Polarization-dependent nonlinear absorption in the Co2+:MgAl2O4 crystal was investigated by the pump-probe technique. The nonlinear transmission curves of the [100]-cut Co2+:MgAl2O4 crystal for the linear polarized probe light were measured experimentally, when the crystal was excited by a linear polarized pump light. The measurement results showed that the transition into the near-infrared (NIR) absorption band was not only polarized along the C3 local symmetry axis, but also along the direction perpendicular to the C3 axis. And the absorption intensity of the latter transition was much weaker than the former. The structural model of Co2+ centers in the MgAl2O4 crystal, in which the Co2+ ion and surrounding O2- ions formed a tetrahedron deformed along the C3 local symmetry axis, was proposed. This structural model allowed us to explain the anisotropy of nonlinear absorption in the Co2+:MgAl2O4 crystal.
Room-temperature cascaded mid-infrared (MIR) pulsed laser output in Er:YAG crystal is reported. The 1469nm characteristic wavelength of the cascade emission is observed. The characteristic wavelength of the excited-state absorption (ESA) is determined as 1676nm. An Er:YAG crystal with concentration of 10at.% is adopted to compare the laser output energy in the cascaded and non-cascaded configuration. The maximum single pulse energy of MIR laser increases from 1.04mJ (non-cascade) to 1.51mJ (cascade), corresponding to a ratio of 45.2%. The “cyclic cascade” is considered to be the mechanism responsible for the laser performance optimization. The experimental results confirm the existance of cascade at room temperature in Er:YAG crystal. Moreover, cascade is helpful to improve the single pulse energy of MIR laser.
We present a novel structure of planar waveguide for Yb:YAG laser amplifiers allowing large absorption length. The structure parameters of the planar waveguide were optimized using an 3D amplification model. The performance of the optimized planar waveguide laser amplifier was simulated, and a comparison between the cases with and without considering pump saturation was carried out. The simulated results show that a high pump absorption efficiency and optical-to-optical efficiency can be expected in addition to a good absorption uniformity. The seeder power is scaled from 200W to 7000W, the corresponding pump absorption and optical-to-optical efficiencies are 98.6% and 68%, respectively. The thermal stress of the designed planar waveguide is analyzed theoretically, the results show that the pump power of 10kW is available without the fracture risk.
Room-temperature cascaded mid-infrared (MIR) pulsed laser output in Er:YAG crystal is reported. The 1469nm characteristic wavelength of the cascade emission is observed. The characteristic wavelength of the excited-state absorption (ESA) is determined as 1676nm. An Er:YAG crystal with concentration of 10at.% is adopted to compare the laser output energy in the cascaded and non-cascaded configuration. The maximum single pulse energy of MIR laser increases from 1.04mJ (non-cascade) to 1.51mJ (cascade), corresponding to a ratio of 45.2%. The “cyclic cascade” is considered to be the mechanism responsible for the laser performance optimization. The experimental results confirm the existance of cascade at room temperature in Er:YAG crystal. Moreover, cascade is helpful to improve the single pulse energy of MIR laser.
Polarization-dependent nonlinear absorption in the Co2+:MgAl2O4 crystal was investigated by the pump-probe technique. The nonlinear transmittance curves of the [100]-cut Co2+:MgAl2O4 crystal for the linear polarized probe light were measured experimentally, when the crystal was excited by a linear polarized pump light. The measurement results showed that the transition into the near-infrared (NIR) absorption band was not only polarized along the C3 local symmetry axis, but also along the direction perpendicular to the C3 axis. And the absorption intensity of the latter transition was much weaker than the former. The structural model of Co2+ centers in the MgAl2O4 crystal was proposed, in which the Co2+ ion and surrounding O2- ions formed a tetrahedron deformed along the C3 local symmetry axis. This structural model allowed us to explain the anisotropy of nonlinear absorption in the Co2+:MgAl2O4 crystal.
We present a novel structure of planar waveguide for Yb:YAG laser amplifiers allowing large absorption length. The structure parameters of the planar waveguide were optimized using an 3D amplification model. The performance of the optimized planar waveguide laser amplifier was simulated, and a comparison between the cases with and without considering pump saturation was carried out. The simulated results show that a high pump absorption efficiency and optical-to-optical efficiency can be expected in addition to a good absorption uniformity. The seeder power is scaled from 200W to 7000W, the corresponding pump absorption and optical-to-optical efficiencies are 98.6% and 68%, respectively. The thermal stress of the designed planar waveguide was analyzed theoretically, showing that the pump power of 10kW is available according to the stress fracture limit.
