I didn't explain that properly in the last post.  We had set up the PD with a low gain because we need to keep the signal low enough for the mixer.  After putting it together and measuring the transfer function we noticed that there was a large peak at high frequency as Zach mentioned in this post.  Today I went back and remeasured it after removing the 200MHz notch, and then started increasing the gain to see if it would go away.  That is the reason why I have plotted the three different gains.

Definitely we need to keep the gain at >=10.  The issue now is whether we need to reduce the gain somehow (ie reduce the transimpedance using a smaller inductor, or finding a low gain opamp).  Any views?