Microchip lasers

Passive Q-switching is a simple and compact method to generate optical pulses with high peak powers and short pulse durations offering low cost and low weight per unit. Diode-pumped passively Q-switched microchip lasers based on short laser crystals and semiconductor saturable absorber mirrors (SESAMs) have been introduced and demonstrated in the past as a promising concept for generation of very short pulses below one hundred picoseconds. Such passively Q-switched lasers offer huge potential and are very interesting for a wide range of applications e.g. light detection and ranging (LIDAR), spectroscopy, metrology and material processing, i.e. wafer dicing and high-speed micromachining. The in-house designed monolithic microchip laser based on the combination of Nd3+:YVO4 crystal and SESAM are capable to generate pulses from 50 ps to 250 ps and pulse energies >150 nJ at repetition rates from 50 kHz to a few MHz.

Bonded microchip laser on a heat sick. For comparison, a 1 Euro-Cent coin is additionally shown.

The monolithic concept is realized by a simple and reliable spin-on-glass bonding technique. The repetition rate of passively Q-switched microchip lasers is varied by changing the launched pump power, while the pulse duration is mainly set by the initial design parameters and stays nearly constant during the entire operation. The emitted pulses feature a linearly polarized radiation, a single longitudinal-mode operation and a nearly diffraction-limited beam quality at 1064 nm central wavelength.

Further, for the applications with requirements for higher pulse energies and peak powers, the microchip pulses can be simply amplified using ytterbium-doped photonic-crystal fibers (PCF) to energies over 100 µJ and peak powers as high as a few of Megawatts. The PCF-based amplifiers provide free-space end-pumped compact systems with large signal cores (30 µm -100 µm), low numerical apertures and a diffraction limited beam quality. Another feature of microchip-laser pulses is their suitability for nonlinear pulse compression and was firstly demonstrated at IAP producing the worldwide shortest Q-switched pulses of less than 5 ps.

Schematic setup of a compact high-power source for picosecond pulses based on a fiber amplified microchip amplifier.

Selected publications:

[1] D. Nodop, J. Limpert, R. Hohmuth, W. Richter, M. Guina, and A. Tünnermann, "High-pulse-energy passively Q-switched quasi-monolithic microchip lasers operating in the sub-100-ps pulse regime," Opt. Lett. 32, 2115-2117 (2007),link to journal

[2] A. Steinmetz, T. Eidam, D. Nodop, J. Limpert, and A. Tünnermann, "Nonlinear compression of Q-Switched laser pulses to the realm of ultrashort durations," Opt. Express 19, 3758-3764 (2011)

[3] A. Steinmetz, D. Nodop, A. Martin, J. Limpert, and A. Tünnermann, "Reduction of timing jitter in passively Q-switched microchip lasers using self-injection seeding," Opt. Lett. 35, 2885-2887 (2010)