Compact particulate material sensor

A portable communication device, the device comprising:

• a semiconductor light source configured to generate a pulsed light in response to a drive pulse and configured to shine a volume including particulate matter;
• and
• one or more photodetectors integrated with an optical filter configured to be transparent to scattered light form the particulate matter within the volume,
• wherein:
• the scattered light has a second wavelength substantially equal to a first wavelength associated with the semiconductor light source, and
• the one or more photodetectors are coupled to a charge sensitive electronic circuit configured to reject background light.

A method comprising:

• integrating a light source with a semiconductor chip, the light source generating a pulsed light at a first wavelength in response to a drive pulse;
• integrating a plurality of photodetectors with the semiconductor chip;
• forming an optical filter over the plurality of photodetectors;
• and
• configuring a charge collection circuit of the plurality of photodetectors to electronically reject a background light,
• wherein:
• the optical filter is transparent to scattered light from particulate matter shined by the light source, and
• the scattered light is produced as a result of scattering of the pulsed light by the particulate matter.