A medium wave （MW） 640×512 （25 μm） Mercury Cadmium Telluride （HgCdTe） polarimetric focal plane array （FPA） was demonstrated. The micro-polarizer array （MPA） has been carefully designed in terms of line grating structure optimization and crosstalk suppression. A monolithic fabrication process with low damage was explored， which was verified to be compatible well with HgCdTe devices. After monolithic integration of MPA， NETD < 9.5 mK was still maintained. Furthermore， to figure out the underlying mechanism that dominated the extinction ratio （ER）， specialized MPA layouts were designed， and the crosstalk was experimentally validated as the major source that impacted ER. By expanding opaque regions at pixel edges to 4 μm， crosstalk rates from adjacent pixels could be effectively reduced to approximately 2%， and promising ERs ranging from 17.32 to 27.41 were implemented.