The saturable absorption properties of Co2 + : MgAl2O4 crystals in three different cutting directions were studied experimentally. The characteristic of the transmission of polarized incidence light through the [100], [110], and [111]-cut Co2 + : MgAl2O4 single crystal was investigated. The [110]-cut crystal had the maximum transmittance observed. We conclude that using a [110]-cut Co2 + : MgAl2O4 crystal to form a Co2 + : MgAl2O4 / Er,Yb:glass passive Q-switched microchip laser can improve the output characteristics of the laser, such as pulse energy and extinction ratio without changing any other parameters.
LD pumped erbium glass passively Q-switched 1.5μm microchip laser is a research hotspot in laser ranging and imaging application. The high repetition rate microchip laser has serious thermal effect problem, so it is difficult to work stably for a long time. This paper reports a passively Q-switched 1535nm laser with erbium-ytterbium co-doped phosphate glass using double-ended adhesive-free bonding technology. The laser combines YAG crystal, Er3+/Yb3+: glass and Co2+[/sup : MgAl2O4 by bonding to improve the thermal effect of the laser. At the same time, by optimizing the size of the pump light spot, the initial transmittance T0 of the saturable absorber and the reflectivity R of the output mirror, the utilization efficiency of the pump light is improved and the influence of thermal effect is further reduced. The results show that the laser output with the repetition rate of 1kHz, the single pulse energy of 40μJ, pulse width of 8ns, peak power of 5kW, beam quality of 1.4, can output stably for a long time.
It’s an effective method to produce mid infrared laser that CO2 laser frequency doubling by using quasi-phase-matched (QPM) crystal. The main problem in the preparing diffusion bonding crystal is controlling the defects. In this paper, the bonding temperature, pressure, time and other parameters are optimized to reduce the interface loss. When the bonding temperature is 700°C , the bonding pressure of 0.27kg/mm2, a 49 layer QPM GaAs crystal was fabricated, and the interface loss of the single layer was less than 0.13%. Using the prepared QPM-GaAs crystal for second harmonic generation, 23% SHG efficiency was achieved in a CO2 laser with 10.56μm wavelength, 219 mJ pulse energy and 110 ns pulse width.
Laser diode end-pumped passively Q-switched Nd:YAG/Cr4+:YAG micro lasers, with short pulse width, high repetition rate, high peak power and compact structure, have widely applications in laser mico processing, optical communication, laser radar, medical and other fields. But its beam quality is not excellent because of short resonant cavity, thermal effect of crystal, and pump laser. The beam quality is promoted in this paper by compressing the pump beam size and confirming the best position of pump beam focus in crystal. The repletion rate of laser is 20kHz. The output single pulse energy is 18.2μJ and pulse width is 1.23ns. The beam quality of laser is M2=1.18.
In this paper, on the basis of the theory of quasi phase matched, CO2 laser spectrum corresponding to GaAs chip within the scope of the matching length was calculated. Through the numerical solution of the wave equation, the relationship between power density of pump laser and frequency doubling conversion efficiency was given under the different crystal length conditions. By adjusting the CO2 laser gas mixture components, we optimized the pump laser pulse wave to meet the requirements in the temporal distribution of the pump light. On the other hand, we optimize the output beam mode to meet the pump light distribution in space requirements. We use the tunable TEA CO2 laser as the light source to pump quasi phase matching GaAs crystal, When the pump wavelength is changed from 9.23μm to 10.75μm range, the conversion efficiency of frequency doubling output is greater than 4%, when the pump wavelength is 10.68um, the frequency doubling efficiency reached 6.58%.
A high average power and high beam quality nanosecond laser is presented that is based on CW diode side-pumped Nd:YVO4 grazing-incidence slab amplifier. A TEM00, passively Q-switched diode-pumped Nd:YAG laser as the seed laser, generating a M2 ≈1.3 beam train of 0.25W, 2.3ns pulses with adjustable repetition rate in the range 5-20kHz. After double-pass amplification, more than 20W of output power with a beam quality of M2 ≈1.4 is obtained at an optical-optical efficiency of 35%. The high brightness of this laser system seems ideal for nonlinear optics and laser processing applications.
