Niven and Egan would be classic examples from different decades (Niven's post-1977 work, and his collaborations, not so much). I'd also point to Hannu Rajaniemi

Niven and Egan would be classic examples from different decades (Niven's post-1977 work, and his collaborations, not so much). I'd also point to Hannu Rajaniemi's Quantum Thief trilogy, Peter Watts (for world-building -- see below) and the cultural/linguistic side of C. J. Cherryh's Foreigner series (at least the first five or so books). One of the less well understood (especially by non-genre reader) aspects of hard SF is that the world the story is set in can be viewed as a character/participant in the plot, or -- in this sub-field -- as a puzzle that the plot depends on; the outcome of the story simply doesn't work without the world being set up the way it is. (A lot of stuff is marketed as hard SF that doesn't fit this criterion; it just has lots of cheap throwaway references to technology. But the core of the field is about solving the puzzle that the universe has thrown in front of the protagonists.)