Sub-20-ps pulses from a passively Q-switched microchip laser at 1  MHz repetition rate

Abstract

We present a 50 μm Nd3+:YVO4 microchip laser that is passively Q-switched by a semiconductor saturable absorber mirror. To reduce handling problems caused by the small crystal dimensions, the 50 μm Nd3+:YVO4 crystal is optically bonded to an undoped YVO4 crystal of a length of about 500 μm. By using a saturable absorber mirror with an effective modulation depth of >10% the system is able to deliver 16 ps pulses at a repetition rate of up to 1.0 MHz. The average laser power is 16 mW at 1064 nm. To our knowledge these are the shortest Q-switched pulses ever reported from a solid-state laser. The limits in terms of pulse width, repetition rate, output power, and system stability are discussed. Additionally, continuous-wave behavior is analyzed. Experimental data is compared with the simulation results of the coupled rate equations.

Passively Q-switched sub-100 ps Yb3+:YAG/Cr4+:YAG microchip laser: experimental results and numerical analysis

“…The models used so far have also been extended to describe ESA. 15 They assume an instantaneous relaxation of the electrons in the higher excited state (4) back to the first excited state (2). Therefore, it is referred to as static ESA in the following.…”

“…Using 50 µm thick Nd 3+ :YVO 4 and a semiconductor saturable absorber mirror (SESAM), pulse widths of 16 ps have been reported. 2 However, the pulse energy is too low (16 nJ) and thus a subsequent amplification of the pulses would be necessary. Other similar concepts also achieve pulse widths below 100 ps, but also do not yield the required energy.…”

1.5-MHz repetition rate passively Q-switched Nd:YVO 4 laser based on WS 2 saturable absorber

“…Compared with active Q-switching, [4] passively Qswitching does not necessarily rely on the high power consumption of external modulating components such as electrooptic or acousto-optic modulators, so that it can completely satisfy the requirements for low cost and equipment miniaturization. [8] The generation of passively Q-switched pulse is due to the energy mutation caused by the nonlinear saturable absorption of intracavity saturable absorber (SA), such as the semiconductor saturable absorber mirror (SESAM) [9,10] or Cr 4+ :YAG. [11][12][13] Considering the expensive cost, complex fabrication, narrow wavelength sensibility from the above SA, carbon nanotubes (CNTs), [14][15][16] graphene, [17][18][19] and some new low-cost two-dimensional (2D) graphene-like materials like topological isolators (TIs), [20][21][22][23][24] transition metal dichalcogenides (TMDs) including WS 2 , molybdenum disulfide (MoS 2 ), etc., [25][26][27][28][29][30][31][32][33] black phosphorus (BP) [34][35][36][37][38] are made into the effective SAs through a simple fabrication process and used for Q-switching technology in SSLs of various wavelength bands.…”

Sub-50 ps pulses at 620 nm obtained from frequency doubled 1240 nm diamond Raman laser

“…While the 1-30 ps pulse region is dominated by mode locked lasers, longer 250 ps -100 ns pulse region is covered by simpler Q-switched lasers. The development of SESAM Q-switched microchip lasers at 1064 nm, has enabled generation of pulses with duration below 100 ps [1], and recently even down to 16 ps [2], already overlapping with the traditional mode locked pulse regime. The main advantages of Q-switched microchip platform compared to mode locked laser system include simpler laser design, potentially lower cost, but in particular the ability to operate at low, sub-MHz repetition rates and pulse energies in µJ range or higher.…”