Hello, It's my pleasure to share that I have an interesting tool "word2vec for Lucene" available at https://github.com/kojisekig/word2vec-lucene .
As you can imagine, you can use "word2vec for Lucene" to extract word vectors from Lucene index. Thank you, Koji -- http://soleami.com/blog/comparing-document-classification-functions-of-lucene-and-mahout.html
