| Research Abstract |
1.Development of software tool MOSIMUL
We developed a simulation software for the analysis and design of multi-mode interference (MMI) couplers based on multiple eigen mode expansion method, and named it MOSIMUL.By utilizing it, we studied MMI couplers with their incident waveguides coupled at large angles, and showed that such couplers could be used as compact bending devices in photonic integrated circuits.
2.Applicability of MMI semiconductor photonic devices to WDM photonic switching
We discussed to what extent the photonic switching devices in this research benefit WDM photonic switching systems, and found that more than 30dB improvement in loss would be achieved. Furthermore, temperature control equipment could be shared by all the elements, and alignment between different devices could become unnecessary.
3.Development of metal-organic vapor-phase-diffusion-enhanced selective-area epitaxy
As an active/passive integration technology in monolithic photonic integrated circuits, we propo
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sed and developed metal-organic vapor-phase-diffusion-enhanced selective-area epitaxy (MOVE2). By utilizing this technique, we could achieve band gap difference between active and passive regions at 1.55mum as large as 200nm in bulk material (due to composition variation), and as large as 500nm in quantum wells (due to composition and thickness variation). These numbers are by far larger than conventional ones. Therefore, we expect minimizing the absorption loss of passive waveguides.
4.First fabrication of MMI couplers by MOVE2
We succeeded in fabricating MMI couplers by selective-area epitaxy for the first time, making use of the above MOVE2 process. InGaAsP of 1.25mum composition was used as a core layr, and an upper InP cladding layr was formed by MOVE2 on its top. The thickness variation in the MMI coupler was as low as 5% in perpendicular direction and 10% in parallel direction with respect to the direction of lightwave propagation. Imbalance of light output was negligible, and insertion loss in a 30mum-long MMI coupler was 2dB. Less
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