Electro-optic Q-switch Research Articles

Double-crystal LiTaO3 electro-optic Q-switch with excellent performances

Double-crystal LiTaO3 electro-optic Q-switch with excellent performances

Electro-optical Q-switched laser array with one lamp pumping six Nd:YAG rods for programmable laser reconstruction in space-power-time domains

We report a novel laser array with one lamp pumping six Nd:YAG rods for programmable laser reconstruction in space-power-time domains. A sextuple ellipse pump cavity is proposed, and this scheme permits one xenon flash lamp with advantageously cylindrical pumping characteristics to simultaneously efficiently pump multiple Nd:YAG lasers in a laser system. The experimental setup was designed, and further experiments were carried out. The laser array can stably operate at a pumping rate of 1 Hz-10 Hz. Each laser beam of the six laser outputs has a divergence angle of less than 1.7 mrad, an output pulse of greater than 208 mJ, and a pulse width of approximately 10 ns, corresponding to a pulse peak power of approximately 20 MW. The laser array has a total output energy of 1.53 J at an electrical input of 93.3 J, corresponding to an overall electro-optical conversion efficiency of 1.64 % and an electro-optical slope efficiency of 3.17 %. Finally, laser array output pulses coded modulation in the space-power-time domains are achieved by electro-optical Q-switching. Therefore, the laser array provides the capability for programmable laser reconstruction in the space-power-time domains in a laser system for multipurpose applications, such as energy-tailored material processing, coded pulse laser ranging for improved signal-to-noise ratio (SNR), active optical remote sensing and scientific research.

Electro-optically Q-switched Tm/Ho: YLF laser via polarization separation between the Tm laser and Ho laser in a coupled cavity

We demonstrate electro-optical Q-switching in a direct 792 nm diode-pumped composite Tm/Ho:YLF laser. Spectral analyses on Tm:YLF and Ho:YLF crystals were studied in detail. A coupled cavity consisting of two identical bi-concave sub-cavities was developed for polarization separation and ensuring rigorous mode-matching between the σ-polarized Tm:YLF and π-polarized Ho:YLF lasers intra-cavity. Together with the negative thermal-optical coefficient with weak thermal lensing of the fluoride host, near diffraction limited Q-switched Ho laser with maximum average power of 389 mW and peak power of 3.3 kW at 2051 nm were obtained at pulse repetition rates of 5 kHz and 1 kHz respectively, which benefits a compact, accessible pulsed seed source at 2.1μm.

Electro-optically Q-switching of dual-diode-pumped Ho-doped lutetium vanadate laser

In this paper we report on a continuous-wave and electro-optically (EO) Q-switched Ho-doped lutetium vanadate (Ho:LuVO4) laser dual end-pumped by two laser diodes at 1.94 µm. Under continuous-wave regime, a maximum output power of 18.8 W at 2058.1 nm was achieved with absorbed pump power of 44.7 W, corresponding to a slope efficiency of 54.1 % with respect to the absorbed pump power. By using a langasite (La3Ga5SiO14, LGS) crystal as the EO Q-switch, at a pulse repetition frequency of 3 kHz, the EO Q-switched Ho:LuVO4 laser produced a maximum pulse energy of 3.2 mJ and a minimum pulse width of 8.9 ns, resulting in a peak power of 358.8 kW.

Growth, spectroscopic, and 2.7-μm Q-switched laser properties of Cr,Er:YAP crystal by xenon-lamp pumping

We demonstrate a high-peak-power and narrow pulse mid-infrared (MIR) laser with xenon-lamp pumping and La3Ga5SiO14 (LGS) Q-switching on the Cr,Er:YAP crystal grown by Czochralski method. X-ray powder diffraction and x-ray rocking curves suggest the crystal has high crystalline quality. Segregation coefficients of the Cr3 + and Er3 + in the as-grown Cr,Er:YAP crystal are 4.96 and 1.07, respectively. The absorption and fluorescence spectra indicate that the Cr,Er:YAP crystal is a promising material for MIR laser by xenon-lamp pumping. The fluorescence lifetimes of the upper (I11/24) and lower (I13/24) laser levels are 0.86 and 3.57 ms, respectively. A maximum energy of 632 mJ is acquired at 5 Hz by xenon lamp pumping. By the LGS electro-optic Q-switching technology, single pulse energy of 148.6 mJ is achieved at 5 Hz with a pulse width of 35.4 ns and peak power of 4.2 MW. The results show that the LGS Q-switched Cr,Er:YAP crystal pumped by xenon lamp possesses potential application as a short-pulse and high-energy laser device.

