Light-emitting device and light source apparatus

A light-emitting device comprising:

• a substrate having a groove extending in a first direction and a first surface and a second surface respectively arranged to sandwich the groove in a second direction crossing the first direction;
• a first electrode provided on the first surface;
• a second electrode provided on the second surface;
• a graphite thin film provided on the first electrode and the second electrode and extending from the first electrode to the second electrode along the second direction in such a way as to be astride the groove;
• a third electrode electrically connected to the first electrode and provided on the graphite thin film in such a way as to be opposite the first electrode via the graphite thin film;
• and
• a fourth electrode electrically connected to the second electrode and provided on the graphite thin film in such a way as to be opposite the second electrode via the graphite thin film.