Yoichi Sakakibara

Mode-locked fiber lasers based on a saturable absorber incorporating carbon nanotubes

A novel passively mode-locked fiber laser is demonstrated using saturable absorber based on single-walled carbon nanotubes. This is the first demonstration of an optical pulsed laser based on carbon nanotube technology.

A noise suppressing saturable absorber at 1550 nm based on carbon nanotube technology

We present an ultra-fast saturable absorber device based on single-walled carbon nanotubes. The saturable absorbing effect was observed using 1 ps optical pulses at 80 GHz. This device possesses promising characteristics for applications such as a noise suppressor or a mode-locker.

Low-Loss Characteristics of a Multimode Polymer Optical Waveguide at 1.3 um Wavelength on an Electrical Hybrid LSI Package Substrate

We propose an optical and electrical hybrid LSI package with high bandwidth of 2.4 Tb/s and parallel multi-mode optical links at 1.3 μm using a polymer optical waveguide and our original optical I/O module. We report a silicate based organic-inorganic hybrid polymer optical circuit fabrication including waveguide, mirror and connector on electrical LSI package substrate. We also present about the propagation loss, bending loss and coupling loss at 1.3 μm using a MMF and a Si photonics transmitter. The propagation loss of the multimode polymer waveguide is 0.3 dB/cm at 1.3 μm. The minimum bending radian and value generated additional loss is 5 mm and 0.2 dB, respectively. The coupling loss of butt-coupling and mirror coupling from the polymer optical waveguide to the MMF is 0.4 dB and 1.2 dB, respectively. In addition, we measure the optical characteristics of LSI package substrate using our Si photonics transmitter integrated with vertical polymer waveguide.

Passive timing synchronization of femtosecond Er-fiber lasers and precise frequency comb control

We demonstrated a timing synchronization between a solid-state laser and Er-fiber lasers with a timing jitter of 2.5 fs from 10-Hz to 100-kHz integration. Femtosecond frequency comb of fiber lasers was observed and controlled precisely.

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.

Mirror-based surface optical input/output technology with precise and arbitrary coupling angle for silicon photonic application

Mirror-based surface optical coupling is an attractive technology for the optical input/output of Si photonics. For the practical use of the mirror-based surface optical coupling, we evaluated its coupling angle controllability. Different angular mirrors were integrated into 3 × 3-µm-square single-mode silicon oxynitride optical waveguides on Si substrates. Near- and far-field patterns of optical beams output from the mirrors were measured to evaluate the beam characteristics and coupling angles. We successfully controlled the coupling angle over a wide range of more than 20° without beam characteristic variation, and perfect vertical output, which is difficult to achieve using grating couplers, was successfully demonstrated. The coupling angle error was less than ±1°, which was sufficiently small to ignore additional coupling loss. The wavelength dependence of the coupling angle was also evaluated and found to be less than ±0.5° over wide wavelength ranges of 1.26–1.36 and 1.52–1.62 µm.

Raman scattering in hydrogenated amorphous silicon waveguides at telecommunication wavelengths

Summary form only given. Raman scattering in crystalline Si waveguides has been in much attention since the measurements of spontaneous and stimulated Raman scattering at telecommunication wavelengths. Various applications such as a Raman laser and a Raman amplifier have been studied. On the other hand, optical waveguides using hydrogenated-amorphous Si (a-Si:H) have also been researched The advantages are low-temperature film deposition for three-dimensional photonic circuits and a highlyreliable fabrication process using CMOS electronics facilities. The a-Si:H is an advantageous nonlinear material due to its expected lower nonlinear absorption resulting from the larger electronic bandgap compared with crystalline Si, and large nonlinear figure of merit in an a-Si:H wire waveguide have been achieved In this talk, we introduce the first observation of Raman emission in a 13-mm-long a-Si:H wire waveguide at telecommunication wavelength of 1550 nm. The a-Si:H wire waveguide has a low propagation loss of 2 dB/cm and ultra-fast carrier decay time of less than 100 fs. Using a continuous wave pump laser at 1443.4 nm, we observe backward spontaneous Raman scattering at a peak wavelength of 1550.1±0.25 nm. The Raman frequency shift is 477±1 cm-1, which agrees with a value obtained from a commonly used a-Si:H film. We estimate Raman gain coefficient from the measured Raman spectrum and discuss the possibility of Raman amplification.

Evaluation of optical coupling characteristics for optoelectronic hybrid LSI package

Optical coupling loss and alignment tolerances between silicon photonics based transmitter chip and PCB with polymer waveguides were evaluated. Owing to adoption of multi-mode transmission, large 1-dB alignment tolerances were obtained with efficient optical coupling.

Dynamics of Er-doped ultrashort pulse fiber laser using single wall carbon nanotube polyimide film

Dynamics of Er-doped ultrashort pulse fiber laser with single wall carbon nanotube polyimide film were investigated both experimentally and numerically. Dependence on output coupling ratio, temporal response of nanotube, and dispersion properties were discussed.

Polarization maintaining passively mode-locked Er-doped ultrashort soliton fiber laser using single wall carbon nanotube polyimide film

All-polarization maintaining Er-doped ultrashort soliton fiber laser using single wall carbon nanotube polyimide film and variable output coupler is constructed and investigated. A 580 pJ and 46 fs ultrashort pulse is generated after compression.