Q-switched Microchip Laser Research Articles

Passively Q-switched Nd:YAG microchip lasers and applications

Passively Q-switched Nd:YAG microchip lasers are robust, compact, economical, all-solid-state sources of coherent, subnanosecond, multikilowatt pulses at high repetition rates. When pumped with the cw output of commercially available infrared diode lasers, these diminutive, quasi-monolithic devices produce 1.064-μm pulses with a pulse width as short as 218 ps, pulse energy up to 250 μJ, and peak power up to 565 kW, without any switching electronics. The high output intensities of the microchip lasers enable the construction of extremely compact nonlinear optical systems capable of operating at any wavelength from 5000 to 190 nm. The short pulses are useful for high-precision ranging and 3-dimensional imaging using time-of-flight techniques. When focused, the output intensities are sufficient to photoablate materials, with applications in laser-induced breakdown spectroscopy and micromachining. The ultraviolet harmonics of the microchip laser have been used to perform fluorescence spectroscopy for a variety of applications, including environmental monitoring. Systems based on passively Q-switched microchip lasers, like the lasers themselves, are small, efficient, robust, and potentially low cost, making them ideally suited for field use.

Q-switched microchip laser with 65 ps timing jitter

Low interpulse timing jitter at a low switching voltage in a Q-switched microchip laser has been reached by using both active and passive modulators.

The pulse shape of a passively Q-switched microchip laser

The shape of the intensity pulse of a passively Q-switched microchip laser is investigated numerically and analytically. Our analysis is motivated by independent microchip laser experiments exhibiting nearly symmetric pulses in the case of a semiconductor saturable absorber and asymmetric pulses in the case of a solid state saturable absorber. Asymptotic methods are used to determine limiting behaviors of the pulse shape for both symmetric and asymmetric pulses. In the first case, we determine a sech2 solution parametrized by one parameter which can be determined by solving two coupled nonlinear algebraic equations. In the second case, the pulse solution is decomposed into two distinct approximations exhibiting different amplitude and time scales properties. We review earlier approximations of the repetition rate and the pulse width.

Nearly Vertical Hopf Bifurcation for a Passively Q-Switched Microchip Laser

Passively Q-switched microchip lasers generate strongly pulsating intensity oscillations that emerge from a Hopf bifurcation point. We show that this bifurcation is nearly vertical and explain why strongly pulsating oscillations are immediately observed as we pass the Hopf bifurcation point. The laser dynamical problem is mathematically a singular perturbation problem which we investigate. The leading order problem is conservative and corresponds to Lotka–Volterra equations.

Pulse train characterisitcs of a passively Q-switched microchip laser

A study of passively Q-switched microchip laser pulse trains yields approximate, yet reliable, formulae for the peak power, pulse energy, half-width, period, and the pulse shape in time. The pulse gain differential equation is made integrable by assuming that the laser absorption cross sections for the gain and saturable absorber are equal. We compare our predictions with an experiment which uses Nd:YAG as a gain medium and Cr:YAG as a saturable absorber. The agreement between theory and experiment for the period, pulse width, and the pulse energy is within 10%.

High-repetition-rate 300-ps pulsed ultraviolet source with a passively Q-switched microchip laser and a multipass amplifier

We demonstrate a new kind of picosecond laser source in the UV at a high repetition rate of -45 kHz , using only passive, compact, and simple elements. This system is based on a microchip laser and a very efficient multipass amplifier, both pumped with recently developed high-brightness laser diodes. The system has been optimized to deliver, at a high repetition rate, subnanosecond pulses at the wavelength 355 nm with an energy per pulse of close to 1 muJ (38-mW average power). This source is to our knowledge the first totally passive 300-ps UV laser source at this high repetition rate.

Experimentally confirmed design guidelines for passively Q-switched microchip lasers using semiconductor saturable absorbers

We present a model for passively Q-switched microchip lasers and derive simple equations for the pulse width, repetition rate, and pulse energy. We experimentally verified the validity of the model by systematically varying the relevant device parameters. We used the model to derive practical design guidelines for realizing operation parameters that can be varied in large ranges by adoption of the parameters of the semiconductor saturable-absorber mirror and choice of the appropriate gain medium. Applying these design guidelines, we obtained 37-ps pulses, which to our knowledge are the shortest pulses ever generated in a passively Q-switched solid-state laser.

Dynamics of passively Q-switched microchip lasers

Self-pulsing in passively Q-switched microchip lasers is investigated in detail. The typical range of values of the parameters motivates a new analysis of the laser rate equations. We determine basic properties of the laser intensity oscillations such as threshold conditions, repetition rate, pulsewidth, peak power, and pulse energy. We show that these oscillations appear through a quasi-vertical Hopf bifurcation located slightly above the lasing threshold. Our bifurcation results are verified numerically by modeling a microchip laser experiment with Nd:YAG as the gain medium and YAG:Cr as saturable absorber. Our results agree with the experiment to within 10%.

