The results of lasing linewidth narrowing on the VEPP-3 storage ring optical klystron

Lasing in the visible and ultraviolet ranges was achieved in the optical klystron installed on the VEPP-3 storage ring in 1988 [1] with a minimum relative linewidth of Δ λ λ = 10^-4. In order to decrease the linewidth we have performed the following experiments. The optical cavity on the VEPP-3 storage ring optical klystron was updated by installing intracavity selective elements. We used the simplest selective element - a glass plate with parallel planes as a natural interferometer. With the use of a 1.2 mm thick glass plate installed inside the optical cavity we have achieved lasing with a very narrow linewidth. The minimum relative lasing linewidth, 2.7 × 10 ^-6 (λ = 6250 A ̊, Δλ = 0.017 A ̊), was 30 times narrower than the minimum without the plate (Δλ = 0.6 A ̊). The average power was the same in both cases. Experiments on lasing linewidth narrowing using plates of different thicknesses are under way.