Efficient electro-optically Q-switched Ho:GdTaO4 laser recycle-pumped by a wavelength-narrowed laser diode

We present a diode-pumped electro-optically (EO) Q-switched Ho:GdTaO4 (Ho:GTO) laser. The langasite (La3Ga5SiO14, LGS) crystal was utilised as the EO Q-switch. With a repetition rate of 2 kHz, a maximum pulse energy of 1.46 mJ at 2067.6 nm and a minimum pulse width of 12 ns were realised at an absorbed pump power of 17.1 W, corresponding to a maximum peak power of as high as 121.3 kW. Moreover, at the maximum average output power, the beam quality factors of the diode-pumped EO Q-switched Ho:GTO laser were estimated to be 1.66 in the x-direction and 1.52 in the y-direction.

Performance of a 968-nm laser-diode side-pumped, electro-optical Q-switched Er,Pr:YAP laser with emission at 2.7 μm

We demonstrate the performance of a 968-nm laser-diode (LD) side-pumped Er,Pr:YAP laser in free-running and electro-optical (EO) Q-switched modes with emission at 2.7 μm, respectively. In the free-running mode, a maximum power of 11 W is achieved at a working frequency of 150 Hz and a pulse width of 200 μs, corresponding to the single pulse output energy of 73.3 mJ and slope efficiency of 13.3%. In the EO Q-switching mode, a giant pulse laser is obtained with pulse energy of 20.5 mJ, pulse width of 61.4 ns, and peak power of 0.33 MW at the highest working frequency of 150 Hz, corresponding to the energy extraction efficiency of 71.4%. In addition, dual-wavelength laser at 2713 and 2732 nm and beam quality factors Mx2/My2 of 6.62/6.66 are measured, respectively. The results indicate that a 2.7-μm laser with a high repetition rate and high peak power can be realized through LD side-pumped and EO Q-switched Er,Pr:YAP crystal.

Mid-infrared 2.8 µm band laser output and pulse modulation

The mid-infrared 2.8 µm band laser has broad application value and development prospects in the fields of medicine, biology, military and remote sensing. At present, MIR 2.8 µm band lasers are mainly produced by solid-state lasers, fiber lasers, semiconductor lasers and chemical lasers, etc. The pulse modulation methods for this band lasers include electro-optical Q-switching, acousto-optic Q-switching, passive Q-switching, mechanical Q-switching and FTIR Q-switching, etc. The main technical difficulty lies in the discovery and utilization of high-performance and high-quality Q-switching new materials. In this paper, the output methods and pulse modulation methods of 2.8 µm band laser are summarized, and its development situation and existing problems are analyzed and prospected.

Pulse peaks synchronize dual-wavelength laser based on Q-switch delay trigger

In this paper, an all-solid-state Nd:YVO4 laser with peak synchronize output of 1064/1342 nm dual-wavelength Q-switched pulse is designed. Double-cavity structure with single Nd:YVO4 crystal and double RbTiOPO4 (RTP) electro-optic (EO) Q-switch is built. At repetition frequency of 10 kHz, taking the trigger time of EO Q-switch at 1342 nm as reference, at the delay time of EO Q-switch at 1064 nm as 1.3 μs, the pulse peak synchronize dual-wavelength laser is obtained, and the pulse power is 1.63 W and 1.63 W with the width is 55.64 ns and 105.2 ns respectively.The beam quality is Mx2=1.61,Mx2=1.64 and Mx2=1.43,My2=1.54, respectively.

Dual-pulse actively Q-switched fiber laser based on EOM and sagnac loop

In this paper, a multi-wavelength fiber laser based on electro-optical Q-switching is proposed to achieve stable dual-pulse output. The addition of a tunable filter outside the cavity to filter out different wavelengths separately proves that the dual-pulse is generated due to the time delay between different wavelengths. When the input power is 160 mW, we observed single pulses with pulse widths of 28.94 μs and 23.25 μs were obtained at 1544.11 nm and 1546.77 nm, respectively. We changed the average output power and pulse width by changing the input power or frequency of the external modulated signal, and simultaneously discussed the effect of the modulation amplitude of the electro-optical modulator (EOM) on the output of dual-pulse.

