Continuous-Wave Nd:YVO4 self-Raman lasers operating at 1109nm, 1158nm and 1231nm

Several continuous-wave Nd:YVO4 self-Raman lasers based on the primary and secondary Raman transitions of YVO4 (893cm−1 and 379cm−1 respectively) are reported in this paper. Laser outputs were obtained at a wavelength of 1109nm, 1158nm and 1231nm with maximum output powers of 1.0W, 700mW and 540mW respectively. The respective absorbed pump power to Raman output power conversion efficiencies were measured at 8.4%, 5.4%, and 5.4%

Dual Q-switched laser outputs from a single lasing medium using an intracavity MEMS micromirror array

An intracavity array of individually controlled microelectromechanical system scanning micromirrors was used to actively Q-switch a single side-pumped Nd:YAG gain medium. Two equal power independent laser outputs were simultaneously obtained by separate actuation of two adjacent micromirrors with a combined average output power of 125 mW. Pulse durations of 28 ns FWHM at 8.7 kHz repetition frequency and 34 ns FWHM at 7.9 kHz repetition frequency were observed for the two output beams with beam quality factors M2 of 1.2 and 1.1 and peak powers of 253 W and 232 W, respectively

Range extension of a bimorph varifocal micromirror through actuation by a Peltier element

A bimorph varifocal micromirror actuated thermoelectrically by a Peltier element is reported. The single crystal silicon micromirror is 1.2 mm in diameter with a centered 1 mm diameter gold coating for broadband reflection. The actuation principle is capable of varying the micromirror temperature above and below the ambient temperature, which contributed to a 57% improvement in the addressable curvature range in comparison to previously reported electrothermal and optothermal actuation techniques for the device. Altering the device temperature from 10 C to 100 C provided a mirror surface radius of curvature variation from 19.2 mm to 30.9 mm respectively. The experimental characterization of the micromirror was used as a basis for accurate finite element modeling of the device and its actuation. Negligible optical aberrations are observed over the operating range, enabling effectively aberration-free imaging. Demonstration in an optical imaging system illustrated sharp imaging of objects over a focal plane variation of 212 mm

Wavelength tuning of a solid-state laser with a tilting mems micromirror

Wavelength tuning of a Yb:KGW solid-state laser is presented using an electrothermally actuated micromirror and a diffraction grating or dispersing prism. 27 nm and 7.5 nm tuning ranges are achieved using extracavity and intracavity configurations respectively

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%

MEMS Q-switched solid-state lasers

This paper reports the incorporation of low-cost, scanning Micro-Electro-Mechanical Systems (MEMS) micromirrors as active Q-switch elements within a solid-state laser cavity. Active Q-switching can be achieved through the rapid scanning of an electro-static, comb-drive actuated micromirror [1]. The use of MEMS devices will allow prospects of miniaturisation of laser systems with lower fabrication costs and energy consumption than common laser Q-switch elements such as acousto-optic or electro-optic devices. To investigate this, a three-mirror, side-pumped Nd:YAG laser cavity (fig.1) incorporating a resonant MEMS micromirror as an active Q-switch element was constructed. The total optical scanning angle of the electrostatically-actuated micromirror was measured at 75⁰ with a mechanical resonance frequency of 7.905kHz. A gold layer was deposited on the micromirror surface to ensure laser conversion efficiency and reduce thermal build-up within the silicon device. However, this coating process led to a concave surface curvature measured at ROC=0.22m. The micromirror was aligned so that the optimum cavity alignment was normal to the mirror surface. Q-switched output beams were obtained in a dual spot pattern (fig.2) with pulse durations as short as 130ns and pulse energies of up to 3.2μJ. Each individual spot was emitted consecutively with a frequency equal to the mechanical resonance frequency of the micromirror. This is due to the bidirectional nature of the MEMS movement and the time delay (measured at ~400ns) between the pulse emission and the scanning through the optimum alignment position. Moreover, an average timing pulse-to-pulse jitter of ~15ns was measured and the beam quality factor of each beam was measured at M2 =1.1. We will present a full characterisation of the novel active Q-switching method as well as the initial steps towards the powerscaling of this technique

Continuous-wave Raman laser pumped within a semiconductor disk laser cavity

A KGd(WO4)(2) Raman laser was pumped within the cavity of a cw diode-pumped InGaAs semiconductor disk laser (SDL). The Raman laser threshold was reached for 5: 6W of absorbed diode pump power, and output power up to 0.8W at 1143nm, with optical conversion efficiency of 7.5% with respect to the absorbed diode pump power, was demonstrated. Tuning the SDL resulted in tuning of the Raman laser output between 1133 and 1157nm

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