I spend my days working in an underground laboratory (albeit not in a hollowed out volcano) with fluorescent lighting and zero natural light. I had also noticed that my sleep was no longer as replenishing as it was when I worked at a desk in front of a south facing window.
So, as an experimental solution I purchased a lamp and daylight bulb and now illuminate my desk with this all day. I have found that gradually I am sleeping better and feeling much more rested when I wake. Correlation, though not necessarily causation – it’s certainly better having the daylight hues lighting the desk.
The lamp and daylight bulb are both available from John Lewis. Although the matching bulb is actually found in the craft department rather than the lighting department?!
This should also help during those long, dark, northern winters!