Tatsuya Tanigawa

Enhanced responsivity in a novel AlGaN / GaN plasmon-resonant terahertz detector using gate-dipole antenna with parasitic elements

Plasmon-resonant terahertz (THz) detection using heterojunction field effect transistors (HFETs) is a promising method to enable compact and efficient THz detectors which can be applied to real-time imaging systems or THz spectroscopic analysis [1–2]. So far, the plasmon-resonant detectors which receive sub-THz and THz radiation at a gate bonding-wire or an external antenna have been reported [3–5]. However, the signal transmission from the antenna to the FET causes large propagation loss which degrades the sensitivity. In this paper, we present a novel AlGaN / GaN heterojunction FET which can detect THz radiation directly at a gate electrode with high responsivity.

High power terahertz emission from a single gate AlGaN/GaN field effect transistor with periodic Ohmic contacts for plasmon coupling

We report on room temperature terahertz (THz) emission by a single, short gate AlGaN/GaN field effect transistor with grating Ohmic contacts. The fingers of metal contacts are fabricated at the nanoscale in length and spacing in order to work as a radiation coupler of electron plasmons in the THz range. Spectrum analysis revealed a broadband emission centered at 1.5 THz with a controlled polarization by the grating contacts. The measured output power is linearly increased with the drain input power and reached up to 1.8 μW.

12.5-gbps operation of 850-nm vertical-cavity surface-emitting lasers with reduced parasitic capacitance by BCB planarization technique

12.5-Gbps operation of 850-nm AlGaAs-based VCSEL fabricated using low-k benzocyclobutene (BCB) planarization technique is reported. The BCB has lowest dielectric constant of 2.65 among conventional passivation dielectrics including polyimide and thick passivation can be easily formed by simple planarization technique, resulting in very low parasitic capacitance especially at around the pad electrode. The thick BCB film buried around the epitaxial post structure reduces the parasitic capacitance down to 0.041 pF which is one third as low as that of the conventional SiN passivated VCSELs. The fabricated BCB-planarized VCSEL exhibits very high relaxation oscillation frequency of 12 GHz for the oxide aperture of 6.5 mum, which corresponds to high modulation bandwidth f3dB of 16 GHz with relaxation oscillation frequency of 11 GHz for the oxide aperture of 8.5 mum. These values are as comparably high as the reported highest values. Open eye-diagrams up to 12.5 Gbps are also confirmed implying that the presented VCSEL is applicable to the optical data network systems such as Giga-bit Ethernet at higher bit rates. Preliminary reliability test result shows stable optical output power at constant operating current at 100 degC over 1000 h

High-speed 850 nm AlGaAs/GaAs vertical cavity surface emitting laser with low parasitic capacitance fabricated using BCB planarization technique

12.5 Gbps operation of low-k benzocyclobutene (BCB)-planarized 850 nm AIGaAs-based VCSEL is presented. The chip capacitance is 70% reduced from that of conventional SiN-passivated one. The VCSEL exhibits very high relaxation oscillation frequency of 12 GHz with stable operation at 70/spl deg/C over 750 hours.

Polarization Control of Vertical-Cavity Surface-Emitting Lasers by Utilizing Surface Plasmon Resonance

We demonstrate polarization control of vertical-cavity surface-emitting lasers (VCSELs) to any desired directions by utilizing surface plasmon resonance at a metal nanohole array. A silver nanohole array is integrated on the p-type distributed Bragg reflector of an 850-nm AlGaAs-GaAs-based VCSEL. The metal nanohole array placed at rectangular lattices with orthogonally different two periods, one of which meets the resonaint condition, exhibits strong polarization preference in optical transmission. Integrated four VCSELs with different directions of the rectangular arrays of nanoholes demonstrate successful control of the polarization angles. The VCSELs are closely located onto a one chip so that the optical outputs are easily coupled to one optical fiber. The presented VCSEL array will open a new horizon of multi-input multi-output communication systems by using polarization multiplexing.

Polarization Control of VCSEL Array by Metal Nanoholes at Rectangular Lattice Utilizing Surface Plasmon Resonance

We report on polarization control of 850 nm 2times2 VCSEL array by metal nanoholes at rectangular lattice utilizing surface plasmon (SP) resonance. The polarization angle can be controlled to any specified directions by the direction of the lattice, of which the pitch meets the SP resonant condition. This VCSEL array is applicable to future polarization multiplexed optical communication

Temperature-stable operating current of surface plasmon VCSELs with metal nanohole arrays

We demonstrate temperature-stable operation of 850nm AlGaAs-based VCSELs in which metal nanohole arrays are integrated as a part of top mirror. The resultant variation of the operating current from 10°C to 90°C is as small as 0.65mA at the output power of 1mW.

Surface Plasmon VCSEL with Metal Nanohole Arrays

This paper presents an AlGaAs/GaAs based vertical cavity surface emitting lasers (VCSELs) in which metal nanohole arrays are formed on the top of the distributed Bragg reflector (DBR) as an application of the surface plasmon resonance. Enhanced output power with lower threshold current is achieved as well as the VCSEL serves temperature stable operating current. In addition, the fabricated Surface Plasmon (SP)-VCSEL enables successful control of the polarization angles to any specified directions.

Low threshold current 850nm surface plasmon VCSEL with sub-micron metal hole arrays

850 nm AlGaAs-based VCSELs with sub-micron hole arrays on the top of the DBR mirror are presented. The VCSEL exhibits lower threshold current down to 0.5 mA with enhanced optical output power by surface plasmon resonance at the Ag/SiO2 interface consisting the sub-micron metal hole arrays.