We report the design and operation of a novel all-fiber bidirectional passively mode-locked ring laser. An erbium-doped fiber was chosen as the active element in a ring cavity arrangement. A short segment of a fiber taper embedded in carbon nanotubes/polymer composite, acting as a saturable absorber, was used to enable bidirectional mode locking. The laser generates two stable femtosecond pulse trains in opposite directions. A beat note of about 2 MHz, having a bandwidth of less than 2 kHz, is measured when the pulses propagating in opposite directions are (temporally) overlapped at a photodetector. We believe this device will find important applications in precision rotation sensing.

All-fiber bidirectional passively mode-locked ring laser.

We present what is, to the best of our knowledge, the first pulsed deep-blue laser at 456 nm by acousto-optical Q-switching and intracavity frequency doubling of a diode-end-pumped Nd:GdVO4 laser on the 4F3/2 → 4I9/2 transition at 912 nm. When the incident pump power is 36 W, the maximum single pulse energy of 44.1 μJ, pulse duration of 140 ns and peak power of 315 W are achieved at 10 kHz; the maximum average power of 770 mW, pulse duration of 200 ns and peak power of 193 W are obtained at 20 kHz. The fluctuation of the blue output power is less than 2.4% within the given 20 min at the maximum blue output power.

Pulsed 456 nm deep‐blue light generation by acoustooptical Q‐switching and intracavity frequency doubling of Nd:GdVO4

A 8.2 W UV laser was reported with the compact extra-cavity sum-frequency mixing. The IR fundamental frequency source was a high power and high beam quality Q-switched Nd:YVO4 oscillator. 38 W fundamental frequency laser at 1064 nm was obtained at the pulse repetition rate of 450 kHz with the beam quality factors of M2x = 1.27, M2y = 1.21. The type I and type II phase-matched LBO crystals were used as the extra-cavity frequency doubling and mixing crystals respectively. At 38 kHz, 8.2 W UV laser at 355 nm was achieved with the pulse duration of 8 ns corresponding to the pulse peak power as high as 27 kW, and the optical-optical conversion efficiency from IR to UV was 25.6%. The output characteristics of the IR and the harmonic generations varying with the pulse repetition rate were also investigated detailedly.

https://iopscience.iop.org/article/10.1002/lapl.200810102/pdf

Over 8 W high peak power UV laser with a high power Q-switched Nd:YVO4 oscillator and the compact extra-cavity sum-frequency mixing

Up to 1 MHz acousto-optics Q-switching operation was obtained in a grazing-incidence Nd:YVO4 laser. At 500 kHz repetition rate, 17.7 W of output power was obtained with 38 W of pump power when 32.4% transmissivity output coupler was used. The beam quality factors were measured as M2x < 4 in the x-axis direction and M2y < 2 in the y-axis direction. For high sable acousto-optics pulse operation, 5% transmissivity output coupler was used and 9.15 W of output power was obtained at 38 W of pump power. The peak-to-peak instability of pulse amplitude was less than ±3.3% at 489.6 kHz repetition rate.

https://iopscience.iop.org/article/10.1002/lapl.200710025/pdf

Stable acousto-optics Q-switched Nd:YVO4 laser at 500 kHz

A laser-diode-pumped passively-Q-switched intracavity-frequency-doubled Nd:YVO4/YVO4 green laser with a MgO-PPLN and Cr4+:YAG is realized. The dependences of pulse width, pulse repetition rate on incident pump power at different small-signal transmissions of Cr4+:YAG are measured for the green-light pulses. The corresponding pulse energy and peak power are also been obtained.

http://iopscience.iop.org/article/10.1002/lapl.200710112/pdf

LD-pumped passively Q-switched Nd:YVO4/YVO4 green laser with a MgO-PPLN and Cr4+:YAG saturable absorber

A simple LD-end-pumped, passively mode-locked Nd:YVO4 ring laser with bidirectional outputs was demonstrated, and the gyroscopic properties of the ring laser was studied. The laser was continuous wave mode-locked by use of a semiconductor saturable absorber mirror (SESAM), and both clockwise and counter-clockwise outputs are stable laser pulse trains with pulse duration of 64 ps. The continuous wave mode-locking was obtained under pump power as low as 540 mW. The average output power is 50 mW for the counter-clockwise laser and 52mW for the clockwise laser under pump power of 1378 mW. The whole slope efficiency of the ring laser is about 9.4%. The two output pulse trains of the ring laser were combined to study its gyroscopic properties. The beat frequency of the pulsed solid-state laser gyro versus the rotation rates follows the Sagnac formula. The laser gyro has a large dead band of 6-8 dec/s, which was believed to be caused by the long pulse duration and the colliding of the opposite pulses on the SESAM.

