Development of A Semiconductor Spatial Light Modulator

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1. Development of surface-illuminated optical modulatorsIn the first year, we fabricated a spatial light modulator in an integrated form of 6*6 elements two dimensional array. Each element of the array was made as a surface-illumimated optical modulators consisting 19 sets of p^+np^+ GaAs crystal layrs. A capital letter 'K' was displayd as a application of the spatial light modulator. The extinction ratio of the modulator was 8dB for 7.5V variation of an applied voltage.In the next year, we developed to make the electric wiring to elements in the spatial light modulator. A wiring pattern was printed on a glass substrate. Then the glass substrate was stuck on the spatial light modulator. Detailed structure of the modulator was also improved. Amount of the wiring pattern was reduced to a half of that in the previously designed modulator. Electrical interference among the elements of the modulator was sufficiently suppressed up to the applied voltage of 10V.Although the yield of fabricate … More d elements was merely 1/3 and the achieved extinction ratio was not enough, that is 50% for the voltage variation of 7V,the pricipal techniqes of the fabrication was established.In a theoretical analysis, the detailed structure of the surface-illuminated modulator was designed. Excellent characteristics in a well-designed device can be predicted as follows : 10dB-20dB extinction ratio for 5V variation of the applied voltage, lower insertion loss than 1dB and operating speed more than several GHz.2. Basic study on the interaction between the opitical traveling-wave and the electron beamPossibility to achieve an unidirectional optical amplifier was theoretically discussed. The phase velocity of the optical beam is slowed down, because the optical beam propagates in a dielectric wave-guide and exudes whose one part into vacuum region in form of the evanescent wave. The propagating electron beam along vacuum surface of the wave-guide excites the optical beam. Quantum mechanical analysis of the interaction between the optical beam and the electron beam is given basing on the density matrix formalism. The conditions to amplify the optical beam were analyzed. As numerical examples, possibility of several ten times optical amplification of 5cm region with 60KV excitation of the electron beam was shown. Less