Design of Nanosecond Pulse Driver Circuit

The laser can achieve high peak power pulse output by electro-optic Q-switch technology. Aiming at the problem of how to achieve Q-switch output with ns level front and kV level amplitude on 100kΩ large load, a method of pulse output by using avalanche conduction state of triode is proposed. By using the 11 stages pulse forming circuit, the DC power supply voltage can be greatly reduced, and the selected devices can work normally under the condition of meeting the first stage derating standard, in order to improve the stability. The key factors affecting the parameters of the output pulse, such as amplitude, pulse width, frequency, leading edge and trailing edge, are analyzed and verified by experiments. Using +150V DC power supply, the experimental results show that the pulse driving source circuit designed in this paper can output a half height width of 12.6ns and an amplitude of 1500V Q-switch regulating signal on a 100kΩ load.

1064/1342 nm dual-wavelength double electro-optical Q-switched Nd:YVO4 laser

An all-solid-state Nd:YVO4 laser producing dual-wavelength of 1064/1342 nm was designed, which took a plan of double RTP (RbTiOPO4) electro-optic Q-switch of 1064 nm and 1342 nm, by controlling the voltage of double RTP crystals to control the output laser power ratio of dual-wavelength. When the repetition rate is 10 kHz, the 1064/1342 nm dual wavelength laser output with 1.6/1.6 W, power ratio of 1:1, and basically overlapping pulse peak time is obtained by changing the crystal voltage.

Compact low-voltage electro-optic Q-switch made of LiNbO3.

This work presents a compact LiNbO3 (lithium niobate, LN) electro-optic (EO) Q-switch with a lower driving voltage than the conventional LN Q-switches. By using non-direct cuts of a certain crystallographic orientation, a LN crystal is used both as a quarter-wave plate (QWP) and a pockels cell in a laser cavity. Through theoretical calculations and experiments, we have determined the optimized crystal orientations with low quarter-wave voltages (QWV). A set of compact LN EO Q-switches were prepared and used successfully in the pulse-on mode in a Nd:YAG laser. The Q-switched laser outputs are comparable to those obtained by using a conventional Z-cut LN Q-switch with a QWP. The QWV of the Q-switch with the optimized crystal orientation is 600V lower than that of the Z-cut LN Q-switch.

In-band pumped, high-efficiency LGS electro-optically Q-switched 2118 nm Ho:YAP laser with low driving voltage

An in-band end-pumped LGS electro-optically (EO) Q-switched Ho:YAP laser has been investigated and demonstrated. The LGS crystal based on EO modulator was designed to operate in pulse-on mode with a 1/4 wave voltage of 2400 V, which was the lowest driving voltage at 2 μm wavelength for LGS crystal as far as we know. Under continuous-wave (CW) regime, a maximum average output power of 6.5 W was obtained from the Ho:YAP laser with a slope efficiency of 50.6% when an incident pump power was 16 W. When running in EO Q-switching regime, a maximum output power of 4 W was obtained with a single pulse energy of 1 mJ and a pulse width of 33 ns at a repetition rate of 4 kHz. At the repetition rate of 2 kHz, the maximum single pulse energy of 1.5 mJ and the shortest pulse width of 23 ns were achieved, corresponding to a pulse peak power of as high as 65 kW.

Nd3+ : YAG laser based on the 4F3/2 → 4I13/2 secondary transition with a phase-conjugate electro-optically Q-switched open multiloop cavity

Lasing on the 4F3/2 → 4I13/2 secondary transition (λ = 1.34 μm) in a Nd3+ : YAG laser with phase conjugation by four-wave mixing directly in the active laser medium was experimentally studied in the regime of electro-optic Q-switching of an open multiloop cavity. The use of an electro-optic Q-switch with a controllable delay of its opening made it possible to increase the amplitude and temporal stabilities of the output laser parameters. The maximum laser pulse energy was 100 mJ at a pulse duration of 120 ns. The phase-conjugate radiation divergence was 0.8 mrad at beam quality . Nonlinear optical conversion of 1.34 μm laser radiation to visible radiation was achieved experimentally. Second and third harmonic generation at wavelengths of 0.67 and 0.446 μm with conversion efficiencies of 25 % and 8 %, respectively, was demonstrated.

Langasite electro-optic Q-switched [formula omitted] laser with high repetition rates and reduced driven voltages

Mid-infrared electro-optic Q-switched lasers with high repetition rates have many vital applications. However, the required voltage of electro-optic Q-switching is proportional to the wavelength leading to the severe piezoelectric ring effect, which limits its developments especially with high repetition rates. Based on the rate equation, this work designs a Langasite (LGS) electro-optic Q-switched laser with high repetition rates at 2μm by balancing the gain and loss in the cavity. The driven voltage determines the rotation of the polarization corresponding the loss in the cavity, and the gain depends on the incident pump power and repetition rate. By theoretical calculation, the driven voltage used in the high repetition rates is reduced to be 3.9 kV, which is 45% lower than the quarter-wave voltage. We demonstrated the LGS electro-optic Q-switched 2μm laser with a repetition rate of 200 kHz and pulse width of 5.52 ns. To the best of our knowledge, this work presents the highest repetition rate in the electric–optic Q-switched laser at 2μm and should be helpful for the design of Q-switched lasers with high repetition rates.

