This Small Business Innovation Research Phase I project begins development of the ideal on-airway carbon dioxide respiratory sensor: a spectroscopic sensor based on vertical-cavity surface-emitting lasers (VCSELs). The proposed sensor is sensitive, low cost, fast, small, lightweight, low power, eye-safe, reliable, and requires no consumables. Spectroscopic sensors based on laser diodes are becoming the sensor of choice due to the qualities listed above. VCSELs have superior spectroscopic and beam qualities over other laser diodes, and are becoming far less expensive than existing lasers. Key to the program is development of VCSELs at the about 1.6 micron wavelength used for carbon dioxide sensing. The VCSEL development and eventual component cost will be greatly leveraged by development of VCSELs at similar wavelengths for optical fiber communications. A about 1.6 micron VCSEL will be produced in Phase I using novel materials. Its wavelength, spectrum, and tuning characteristics will be verified in a setup using carbon dioxide gas. The phase II program will produce a sensor nearly ready for use in hospitals. The sensor will also be ideal for monitoring carbon monoxide in homes and industry. PROPOSED COMMERCIAL APPLICATION: The proposed carbon dioxide sensor will find pervasive use for monitoring respiration and metabolic function in hospitals. Closely related sensors will monitor carbon dioxide and carbon monoxide and other gases in homes and industrial sites. Such sensors may become part of household building codes, generating a multi-billion dollar industry for home use alone.