving on inter or inner chips of semiconductors, hydrogenated amorphous silicon (a-Si:H), unlike conventional crystal Si (c-Si), promises optical multilevel wiring on a Si IC. For three-dimensional (3D) crossing of Si/a-Si:H photonic wire waveguides, the loss and crosstalk as S-parameters of the two propagation modes are evaluated by numerical analysis at the C-band when the waveguide core is 200 ×400 nm2. Whether the crosstalk can be suppressed to -50 dB or less is to be a criterion. Even at the crossing angle of 30°, when the distance between the waveguides of the crossing is 1 µm or less, the crosstalk is suppressed sufficiently, while the radiation loss is also small if a TE-like mode propagates. These quantitative results are derived for the first time and show that the photonic 3D crossing can rival the present electric multilevel wiring from the viewpoint of device height. An important index for the 3D waveguide crossing fabrication is obtained.

Basic Study of Coupling on Three-Dimensional Crossing of Si Photonic Wire Waveguide for Optical Interconnection on Inter or Inner Chip

Basic Study of Coupling on Three-Dimensional Crossing of Si Photonic Wire Waveguide for Optical Interconnection on Inter or Inner Chip

Nonlinear light propagation in chalcogenide photonic crystal slow light waveguides

Optical nonlinearity can be enhanced by the combination of highly nonlinear chalcogenide glass and photonic crystal waveguides (PCWs) providing strong optical confinement and slow-light effects. In a Ag-As(2)Se(3) chalcogenide PCW, the effective nonlinear parameter γeff reaches 6.3 × 10(4) W(-1)m(-1), which is 200 times larger than that in Si photonic wire waveguides. In this paper, we report the detailed design, fabrication process, and the linear and nonlinear characteristics of this waveguide at silica fiber communication wavelengths. We show that the waveguide exhibits negligible two-photon absorption, and also high-efficiency self-phase modulation and four-wave mixing, which are assisted by low-dispersion slow light.

Si Photonic Wire Waveguide Devices

Si photonic wire waveguides are attractive for constructing various optical devices that are extremely small because the waveguides can be bent with extremely small curvatures of less than a few micrometers of bending radius. We have fabricated optical directional couplers with the waveguides and demonstrated their fundamental characteristics. Their coupling length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. We have also demonstrated wavelength-demultiplexing functions for these devices with a long coupled waveguide. Optical outputs from a device with a 100-mum-long coupled waveguide changed reciprocally with a 20-nm wavelength spacing between the parallel and cross ports. We also demonstrated the operation of ultrasmall optical add-drop multiplexers (OADMs) with Bragg grating reflectors made up of the waveguides. The dropping wavelength bandwidth of the OADMs was less than 0.7 nm, and these dropping wavelengths could be precisely designed by adjusting the grating period. Using the Si photonic wire waveguide, we have also demonstrated thermo-optic switches. Metal thin-film heaters were evaporated onto the branch of a Mach-Zehnder interferometer that incorporated the waveguide to achieve switching operations by thermo-optic effects. In these switching operations, we observed more than 30 dB of extinction ratio, less than 90 mW of switching power, and less than 100 mus of switching speed

Cross-phase modulation-induced spectral and temporal effects on co-propagating femtosecond pulses in silicon photonic wires

By performing time-resolved experiments and power-dependent measurements using femtosecond pulses inside submicron cross-section Si photonic-wire waveguides, we demonstrate strong cross-phase modulation (XPM) effects. We find that XPM in Si wires can be significant even for low peak pump powers, i.e., ~15 mW for pi phase shift. Our experimental data closely match numerical simulations using a rigorous coupled-wave theoretical treatment. Our results suggest that XPM is a potentially useful approach for all-optical control of photonic devices in Si wires.

A Silicon-on-Insulator Photonic Wire Based Evanescent Field Sensor

We demonstrate a new, highly sensitive evanescent field sensor using silicon-on-insulator (SOI) photonic wire waveguides. Theoretical analysis shows that thin SOI waveguides can provide higher sensitivity over devices based in all other common planar waveguide material systems for the probing of both thin adsorbed biomolecular layers and bulk homogeneous solutions. A Si photonic wire waveguide was incorporated into a Mach-Zehnder interferometer based sensor, configured to monitor the index change of a homogeneous solution. High effective index change of 0.31 per refractive index unit (RIU) change of the solution was measured, confirming theoretical predictions

