Rakesh Bhandari

> 6 MW peak power at 532 nm from passively Q-switched Nd:YAG/Cr 4+ :YAG microchip laser

Megawatt peak power, giant pulse microchip lasers are attractive for wavelength conversion, provided their output is linearly polarized. We use a [110] cut Cr(4+):YAG for passively Q-switched Nd:YAG microchip laser to obtain a stable, linearly polarized output. Further, we optimize the conditions for second harmonic generation at 532 nm wavelength to achieve > 6 MW peak power, 1.7 mJ, 265 ps, 100 Hz pulses with a conversion efficiency of 85%.

Palm-top size megawatt peak power ultraviolet microlaser

Abstract. The development of a very compact, highly efficient, megawatt peak power, subnanosecond pulse width, 266 nm ultraviolet (UV) microlaser is reported. It contains a specially designed passively Q-switched Nd∶YAG/Cr4+∶YAG microchip laser whose high output peak power of 13 MW enables an efficient wavelength conversion without using any optics before the nonlinear crystals. The subnanosecond pulse width region, which delivers high peak power even at moderate pulse energy, is very useful for an efficient wavelength conversion. We achieve 73% second harmonic generation efficiency using a LiB3O5 (lithium triborate) crystal and 45% fourth harmonic generation efficiency using a β−BaB2O4 (β-barium borate) crystal. As a result, we obtain 650 μJ, 4.3 MW peak power, 150 ps, and 100 Hz pulse output at 266 nm. We use an original design for the nonlinear crystal holders to reduce the size of the microlaser. This palm-top size 266 nm UV microlaser will be useful for many applications, such as materials microprocessing, pulsed laser deposition, UV laser induced breakdown spectroscopy, and photoionization.

Megawatt level UV output from [110] Cr 4+ :YAG passively Q-switched microchip laser

Recent development of megawatt peak power, giant pulse microchip lasers has opened new opportunities for efficient wavelength conversion, provided the output of the microchip laser is linearly polarized. We obtain > 2 MW peak power, 260 ps, 100 Hz pulses at 266 nm by fourth harmonic conversion of a linearly polarized Nd:YAG microchip laser that is passively Q-switched with [110] cut Cr⁴⁺:YAG. The SHG and FHG conversion efficiencies are 85% and 51%, respectively.

Efficient second to ninth harmonic generation using megawatt peak power microchip laser

We report the design and use of a megawatt peak power Nd:YAG/Cr4+:YAG microchip laser for efficient second to ninth harmonic generation. We show that the sub-nanosecond pulse width region, between 100 ps and 1 ns, is ideally suited for efficient wavelength conversion. Using this feature, we report 85% second harmonic generation efficiency using lithium triborate (LBO), 60% fourth harmonic generation efficiency usingß-barium borate, and 44% IR to UV third harmonic generation efficiency using Type I and Type II LBO. Finally, we report the first demonstration of 118 nm VUV generation in xenon gas using a microchip laser.

All polarization-maintaining fiber chirped-pulse amplification system for microjoule femtosecond pulses

A femtosecond fiber system based on nonlinear chirped-pulse amplification is investigated. It is the first investigation on pulse properties from all-normal-dispersion fiber laser after amplification. Nonlinearities due to fibers are carefully managed. The system generates up to 5-μJ pulses, and delivers near diffraction-limit beam (M2 < 1.1), polarization extinction ratio (40 dB) and polarization extinction ratio (36 dB).

Long-Pulse Q-Switched Operation of Tunable Micro-Rod Yb:YAG Laser

A new method for generating microsecond-long pulses is proposed. Using this method, a micro-rod Yb:YAG laser, tunable over 27 nm, has been developed, which can generate 3.6 microsecond-long pulses in single axial mode.

Megawatt Level UV Output from Cr4+:YAG Passively Q-Switched Microchip Laser

> 2 MW peak power, 260 ps, 100 Hz pulses at 266nm are obtained by fourth harmonic conversion of a linearly polarized Nd:YAG microchip laser passively Q-switched with cut Cr4+:YAG.

> 3 MW Peak Power at 266 nm Using Nd:YAG/Cr4+:YAG Microchip Laser and Fluxless-Grown BBO

We use fluxless-grown BBO to obtain fourth harmonic conversion of a linearly polarized Nd:YAG microchip laser, passively Q-switched with [110] cut Cr4+:YAG, achieving 3.4 MW peak power, 250 ps, 100 Hz pulses at 266 nm.

6 MW peak power at 532 nm by using linearly polarized passively Q-switched microchip laser

Compact, passively Q-switched, microchip lasers are attractive for many applications, such as, microprocessing, remote sensing, laser ignition, etc., due to their short pulse-width and high peak power characteristics [1–5]. The high peak power of microchip lasers can also be used for efficient harmonic conversion to the green and UV wavelengths for a variety of applications. However, Nd:YAG microchip lasers normally use &#60;100> cut Cr4+:YAG as the saturable absorber for passive Q-switching. This generates unpolarized laser output that is not suitable for efficient nonlinear wavelength conversion.

Novel end-pumping method for stable and compact microchip laser

Passively Q-switched microchip lasers are very attractive for various applications because of their sub-nanosecond pulse width, simple and rugged construction and low-cost [1]. We have earlier reported the design of Nd:YAG/Cr4+:YAG passively Q-switched microchip lasers for efficient wavelength conversion from the second to the ninth harmonic [2]. These lasers are useful for spectroscopy, LIDAR, LIBS, materials micro-processing, etc.