Characterization of Single-Frequency Yb:$ \hbox{KYF}_{4}$ Lasers at 1.03 $\mu\hbox{m}$ for Optical Frequency Metrology

A longitudinally pumped, widely tunable, solid-state Yb:KYF
₄
laser was developed with special design for applications to optical frequency metrology and absolute frequency stabilization. The KYF
₄
crystalline host, combined with efficient diode pumping, allows for wide wavelength tunability at about 1.03 mum in a single transverse mode. Two different laser cavity designs were experimentally investigated. The combined use of an intracavity birefringent filter and uncoated glass etalons provides single-frequency output power at the 100-mW level in a folded-cavity resonator. A second hemispherical linear cavity was also developed with one or two coated intracavity etalons for single-frequency operation. The novel laser sources were thoroughly characterized in terms of output power and beam quality, amplitude noise, wavelength tunability, and single-axial-mode operation. High-quality TEM
₀₀
single-frequency laser radiation opens the way to the development of a new optical frequency standard based on the
I

₂
molecule at 0.5- mum wavelength.