Xiuhua Ma

Single wall carbon nanotube absorber with polarization absorption grown by vertical evaporation method

We have demonstrated single wall carbon nanotube absorber fabricated by vertical evaporation method. The saturation intensity of the absorber is 600 μJ/cm2 at 940 nm and 200 μJ/cm2 at 1060 nm. The modulation depth of the absorber is as high as 4% at 940 and 1060 nm. Furthermore, we found the Modulated probe signal is related to the polarization of the pump laser in pump-probe experiment.

Conductively cooled all-solid-state zigzag slab laser

A diode pumped, Q-switched Nd:YAG zigzag slab laser is developed using passive conduction cooling. Flat-flat and unstable resonators are adopted in this experiment. The 150-mJ multi-mode and 100-mJ single-mode laser outputs with pulse width of 10 ns are achieved, corresponding to optical efficiencies of 19% and 13%, respectively. The experimental result demonstrates that the laser has the property of compact structure, high efficiency, reliability, and high beam quality. The design of laser has a potential application in space environment.

Compact and high-energy diode-side-pumped Q-switched Nd:YAG slab laser system for space application

We develop a compact and high-energy Nd:YAG slab laser system consisting of an oscillator and an amplifier for space applications. The oscillator is a diode-side-pumped electro-optically Q-switched slab laser with a cross-Porro resonator. The KD*P Pockels cell with a low driving voltage of 950 V is used to polarization output coupling. The amplifier is a Nd:YAG zigzag slab pumped at bounces. The maximum output pulse energy of 341 mJ with 13 ns pulse duration is obtained from the system at the repetition rate of 20 Hz and the beam quality factors are M 2 x = 3.1 and M 2 y = 3.5. The beam pointing stabilities of the laser system are 3.05 ?rad in the X-direction and 3.99 ?rad in the Y-direction, respectively.

High average power and short pulse duration continuous wave mode-locked Nd : GdVO4 laser with a semiconductor absorber mirror

Passive mode locking of a solid-state Nd:GdVO4 laser is demonstrated. The laser is mode locked by use of a semiconductor absorber mirror (SAM). A low Nd3+ doped Nd:GdVO4 crystal is used to mitigate the thermal lens effect of the laser crystal at a high pump power. The maximum average output power is up to 6.5 W, and the pulse duration is as short as 6.2 ps. The optic-to-optic conversion efficiency is 32.5% and the repetition rate is about 110 MHz.

Simultaneous Q switching and mode locking with narrow envelope width in a microchip Nd:YVO4 laser with a composite semiconductor absorber

By using a composite semiconductor absorber and an output coupler, we demonstrated a Q-switched and mode-locked diode-pumped microchip Nd:YVO4 laser. With a 350-μm-thick crystal, the width of the Q-switched envelope was as short as 12 ns; the repetition rate of the mode-locked pulses inside the Q-switched pulse was more than 10 GHz. The average output power was 335 mW at a maximum pump power of 1.6 W. Q-switched envelope widths of 21 and 31 ns were also achieved with crystals 0.7 and 1.0 mm thick, respectively.

High energy single-frequency double-pulse hybrid MOPA system

A laser system capable of offering double single-frequency pulses based on a hybrid master oscillator power amplifier structure is presented. Combining the advantages of all-fiber amplifier, bulk-amplifier-chain of Nd:YVO4 and Nd:YAG, this novel design is capable of providing a pair of nanosecond laser pulses at 1064 nm wavelength with a temporal interval of 200 μs. Approximately 13 mJ of output pulse energy is recorded at a repetition rate of 30 Hz. The pulse width is around 20 ns and the spectrum linewidth is 34.1 MHz. The beam quality factor M 2 of output radiation is less than 1.30.

Double-pulse single-longitudinal-mode operation of injection-seeded laser using intracavity phase modulator

A single-longitudinal-mode (SLM) double-pulse injection-seeded neodymium-doped yttrium aluminium garnet (Nd:YAG) laser was established utilizing an RbTiOPO4 electro-optic crystal to modulate the optical path of the slave resonator for generating a resonance condition. The Q-switcher was fired twice during every pump period. This enabled the laser to emit a pair of SLM laser pulses with a time separation of 200 mu s. Each pulse had a pulse energy of 13 mJ at 50-Hz repetition rate, pulse duration of 20 +/- 0.5 ns, and linewidth of 30 +/- 0.3 MHz (within 2 min). The beam quality factor of M-2 was <1.22. A frequency jitter of 1.4 MHz was obtained within 2 min

High efficiency single frequency 355 nm all-solid-state UV laser

A novel conductively cooled high energy single-frequency 355 nm all-solid-state UV laser is presented based on sum-frequency mixing technique. In this system, a pulsed seeder laser at 1064 nm wavelength, modulated by an AOM, is directly amplified by the cascaded multi-stage hybrid laser amplifiers, and two LBO crystals are used for the SHG and SFG, finally a maximum UV pulse energy of 226 mJ at 355 nm wavelength is achieved with frequency-tripled conversion efficiency as high as 55%, the pulse width is around 12.2 ns at the repetition frequency of 30 Hz. The beam quality factor M-2 of the output UV laser is measured to be 2.54 and 2.98 respectively in two orthogonal directions.

1KHz high average power single-frequency Nd:YAG laser

A laser-diode-pumped master oscillator and power amplifier was developed with high efficiency, high average power and high beam quality. The oscillator is an injection-seeding, fiber coupled diode-end-pumped E-O Q-switched Nd:YAG laser, producing single frequency pulse laser output with pulse energy of 8mJ and pulse width of 11ns at a pulse repetition rate of 1KHz，The 1KHz was divided into four chains with frequency of 250Hz, through E-O modulation technology, The power amplifier utilizes conductively-cooling Nd:YAG zigzag slab with two sides’ pump architecture at bounce point. Pulse energy of more than 800mJ with pulse widths of 12.6ns was obtained at repetition rate of 250Hz in every amplifier chain, the frequency-doubled pulse energy of 360mJ when KTP crystal was used was obtained at a repetition of 250Hz.

1047nm 270mJ all solid state diode pumped MOPA at 50 Hz

A diode-pumped nanosecond Master Oscillator Power Amplifier (MOPA) system based on Nd:YLF crystal slabs has been demonstrated. The seed pulses with pulse duration of 11 ns were generated in an EO Q-switched Nd:YLF laser, with single pulse energy of 10 mJ. The 1047 nm signal pulses were amplified in a double-pass amplification system. Maximum output pulse energy of 270 mJ at a repetition rate of 50 Hz has been achieved with effective optical-to-optical efficiency of 14.5%.