A family of Microsoft word processing software products for creating web, email, and print documents.
You can't use the \L switch to specify heading levels. For that, you need the \o switch:
{ TOC \b section_1 \o "2-3" }
\o "2-3" includes heading levels 2 and 3. If you want just level 2, use \o "2-2".
I'm assuming here that "section_1" is your actual bookmark name.