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We demonstrated group velocity delay using a metal–insulator–metal structure for slow light that would be very simple to fabricate. A negative Goos–Hanchen shift of the surface plasmon resonance can be caused by incident radiation while reflecting, resulting in a general group delay. Using this phenomenon, we induced a group delay of 70 fs using a very simple 20-μm-long waveguide.

We have investigated the electric-field intensity distributions and characteristics of the whispering-gallery mode (WGM) from a planar microdisk using a three-dimensional finite-difference time-domain method. Silicon nitride (Si 3 N 4 ) planar microdisks on silica (SiO 2 ) substrates have been systematically analyzed considering the effects of the sidewall angle, etching depth, and height. Superpositioning of the TE and TM modes which is caused by the skew effect according to the sidewall angle has been demonstrated. Furthermore, the mode splitting caused by the change from single mode to multi-mode regimes due to an increase in the height has been analyzed. Several planar microdisks of Si 3 N 4 on SiO 2 were fabricated, and their resonance characteristics were probed by using micro-photoluminescence spectroscopy. A quality factor of 5×10 3 for microdisks with a diameter of 3.5 μm and sidewall angle of 35° was observed in the visible range. The WGMs of fabricated microdisk were analyzed according to the details of the model and found to be in good agreement

We present an opto-electrical predistortion optical transmitter showing significant reductions in both 3rd-order and 5th-order intermodulations (IM3 and IM5). The simultaneous reductions of IM3 and IM5 are achieved by choosing an appropriate bias current and RF input power for the LD, obtained by the analysis of the 3rd-order to 5th-order intermodulation distortion ratio (TFR). In our experiments, two DFB-LDs (master and slave LDs) with a similar performance are used; the matching circuits of the two LDs are designed to have equal properties. The experimental results show that reductions of 30 dB in the IM3 and 12 dB in the IM5 are achieved simultaneously under the optimum TFR conditions of a 12 mA bias current and a 0 dBm RF power at 2.2 GHz.

We propose and analyze a high effective Q-factor triangular ring resonator (TRR) coupled with an asymmetric Mach–Zehnder interferometer (AMZI), in which the long evanescent fields on a total internal reflection (TIR) mirror in the TRR and the field cancelation by the phase difference of each path in the AMZI are utilized. The TRR is employed in order to more effectively measure the quantities that occur during biological events because the evanescent field of the TIR mirror with its sharp incident angle is influenced by the Goos–Hanchen shift. In this paper, we report upon the AMZI-coupled TRR sensor structure with the high effective Q-factor of about 10 5 obtained through the optimization of the AMZI path-length. The sensitivity of the resonance shift when changing the refractive index of 1 × 10 − 4 at the incidence angle of 22.92° has been identified to be as high as 0.48 × 10 4 nm/RIU. In addition, the power sensitivity of the AMZI-coupled TRR with a 17 dB attenuation is 5.7 × 10 5 dB/RIU.

The direct intensity modulation of a three-guide coupled rectangular ring laser having bidirectional lasing characteristics is reported for the first time. The rectangular laser cavity consists of four low loss total internal reflection mirrors and an output coupler made out of three passive coupled waveguides. The laser is fabricated using a total cavity length of 580 μm with active section lengths of 250 μm. For both the clockwise and counterclockwise circulating directions, a lasing threshold of around 38 mA is obtained at room temperature under continuous wave operation. A maximum 3-dB modulation bandwidth of approximately 3.2 GHz is observed in both circulating directions.

The wide tuning characteristics of double-ring coupled lasers with/without an extended waveguide are analyzed and optimized using the scattering matrix formalism. To obtain the optimum design schemes of the tunable laser diodes, the cross coupling ratios of two rings, the tuning enhancement factor, the propagation loss of passive waveguides, the optical gain of an active region, and the back and front-facet reflectivity of the waveguide are taken into account. When the coupling ratio of the ring and input/output waveguides is fixed, the extinction ratio and the linewidth are decreased as the tuning enhancement factor is increased, while the tuning range is increased.

We have experimentally and theoretically demonstrated the transmission performance of a feedforward optical transmitter using an external light injection technique. The feedforward compensation method shows 31 dB intermodulation distortion suppression and 2.2 dB noise reduction. The feedforward architecture used a wavelength-locked Fabry–Perot laser diode whose side-mode suppression ratio about 35 dB over a 12-nm range. The suppression characteristics of the intermodulation distortion for various wavelength differences and transmission lengths were measured and analyzed as the evaluation criteria for the system performance in WDM/SCM based radio-over-fiber systems.