Nec Corporation

Hiroyoshi Rangu

Kenichi Nishi

Kazuhisa Kaede

Tomoo Yanase

An optical modulator for varying intensity, frequency, phase and other information associated with input light in response to a voltage which is applied thereto from outside is disclosed. The modulator comprises a semiconductor substrate, at least one semiconductor ultrathin layer which is thinner than an order of electron mean free path, and electrodes capable of applying an electric field to said ultrathin layer in a perpendicular direction to the layers. The band gap of narrow band gap layers in the ultrathin layer is spatially varied with respect to the perpendicular direction to the layers. The band gap of the narrow band gap layers is monotonously varied in the perpendicular direction to the layers. The ultrathin layer is interposed between a p-type semiconductor and an n-type semiconductor with respect to the perpendicular direction to the layers, a band gap of semiconductor layers in the ultrathin layer and having a narrow band gap being sequentially narrowed toward the p-type semiconductor layer. The band gap of semiconductor layers in the ultrathin layer and having a narrow band gap is largest in the vicinity of the center and sequentially reduced toward opposite ends.

Optical modulator

A frequency-stabilized semiconductor laser oscillator in which a control signal derived from a modulation signal is applied to a second optical waveguide adjacent the first optical waveguide in order to make the overall optical path between both waveguides constant despite variations in the refractive index of the optical path in the first optical waveguide. The control signal may be a current signal derived by shifting the phase of the variation of the current of the modulation signal with respect to time, or a voltage signal derived by shifting the phase of the variation of the voltage of the modulation signal with respect to time. If a current control signal is used, the compensation mechanism is an increase in the carrier density in a second optical waveguide. If a voltage control signal is used, the compensation mechanism is an electro-optic variation of the refractive index in the second optical waveguide.

Frequency-stabilized semiconductor laser oscillator

A surface-emitting semiconductor light emitting element, such as a laser or a light emitting diode, having at least one active light emitting layer on a semi-insulating substrate, with p-type and n-type semiconductor regions also on the substrate and in contact with opposite side faces of the active layer. The active layer has a narrower band gap than the semiconductor regions. The light emitting region may comprise a multilayer structure of plural active light emitting layers sandwiched between alternating p-type and n-type semiconductor layers.

Growing community of inventors

Tokyo, Japan

Hiroyoshi Rangu