Intracavity Frequency Tripling Research Articles

Intracavity third-harmonic generation in a continuous-wave/self-mode-locked semiconductor disk laser

The high peak power of picosecond pulses produced by a self-mode-locked semiconductor disk laser can effectively improve the efficiency of nonlinear frequency conversion. This paper presents the intracavity frequency tripling in a self-mode-locked semiconductor disk laser, and a picosecond pulse train at 327 nm wavelength is achieved. The pulse repetition rate is 0.49 GHz, and the pulse width is 5.0 ps. The obtained maximum ultraviolet output power under mode locking is 30.5 mW, and the corresponding conversion efficiency is obviously larger than that of continuous-wave operation. These ultraviolet picosecond pulses have high spatial and temporal resolution and can be applied in some emerging fields.

High efficiency 355 nm laser by employing a flat-flat cavity with improved harmonic beam quality

A high efficiency 355 nm ultraviolet (UV) laser is obtained by intracavity frequency-tripling of a 1064 nm Nd:YVO4 laser in a flat-flat cavity. The 5.6 W UV maximum average output power is obtained at the incident pump power of 29 W at 808 nm and the repetition rate of 50 kHz, corresponding to the pump-UV conversion efficiency of 19.3%. The corresponding pulse width is 14.2 ns, with the energy of a single pulse and corresponding peak power estimated to be 112 μJ and 7.89 kW, respectively. The frequency doubling and tripling lasers are obtained by employing type-I phase-matching LiB3O5 (LBO) crystal with parallel surfaces and a type-II phase-matching LBO crystal with Brewster angle-cut uncoated surface, respectively. The beam quality of the 355 nm laser is measured to be M x 2 = 1.257 and M y 2 = 1.173, respectively. The reasons for improvement of harmonic beam quality are explained by simulating the laser field intensity distribution changes in two special directions during the nonlinear conversion process.

Tunable, CW Laser Emission at 225 nm via Intracavity Frequency Tripling in a Semiconductor Disk Laser

Numerous applications would benefit from a compact laser source with tunable, continuous-wave emission in the deep ultraviolet (wavelengths <250 nm); however, very few laser sources have been demonstrated with direct emission in this spectral region and options are generally limited to pulsed, fixed wavelength sources or complex and impractical setups for nonlinear frequency mixing of the emission of several infrared lasers in various external enhancement cavities. Here, we propose an all-solid-state, continuous-wave, tunable laser with emission between 224 and 226 nm via intracavity frequency tripling in an AlGaInP-based semiconductor disk laser (SDL). Output power up to 78 μW is achieved in continuous wave operation, with a tuning range over 350 cm−1. AlGaInP-based SDLs may be designed to emit anywhere between ∼640–690 nm such that wavelengths between 213 and 230 nm may be targeted for specific applications using a similar set-up. An in-depth study of the nonlinear conversion has been carried out to understand the limitations of the set-up, namely large walk-off angles for phase-matching in the nonlinear crystals, and the potential for increasing the output power to several milli-Watts. This is, to the authors’ knowledge, the first implementation of intracavity frequency tripling in a visible SDL and the shortest wavelength emitted from an SDL system.

应用于光刻领域中的固态紫外激光源的制作

An intracavity frequency-tripling of a diode-edge-pumped passively Q-switched 1 064 nm Nd∶YAG laser is presented to generate high power 355 nm UV laser.Several essential technologies are put forward to achieve the best beam quality such as a volume grating to maintain quasi phase matching with narrow linewidth,optimization and thermal effects compensation for cavity.The task first takes advantage of volume grating and two CBO crystals as SHG and THG nonlinear optical conversion material to obtain high UV laser power output more than 4 W,light quality factor M22.5,meanwhile it is the first time to realize thermal effect using 45° Faraday rotator.The achievement is expected to be the popular light source system in lithography instead of conventional excimer laser.

355-nm UV Generation by Intracavity Frequency Tripled Passively $Q$-Switched Nd:YAG/Cr$^{4+}$:YAG Laser

In this letter, intracavity frequency-tripling of a diode-end-pumped passively <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -switched Nd:YAG/Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> :YAG composite laser has been demonstrated for the first time. Under the absorbed pump power of 7.2 W, the maximum UV output power of 110 mW is obtained with the beam quality parameter <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 2.95. The minimum pulsewidth and the highest repetition rate are 23.9 ns and 19.6 kHz, respectively. The corresponding single pulse energy and pulse peak power are 5.6 μJ and 0.23 kW. The fluctuation of the average output power at 110 mW within an hour operation is tested and determined to be 4.7%.

