OBJECTIVE: Develop a high-power semiconductor-based laser source operating at room temperature in the wavelength range between 3.0 and 3.5 um. DESCRIPTION: High-power, reliable semiconductor laser sources in the wavelength range between 3.0 and 3.5 um are very desirable for a number of naval applications such as advanced chemical sensors, and laser identification detection and ranging (LIDAR). Current means to generate coherent optical radiation in this spectral band such as optical parametric oscillators (OPOs), super-continuum fiber sources, or Raman-shifted lasers are in too bulky in terms of size, weight and power (SWaP), too complicated of an architecture, or simply inefficient. Therefore, a semiconductor-based laser source in the 3.0- to-3.5- um range would significantly improve the development of next generation sensors. While the coherent light sources at or near the 3-um spectral range have tremendous potential for numerous DoD applications, the availability of reliable, small-footprint and high-power semiconductor laser sources, in the wavelength range of interest, is very limited. Watts-level continuous wave (CW) quantum cascade lasers (QCLs) have been demonstrated at wavelengths as short as 3.76 um but the performance of QCLs drops significantly as the wavelength approaches 3.0 um. The main limitation comes from the presence of satellite valleys, which limit the band-offset available to build population inversion efficiently. New material systems such as highly strained InGaAs/Al(In)As, InGaAs/AlAsSb alloys on InP substrate, and/or InAs/AlSb on InAs substrates have been used to remedy this problem but only pulsed operation has been demonstrated so far. Many technological advances have been demonstrated in devices based on the concept of interband cascade lasers (ICLs), which constitute a great alternative to traditional QCLs, although CW power has not exceeded 100 mW at room temperature. Rapid progress has also been made recently in GaSb-based mid-infrared diode lasers and watt level output power was demonstrated in the range of 2.0 to 2.4 um. At ~2.9 um, CW operation with up to 200 mW at room temperature has been demonstrated with a broad area device. The performance of this class of diode lasers at wavelengths near 3 um is however limited by a variety of factors, including the confinement for hole carriers that decreases rapidly for laser structures with emission wavelengths longer than 3 um. The goal of this topic is to seek the development of high-performance semiconductor laser sources with high CW power and excellent beam quality within the 3 um to 3.5 um spectral range, which consist of either a single semiconductor laser device or an integrated beam-combined semiconductor laser array with a single output aperture without using any external optical elements. Hybrid integration of laser array with external optical elements and/or electronics are often more cumbersome, bulky, costly and much less reliable platform and therefore undesirable for demanding field applications in harsh operating conditions. PHASE I: Determine the feasibility of designing a semiconductor laser source operating within the spectral range of 3 - 3.5 um, operating at room temperature, and capable of producing 500 mW in CW mode with beam quality of M2<1.3. Provide a development plan that describes the power scaling architecture with a power and beam quality of the scaled device(s) at least 5-10 watts with M2<1.3. PHASE II: Design and develop a prototype of the semiconductor laser source operating within the spectral range of 3 - 3.5 um, operating at room temperature, and produce at least 500 mW in CW mode with beam quality of M2<1.3. Assess the manufacturing yield and product reliability of the single laser or monolithically integrated laser array solution. PHASE III: Fully develop and transition the high-performance semiconductor laser source architecture developed in the Phase II effort for maritime sensing, naval aviation LIDAR, and advanced chemical sensor applications. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial sector can significantly benefit from this technology development in the areas of detection of toxic industrial gases, environmental monitoring, and non-invasive medical health monitoring and sensing.