Design and optimization of a grating-free external cavity diode laser with over 6 THz phase-continuous tunability

A novel grating-free tunable external cavity diode laser has been designed and optimized, featuring an impressive phase-continuous tuning range exceeding 6 THz. The laser cavity is constructed from two sets of right-angled mirrors arranged in a rectangular configuration. These mirrors are symmetrically positioned relative to the central axis and are parallel in pairs, effectively forming two periscopic assemblies. Wavelength adjustment is achieved by rotating a double-sided mirror positioned centrally within the mirror sets, and an etalon is utilized as the wavelength selector. This pivot-point-free rotation simultaneously tunes both the cavity length and the etalon mode wavelength, ensuring high synchronization between the two. With a low refractive index material used for the etalon, the tuning range can theoretically extend up to 6.022 THz. • External cavity design with right-angled mirrors achieves phase-continuous tuning. • Tuning scheme on single double-sided mirror rotation improves the tuning speed. • Cavity length mathematically matches etalon characteristic optical length. • Error analysis guides the further experiments.