Electronic devices with coherent self-mixing proximity sensors

An earbud, comprising:

• a housing having a speaker port;
• a self-mixing proximity sensor in the housing, wherein the self-mixing proximity sensor includes a laser with a laser cavity configured to emit output light that illuminates a target and wherein a portion of the output light that has illuminated the target reenters the laser cavity and causes self-mixing fluctuations in a power of the output light;
• a speaker configured to supply audio through the speaker port;
• and
• control circuitry configured to adjust earbud operation in response to measurements from the self-mixing proximity sensor.

An earbud, comprising:

• a housing having a stalk portion and an ear portion with a speaker port;
• a self-mixing proximity sensor in the stalk portion, wherein the self-mixing proximity sensor includes a laser with a laser cavity configured to emit output light that illuminates a target and wherein a portion of the output light that has illuminated the target reenters the laser cavity and causes self-mixing fluctuations in a power of the output light;
• a speaker configured to play audio through the speaker port;
• and
• control circuitry configured to gather finger touch input using a measurement from the self-mixing proximity sensor.