SBIR Phase I: Single-Mode Single-Polarization VCSELs at any Wavelength

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This Small Business Innovation Research Phase I project proposes to use a novel approach to fabricate Vertical Cavity Surface Emitting Lasers (VCSELs) that are free from any wavelength limitations imposed by their host semiconductor substrate. These revolutionary VCSELs will operate in a single mode with high output power, narrow linewidth and stable linear polarization for use in spectroscopy and communications. In this approach, both semiconductor distributed bragg reflectors (DBRs) of the VCSEL are mostly eliminated. On one side, a high-contrast subwavelength grating (HCG) mirror is used for single-mode linearly polarized output. On the other side, the high reflector is replaced with a dielectric DBR. Using this combination, it is possible to build efficient single mode VCSELs at any wavelength covering near-infrared and approaching mid infrared (800nm to 2,500nm). High efficiency and high output power are achieved by very low electrical resistance and efficient heat sinking. The first prototype will have an emission wavelength of 1550nm with the ambitious goal of offering a preferred alternative to DFB lasers in long-haul fiber optic communications and near infrared spectroscopy. HCG fabrication and a complete design followed by epitaxial growth will be done in Phase I.The Broader Impacts / Commercial Potential of this project range from telecommunications to spectroscory. The developed devices will have the mode purity and linewidth of DFB lasers and the beam quality and low cost of a VCSEL at any near infrared wavelength with stable linearly polarized output. Immediate application areas are in telecommunications and spectroscopy. Of particular interest in communication systems are the reduction of cost per bit, and power consumption per bit of transmitted data. Implementing the proposed VCSELs in fiber optic transceiver units results in reduced cost and reduced power consumption over existing edge emitter based solutions. Reducing power consumption in turn leads to miniaturization and high density assembly that lead to further cost reduction. Up to now, long wavelength 1550nm VCSELs have not had the required characteristics to gain widespread use. Particularly challenging requirements for VCSELs to meet are high optical output power and narrow linewidth for long haul transmission. The proposed approach makes possible for these VCSELs to meet all the requirements and to potentially become an attractive alternative to edge emitting DFB lasers. The lack of wavelength constraints makes these sources ideal for overtone spectroscopy in the near infrared for environmental and security applications.