The invention relates to optical system including light sources that amplify light using a gain medium. Systems and method of the invention are provided for amplifying light while inhibiting reflections at a peak gain of the gain medium, thereby suppressing parasitic lasing. This allows a system to use a broad range of wavelengths without parasitic lasing, thereby increasing the useable range of a tunable optical filter. In this manner, light at wavelengths not at a peak gain can be used effectively, and the gain medium of an optical amplifier does not limit use of a system to a narrow range of wavelengths associated with a peak gain of the gain medium. A single optical system according to the invention can thus be used for applications that require a broad range of wavelengths.