1.3 ?m-wavelength mode controlled GaInAsP/InP etched laser

A mode controlled GaInAsP/InP (?=1.3 ?m) etched laser with a lens-like narrow strip waveguide along the <01> direction has been fabricated. The minimum threshold current was 160 mA for 170 ?m cavity length, and a single longitudinal mode operation has been obtained up to 1.3 times the threshold.     

An InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs(311)A substrate having low threshold and stable polarization

We have fabricated an InGaAs-GaAs vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs(311)A substrate by molecular beam epitaxy (MBE) and demonstrated continuous wave operation at room temperature. A threshold current density of 80 A/cm/sup 2//well and very stable polarization characteristics up to 2.7 times the threshold were achieved. The polarization state with the highest optical intensity was oriented along the [2~33] direction, which is the crystallographic axis exhibiting the maximum gain. An extinction ratio of more than 12.7 dB was obtained between two orthogonal polarization states. The high and anisotropic gain of a (311)A-oriented VCSEL will drastically improve the device performance by optimization and process engineering.     

Spectral linewidth of AlGaAs/GaAs surface-emitting laser

The spectral linewidth Delta nu of a vertical cavity surface-emitting (SE) laser was measured for the first time. The linewidth measured by a delayed self-homodyne method was 50 MHz at an output power of 1.4 mW under room-temperature CW operation. The linewidth obtained was guite narrow in spite of the short cavity configuration of the SE laser. This narrow linewidth is attributed to the high-reflectivity mirrors. The measured linewidth is in good agreement with theoretical values.<>     

Mesh waveguide optical star coupler

A new multimode optical star coupler with a mesh waveguide configuration is proposed to reduce the device length by stimulating light mixing in a short waveguide. A 4×4 optical star coupler has been fabricated and its branching variation of 2.8 dB is realised with the device length as short as 14.5 mm.     

An experimental investigation of transient cavitation control on a hydrofoil using hemispherical vortex generators

Unsteady cavitation causes noise,damage,and performance decline in the marine engineering and fluid machinery systems.Therefore,finding a method to control the ...