研究目的
To demonstrate a simplified polarization diverse photodetector without requiring passive components like polarization beam splitter as for conventional designs.
研究成果
The MQW photodiode demonstrates sufficient performance for 25 GBaud with a BER below 10-5 for single and dual-polarization signals at input powers of -6 dBm. Low-speed polarization tracking DSP techniques could further improve PDL and hence BER of this device.
研究不足
The hole transit time in the MQW results in a reduction of the MQW bandwidth, causing eye distortion. The TE-light not absorbed in the MQW contributes to the photocurrent of the bulk photodiode due to its low PDL, leading to crosstalk.
1：Experimental Design and Method Selection:
The chip detects polarization diverse signals by utilizing a waveguide integrated MQW photodiode serially coupled to a bulk photodiode. TE- and TM-polarized light is coupled into the MQW photodiode, with TE polarized light absorbed first in the MQW layers and the remaining TM fraction guided into the bulk photodiode.
2：Sample Selection and Data Sources:
The MQW structure consists of 14 quaternary InGaAsP quantum wells and barriers. All layers are grown by MOVPE and structured by dry and wet etching.
3：List of Experimental Equipment and Materials:
The chip was tested in a back-to-back (B2B) system experiment for 25 Gbit/s input signals per polarization. The data signal is generated from an external cavity laser and a Mach-Zehnder modulator.
4：Experimental Procedures and Operational Workflow:
The chip was connected with two RF probes and additional bias-tees for supplying the DC voltage at each photodiode. Eye-diagrams and the bit-error rate (BER) for different optical input powers were recorded.
5：Data Analysis Methods:
The performance was evaluated based on the responsivity and polarization extinction ratio (PER) of the photodiodes.
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