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

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

We report on a compact high-power passively mode-locked Nd:LuVO4 laser by use of semiconductor saturable absorber mirror (SESAM). The laser generated clean CW mode-locked pulses with an average output power of 8.6 W, a repetition rate of 144 MHz, and a pulse duration of 13.2 ps. By employing a three-mirror cavity scheme, the laser setup has only a footprint size of 70×30 cm2, which can be packaged to a portable laser system for convenient applications.

High-power passive mode locking of a compact diode-pumped Nd:LuVO4 laser

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 simple cw mode-locked solid-state laser, which is end-pumped by a low-power laser diode, was demonstrated by optimizing the laser-mode size inside the gain medium. The optimum ratio between mode and pump spot sizes inside the laser crystal was estimated for a cw mode-locked laser, taking into account the input pump power. Calculation and experiment have shown that the optimum ratio was about 3 when the pump power is 2 W, which is different from the value regularly used in passively mode-locked solid-state lasers. This conclusion is also helpful in increasing the efficiency of high-power ultrashort lasers. (C) 2006 Society of Photo-Optical Instrumentation Engineers.

End-pumped continuous-wave passively mode-locked Nd:YVO4 laser with low pump power

This paper reports an experimental research on the stability of bidirectional outputs and multi-longitudinal mode interference of laser diode end-pumped Nd:YVO4 solid-state ring laser (DPSSL). The bidirectional, multi-longitudinal and TEM00 mode continuous wave outputs are obtained and the output powers are measured and their stabilities are analyzed respectively. The spectral characteristic of the outputs is measured. The interfering pattern of the bidirectional longitudinal mode outputs is obtained and analyzed in the condition of the ring cavity with rotation velocity. The movement of the interfering fringe of the multi-longitudinal modes is very sensitive to the deformation of the setup base and the fluctuation of the intracavity air, but is stationary or
randomly dithers when the stage is rotating.

Experimental research on the stability and the multilongitudinal mode interference of bidirectional outputs of LD-pumped solid state ring laser

A deep self modulation output in the diode pumped Bi-directional CW Nd:YVO4 ring laser is observed. The self-modulation has multiple styles and in certain style it shows the distinctness sensitive of rotation. The phenomenon in our experiment is reported in detail. There will be a potential application to the rotation sensor or gyroscope.

Rotation sensitivity self-modulation in bi-directional CW Nd:YVO4 ring laser

Simultaneous passive Q-Switching and mode locking at low pump power was observed in a Laser Diode (LD) pumped Nd3+:YVO4-Cr4+:YAG laser, detailed studies were experimentally carried out. A fiber-coupled LD with maximum output power of 2 W is used as pump source. In a 50cm long cavity, the repetition rate of obtained mode-locking pulse train is about 300MHz, and the pulse duration was estimated to be at sub-nanosecond level. The repetition rate of the passive Q-Switched pulse train varies from 10kHz~130kHz with the increasing of the pump power. It was found that the threshold of incident pump power to generate mode-lock in such a laser is dependent on the position of Cr4+:YAG crystal inside the cavity. Select proper Cr4+:YAG as saturable absorber and optimize its position, simultaneous Q-Switching and mode-locking occurred in the Nd3+:YVO4 laser at pump power as low as about 200 mW. The experimental result demonstrates the possibility of obtains ultra short optical pulse in a simple and low cost way, which is of great interest in some applications.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Hongyun Qiu

Papers

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

End-pumped continuous-wave passively mode-locked Nd:YVO4 laser with low pump power

Experimental research on the stability and the multilongitudinal mode interference of bidirectional outputs of LD-pumped solid state ring laser

Rotation sensitivity self-modulation in bi-directional CW Nd:YVO4 ring laser

Study on simultaneous passive Q-switching and mode-locking at low-pump power in a LD-pumped Nd3+:YVO4-Cr4+:YAG laser