A high-power harmonically self-mode-locked Nd:YVO₄1.34-μm laser with repetition rate up to 32.1 GHz

Abstract

We develop a practical method to achieve harmonically self-mode-locked operation in a Nd:YVO 4 1.34-µm laser for the generation of high-repetition-rate pulse trains. We exploit a gain medium with partial-reflection coating at the lasing wavelength to introduce effective mode selection. We numerically demonstrate that the coated gain medium can effectively modify the mode spacing of the laser cavity to be the harmonics of the free spectral range of the gain medium when the optical cavity length is adjusted to be commensurate with the optical length of the gain medium. We further employ a coated Nd:YVO 4 crystal to realize harmonically mode-locked operation with a highest repetition rate of up to 32.1 GHz. At a pump power of 11.5 W, the average output power of 2.3 W is generated with a pulse duration as short as 5.7 ps. The locking range for the cavity length is also experimentally explored.

Manipulating the longitudinal mode distribution in the self-mode-locked Nd:YVO4 laser with flexible reflectivity and tilted mirror

“…L opt is the optical cavity length; L cav and L cry are the geometric lengths of laser cavity and gain medium, respectively; and n is the refractive index of the gain medium. When 2N þ 1 longitudinal modes exceed the laser threshold, the Gaussian-enveloped intensity spectrum of the oscillation modes are ideally expressed as 10,15 E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 1 ; 1 1 6 ; 1 1 7…”

“…For the multilongitudinal-mode laser, the longitudinal mode spacing is expressed as Δλc=λ02/2Lopt, where Lopt=Lcav+Lcry(n−1); Lopt is the optical cavity length; Lcav and Lcry are the geometric lengths of laser cavity and gain medium, respectively; and n is the refractive index of the gain medium. When 2N+1 longitudinal modes exceed the laser threshold, the Gaussian-enveloped intensity spectrum of the oscillation modes are ideally expressed as 10 , 15 I(λ)=∑q=−NN(λ−λ0)2Γc[(λ−λ0)2−(qΔ…”

“…Next, we analyze the situation of the crystal pump facet and the front mirror forming an intracavity etalon for mode selection 10 , 14 , 15 . According to the equation, the finesse of the etalon F=4r/(1−r)2, where r is the reflectivity of the gain medium pump facet.…”

“…[6][7][8] Among them, the SML technique is a promising method with the advantages of compactness and low cavity losses. According to previous research, since the pulse time characteristics in SML lasers mainly depend on the longitudinal mode oscillation states, [9][10][11] lots of approaches have been employed to investigate the longitudinal mode oscillation states of the SML lasers, such as controlling the laser gain, adjusting the resonant cavity length, and introducing a wavelength selector. Schfer et al controlled the longitudinal mode distribution in an Nd∶YVO 4 laser by tuning the length of the gain medium.…”

Theoretical and experimental studies for high-repetition-rate disordered crystal lasers with harmonic self-mode locking

“…Among these methods, harmonic mode locking is a promising approach with the advantages of compactness and low cavity losses. In the past few years, harmonically mode-locked operation has been explored in numerous traditional solid-state lasers, such as Nd:YVO 4 lasers, Nd:YLF lasers, and Yb:YAG lasers [12][13][14][15].…”