Alternative approaches for developing 2.0-2.5 μm single frequency semiconductor lasers are reviewed. Room temperature lasers in this wavelength range are important for the development of absorption spectroscopy instruments used in environmental monitoring and life support for space applications. In spite of significant efforts towards the growth and fabrication of lasers using the GaSb-based material system, room temperature, single frequency lasers in the 2-2.5 μm wavelength range are not yet available. As an alternative to the GaSb-based material system, novel techniques using the mature InP-based material system (which is potentially more suitable for single frequency laser fabrication) are being investigated. These include: highly strained InGaAs quantum well layers, graded buffer layers, laterally confined growth, and InGaAsN quantum well layers. In this paper, we will review the current status and limitations of these techniques to develop ambient temperature, single frequency lasers.