Microchip lasers

Microchip lasers are miniature diode-pumped solid-state devices formed by dielectrically coating thin platelets of gain media. Their simplicity and small size give them the potential for inexpensive mass production, while their cw output characteristics are comparable to those of the best conventional devices. By incorporating a thin platelet of a second material into the device, tunable cw lasers and picosecond Q-switched microchip lasers have been produced which outperform larger devices in many aspects. Electrooptically tuned devices have demonstrated a flat-band tuning response of 15 MHz/V at modulation rates from dc to 1.3 GHz. Pulses as short as 115 ps, with peak powers of 80 kW, have been generated by electrooptically Q-switched microchip lasers, and pulse repetition rates as high as 2.25 MHz have been demonstrated. Passively Q-switched devices generate pulses as short as 218 ps and produce peak powers in excess of 130 kW, without the need for switching electronics. A variety of miniature nonlinear optical devices, including harmonic generators, parametric amplifiers, parametric oscillators, and fiber-based Raman amplifiers, have been used to frequency convert the output of these lasers, accessing the entire spectrum from 5 μm to 190 nm in extremely compact optical systems.

Topical Papers on Microchip Lasers and Applications. Passively Q-Switched Microchip Lasers and Applications.

Passively Q-switched Nd: YAG microchip lasers are robust, compact, economical, all-solid-state sources of coherent, subnanosecond, multikilowatt pulses at high repetition rates. These diminutive, quasi-monolithic devices produce pulses as short as 218 ps, pulse energies up to 250μJ, and peak powers up to 565 kW. The high output intensities enable the construction of extremely compact nonlinear optical systems. The short pulses are useful for high-precision ranging using time-of-flight techniques. The short pulse durations and ideal mode properties can also be used to advantage in the characterization of materials. When focused, the output intensities are sufficient to photoablate materials, with applications in laser-induced breakdown spectroscopy and micromachining. The ultraviolet harmonics of the microchip laser have been used to perform fluorescence spectroscopy for a variety of applications. Systems based on the passively Q-switched microchip lasers, like the lasers themselves, are small, efficient, robust, and potentially low cost, making them ideally suited for field use.

56-ps passively Q-switched diode-pumped microchip laser

We passively Q switched a diode-pumped Nd:YVO4 microchip crystal with an antiresonant Fabry-Perot saturable absorber and achieved single-frequency pulses as short as 56 ps. We can vary the pulse width from 56 ps to 30 ns and the repetition rate from 27 kHz up to 7 MHz by changing the design parameters of the saturable absorber and the pump power.

Periodically poled lithium niobate optical parametric amplifiers pumped by high-power passively Q-switched microchip lasers

High-power passively Q-switched microchip lasers produce 157-muJ pulses of 1-ns duration in a single-frequency, diffraction-limited output beam. The unfocused 1.064-mum output of these devices has been used to drive periodically poled lithium niobate optical parametric amplifiers at wavelengths between 1.4 and 4.3 mum . With a peak conversion efficiency of nearly 100%, these devices generate 100-kW, subnanosecond pulses in the mid IR, with a beam quality that is better than two times diffraction limited.

Ultraviolet generation with passively Q-switched microchip lasers: errata

First, second, third, fourth, and fifth harmonics of the output of a fiber-pumped passively Q-switched Nd:YAG microchip laser have been obtained at pulse energies of 8.0, 3.5, 0.3, 0.7, and 0.01 μJ, respectively, in an optical head occupying a volume of less than 3 cm3. This compact, economical all-solid-state source provides coherent subnanosecond multikilowatt infrared, visible, and ultraviolet pulses at repetition rates in excess of 10 kHz.

Ultraviolet generation with passively Q-switched microchip lasers

First, second, third, fourth, and f ifth harmonics of the output of a f iber-pumped passively Q-switched Nd:YAG microchip laser have been obtained at pulse energies of 8.0, 3.5, 0.3, 0.7, and 0.01 microJ, respectively, in an optical head occupying a volume of less than 3 cm(3). This compact, economical all-solid-state source provides coherent subnanosecond multikilowatt infrared, visible, and ultraviolet pulses at repetition rates in excess of 10 kHz.

Diode-pumped passively Q-switched picosecond microchip lasers

Passively Q-switched 1.064-microm microchip lasers have been constructed from thin pieces of Nd(3+):YAG bonded to thin pieces of Cr(4+):YAG. When pumped with the unfocused 1.2-W output of a fiber-coupled diode, these devices produced 11-microJ pulses of 337-ps duration at a pulse repetition rate of 6 kHz in a single-frequency TEM(00) mode. The peak power of the lasers was in excess of 180 MW/cm(2).