Shunya Inoue

Highly angular dependent high-contrast grating mirror and its application for transverse-mode control of VCSELs

We report on the design and fabrication of a highly angular dependent high contrast grating (HCG) mirror. The modeling and experiment on amorphous-Si/SiO2 HCG clearly show the large angular dependence of reflectivity, which enables single transverse-mode operations of large-area VCSELs. We fabricate 980 nm VCSELs with the angular dependent HCG functioning as a spatial frequency filter. We obtained the single transverse mode operation of the fabricated device in contrast to conventional VCSELs with semiconductor multilayer mirrors

Tuning Characteristics of Monolithic MEMS VCSELs With Oxide Anti-Reflection Layer

We demonstrate a micromachined tunable vertical-cavity surface-emitting laser with a monolithically formed anti-reflection (AR) layer for highly efficient electro-thermal wavelength tuning. The AR layer is formed by the lateral oxidation of an aluminum-rich AlGaAs layer and no extra process is needed. We fabricated a micromachined GaAs vertical-cavity surface-emitting laser and measured its wavelength tuning characteristic. The measurement result shows that the oxide layer functions as an AR layer for linear and efficient tuning characteristics. A large negative temperature dependence of wavelength from -0.24 to -2.0 nm/K was demonstrated using a thermally actuated cantilever for efficient electro-thermal wavelength tuning. An electro-thermal tuning efficiency of -2.3 to -4.8 nm/mW was obtained.

Wavelength tuning and controlled temperature dependence in vertical-cavity surface-emitting lasers with a thermally and electrostatically actuated cantilever structure

We demonstrate the wavelength tuning and the control of its temperature dependence in 850 nm GaAs vertical cavity surface emitting lasers (VCSELs) using a thermally and electrostatically actuated cantilever structure. The temperature dependence can be controlled from +0.035 to −0.14 nm/K by changing the length of a micromachined cantilever, which can be electrostatically actuated for wavelength tuning. Continuous wavelength tuning over 36 nm was obtained keeping almost constant temperature dependence. The result indicates a possibility of realizing widely-tunable VCSELs with engineered temperature dependence.

Dual beam single-mode vertical cavity surface emitting lasers using high-index contrast grating

We demonstrate the dual beam emission from single-mode vertical cavity surface emitting lasers (VCSELs) with high-index contrast sub-wavelength grating (HCG) as a top mirror. The modeling and experiment on amorphous-Si/SiO2 HCG clearly shows the large angular dependence of reflectivity, which enables the dual beam emission with a large tilt angle. We fabricated VCSELs with the angular dependent HCG. We observed dual beams with 45° tilted directions which are engineered by the angular dependence of HCG.

Electro-thermally tunable 850nm VCSELs with metal/semiconductor thermally actuated mirror

We report on an electro-thermally tunable 850nm VCSEL, exhibiting a large negative wavelength drift of 2.0nm/K. Continuous and linear wavelength tuning of 25 nm was obtained with heating power of 9.4 mW.

Giant wavelength-temperature dependence of 850nm VCSELs with a metal/semiconductor thermally actuated mirror

We demonstrate a giant wavelength-temperature dependence of wavelength of a micromachined 850nm VCSEL with a thermally actuated metal/semiconductor cantilever mirror. The modeling shows a possibility of giant temperature dependence of wavelength of several nm/K, which is determined by cantilever length and metal thickness. The fabricated 850nm VCSEL exhibits a temperature dependence of -1.6 nm/K, and a wavelength tuning of 35 nm in 850 nm band was obtained by changing the device temperature by 12K. In addition, electro-thermal tuning was demonstrated using integrated micro heater. Continuous wavelength shift of 15 nm was obtained with heating power of 40 mW.