True zero-order ADP crystal waveplate with millimeter thickness

For the first time, a series of true zero-order waveplates with millimeter thicknesses are designed and fabricated from ADP crystal. The basic principle is that the birefringence of crystal varies continuously with respect to the propagating direction of light wave. The characteristic parameters including angle, wavelength, temperature sensitivities are measured by the polarization interference method, at the same time the related theoretical analysis is given. The linear polarization rotation and add-voltage electro-optic Q-switching are realized with ADP half-waveplate (HWP) and quarter-waveplate (QWP), respectively. As a new-type polarization element with low-cost, large size and high optical damage threshold, true zero-order ADP waveplate is possible to find important applications in large-aperture and high-power laser systems.

Research on laser interference lithography based on mutual injection dual-output laser

In this paper, a laser interference lithography technology which based on the mutual injection dual-output laser is innovatively developed. The experimental study of two beams of laser interference lithography on the material surface is carried out by using two beams of phase locking and the same frequency output. In order to solve the problems caused by beam splitter in laser interference lithography in the past, such as unequal energy, high loss and unsatisfactory interference pattern. U cavity structure is constructed by using two pump gain dielectric devices and two perpendicular 45° total reflection mirrors in the experiment. Outputing two parallel beams with pulse width of 8.2 ns and energy of 186 mJ after intracavity electro-optic Q-switching. Then using two other reflection mirrors to make the two beams of light reflection convergence onto the surface of the silicon material for interference lithography. When the angles of two beams are 12°, 9°and 6°, the clear interference fringes with periods of 5.1 μm, 6.9 μm and 10.4 μm are obtained. The interference photolithography using a dual-output laser with mutual injection has a positive significance for micromachining technology, and it can be extended to multi-channel laser interferometry processing using multi-channel mutual injection lasers.

Preparation, Characterization and Application of Ultrathick True Zero-Order KDP Crystal Waveplates

In crystal space, the birefringence varies continuously with respect to the propagating direction of the light wave. By utilizing this property, we design and fabricate a series of ultrathick true zero-order (TZ) waveplates based on KH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> PO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals with different orientations for the first time. When the cutting angle θ is 5°, the thickness d of the 1,064-nm TZ half-wave plate (HWP) is 2.0 mm, which is 33 times larger than that of the traditional quartz TZ device (~0.06 mm). At a temperature of 30 ° C, its extinction ratio for the Nd:YAG pulse laser reaches 1,970:1. When the temperature increases to 80 ° C, the extinction ratio remains above 1,000:1. When the extinction ratio decreases to 200:1, the angular acceptance bandwidth and wavelength acceptance bandwidth are determined to be 0.3° and 45 nm, respectively. With the ultrathick TZ HWP and a quarter-wave plate (QWP), efficient type-II frequency doubling and electro-optic Q-switching, respectively, are achieved. As a famous optical crystal, KDP has been popularly used as a frequency converter, a laser Q-switcher, an electro-optic modulator, and a solid-state light valve display. This paper disclosure a new application of this traditional material, i.e. large size, high mechanical strength, low-cost, and high-quality TZ crystal waveplates. Such components have wide application prospects in various optical and laser systems which need controlling the polarization of light.

RTP voltage-increased electro-optic Q-switched Ho:YAG laser with double anti-misalignment corner cubes

We describe a pulsed Ho:YAG laser with double anti-misalignment corner cubes that uses an RbTiOPO4 crystal as the electro-optic Q-switch. Two polarizers coated with high reflectivity coatings for the s-polarized light at the laser wavelength were employed to achieve linearly polarized laser output. The maximum s-polarized output power of 2.95 W at 2091.3 nm was obtained under the absorbed pump power of 12.9 W by increasing the voltage applied on RbTiOPO4 electro-optic crystal to 1000 V. The corresponding optical-to-optical conversion efficiency was 22.9% and the slope efficiency was 67.9%. For the Q-switched operation, the pulse energy of Ho:YAG laser was 7.8 mJ with a pulse width of 57 ns at the repetition rate of 100 Hz, resulting in a peak power of 136.8 kW. The beam quality factor M2 of Ho:YAG laser was 1.33.