Light emitting device, ranging device, and movable object

A light emitting device comprising:

• a first semiconductor light emitting element that includes a first active layer and a first resonator portion over a semiconductor substrate, and emits a first light;
• a second semiconductor light emitting element that includes a first reflector, a second resonator portion including a second active layer excited by the first light, and a second reflector stacked in this order over the first semiconductor light emitting element, and emits a second light;
• and
• a driving unit that injects a current into the first semiconductor light emitting element,
• wherein an oscillation wavelength of the second semiconductor light emitting element is longer than an oscillation wavelength of the first semiconductor light emitting element,
• wherein the second semiconductor light emitting element includes a saturable absorption layer between the second resonator portion and the second reflector, and
• wherein a thickness L of the second active layer and an absorption coefficient α of the second active layer satisfy the following inequality.
• 3.45
• ≤
• α
• ×
• L
• ≤
• 15