A Ge-on-Si laser operating at room temperature has been experimentally demonstrated. The laser utilizes a Ge waveguide on a silicon substrate, with tensile strain and n-type doping to enable direct gap behavior. The device emits light in the 1590-1610 nm range, showing line narrowing and polarization evolution from a mixed TE/TM to predominantly TE mode as gain increases. A clear threshold behavior is observed, indicating the onset of lasing. The Ge waveguide is 1.6 μm wide and 500 nm high, with a length of 4.8 mm. The emission is optically pumped using a 1064 nm Q-switched laser, achieving a peak pump power density of ~300 kW/cm². The emission spectrum shows multiple peaks, with the strongest at 1594 nm, consistent with the band structure of tensile strained Ge. The laser operates at room temperature, with a gain spectrum matching previous observations. The Ge-on-Si laser is a promising candidate for monolithic electronic-photonic integration due to its compatibility with silicon CMOS technology. The study highlights the potential of Ge-on-Si for high-volume, large-scale integration in photonic systems. The results demonstrate the feasibility of room-temperature Ge-on-Si lasers, with implications for future photonic integrated circuits. The work is supported by the Si-based Laser Initiative of the Multidisciplinary University Research Initiative (MURI) sponsored by the Air Force Office of Scientific Research (AFOSR).A Ge-on-Si laser operating at room temperature has been experimentally demonstrated. The laser utilizes a Ge waveguide on a silicon substrate, with tensile strain and n-type doping to enable direct gap behavior. The device emits light in the 1590-1610 nm range, showing line narrowing and polarization evolution from a mixed TE/TM to predominantly TE mode as gain increases. A clear threshold behavior is observed, indicating the onset of lasing. The Ge waveguide is 1.6 μm wide and 500 nm high, with a length of 4.8 mm. The emission is optically pumped using a 1064 nm Q-switched laser, achieving a peak pump power density of ~300 kW/cm². The emission spectrum shows multiple peaks, with the strongest at 1594 nm, consistent with the band structure of tensile strained Ge. The laser operates at room temperature, with a gain spectrum matching previous observations. The Ge-on-Si laser is a promising candidate for monolithic electronic-photonic integration due to its compatibility with silicon CMOS technology. The study highlights the potential of Ge-on-Si for high-volume, large-scale integration in photonic systems. The results demonstrate the feasibility of room-temperature Ge-on-Si lasers, with implications for future photonic integrated circuits. The work is supported by the Si-based Laser Initiative of the Multidisciplinary University Research Initiative (MURI) sponsored by the Air Force Office of Scientific Research (AFOSR).