| CPC H01S 5/0085 (2013.01) [G02F 1/0155 (2021.01); G02F 1/025 (2013.01); H01S 5/12 (2013.01)] | 5 Claims |

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1. An optical semiconductor chip, comprising:
a laser light source;
an optical modulator optically connected to the laser light source and having an optical waveguide structure, the optical waveguide structure having a first type semiconductor base layer, a light absorption layer and a second type semiconductor layer arranged in this order;
an electrode pad receiving a modulation signal;
a modulation electrode formed on the second type semiconductor layer; and
a high frequency line connecting the electrode pad and the modulation electrode and providing inductance in series with respect to a depletion layer capacitance of the optical waveguide structure;
wherein a portion under the high frequency line and the electrode pad is composed of a material having a dielectric constant lower than a dielectric constant of the semiconductor base layer,
the material is configured such that the electrode pad is higher than the modulation electrode, and
the high frequency line is a meander wiring.
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