50 μJ, 90 ps monolithic fiber amplifier passively Q-switched microchip laser with low timing jitter

Guillaume Machinet1*, Christophe Pierre1 and Pascal Dupriez1

1. Alphanov, centre technologique optique et laser, 351 Cours de la Libération, F-33405 Talence, France

* Email: guillaume.machinet@alphanov.com

Diode-pumped passive Q-switched Nd: YVO4 microchip lasers are a simple low cost approach to generate optical pulses with high peak power and pulse durations below 100 ps [1] [2]. These lasers have a great potential for scientific and industrial applications. However the inherently large timing jitter of the interpulse period of the microchip laser may limit its applications, even if some relatively cumbersome techniques have been developed to reduce it [3]. Another limitation comes from high peak power which requires the use of large core microstructured fiber amplifiers to produce the required high energy. These fibers are not fully integrated because of the difficulty to splice them and unavailability of fiber components. In this study, we demonstrate reduction of timing jitter of a picosecond microchip Nd:YVO4 laser using a simple method and subsequent high energy amplification of these pulses in a fully integrated monolithic fiber amplifier system. This was enabled by the development of a 2+1x1 pump combiner designed for microstructured fiber.

Fig. 1 Experimental setup

The experimental setup is sketched in figure 1. An integrated and stabilized Nd:YVO4 microchip laser delivers 90 ps pulses, linearly polarized @ 1064 nm. The microchip can work on a wide frequency repetition rate range up to 1 MHz perfectly controlled with a timing jitter below than 2 ns (Figure 2). In this experiment, we operate at a repetition rate of 100 kHz. Pulses seed two preamplifiers stages to reach an average power of 20 mW. The main amplifier consists in a photonic crystal fiber DC 40/200 fully spliced via a 2+1x1 pump combiner to produce an average power of 5W (Figure 3). The output energy is limited by the onset of Stimulated Raman Scattering (SRS). At this power level, ASE signal is more than 30 dB lower than the 1064nm signal.

Fig. 2 Top: Conventional microchip with timing jitter > 100 ns Fig. 3 Main amplifier characteristics. Inset: @ 350 kHz. Bottow: Microchip with timing jitter < 2ns. Below 200 Spectrum at full power. kHz, the free running timing jitter exceeds the pulse period.

In conclusion we have demonstrated a fully integrated low cost picosecond fiber system with timing jitter compatible for most applications. This source will be used for micromachining applications

References [1] B. Braun et al, "56-ps passively Q-switched diode-pumped microchip laser," Opt. Lett. 22, 381-383 (1997). [2] A. Steinmetz et al, "Sub-5-ps, multimegawatt peak-power pulses from a fiber-amplified and optically compressed passively Q-switched microchip laser," Opt. Lett. 37, 2550-2552 (2012). [3] A. Steinmetz et al, "Reduction of timing jitter in passively Q-switched microchip lasers using self-injection seeding," Opt. Lett. 35, 2885-2887 (2010).

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978-1-4799-0594-2/13/$31.00 ©2013 IEEE