Semiconductor laser and atomic oscillator

An atomic oscillator comprising:

• a semiconductor laser;
• an atom cell irradiated with light emitted from the semiconductor laser and containing alkali metal atoms;
• and
• a light receiving element that detects intensity of light transmitted through the atom cell and outputs a detection signal, wherein
• the semiconductor laser includes
• a first mirror layer,
• a second mirror layer,
• an active layer disposed between the first mirror layer and the second mirror layer,
• a current confinement layer disposed between the first mirror layer and the second mirror layer,
• a first region provided continuously with the first mirror layer and including a plurality of first oxidized layers, and
• a second region provided continuously with the second mirror layer and including a plurality of second oxidized layers,
• the first mirror layer, the second mirror layer, the active layer, the current confinement layer, the first region, and the second region constitute a laminated body,
• the first region and the second region constitute an oxidized region of the laminated body,
• in a plan view, the laminated body includes a first part, a second part, and a third part disposed between the first part and the second part and resonating light generated in the active layer, and
• in a plan view, at least at a part of the third part,
• W1>W3 and W2>W3 (1)
• W1 is a width of the oxidized region of the first part,
• W2 is a width of the oxidized region of the second part, and
• W3 is a width of the oxidized region of the third part.