https://iopscience.iop.org/article/10.1002/lapl.200610079/pdf

Bidirectional operation and gyroscopic properties of passively mode-locked Nd:YVO4 ring laser

A miniature, high repetition rate, short pulse width acousto-optically Q-switched Nd:YVO4 laser in fundamental mode is presented. Miniature solid-state lasers have the characteristics of short cavity length and small mode area in the cross section, which, on the one hand, benefits high gain, high repetition rate and short pulse width, on the other hand, makes it difficult to achieve high mode-matching efficiency and causes higher order modes oscillation. The thermal lens in Nd:YVO4 is treated as thick lens under high pump intensity. The mode-matching efficiency is analyzed with the thermal lens being equivalent to a thin lens array. In high repetition rate Q-switching operation, 3.6 ns pulses at 500 kHz repetition rate with 20 mm cavity length and 4.1 kW peak power are achieved, without active control of pump beam quality. The laser beam quality factors were measured to be Mx2 = 2.03, My2 = 2.46. By improving the pump beam quality and utilizing the optimal pump beam waist radius and location, the mode-matching efficiency and laser beam quality are improved. 4.0 ns pulses at 500 kHz with 2.5 kW peak power are produced. The beam quality factors were measured to be Mx2 = 1.31, My2 = 1.43.

https://iopscience.iop.org/article/10.1002/lapl.200710127/pdf

A fundamental mode miniature acousto‐optically Q‐switched Nd:YVO4 laser with short pulse width at high repetition rates

An one-end-pumped Nd:YVO4 laser with fiber- coupled diode is designed. The mode matching between pump mode and laser mode is analyzed, and the optimum mode matching coefficient is obtained by optimizing the pump mode. Based on the optimal pump mode, a 14.2W TEM00 mode CW laser is obtained with a optical-optical efficiency of 55.7% at 1064 nm, with M2 factors of M2x = 1.16, M2y = 1.15. In Q-switching operation, 13.8W average power at a pulse repetition rate of 200 kHz is produced, with a stability of pulse peak value < 5%.

https://iopscience.iop.org/article/10.1002/lapl.200710109/pdf

A high efficient one-end-pumped TEM00 laser with optimal pump mode

A high power, dual-end-pumped Nd:YVO4 laser with a MOPA configuration was stably Q-switched at repetition rate up to 500 kHz. The thermally bonded Nd:YVO4 crystal was used in our experiment. In acousto-optically Q-switching operation at repetition rate of 500 kHz, 35 W average power was produced by the oscillator, with optical-optical efficiency of 41.7%. 108 W average power was obtained by a master oscillator power amplifier (MOPA) configuration including two amplifier stages, corresponding to the total optical-optical efficiency of 42.2%. The pulse duration was 48 ns, with a stability of pulse peak value <2.5%. The beam quality was better than two-times diffraction-limit (M2x=1.99, M2y=1.76).

A 108 W, 500 kHz Q-switching Nd:YVO4 laser with the MOPA configuration.

Gain-switched Nd:YAG microchip lasers have produced 1 MHz repetition rate, single-frequency pulses with a pulse width of 32 ns. This is, to our knowledge, the highest repetition rate obtained in a single-frequency gain-switched solid state laser. The laser peak power and pulse width are mainly determined by the peak power of the pumping pulse and independent of the pulse repetition rate. Single-frequency operation is realized by temperature-tuning of the laser wavelength to the peak of the gain profile. Gain-switching at high repetition rates significantly improves the optical efficiency of the device.

http://iopscience.iop.org/article/10.1002/lapl.200710034/pdf

Y. Wang

Papers

Bidirectional operation and gyroscopic properties of passively mode-locked Nd:YVO4 ring laser

A fundamental mode miniature acousto‐optically Q‐switched Nd:YVO4 laser with short pulse width at high repetition rates

A high efficient one-end-pumped TEM00 laser with optimal pump mode

A 108 W, 500 kHz Q-switching Nd:YVO4 laser with the MOPA configuration.

1 MHz repetition rate single-frequency gain-switched Nd:YAG microchip laser