Research achievements

  • FY
    2016
  • FY
    2017
  • FY
    2018
  • FY
    2019
  • FY
    2020

Achievements in FY 2016

Surface-emitting laser

1 device: 3 mW （highest power output in the world）

Ultraviolet sensor

High-performance photosensor with high photosensitivity and low dark current density
The level of light sensitivity is equivalent to that of photo-electron multipliers.
→Response speed is relatively high.

Vertical-cavity surface-emitting laser (VCSEL)

VCSEL design structure

Electric field distribution and refractive index distribution in an active layer

  • Vertical current injection structure penetrating through lower DBR
  • 1.5 λ resonator length is close to that of infrared VCSEL

Vertical-cavity surface-emitting laser (VCSEL)

Current – Voltage – Optical output characteristics

Laser oscillation

  • Threshold current: 2.6 mA (5.2 kA/cm2)
  • Threshold drive voltage: 5.0 V
  • Series resistance: 135 Ω (when high current is injected)

First nitride surface-emitting laser to achieve continuous oscillation at room temperature by vertical drive current injection penetrating through lower DBR

Using the combination of vertical conducting DBR and tunnel junction

Purpose: To lower the threshold level and improve the slope efficiency of blue surface-emitting laser (VCSEL)

→Application of current constriction structure through buried tunnel junction

Present status

  • Drive voltage: 6.16 V @ 5 kA/cm2
  • Clear current constriction
  • Relatively favorable surface shape

Future

  • Application to surface-emitting lasers
  • Application to other optical devices
  • Solutions in physics

Electron beam excitation GaN-based ultraviolet semiconductor laser

Optical intensity – Injection power – Density dependence

Sample structure

Spectrum

Polarization property