External-cavity semiconductor laser

An external-cavity semiconductor laser comprising:

• a semiconductor laser element containing a gallium nitride material;
• a first lens disposed in an optical path of light emitted from the semiconductor laser element;
• a wavelength selective element disposed in an optical path of light transmitted through the first lens and configured to selectively transmit light having a predetermined wavelength;
• a second lens disposed in an optical path of light transmitted through the wavelength selective element;
• an output coupler disposed in an optical path of light condensed through the second lens, the output coupler having a reflection surface, and a transmission surface opposite the reflection surface;
• and
• a light-transmissive protective member bonded to and facing the reflection surface of the output coupler,
• wherein a cavity is located between the semiconductor laser element and the output coupler,
• wherein the second lens is configured to cause light transmitted through the second lens and incident on the output coupler to form an image on a portion of the reflection surface of the output coupler, and
• wherein the protective member covers the portion of the reflection surface of the output coupler on which the image is formed.