Patent ID: 8238387

Claim:
A mode-locked laser device comprising: a resonator; a solid-state laser medium that is disposed in the resonator and outputs oscillation light in accordance with the incidence of excitation light; a saturable absorber that is disposed in the resonator and induces soliton mode-locking; a group velocity dispersion correction component that is disposed in the resonator and controls group velocity dispersion in the resonator; and an excitation portion that causes excitation light to be incident at the solid-state laser medium, wherein a resonator length of the resonator is at least a resonator length with which soliton mode-locking is inducible and is less than a resonator length with which non-soliton mode-locking is inducible; wherein the resonator length satisfies the following equation (1): c × E c , p , s × T 2 × P out ≤ L < c × E c , p × T 2 × P out ( 1 ) in which L is the resonator length, c is the speed of light, E c,p,s is a mode-locking threshold energy of soliton mode-locking, which is expressed in the following equation (2), T is transmissivity of an optical member at a side at which the oscillation light is outputted, Pout is a desired average output power of the oscillation light outputted from the solid-state laser medium, and E c,p is a mode-locking threshold energy of non-soliton mode-locking, which is expressed in the following equation (3): E c , p , s = 1 3 ⁢ E sat , L ⁢ g ⁢ ⁢ K 2 + 2 1 / 3 3 ⁢ E sat , L ⁢ g ⁢ ⁢ K 2 ( - 2 + 27 ⁢ E sat , L 2 ⁢ g 2 ⁢ K 4 ⁢ E c , p 2 + - 4 + ( - 2 + 27 ⁢ E sat , L 2 ⁢ g 2 ⁢ K 4 ⁢ E c , p 2 ) 2 ) 1 / 3 + ( - 2 + 27 ⁢ E sat , L 2 ⁢ g 2 ⁢ K 4 ⁢ E c , p 2 + - 4 + ( - 2 + 27 ⁢ E sat , L 2 ⁢ g 2 ⁢ K 4 ⁢ E c , p 2 ) 2 ) 1/3 3 × 2 1/3 ⁢ E sat , L ⁢ g ⁢ ⁢ K 2 K being expressed by the following equation K = 4 ⁢ ⁢ π ⁢ ⁢ n 2 ⁢ L K D 2 ⁢ A L ⁢ λ o ⁢ Δ ⁢ ⁢ v g · 0.315 1.76 ⁢ ⁢ E c , p = F sat , L × F sat , s × A L × A S × Δ ⁢ ⁢ R ( 3 ) in which E sat,L is expressed by F sat,L *A L , F sat,L is a saturation fluence of the solid-state laser medium, and A L is a beam diameter of the oscillation light in the solid-state laser medium, and g is a gain of the solid-state laser medium, n 2 is a non-linear refractive index of the solid-state laser medium, L K is a length of the solid-state laser medium, D 2 is a negative dispersion amount in the resonator λ 0 is a central wavelength of the oscillation light, Δν g is a bandwidth of the oscillation light, F sat,S is a saturation fluence of the saturable absorber, A S is a beam diameter of the oscillation light in the saturable absorber, and ΔR is a modulation depth of the saturable absorber.