On your Bootcamp drivers there should be a driver named AppleODDInstaller64.exe which is the Optical Disk Drive installer. You can copy this to the a USB and install it on the Windows side for it to recognize the Optical disk and the eject button should work. You are also going to need AppleKeyboardInstaller64.exe for the keyboard to be recognized.
There is also a mechanism to eject the disk using OSX terminal and using diskutil eject on the OSX side. See man diskutil for the OSX side.
eject device
Eject a disk. Media will become offline for the purposes of being a data store for file systems or being a member of constructs such
as software RAID or direct data. Additionally, removable media will become eligible for safe manual removal; automatically-removable
media will begin its physical (motorized) eject sequence.