Sending a thank you letter to a research professor?

I had an amazing research professor I conducted research under for my last two semesters of undergrad. I graduate in December and am currently waiting to hear back from graduate programs. This professor wrote me a letter of recommendation and I sent him a thank you email. However, I wanted to send him a hand written thank you letter for the letter of recommendation, all I learned while researching under him, and to see how several projects are going since I've graduated and left his lab.

Is it too late or "awkward" to send him a handwritten thank you note now that it's been about one and a half months since I've last contacted him?