INSIDE the Laboratory

Broadband Engineering Division

Applied Quantum Optics Laboratory

Hiroshi Yasaka, Professor
Nobuhide Yokota, Assistant Professor

Since the foundation of the laboratory in 2008, we have been researching innovative functional optical semiconductor devices for realizing new generation optical communication network systems. The research is being performed by Hiroshi Yasaka, Professor and Nobuhide Yokota, Assistant Professor (since 2014) together with two doctor course and six master course students in the graduate school. Two bachelor course students in the undergraduate school are also studying in our laboratory.
To realize innovative functional optical semiconductor devices, we focus on the following three themes.

1. High function semiconductor light sources:

High speed semiconductor lasers operating up to 100 Gb/s are being investigated. We made clear that the modulation bandwidth of semiconductor lasers can be enhanced drastically by modulating the modal gain of a distributed feedback (DFB) laser integrated with external cavity. By applying this principle, we are investigating an ultra-high speed semiconductor laser which can be operated directly by applied RF signal. We are also trying to realize compact and narrow linewidth laser sources by introducing an optical negative feedback scheme we have developed. It needs only an optical filter and does not require an increase of the laser cavity’ s Q-value. From the proof-of-concept experiment, we confirmed that the scheme successfully reduces the semiconductor laser’ s phase noise and spectral linewidth.

2. High function semiconductor optical modulators:

We are investigating an InP Mach-Zehnder modulator. The refractive index of an InP material changes through the quantum confined Stark effect (QCSE) in conjunction with Pockels effect. By applying the QCSE, we successfully generated an ultra-flat 9 channel optical frequency comb with intensity deviation of less than 1 dB.

3. New function semiconductor integrated circuits:

In our laboratory we are researching high function photonic integrated circuits by integrating high performance and highly functional solitary semiconductor photonic devices we have developed.

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