Integration of A Semiconductor Optical Modulator for Parallel Information

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1. Development of planar-illuminated semiconductor optical modulators1-1)Fabrication of a planar-illuminated-type array optical modulator with GaAs system :Fabrication of an array optical modulator into which 10 × 10 elements were integrated monolithically has been achieved. Each element of the array has been made as a planar-illuminated optical modulator composed of 20 sets of pィイD1+ィエD1-n-nィイD1+ィエD1 : GaAs crystal layers. Perfarmance of 10dB extinction ratio for 7.5V variation of the applied voltage is obtained. The insertion loss is 5dB and the oprating speed is 1.5MHz. A capital letter 'K' was displayed as an application of the array optical modulator.1-2) Trial to make a planar-illuminated-type optical modulator element with InGaAsP system :We tried to fabricate a planar-illuminated optical modulator element made of InGaAsP material system. In reality, a planar-illuminated optical modulator element could not be fabricated because of a meltback problem that InGaAs multi-layers dissolve in the solution when re-growth layer of InP is buried. However, fundamental technologies of InGaAs multi-layers crystal growth and fabrication processes so on have been established to make a planar-illuminated-type optical modulator element.2. Deign of a planar-illuminated-type semiconductor optical modulator with multi-quantum well structuresA planar-illuminated-type semiconductor optical modulator using multi-quantum well structure has been designed in form of tranmision type. To realize low oprating voltage, high extinction ratio and low insertion loss, we proposed a structure in which voltage is applied from the transverse direction of quantum wells through p- and n- conductive layers having a comb-shape. Excellent characteristics in a well-designed device can be predicted as follows : 10〜20dB on-off extinction ratio for 5V variation of the applied voltage, insertion loss lower than 2dB and oprating speed higher than several GHz.