For a particular theme in a Shakespeare play, the Shakespeare Criticism reference set has a “Cumulative Topic Index, by play.”  It is organized by play and then underneath each play, gives various topics and the volumes and page #’s that refer to that play and that topic. When doing research on themes in Shakespeare Criticism you may need to look under different headings. For example "romantic love" is listed under “passionate, or romantic love.” 

Shakespeare Criticism also has a “Cumulative Character Index”,  “cumulative topic index” organized by topic and then broken down by play. These indexes are at the back of every volume.

Library databases are also helpful for finding information on a particular them in a Shakespeare play. For information specifically on the "love" theme go to the library homepage, select the link for Literary Criticism under Topic Databases on the right-hand column Start with Bloom's Literary Reference Online and key in "midsummer night's dream" and love. This search lists 150 articles of literary criticism.

The second article," A Midsummer Night's Dream" from The Drama 100  has several references on the theme of love. If you select the Topics and Themes tab you will find a good definition of the meaning of romance during the Renaissance.

In Literature Resource Center, type a keyword search for "midsummer night's dream" and romantic love for several references from Shakespearean Criticism that address this theme.  

Under the EBSCO database link, select MagillOnLiterature Plus and type in midsummer night's dream. The articles in the Masterplot articles address the theme of romantic love.