1.6 W continuous-wave Raman laser using low-loss synthetic diamond

Low-birefringence (Δn<2x10−6), low-loss (absorption coefficient <0.006cm−1 at 1064nm), single-crystal, synthetic diamond has been exploited in a CW Raman laser. The diamond Raman laser was intracavity pumped within a Nd:YVO4 laser. At the Raman laser wavelength of 1240nm, CW output powers of 1.6W and a slope efficiency with respect to the absorbed diode-laser pump power (at 808nm) of ~18% were measured. In quasi-CW operation, maximum on-time output powers of 2.8W (slope efficiency ~24%) were observed, resulting in an absorbed diode-laser pump power to the Raman laser output power conversion efficiency of 13%

Mapping the dynamical regimes of a SESAM mode-locked VECSEL with long cavity using time series analysis

The different dynamical regions of an optically-pumped SESAM mode-locked, long-cavity VECSEL system with a fundamental pulse repetition frequency of ~200 MHz are investigated. The output power, captured as 250 μs long time series using a sampling rate of 200 GSa/s, for each operating condition of the system, is analyzed to determine the dynamical state. A wavelength range of 985-995 nm and optical pump powers of 10 W-16.3 W is studied. The system produces high quality fundamental passive mode-locking (FML) over an extensive part of the parameter space, but the different dynamical regions outside of FML are the primary focus of this study. We report five types of output: CW emission, FML, modelocking of a few modes, double pulsing, and, semi-stable 4th harmonic mode-locking. The high sampling rate of the oscilloscope, combined with the long duration of the time series analyzed, enables insight into how the structure and substructure of pulses vary systematically over thousands of round trips of the laser cavity. Higher average output power is obtained in regions characterized by semi-stable 4th harmonic mode-locking than observed for FML, raising whether such average powers might be achieved for FML. The observed dynamical transitions from fundamental mode-locking provide insights into instability challenges in developing a stable, widely tunable, low repetition rate, turn-key system; and to inform future modelling of the system

Q-switching of Nd:YAG solid-state laser with intra-cavity MEMS resonant scanning mirror

A comb-drive actuated MEMS scanning mirror is used to actively Q-switch a side-pumped Nd:YAG laser. Minimum pulse durations of 38 ns are observed and maximum average output powers of 55 mW at 17.625 kHz pulse repetition frequency

SOI based electromagnetic MEMS scanners and their applications in laser systems

MEMS scanners are of interest for their potential as low-cost, low operating power devices for use in various photonic systems. The devices reported here are actuated by the electromagnetic force between a static external magnetic field and a current flowing through an SOI MEMS scanner. These scanners have several modes of operation: their mirrors may be rotated and maintained at a static angle (up to ± 1.4 degrees), scanned rapidly (up to 500 Hz); or may be operated in a resonance mode, at the device's mechanical resonance frequency (∼1.2 kHz) for higher rate scanning. The use of these scanners as a Q-switching element within a Nd:YAG laser cavity has been demonstrated. Pulse durations of 400 ns were obtained with a pulse energy of 58 μJ and a pulse peak power of 145 W. The use of an external magnetic field, generated by compact rare-earth magnets, allows a simple and cost-effective commercial fabrication process to be employed (the multi-user SOI process provided by MEMSCAP Inc) and avoids the requirement to deposit magnetic materials on the MEMS structure

Thermoelectrically controlled varifocal micromirror for near aberration free imaging

A close-loop-controlled miniature Peltier element was used to vary the temperature of a 1.2 mm diameter silicon-gold bimorph varifocal micromirror (VFM), thereby changing its radius of curvature due to differential thermal expansion of the two materials. By varying the VFM temperature from 10°C to 100°C, the radius of curvature (ROC) of the micromirror was measured to vary from 19.2mm to 30.9mm. The Zernike coefficients over this operational range were analysed to be less than a few micrometres. An imaging system utilising the VFM was assembled, and examples of the near aberration-free images obtained are presented

Automatic transverse mode optimization of an all-solid-state laser using an adaptive-optic mirror

This paper is about automatic transverse mode optimization of an all-solid-state laser using an adaptive-optic mirror. It was presented at the international conference on lasers, applications, and technologies in 2002

Ultrasonic Imaging In Liquid Sodium: A Differential Method For Damages Detection

International audienc

Sensitivity enhancement of the topological imaging method: Application to weld inspection

International audienc

Sensitivity enhancement of the topological imaging method: Application to weld inspection

International audienc

Multi-output Q-switched solid-state laser using an intra-cavity MEMS micromirror array

Multiple individually-controllable Q-switched laser outputs from a single diode-pumped Nd:YAG module are presented by using an electrostatic MEMS scanning micromirror array as cavity end-mirror. The gold coated, 700 μm diameter and 25 μm thick, single-crystal silicon micromirrors possess resonant tilt frequencies of ~8 kHz with optical scan angles of up to 78°. Dual laser output resulting from the actuation of two neighboring mirrors was observed resulting in a combined average output power of 125 mW and pulse durations of 30 ns with resulting pulse energies of 7.9 μJ and 7.1 μJ. The output power was limited by thermal effects on the gold-coated mirror surface. Dielectric coatings with increased reflectivity and therefore lower thermal stresses are required to power-scale this technique. An initial SiO2/Nb2O5 test coating was applied to a multi-mirror array with individual optical scan angles of 14° at a resonant tilt frequency of 10.4 kHz. The use of this dielectric coated array inside a 3-mirror Nd:YAG laser cavity led to a single mirror output with average Q-switched output power of 750 mW and pulse durations of 295 ns resulting in pulse energies of 36 μJ