Optical functional device by vertical and direct integration of heterojunction phototransistor and laser diode

An optical device with various functions is actualized by integrating vertically and directly heterojunction phototransistors and a laser diode and by adjusting the internal optical feedback. The optical amplification with a good linearity between input and output lights is realized by suppressing the internal optical feedback. The large gain of over 100 is achieved in the wide wavelength range from 0.75 to 1.25 μm. The optical thresholding function is achieved by changing the load line in the case of the optical amplification. The optical switching function with large gain and high sensitivity is obtained by utilizing the internal optical feedback most effectively. The optical bistable function is obtained when the amount of the optical feedback becomes moderate. The optical feedback inside the device is theoretically investigated to explain these functions systematically