We use concentrated laser light in laser spectroscopy to make atoms or molecules do something special — called 'excitation'. This special state can help us understand more about these atoms or molecules. Imagine you're creating a setup for this kind of experiment. You're using a red laser that emits light with a wavelength of 633 nm. In your setup, what you want to study is placed at the focus 1.0 m away from the lens. Your calculations tell you that the laser light must be narrowed down to a 0.5 mm in diameter spot. With this in mind, what is the smallest diameter your lens can be to achieve this?