Extracting specific pair of information from Lucene index output

Question

I have used Lucene library as the indexing and keyword extracting tool to index my document. However, I don't want to use the search query provided in Lucene as I wish to develop my own separate searching algorithm/program.

May I know is there any way to extract only the keyword-document ID pair in a readable manners apart from using Luke (like an text file that can later be read/used in my own developed program).

OR

Is there any way to encrypt the Lucene index but still searchable using searchable encryption. If yes, may I know how will it works?

OR

Is there any other indexing library that can extract the keyword pair in the program readable manner?