Research

Membrane photonic circuits

An introduction of photonic integrated circuits (PICs) for on-chip interconnects is considered as a promising solution to replace global electrical wiring on Si-LSIs. For this purpose we have proposed the concept of a membrane PIC composed of InP-based photonic platform with a membrane structure (high-index-contrast waveguide with the thickness of around 200 nm) bonded on Si or SOI substrate using a benzocyclobutene (BCB) adhesive wafer bonding method. The high index contrast (HIC) waveguide structure which enables ultra-small and highly integrated optical circuits is very attractive for realization of low power dissipation photonic devices. Recently, lateral current injection (LCI)lasers with thin core layers have been demonstrated as an application for current injection structure. As a results, very low threshold lasing of optically and also electrically pumped membrane DFB laser have been obtained. With these technologies, we are also engaged in membrane based photodetectors, modulators and waveguides to realize photonic integrated circuits on membrane platform.

Si/III-V Hybrid integration

In recent years, with the rapid increasing of internet traffic, researches are being done to produce large-scale Optical Integrated Circuit possessing high efficient and high capacity optical routing tool. AS an approach, to manufacture optically active devices like optical source and amplifier using III-V semiconductors on Si platform ‘III-V/Si Hybrid Integration process’ is available. Si is a transparent and low-loss medium within communication wavelength band and small-size optical circuit can be manufactured using Si, it is possible to do large-scale integration by CMOS process at low cost. As III-V group semiconductors like InP are direct-bandgap semiconductors, it is possible to realize optical devices using III-V semiconductors which will be difficult to realize using indirect-bandgap Si. In this group, we emphasize on the characteristics of each InP optical source and Si optical waveguides and use their combined structure to realize multi-function optical integrated circuit which is difficult to realize with only InP or Si.

Heterogeneous Integration

Heterogeneous material integration is an essential future technology for the advantages of multiple materials. For example, hybrid optical integrated circuits, which we are working on separately, are predicated on the use of this technology. The key point is that bonding is done without using glue. However, which heterogeneous material integration technology to use depends on the materials used and the application. We have several technologies, including surface-activated room temperature bonding, plasma-activated bonding, hydrophilic bonding, and resin bonding, as well as various forms of Chip-On-Wafer bonding, which is not only wafer bonding, but also bonding large numbers of small chips on large substrates.

Topological Photonic Circuits

Optical vortex modes can transmit information over the spiral period of their wavefronts (optical vortex multiplexing method OAM: orbital angular momentum multiplexing), and there are high expectations for this as a future multiplexing technology. However, one of the barriers to this realization is that the operating mode in optical circuits used in current optical communications is restricted to TE/TM. Therefore, we are working on the invention of optical circuits with new functions using optical vortices by incorporating topological photonics devices as part of conventional optical circuits.

    

Deep Learning for Photonic Crystals

    
    

The application of machine learning are investigated to determine the arrangement of circular hole photonic crystals as a method of structural optimization of topological photonic crystals for a desired requirement. We are also working on structure determination using deep learning for the coupling from the Si wire waveguide to the topological photonic crystal waveguide.

    
    

Diamond NV Center

    
    

Diamond NV centers are expected to be applied as element materials for magnetic field sensors, and optical integrated circuits are being considered to realize small and large sensors. In our laboratory, we are measuring the absorption properties of diamond NV centers and designing optical integrated circuits specialized for their absorption wavelength peaks.

    

Nishiyama Laboratory
Quantum Nanoelectronics Research Core, Tokyo Institute of Technology

7F, S9-1, 2-12-1 O-okayama, Meguro-ku Tokyo 152-8552, Japan +81-3-5734-2555 ee.e titechnishiyama

Nishiyama lab. Student's room : South Bldg. 9 #701, #706, #707 | Measurement room : South Bldg. 9 #604, #502, #201 |
Clean room : South Bldg. 9 #202, B1F Exposure house | Research Laboratory of Ultra-High Speed Electronics