Generation of 7.8 W at 355 nm from an efficient and compact intracavity frequency-tripled Nd:YAG laser

A high power, quasi-continuous wave ultraviolet laser at 355 nm was obtained by intracavity frequency tripling of a diode side-pumped acousto-optic (AO) Q-switched Nd:YAG laser. Type II critical phase-matched KTP and LBO crystals were used for the second harmonic generation and the third harmonic generation, respectively. Under the pump power of 180 W, 7.8 W average output power at 355 nm was obtained at 8 kHz with the pulse width of 50 ns, corresponding to the pump-to-ultraviolet conversion efficiency of 4.3%. The peak power and single pulse energies were estimated to be 18.8 kW and 938 μJ. Its far-field divergence was measured to be about 3.8 mrad. The instability of the 355 nm laser was less than 1% at an output power of 6.3 W for 2 h operation.

Completely solid-state LD-side-pumped Nd:YAlO3 CW blue laser with intracavity frequency tripling

We report a completely solid-state continuous-wave (CW) blue laser operating at 447 nm utilizing intracavity frequency tripling of an LD-side-pumped Nd:YAlO3 (Nd:YAP) laser operating at 1341.4 nm. An LBO crystal with type-I critical phase matching and a KTP crystal with type-II critical phase matching (CTM) were used for the second harmonic generation (SHG) and the third harmonic generation (THG), respectively. In view of the analysis of the cavity stability, a four-mirror folded cavity was designed and the output characteristics were theoretically analyzed. Experimental characteristics obtained were shown to be in agreement with the theoretical analysis. The maximum output power of the 447 nm CW blue laser reached 114 mW, which corresponds to a red-to-blue conversion efficiency of 9%.

Generation of 7.6-W blue laser by frequency-tripling of a Nd:YAG laser in LBO crystals

High-power, quasi-continuous wave blue laser output is obtained by intracavity frequency-tripling of a 1.319 microm Nd:YAG laser with two LiB(3)O(5) crystals. The conversion efficiency and the stability of the blue laser output power at 439.7 nm were both improved through the suppression of 1.338 microm operation by means of a thin YAG etalon. 7.6 W average power at 439.7 nm was demonstrated at 5 kHz with pulse width of 170+/-10 ns (FWHM). The beam quality factor M(2) is 12+/-2 in both horizontal and vertical directions. The long-term stability of the blue light is better than 1% at an output of 6 W for 200 operation hours.

Compact efficient diode-pumped Nd:YVO4 Q-switched blue laser with intracavity frequency tripling

We demonstrate a compact efficient diode-pumped acousto-optically Q-switched intracavity-frequency-tripled Nd:YVO4 blue laser. The optimum polarization state is experimentally investigated to optimize the output performance. Greater than 280 mW of 447-nm average power at a repetition rate of 25 kHz was generated with a 15-W diode pump power. At 25 kHz, the pulse width is shorter than 15 ns and the peak power is higher than 800 W.

Intracavity frequency-tripling of actively mode-locked diode-pumped Nd:YAG laser

We report the first diode-pumped solid-state laser operating in cw-mode-locked regime and simultaneously achieving intracavity frequency-tripling. This laser provide UV picosecond pulses (λ=355 nm) of 10 ps duration with 0.5 mW average power at 150 MHz repetition rate. A different set of adjustments gave rise to a Q-switched mode-locked regime. Trains of hundred UV pulses of 60 ps duration and 4 W peak power were produced in this latter case at 50 kHz repetition rate.

High-efficiency and compact blue source: intracavity frequency tripling by using LBO and BBO without the influence of birefringence

A new intracavity frequency-tripled laser resonator design that circumvents the birefringence interference problems normally associated with a laser resonator with two intracavity nonlinear crystals is developed. Two hundred mW of UV laser output in a TEM(00) mode is obtained from an intracavity frequency-tripled Nd:YAG laser; the 250-Hz pulsed input does not exceed 400 W. LBO and BBO nonlinear crystals are utilized for second-harmonic generation and third-harmonic generation, respectively. The peak power of the UV output measures 90 kW.