A. Shinya

Ultralow Operating Energy Electrically Driven Photonic Crystal Lasers

The introduction of the photonic crystal (PhC) wavelength-scale cavity as a laser cavity enables us to obtain both ultralow threshold current and operating energy. These parameters are essential when using the transmitters in chip-to-chip and on-chip interconnections. To improve the device performance, we employ an ultracompact embedded active region that we call a lambda-scale embedded active-region PhC laser or LEAP laser. We have developed an electrically driven LEAP laser, which operates under room-temperature continuous-wave conditions. To fabricate the electrically driven LEAP laser, we used Zn thermal diffusion and Si ion implantation, respectively, for p-type and n-type doping in an undoped InP layer. However, with previous fabricated devices there was a large leakage current through the substrate and the threshold current was 0.39 mA, which is larger than the expected threshold obtained by optical pumping. To reduce the leakage current, we propose using an InAlAs sacrificial laser instead of an InGaAs layer. The leakage current path through the substrate is effectively suppressed, and as a result, the threshold current is reduced to 7.8 μA, which is the lowest threshold current reported for any laser. Furthermore, the LEAP laser operates at up to 95 °C by using an InGaAlAs-based multiple quantum well structure. We also describe the dynamic characteristics of the laser. The LEAP laser exhibits a maximum 3-dB bandwidth of 16.2 GHz and the modulation current efficiency factor is 53.8 GHz/mA0.5 or 1.7 GHz/μA0.5, which is four times that of a vertical cavity surface-emitting laser. The device is directly modulated by a 12.5-Gb/s nonreturn-to-zero signal with a bias voltage of 1.6 V and a bias current of 109 μA, resulting in an energy cost of 14.0 fJ/b. This is the smallest operating energy for any laser. These results indicate that the LEAP laser is highly suitable for use as a transmitter in computercom applications.

Resonant tunneling wavelength filters with high Q and high transmittance based on photonic crystal slabs

This paper demonstrates the design scenario of resonant tunneling filters to achieve high Q and high transmission simultaneously, which are constructed by point-defect cavities and line-defect waveguides on 2D PhC-slabs. Furthermore, these devices are fabricated based on the proposed design in Si PhC slabs. The measured characteristics of fabricated devices show good agreement with calculation results. This demonstrates that a resonant filter device can be developed in 2D PhC slabs with higher Q and higher transmission if Q/sub v/ and Q/sub h/ are properly designed.

Scattering Loss of Photonic Crystal Waveguides and Nanocavities Induced by Structural Disorder

We achieve very low loss (2 dB/cm) photonic crystal slab waveguides by using improved electron beam lithography. The loss of our sample is largely determined by lithography-induced disorder, which is supported by a theory based on the photon Green function formalism. We find that this disorder effect is also significant in high quality factor nanocavities.

All-optical switching with extremely-small control energy in InGaAsP-based photonic crystal nanocavity

An ultralow switching energy of 1 fJ is demonstrated in an InGaAsP-based photonic crystal nanocavity with ultrasmall volume, which also contributes to the switching time window of 30 ps owing to the fast carrier diffusion.

Low loss photonic crystal slab waveguides: fabrication, experiment, and theory

This study fabricates state-of-the-art PCS waveguides with a 5 dB/cm propagation loss using precise EBL. This work demonstrates that the transmission characteristics of the PCS waveguides can be well explained by a new theoretical loss formalism based on photon Green functions. These results have profound implications for reliably designing high quality and substantially improved PCS based devices.

Extremely-Low-Power Nanophotonic Devices Based on Photonic Crystals

Photonic crystal nanocavities are expected to greatly reduce the size and energy consumption of a wide variety of optical devices. We have successfully demonstrated this feature in all-optical switches, bistable memories, and other optical functionalities.

Dynamic control of light by photonic-crystal resonator-waveguide-coupled system

Recent leading-edge status of waveguide-loss and cavity-Q for photonic crystals and all-optical switching action in resonator-waveguide-coupled systems are described. All-optical digital processing chips and novel ways of dynamic controlling light will be also discussed.

Fast All-Optical Pulse Train Modulation by Silicon Photonic Crystal Nanocavities

A 5 GHz RZ clock optical pulse is modulated by a random control optical pulse train using photonic crystal nanocavity switches. In addition, we significantly improve the switching speed by introducing argon ions

Multi-port PBG components in SOI photonic crystal slabs

Recent progress on various components consisting of PBG waveguides and resonators in SOI photonic-crystal slabs are reviewed. We have achieved significant improvement in loss for waveguides and Q for resonators. By combining these PBG waveguides and resonators, we have designed and fabricated several multi-port devices, such as resonant-tunneling filters, and channel-drop filters.

Slow-light waveguides and high-Q nano-resonators in photonic crystal slabs

Recent progress on various components consisting of PBG waveguides and resonators in SOI photonic-crystal slabs are reviewed. We have demonstrated slow-light modes in PBG waveguides, and significantly high-Q in ultrasmall PBG resonators. By combining waveguides and resonators, we have realized several multi-port devices, such as resonant-tunneling filters and channel-drop filters.