Self-mixing particulate matter sensors using VCSELs with extrinsic photodiodes

An apparatus for PM sensing, the apparatus comprising:

• a light source disposed on a first chip and configured to generate a first light beam to illuminate a particulate matter (PM);
• a light detector extrinsic to the light source;
• and
• a beam splitter configured to split the first light beam to generate a second light beam directed to the light detector,
• wherein:
• the light source comprises a vertical-cavity surface-emitting laser (VCSEL),
• the light detector comprises a photodiode (PD) positioned on a second chip that includes a VCSEL structure, and
• the PD is configured to measure the second light beam and variations of the second light beam resulting from a back-scattered light created due to back scattering of the first light beam from the PM and to generate a self-mixing signal.

An electronic device comprising:

• a processor;
• and
• a particulate matter sensing device comprising:
• a dual-emitting vertical-cavity surface-emitting laser (VCSEL) disposed on a first chip and configured to generate a first light beam and a second light beam, the first light beam being configured to illuminate a particulate matter (PM);
• and
• a photodiode (PD) extrinsic to the first chip
• and is configured to measure the second light beam and variations of the second light beam and to generate a self-mixing signal,
• wherein:
• the PD is disposed on a second chip underneath the VCSEL,
• the variations of the second light beam are caused by recoupling into a resonant cavity of the dual-emitting VCSEL by a back-scattered light,
• the back-scattered light results from back-scattering of the first light beam from the PM,
• the PD is coupled to the dual-emitting VCSEL,
• a direction of the second light beam is opposite to the direction of the first light beam, and
• the second light beam is directed from the dual-emitting VCSEL to PD through an optically transparent layer that is electrically and thermally conductive and is attached to the PD.