Design of a 1550nm SiGe/Si quantum-well optical modulator
Résumé
An electrooptic modulator containing a single SiGe/Si quantum-well has been designed for operation at lambdaO= 1.55 µm. This single quantum-well modulator has a lower VpiLpi than the 3 quantum-well modulator recently designed and optimized by Maine et al. for operation at lambdaO = 1.31 µm, for which the VpiLpi product was 1.8 V cm. This single quantum-well modulator contains a Si0.8Ge0.2 quantum-well with Non-Intentionally Doped (NID) and P+ highly doped layers on either side. With no field applied, holes from the P+ layers are captured by and confined in the quantum-well and when a reverse bias is applied holes are released from the quantum well and drift to the P+ contact layer. Variations of the hole distribution lead to changes in the free-carrier absorption and the refractive index of each layer and subsequently to phase modulation of guided TE modes. The VpiLpi product of the single quantum-well modulator is estimated 1.09 V cm for low voltage linear modulation and 1.208 V cm for 0 to 1.6 V digital modulation, whereas the 3 quantum-well modulator gives a VpiLpi of 2.039 V cm for 0 to 6 V digital modulation for operation at lambdaO = 1.55 µm. Also, the optical loss in the single quantum-well (5.36 dB/cm at V = 0 V ) is lower than that of the 3 quantum-well structure (5.75 dB/cm at V = 0 V ). This single quantum-well modulator should also offer higher frequency operation than the 3 quantum-well modulator.