My Interest

Quantum electronics, Photonics, Quantum optics, Cavity quantum electrodynamics (cavity QED),
Nano laser and nano emitter, Photonic crystal, Plasmonics, Nanowire, Nanofiber (taper fiber),
Nanomanipulation, Carrier dynamics, Laser spectroscopy, Photon level measurement

My research

Nanocavity-implemented semiconductor nanowire lasers 

We fabricated GaN based hollow nanowires standing upright on a sapphire substrate by the sublimation method and found that they exhibit laser oscillation at room temperature. These very long, hollow, nano-sized structures cannot be fabricated by other means. Furthermore, we determined the condition under which the fundamental mode is azimuthally polarized by investigating the dispersion of the hollow structure. Examination of the measured emission properties indicates that the hollow nanowire operates as a topological, vector-beam, light source  [M. Takiguchi, et. al., ACS Photonics 2024]. 

Nanocavity-implemented semiconductor nanowire lasers 

We found that the nanowire can be protected against FIB (Focused Ion Beam) damage by coating it with alumina by atomic layer deposition, because the emission lifetime did not change before and after the FIB process. This indicates that their optical properties are well maintained. Thus nanostructures were fabricated on both sides of the active layer region in nanowires by using a FIB. The nanowires still showed lasing behavior even after FIB processing had been carried out to implement nanostructures. Thus, our study proves the usefulness of FIBs for future nanofabrication  [M. Takiguchi, et. al., Nanotechnology 2023]. 

Large excitonic nonlinearity induced by a photonic crystal cavity 

We investigate strong excitonic absorption and large nonlinear wavelength shifts in buried-multiple-quantum-well photonic crystal L3 nanocavities [M. Takiguchi, et. al., Appl. Phys. Lett. 2021]. Strong optical confinement and small mode volume by photonic crystals can enhance excitonic nonlinearity. Therefore, our structure can show a strong excitonic effect that induces large refractive index changes by exciton bleaching and obtain a large cavity-frequency shift. This work was chosen as Editors' Pick.

InP/InAs nanowire lasers integrated on different optical platforms 

We systematically investigated the heating effects limiting laser performance for nanowires placed on Au-coated substrates before and after Al2O3 deposition and on Si and SiN waveguides [M. Takiguchi, et. al., OSA Continuum 2021]. Our findings indicate that nanowire heating is strongly related to the thermal resistance between the nanowires and substrates. Our results reveal the potential for continuous-wave nanowire laser operation, towards future photonic on-chip processors with nanowires integrated on photonic platforms.

Nanowire photodetector integrated in Si photonic crystal 

We report novel nanowire photodetectors in Si photonic crystals [M. Takiguchi, et. al., ACS photon. 2020] and determines their feasibility for future on-chip optical processors. This is the first reported photodetection coupled with the input Si PhC waveguide via transparent Al:ZnO electrodes. The photocurrent is strongly enhanced by the Si PhC waveguide. We also conclude there exists an inherent nanoantenna effect which can strongly enhance the TE mode in this system [Also see Suppl. Journal Cover].

All-optical switching with nanowires on Si photonic crystal

We report the successful demonstration of all-optical switching using a sub-wavelength InP/InAsP nanowire on a silicon photonic crystal at telecom wavelength [M. Takiguchi, et. al., ACS photon. 2020]. In this work, we employ two different hybrid nanowire cavities (L3 type and The line defect type). The line defect photonic crystal cavity with a nanowire shows the highest Q-factor ~ 25000. The switching time is obtained 150 ps and it is the fastest in nanowire switches [Also see Suppl. Journal Cover].

Gbps operation of telecom-band single nanowire LED on Silicon

High speed operation of a current injection p-i-n InAs/InP nanowire at telecom band is important for future on-chip signal processing. In this study, we explore a telecom-band single nanowire light-emitting diode (LED) on Si and demonstrated the dynamic properties. The nanowire LED shows Gbps modulation and clear eye pattern [Takiguchi, et. al., Appl. Phys. Lett. 2018]. We believe that our NW-LED represents a major step in the development of an on-chip light source.

CW operation of telecom-band nanowire photonic crystal laser

We demonstrate an InAsP/InP single-nanowire telecom-band CW laser (diameter ~100 nm) on Si photonic crystal platform for the first time. Using this laser, we measure 10 Gbit/s signal modulation using a SSPD and a TCSPC module and obtain clear opened eye-diagram by superimposing the averaged PRBS data over a specific time period [M. Takiguchi, et. al., APL photon. 2017]. About this result, NTT and AIP have sent out a press release [NTT press release, AIP Journals in the News].

Fast & High β embedded MQW photonic crystal laser

We study spontaneous emission control and lasing oscillation of embedded multiple quantum well (MQW) in InP photonic crystal nanocavities. We observed large emission rate ratio between the on- and off-resonant conditions (30:1). This is the highest ratio reported for MQW nano-laser[M. Takiguchi, et. al., Appl. Phys. Lett. 2013] . By adopting high β embedded multiple quantum well photonic crystal nanocavities, we have also demonstrated smooth-lasing transition, which indicates thresholdless-like lasing theoretically predicted, by mean of L-L curve analysis, linewidth analysis, and photon correlation measurements[M. Takiguchi, et. al., Opt. Express 2016].