Si Photonic Wire Waveguide Devices

Si photonic wire waveguides are attractive for constructing various optical devices that are extremely small because the waveguides can be bent with extremely small curvatures of less than a few micrometers of bending radius. We have fabricated optical directional couplers with the waveguides and demonstrated their fundamental characteristics. Their coupling length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. We have also demonstrated wavelength-demultiplexing functions for these devices with a long coupled waveguide. Optical outputs from a device with a 100-mum-long coupled waveguide changed reciprocally with a 20-nm wavelength spacing between the parallel and cross ports. We also demonstrated the operation of ultrasmall optical add-drop multiplexers (OADMs) with Bragg grating reflectors made up of the waveguides. The dropping wavelength bandwidth of the OADMs was less than 0.7 nm, and these dropping wavelengths could be precisely designed by adjusting the grating period. Using the Si photonic wire waveguide, we have also demonstrated thermo-optic switches. Metal thin-film heaters were evaporated onto the branch of a Mach-Zehnder interferometer that incorporated the waveguide to achieve switching operations by thermo-optic effects. In these switching operations, we observed more than 30 dB of extinction ratio, less than 90 mW of switching power, and less than 100 mus of switching speed

Ultrafast-pulse self-phase modulation and third-order dispersion in Si photonic wire-waveguides

By propagating femtosecond pulses inside submicron-crosssection Si photonic-wire waveguides with anomalous dispersion, we demonstrate that the pulse-propagation dynamics is strongly influenced by the combined action of optical nonlinearity and up to third-order dispersion with minimal carrier effects. Because of strong light confinement, a nonlinear phase shift of a few pi due to self-phase modulation is observed at a pulse peak-power of just ~250 mW. We also observe soliton-emitted radiation, fully supported by theoretical analysis, from which we determine directly the third-order dispersion coefficient, beta(3) = -0.73 +/- 0.05 ps(3)/m at 1537 nm.

Arrayed waveguide grating of 70×60 µm 2 size based on Si photonic wire waveguides

A miniature arrayed waveguide grating of 70/spl times/60 /spl mu/m/sup 2/ size consisting of Si photonic wire waveguides was designed using complete modelling in the finite-difference time-domain simulation. The device was fabricated onto a silicon-on-insulator substrate and evaluated in the wavelength range around 1.55 /spl mu/m. The clear demultiplexing characteristics were observed with a channel spacing of 11 nm and a loss of less than 1 dB.

Mach–Zehnder Interferometers Composed of µ-Bends and µ-Branches in a Si Photonic Wire Waveguide

We fabricated compact Mach–Zehnder interferometers consisting of µ-branches and/or µ-couplers in a Si photonic wire waveguide. Clear interference spectra with a maximum extinction ratio of more than 20 dB and an alternating light output between two output ports were observed. A high diffraction order of 300 was also demonstrated within a small foot space of 30×20 µm2.

C-band wavelength conversion in silicon photonic wire waveguides

We demonstrate C-band wavelength conversion in Si photonic-wire waveguides with submicron cross-section by means of nonresonant, nondegenerate four-wave mixing (FWM) using low-power, cw-laser sources. Our analysis shows that for these deeply scaled Si waveguides, FWM can be observed despite the large phase mismatch imposed by strong waveguide dispersion. The theoretical calculations agree well with proof-of-concept experiments. The nonresonant character of the FWM scheme employed allows to demonstrate frequency tuning of the idler from ~ 20 GHz to > 100 GHz thus covering several C-band DWDM channels.

Low Loss Intersection of Si Photonic Wire Waveguides

We fabricated a low loss elliptical intersection of Si photonic wire waveguides on a silicon-on-insulator substrate. An insertion loss of less than 0.1 dB was achieved at a wavelength of 1.55 µm. The experimental loss characteristic closely agreed with the theoretical one. We also used this intersection as a suspension of an air-bridge-type waveguide and evaluated a low loss characteristic similar to that mentioned above.

Estimation of Polarization Crosstalk at a Micro-Bend in Si-Photonic Wire Waveguide

The singlemode Si-photonic wire waveguide allows sharp bends, which significantly expands the design flexibility of optical devices and circuits. Here, the suppression of the polarization crosstalk at a sharp bend will be an important issue, since a large crosstalk affects the performance of devices and circuits. In this study, the three-dimensional (3-D) finite-difference time-domain (FDTD) simulation showed that the crosstalk at a 90/spl deg/-bend with a radius of 0.35-1.75 /spl mu/m is less than -25 dB at a wavelength of 1.55 /spl mu/m. In the experiment, the crosstalk from TE-like to TM-like polarization was evaluated to be -13 dB to -10 dB. This large value was explained by a small tilt of waveguide sidewalls, which seriously increased the crosstalk. In addition, it was found in the calculation that some combinations of bends increase or decrease the crosstalk, and that a U-shape bend is the most effective for the suppression of the crosstalk.