In this paper a Xenon-lamp-pumped four rods pulsed Nd:YAG laser is presented. The influence of offset angle of
Nd:YAG rods and thermal stable regions in the resonator have been analyzed theoretically, and tolerance of offset angle
and is given. A plane-plane symmetrical resonator has been used in the experiment, and the distance between two
neighbor rods is two times of that between the mirrors and rods. While input electric power is 58 kW and the duty cycle
is 17%, an output laser with an average power of 2026 W, a peak power of 11.9 kW, maximum single pulse energy of 60
J and a beam parameters product of 24.5 mm×mrad has been obtained. The electro-optical conversion efficiency is
3.49 %, and instability of the laser is less than 2 %.
A method computing the absorption efficiency with the difference between pump power entering the thin disk and pump
power transmitted through the disk is introduced. Compared with directly computing the absorbed power, the method
presented here needs much less computation to achieve the same accuracy, making it possible to compare much more
absorption efficiency values at higher accuracy with a few parameters varied within certain ranges. Nonabsorption loss
values were calculated with absorption coefficient, array distance and round disk radius varied within certain ranges.
Results of calculation showed that the nonabsorption loss generally increases with increasing array distance, decreases
with increasing round disk radius and decreases with increasing absorption coefficient. The method introduced by this
paper presents a theoretical reference for the optimal design of thin disk lasers.
This paper introduces a novel kind of E-O Q-switched Nd:YVO4 compact laser with ultra-narrow pulse width. In this
paper, the general equations describing Q-switched laser operation are given and the factors about cavity length, laser
gain medium, the loss inner resonator and pump energy to influence the laser pulse width are analyzed theoretically. These parameters greatly optimized experiment. The fiber-coupled laser-diode end-pumped laser we developed
simplifies the conventional structure of E-O Q-switched lasers. The cavity length is effectively reduced to 19mm to narrow the pulse width. The pulse width of 1.049ns is obtained and the single pulse energy reaches to 0.32mJ. This 1
nanosecond laser has the advantage in reliable and outstanding performance with simplified structure. Most importantly, we investigated the performance of an innovative RTP crystal in the Q-switched laser with high repetition frequency. It was experimentally proven that this narrow pulse width laser can operate with high repetition frequency because of the
novel Q-switched crystal RTP with great performance. Both theoretical analysis and experiment data demonstrate that sub-nanosecond pulses can also be produced with E-O Q-switching technique. Thus, this technique can be widely applied.
According to the requirement of high power laser beams and beam focus diagnostic instrument for measuring laser transverse intensity distribution, a new method of CO2 laser rapid detecting by pyroelectric detector is given. The rapid response of photoelectric transformation with large enough gain is obtained. The response time is shorter than an order of magnitude comparing with common method. The detector can operate in normal room temperature, and need no cooling set. The photoelectric transformation system satisfies the measurement requirement of high power laser density cross-section distribution. The method can be employed for application concerning with rapid response of pyroelectric detector.
This paper reports on the characterization and analysis of drilling with a novel high power acousto-optical Q-switch pulse laser. The laser is a flash-lamp pumped pulse Nd:YAG laser which can be used in the free running mode with repetition rates up to 10Hz. Additionally it is possible to modulate these pulses using acousto-optical modulator which enables a burst between 1 and 10 Q-switch pulses with a duration of typically 200ns during each flash-lamp pulse. The repetition rate of the burst is 5kHz-50kHz, the pulse energy is 30-8OmJ, and the peak power is more than 400kW with a beam parameter product of about 5mm mrad. The drilling process and the combination of different repetition rate of the bursts enables drilling 2.5mmthick Cu and Ni-alloy for 0.2mm micro-hole. The recast layer is nanower. Oxidation of the walls of the hole is prevented by a high-pressure inert gas.
Using the method of rotating hollow probe, the measuring system which can directly measure laser transverse intensity distribution of high power laser beams/focus for laser processing is studied. The mathematical and physical models of measured laser beams/focus propagation in hollow probe are founded. According to the calculation, the system parameters, including pinhole diameter of hollow probe, dimension of propagation channel, dot number of sampling, are discussed. A new measuring system is designed. The measuring of high power laser beams/focus by this system is realized. The calculation results are satisfied with the measuring results. The instrument can measure CO2 and YAG laser, measured power larger than 10kW, maximal measured power density up to 107w/cm2, maximal diameter 60mm, laser focus minimal diameter smaller than 0.5mm.
The optical parametric process with ultrashort pulse is investigated theoretically and experimentally. Reliable numerical method is used. The comparison between the theory and the experiments shows the directing bearing of our work.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.